Liquid fuel production process from waste plastics

Abstract

The present invention relates to a liquid fuel production process from waste plastics. A liquid fuel production process from waste plastics according to an embodiment of the present invention comprises the steps of: preparing a catalyst; stirring the catalyst, water, and waste plastic materials in a stirrer to form a mixture; and placing the mixture into a reactor and decomposing waste plastics.

Description

Liquid fuel production process from waste plastic

[0001] The present invention relates to a process for producing liquid fuel from waste plastics.

[0002] Global plastic production has surged over the past few years, increasing from 1.7 million tons in 1954 to 403 million tons in 2022. However, plastic waste management relies primarily on landfilling (~75%) or incineration (~14%), with the recycling rate remaining at only 11%. This trend exacerbates environmental pollution and highlights the urgent need for sustainable solutions in plastic waste management. In response to these challenges, innovative recycling technologies aimed at mitigating environmental risks are critically required. While mechanical recycling has traditionally been utilized, it often leads to the downcycling of plastics, damaging their mechanical properties. Chemical recycling methods, particularly catalytic recycling, are increasingly recognized as promising alternatives. Catalytic recycling can convert plastic waste into high-value chemicals and fuels at lower temperatures (250–400°C) compared to conventional chemical recycling methods (500–800°C). Furthermore, this facilitates the selective cleavage of CC bonds in plastic waste, producing liquid fuel with a higher yield compared to conventional methods. These advantages reduce separation costs and energy input, providing an economical and environmentally friendly solution to the growing challenges associated with plastic waste management.

[0003] There is an urgent need for technology that can selectively produce high-value-added liquid fuels from waste plastics through the catalytic cracking method (less than 0.1% of the total), which is considered a more advanced method among the chemical recycling technologies for waste plastics (less than 1% of the total).

[0004] The aforementioned background technology is one that the inventor possessed or acquired in the process of deriving the disclosure of the present invention, and it cannot be considered as prior art disclosed to the general public prior to the filing of this application.

[0005] The objective of the present invention is to provide a process for producing liquid fuel from waste plastics capable of converting waste plastics into high-value-added compounds.

[0006] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0007] A process for producing liquid fuel from waste plastic according to one embodiment of the present invention comprises: a step of preparing a catalyst; a step of stirring the catalyst, water, and waste plastic material in a stirrer to form a mixture; and a step of placing the mixture into a reactor and decomposing the waste plastic.

[0008] According to one embodiment, the step of preparing the catalyst may involve using a wet impregnation method.

[0009] According to one embodiment, the step of preparing the catalyst may comprise: a step of forming a suspension by adding a stirring rod, a metal precursor, water, and a support in sequence and stirring in a stirrer at a temperature of 100 rpm to 800 rpm for 60 minutes to 300 minutes; a step of evaporating water from the suspension in a constant temperature water bath at a temperature range of 40 ℃ to 80 ℃; a step of drying the water-evaporated suspension in an oven at a temperature range of 80 ℃ to 150 ℃ for 6 hours to 24 hours; and a step of pre-treating the dried suspension in a tube furnace at a heating rate of 2 ℃ / min to 10 ℃ / min for 30 minutes to 300 minutes under a 10% H2 / Ar flow (50 mL / min) to a temperature range of 300 ℃ to 800 ℃, and maintaining it for 30 minutes to 300 minutes to synthesize the catalyst.

[0010] According to one embodiment, the metal precursor may comprise at least one selected from the group consisting of ruthenium (Ru), platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W), rhodium (Rh), and palladium (Pd).

[0011] According to one embodiment, the support may be a zeolite catalyst having Brønsted acid sites.

[0012] According to one embodiment, the zeolite catalyst may comprise at least one selected from the group consisting of zeolite Y, zeolite Socony Mobil-5 (ZSM-5), beta zeolites (BEA), and mordenite zeolite (MOR).

[0013] According to one embodiment, after the pretreatment step, the synthesized catalyst may be heated using a heating furnace at a heating rate of 2 ℃ / min to 10 ℃ / min under a 10% H2 / Ar flow from room temperature to a temperature range of 200 ℃ to 600 ℃ for 30 minutes to 300 minutes, and then ex-situ reduced at the said temperature for 30 minutes to 300 minutes.

[0014] According to one embodiment, the waste plastic may comprise at least one selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), and ethylene vinyl acetate (EVA).

[0015] According to one embodiment, the step of forming the mixture may be to sequentially add the catalyst, water, and waste plastic material to a stirrer and then stir to form the mixture.

[0016] According to one embodiment, in the step of forming the mixture, the mass ratio of the catalyst to water may be 1:0.5 to 1:2.

[0017] According to one embodiment, the step of decomposing the waste plastic may be performed in a temperature range of 200 ℃ to 700 ℃ and a pressure range of 0.01 MPa to 10 MPa.

[0018] In a process for producing liquid fuel from waste plastic according to one embodiment of the present invention, water is added to the waste plastic catalytic decomposition reaction to increase the waste plastic conversion rate and liquid fuel yield, thereby converting the waste plastic into a high-value compound.

[0019] The effects of the present invention are not limited to the above effects and can be extended in various ways without departing from the technical concept and scope of the present invention.

[0020] FIGS. 1a to 1c are drawings showing the conversion rate under various reaction conditions and the results of reusability using 5% Ru / zeolite-Y according to an embodiment of the present invention.

[0021] FIGS. 2a and 2b are diagrams illustrating the role of the acid site in the LDPE depolymerization according to an embodiment of the present invention.

[0022] FIGS. 3a to 3f are drawings showing the product distribution after the LDPE depolymerization reaction according to an embodiment of the present invention.

[0023] FIGS. 4a to 4f are drawings showing the results of a depolymerization reaction using a substitute according to an embodiment of the present invention.

[0024] FIGS. 5a to 5e are drawings showing PE depolymerization results as a function of metal acid balance (MAB) according to an embodiment of the present invention.

[0025] FIGS. 6a and 6b are diagrams illustrating an LDPE depolymerization mechanism according to an embodiment of the present invention.

[0026] FIGS. 7a to 7d are drawings showing the results of a depolymerization reaction using various types of plastic according to an embodiment of the present invention.

[0027] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0028] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0029] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0030]

[0031] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. When describing embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiment, such detailed description is omitted.

[0032] In addition, terms such as first, second, A, B, (a), (b), etc. may be used when describing the components of the embodiments. These terms are used merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the terms.

[0033] Components included in any one embodiment and components having common functions shall be described using the same names in other embodiments. Unless otherwise stated, the description in any one embodiment may also apply to other embodiments, and specific descriptions shall be omitted to the extent of overlap.

[0034]

[0035] Hereinafter, the process for producing liquid fuel from waste plastics according to the present invention will be described in detail with reference to the examples and drawings. However, the present invention is not limited to these examples and drawings.

[0036]

[0037] A process for producing liquid fuel from waste plastic according to one embodiment of the present invention comprises: a step of preparing a catalyst; a step of stirring the catalyst, water, and waste plastic material in a stirrer to form a mixture; and a step of placing the mixture into a reactor and decomposing the waste plastic.

[0038] A process for producing liquid fuel from waste plastics according to one embodiment of the present invention may involve depolymerizing waste plastic materials into a new product comprising a hydrocarbon oil having valuable and useful properties. In particular, the present invention relates to a process for converting plastics into liquid hydrocarbons for use as a hydrocarbon feedstock.

[0039] A process for producing liquid fuel from waste plastic according to one embodiment of the present invention may use a 50 mL 316 L stainless steel high-pressure batch reactor using a spiral wound gasket.

[0040] According to one embodiment, the step of preparing the catalyst may involve using a wet impregnation method.

[0041] According to one embodiment, the step of preparing the catalyst includes a suspension formation step, a water evaporation step, a drying step, and a pretreatment step.

[0042] The above suspension formation step may involve forming a suspension by adding a stirring rod, a metal precursor, water, and a support in sequence.

[0043] According to one embodiment, the metal precursor may comprise at least one selected from the group consisting of ruthenium (Ru), platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W), rhodium (Rh), and palladium (Pd).

[0044] Preferably, the metal precursor may include ruthenium (Ru).

[0045] According to one embodiment, the support may be a zeolite catalyst having a Brønsted acid site.

[0046] According to one embodiment, the zeolite catalyst may comprise at least one selected from the group consisting of zeolite Y, zeolite Socony Mobil-5 (ZSM-5), beta zeolites (BEA), and mordenite zeolite (MOR).

[0047] Preferably, the zeolite catalyst may be a hydrophilic zeolite.

[0048] Preferably, the zeolite catalyst may be zeolite Y.

[0049] The formation of the above suspension is achieved by adding a stir bar, a metal precursor, water, and a support in sequence to a double jacket at 100 rpm to 800 rpm; 100 rpm to 600 rpm; 100 rpm to 400 rpm; 100 rpm to 200 rpm; 300 rpm to 800 rpm; 300 rpm to 600 rpm; or 500 rpm to 800 rpm for 60 minutes to 300 minutes; 60 minutes to 240 minutes; 60 minutes to 180 minutes; 60 minutes to 120 minutes; 120 minutes to 300 minutes; 120 minutes to 240 minutes; 120 minutes to 180 minutes; 180 minutes to 300 minutes; 180 minutes to 240 minutes; Or, a mixture may be formed by stirring for 240 to 300 minutes.

[0050] Preferably, the suspension may be formed by adding a stirring rod, a metal precursor, water, and a support in sequence to a double jacket and stirring for 60 minutes to 180 minutes at 500 rpm to 800 rpm.

[0051] The above water evaporation step is a step of evaporating water from the suspension in a constant temperature water bath at a temperature range of 40 ℃ to 80 ℃; 40 ℃ to 70 ℃; 40 ℃ to 60 ℃; 40 ℃ to 50 ℃; 50 ℃ to 80 ℃; 50 ℃ to 70 ℃; 50 ℃ to 60 ℃; 60 ℃ to 80 ℃; 60 ℃ to 70 ℃; or 70 ℃ to 80 ℃.

[0052] Preferably, the water evaporation step may be performed at 40°C to 60°C.

[0053] The above drying step is a step of drying the water-evaporated suspension in an oven at a temperature range of 80°C to 150°C for 6 to 24 hours.

[0054] The above pretreatment step comprises heating the dried suspension in a tube furnace under a 10% H2 / Ar flow (50 mL / min) at a heating rate of 2 ℃ / min to 10 ℃ / min; 2 ℃ / min to 8 ℃ / min; 2 ℃ / min to 5 ℃ / min; 5 ℃ / min to 10 ℃ / min; 5 ℃ / min to 8 ℃ / min; 8 ℃ / min to 10 ℃ / min; for 30 to 300 min; 30 to 240 min; 30 to 180 min; 30 to 120 min; 30 to 60 min; 60 to 300 min; 60 to 240 min; 60 to 180 min; 60 to 120 min; 120 to 300 min; 120 to 240 min; For 120 to 180 minutes; 180 to 300 minutes; or 180 to 240 minutes; at room temperature for 300 ℃ to 800 ℃; 200 ℃ to 700 ℃; 300 ℃ to 600 ℃; 300 ℃ to 500 ℃; 300 ℃ to 400 ℃; 400 ℃ to 800 ℃; 400 ℃ to 700 ℃; 400 ℃ to 600 ℃; 400 ℃ to 500 ℃; 500 ℃ to 800 ℃; 500 ℃ to 700 ℃; 500 ℃ to 600 ℃; 600 ℃ to 800 ℃; 600 ℃ to 700 ℃; Or, the step of synthesizing a catalyst by pre-treating by raising the temperature to a range of 700 ℃ to 800 ℃ and maintaining it for 30 minutes to 300 minutes; 30 minutes to 240 minutes; 30 minutes to 180 minutes; 30 minutes to 120 minutes; 30 minutes to 60 minutes; 60 minutes to 300 minutes; 60 minutes to 240 minutes; 60 minutes to 180 minutes; 60 minutes to 120 minutes; 120 minutes to 300 minutes; 120 minutes to 240 minutes; 120 minutes to 180 minutes; 180 minutes to 300 minutes; or 180 minutes to 240 minutes.

[0055] Preferably, pretreatment may be performed by using a tube furnace with a 10% H2 / Ar flow (50 mL / min) and setting the heating rate to 2.5℃ / min to raise the temperature from room temperature (25℃) to 500℃ (i.e., 3 hours and 10 minutes) and maintaining it under the said conditions for 3 hours.

[0056] According to one embodiment, the synthesized catalyst may be pretreated in an amount to be used before the reaction to decompose waste plastic.

[0057] After the above pretreatment step, the synthesized catalyst is heated using a furnace under a 10% H2 / Ar flow at a heating rate of 2 ℃ / min to 10 ℃ / min; 2 ℃ / min to 8 ℃ / min; 2 ℃ / min to 5 ℃ / min; 5 ℃ / min to 10 ℃ / min; 5 ℃ / min to 8 ℃ / min; 8 ℃ / min to 10 ℃ / min; from room temperature to a temperature range of 200 ℃ to 600 ℃ for 30 minutes to 300 minutes; 30 minutes to 240 minutes; 30 minutes to 180 minutes; 30 minutes to 120 minutes; 30 minutes to 60 minutes; 60 minutes to 300 minutes; 60 minutes to 240 minutes; 60 minutes to 180 minutes; 60 minutes to 120 minutes; It may be heated for 120 to 300 minutes; 120 to 240 minutes; 120 to 180 minutes; 180 to 300 minutes; or 180 to 240 minutes; and ex-situ reduction at the said temperature for 30 to 300 minutes.

[0058] According to one embodiment, the waste plastic may comprise at least one selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), and ethylene vinyl acetate (EVA).

[0059] Preferably, the waste plastic may be high-density polyethylene (HDPE) or low-density polyethylene (LDPE).

[0060] According to one embodiment, a procedure prior to the decomposition reaction may be performed prior to the step of decomposing the waste plastic.

[0061] The above procedure prior to the decomposition reaction may be carried out using a 50 mL 316 L stainless steel high-pressure batch reactor (Hanul Engineering) with a spiral wound gasket.

[0062] First, it may be to insert a glass-coated magnetic bar (stir bar) into a glass liner.

[0063] Next, a catalyst (e.g., 50 mg), water (e.g., 50 mg), and plastic (e.g., 1.7 g) may be added in the order and amount of water added, and then stirred in a stirrer for 1 to 5 minutes; 1 to 3 minutes; under conditions of 100 rpm to 500 rpm; 100 rpm to 400 rpm; 100 rpm to 300 rpm; 100 rpm to 200 rpm; 200 rpm to 500 rpm; 200 rpm to 400 rpm; 200 rpm to 300 rpm; 300 rpm to 500 rpm; 300 rpm to 400 rpm; or 400 rpm to 500 rpm.

[0064] Next, a glass liner may be placed in the reactor and sealed.

[0065] A sealed reactor may be purged multiple times, for example, three times, to remove oxygen from the reactor under 10 bar to 50 bar; 10 bar to 30 bar; or 30 bar to 50 bar; argon (Ar) conditions.

[0066] Next, the sealed reactor may be purged multiple times, for example, three times, under conditions of 10 bar to 50 bar; 10 bar to 30 bar; or 30 bar to 50 bar; hydrogen (H2).

[0067] After purging is complete, the pressure corresponding to the reaction conditions is increased to 10 bar to 50 bar; 10 bar to 30 bar; or 30 bar to 50 bar; for example, up to the hydrogen (H2) condition of 30 bar.

[0068] The reaction temperature may be raised to the reaction temperature (generally 250°C), but to prevent overshooting, the temperature may be raised using an OMEGA PID Controller by subdividing it into the following conditions.

[0069] The reaction may be carried out sequentially for 10 to 20 minutes at 150 ℃ to 200 ℃, 10 to 20 minutes at 200 ℃ to 259 ℃, 20 to 30 minutes at 230 ℃ to 280 ℃, and finally for 1 to 6 hours at 240 ℃ to 280 ℃.

[0070] According to one embodiment, the step of forming the mixture may be to sequentially add the catalyst, water, and waste plastic material to a stirrer and then stir to form the mixture.

[0071] According to one embodiment, the step of decomposing the waste plastic may go beyond a general approach of simply adding water, as the reactivity varies significantly depending on the order and amount of water added in the step of forming the mixture.

[0072] According to one embodiment, in the step of forming the mixture, the mass ratio of the catalyst to water may be 1:0.5 to 1:2.

[0073] Preferably, the mass ratio of the catalyst to water may be 1:1.

[0074] When the amount of water is excessively large or small, the liquid fuel conversion rate may vary depending on the ratio of water to catalyst addition. In the present invention, the highest reactivity was observed when the mass ratio of water to catalyst was 1:1. The amount of water added to obtain optimal reactivity is determined, and the present method proposes an optimal method for producing high value-added liquid fuel from plastic waste.

[0075] According to one embodiment, the step of decomposing the waste plastic comprises a temperature range of 200 ℃ to 700 ℃; 200 ℃ to 600 ℃; 200 ℃ to 500 ℃; 200 ℃ to 400 ℃; 200 ℃ to 300 ℃; 300 ℃ to 700 ℃; 300 ℃ to 600 ℃; 300 ℃ to 500 ℃; 300 ℃ to 400 ℃; 400 ℃ to 700 ℃; 400 ℃ to 600 ℃; 400 ℃ to 500 ℃; 500 ℃ to 700 ℃; 500 ℃ to 600 ℃; or 600 ℃ to 700 ℃; and 0.01 MPa to 10 MPa; It may be performed in a pressure range of 0.01 MPa to 5 MPa; 0.01 MPa to 1 MPa; 0.01 MPa to 0.1 MPa; 0.1 MPa to 10 MPa; 0.1 MPa to 5 MPa; 0.1 MPa to 1 MPa; 1 MPa to 10 MPa; 1 MPa to 5 MPa; 2 MPa to 10 MPa; 2 MPa to 5 MPa; or 5 MPa to 10 MPa.

[0076] Preferably, the step of decomposing the waste plastic may be performed in a temperature range of 200 ℃ to 300 ℃ and a pressure range of 1 MPa to 5 MPa.

[0077] Waste plastic depolymerized by a waste plastic liquid fuel production process according to one embodiment of the present invention can be converted into liquid fuel.

[0078] The above liquid fuels can be classified according to the number of carbon atoms: Gas: C1-C4, Gasoline: C5-C 12 , Jet Fuel: C8-C 16 , Diesel: C9- C 22 , Lubricant: C 20 - C 35

[0079] In one embodiment of the present invention, the reactivity of the waste plastic liquid fuel production process varies significantly depending on the order and amount of water added.

[0080] Following precise procedures to enhance reactivity through the interaction of water and catalyst may be the key to the waste plastic liquid fuel production process of the present invention.

[0081] For example, the liquid fuel conversion rates of experimental groups 1 to 3 and the control group are as follows:

[0082] Experimental Group 1: When catalyst, water, and plastic were added in that order and stirred (Liquid fuel conversion rate 96.9%)

[0083] Experimental Group 2: When catalyst, plastic, and water are added in that order and stirred (Liquid fuel conversion rate 33.5%)

[0084] Experimental Group 3: Case where water is added after stirring following the addition of catalyst and plastic (Liquid fuel conversion rate 38.9%)

[0085] Control group (no water added): When stirring after adding catalyst and plastic (liquid fuel conversion rate 80.6%)

[0086] As experimental group 1, reactivity was improved compared to the control group only when the sequence of catalyst, water, and plastic addition was followed, whereas for experimental groups 2 and 3, which followed different methods, the liquid fuel conversion rate may have decreased significantly compared to the reaction without adding water.

[0087] Since reactivity varies significantly depending on the order of water addition and may actually decrease if added in an inappropriate manner, the order and amount of water addition are very important in the waste plastic liquid fuel production process of the present invention, as reactivity varies greatly depending on the order and amount of water addition.

[0088] The waste plastic liquid fuel production process of the present invention can increase the waste plastic conversion rate and liquid fuel yield by adding water to the waste plastic catalytic decomposition reaction.

[0089] The process for producing liquid fuel from waste plastics according to one embodiment of the present invention is an optimal technology capable of simultaneously resolving the low energy efficiency and economic feasibility of conventional waste plastic pyrolysis processes through research on converting waste plastics, which are identified as a major culprit of environmental pollution, into high-value-added compounds.

[0090] Furthermore, unlike conventional waste plastic recycling processes that convert materials into substances of lower value than before recycling, catalytic waste plastic upcycling technology that converts them into high-value fuels and compounds is expected to bring about a shift in economic and industrial paradigms.

[0091] In particular, by adding water, improvements in economic efficiency can be expected due to the increased waste plastic conversion rate and liquid fuel yield.

[0092]

[0093] The present invention will be described in detail below with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited or restricted by such examples.

[0094]

[0095] Hydrogenolysis and hydrocracking are catalytic recycling methods that have been widely recognized for their effectiveness in upcycling polyolefin plastic waste, which accounts for more than half of the world's plastic waste due to their short life cycles.

[0096] Hydrogenolysis produces liquid fuels in high yields by operating at relatively low temperatures using Ru or Pt supported on metal oxides such as CeO2, TiO2, Al2O3, SBA-15, and ZrO2. In hydrogenolysis, CH bond activation and CC bond cleavage occur mainly at the metal sites, which highlights the important role of the geometry of Ru and Pt in influencing activity.

[0097] Conversely, hydrocracking involves CH bond activation at the metal site and the CC bond cracking acid site, and generally uses Pt and Ru metals paired with acidic supports such as WO3 / ZrO-2 or zeolites. The metal-acid molar ratio, known as metal-acid balance (MAB), has been reported to have a significant effect on hydrocracking reactivity.

[0098] Previous studies on the hydrogenolithism and hydrocracking of polyolefin plastics were primarily conducted without solvents, but recent research has elucidated the effect of solvents on catalytic activity, particularly in the hydrogenolithism of HDPE for Ru / C. Among the various solvents tested, including water, n-pentane, n-hexane, methylcyclohexane, and decalin, only n-hexane and methylcyclohexane were found to enhance HDPE hydrogenolithism activity. Molecular dynamics simulations revealed that interactions between HDPE and solvent molecules alter the morphology of HDPE. For example, in n-hexane, HDPE tends to coil, facilitating access to the active sites of the catalyst and increasing activity, whereas in decalin, HDPE maintains an extended morphology, resulting in reduced catalytic activity. In particular, previous studies investigated the effect of water on the hydrocracking of n-hexadecane. It was found that the addition of water reduced the hydrocracking conversion of n-hexadecane compared to H-ZSM-5 due to competitive adsorption between water and reactants on the acidic sites of the zeolite at relatively low reaction temperatures (<350℃). Conversely, it was reported that the addition of water promoted the activity of Pd / NaX zeolite in the hydrocracking of n-hexadecane. Therefore, it was hypothesized that the addition of water enhances the depolymerization of polyolefin plastic waste in which both metal and acidic sites are present.

[0099] In an embodiment of the present invention, a series of Ru catalysts supported on various materials such as SiO2, SBA-15, γ-Al2O3, TiO2, and zeolite-Y were synthesized to investigate the effect of water on the depolymerization of polyolefin plastics.

[0100] According to an embodiment of the present invention, the promoting effect of water was shown to increase the conversion rate from approximately 51% to approximately 82% through metal-acid interactions only in the presence of metal and acid sites, particularly Brønsted acid sites. Furthermore, the MAB and its proximity are identified as important factors promoting metal-acid interactions. In particular, the presence of water affects the degree of isomerization; the selectivity for isomers is 1.6% in the presence of water, compared to 72.1% in the absence of water. A reaction mechanism for difunctional depolymerization is proposed using a comprehensive set of characterization techniques, including GC-MS, mass spectrometry, and pyridine IR, explaining the key differences between the hydrogenolysis and hydrocracking processes. Techno-economic analysis (TEA) and life-cycle assessments (LCA) further demonstrate that the addition of water has a positive impact on both economic and environmental performance. These mechanical insights not only enhance the understanding of catalytic activity but also provide strategies for controlling the degree of isomerization in polyolefin plastic waste catalytic processes.

[0101]

[0102] Chemicals and materials

[0103] All chemicals were of analytical grade or higher and were used as received without further processing.

[0104] RuCl3·xH2O (product number 11043) was purchased from Alfa Aesar. Davisil Grade 646 SiO2 (product number 236845), SBA-15 (product number 806862), γ-Al2O3 (product number 544833), and TiO2 (product number 634662) P25 were purchased from Sigma-Aldrich. Zeolite Y with Si:Al ratios of 30:1 (product number 045870), 60:1 (product number 045871), and 80:1 (product number 045872) was purchased from Alfa Aesar. PE (Mn: ~1,700, Mw: ~4,000, Product No. 427772) was purchased from Sigma-Aldrich, commercial LDPE was purchased from Hanwha Total (Product Code: 530G), and LDPE bottles were purchased from Korea Ace Scientific. Mesitylene (Product No. 12558) was purchased from Acros Organics, toluene (Product No. 22903) was purchased from Alfa Aesar, and pyridine (Product No. 270407) was purchased from Sigma-Aldrich. High-density polyethylene (Product No. 427985), polypropylene (Product No. 427888), deuterium water (Product No. 151882), and alkane standard solution C8-C were purchased. 20 (Product Number 04070) and C 21 -C 40 (Product No. 04071) was purchased from Sigma-Aldrich. n-Pentane (Product No. 16787) and n-Dodecane (Product No. 43459) were purchased from Acros Organics. n-Hexane (Product No. L09938), n-Heptane (Product No. A19894), n-Octane (Product No. A13181), n-Nonane (Product No. A16177), and n-Docosan (Product No. A18050) were purchased from Alfa. n-Octadecane (Product No. O652) was purchased from Sigma-Aldrich.

[0105]

[0106] Catalyst preparation

[0107] The supported Ru catalyst was prepared by a wet impregnation method. A 5 wt% Ru / support catalyst was obtained by adding the support (0.96 g) and RuCl3·xH2O (133.0 mg, 0.50 mmol) to deionized water (100 mL). The suspension was stirred at 600 rpm for 2 hours for mixing and heated to 50 °C until completely dried. Subsequently, the obtained catalyst was dried at 100 °C for 12 hours and reduced at 500 °C for 3 hours under a 10% H2 / Ar flow (50 mL / min) at a heating rate of 2.5 °C / min. Prior to the reaction, the catalyst was ex-situ reduced at 400 °C for 1.5 hours under a 10% H2 / Ar flow (50 mL / min) at a heating rate of 5 °C / min. A similar procedure was performed using a support (2.50 g) and RuCl3·xH2O (66.5 mg, 0.25 mmol) for the 1 wt% Ru / support catalyst, and a support (3.78 g) and RuCl3·xH2O (19.9 mg, 0.075 mmol) for the 0.2 wt% Ru / support catalyst. Subsequently, to distinguish between zeolites with different Si:Al ratios, zeolite-Y with a Si:Al ratio of 30:1 is named Ru / zeolite-Y (Si / Al= 30), zeolite-Y with a ratio of 60:1 is Ru / zeolite-Y, and zeolite-Y with a ratio of 80:1 is Ru / zeolite-Y (Si / Al= 80).

[0108]

[0109] polyethylene decomposition reaction

[0110] A glass-coated magnetic stir bar, pre-treated catalyst, water (if necessary), and PE were added to the glass liner in this order, and then the liner was placed in a 50 mL 316 L stainless steel high-pressure batch reactor equipped with a spiral-wound gasket (Hanwoul Engineering CO., LTD). For the depolymerization of used plastic waste, commercial LDPE was used as received, and the LDPE bottles were cut into small pieces (3 mm x 3 mm). The sealed reactor was purged three times under Ar (30 bar) conditions to remove oxygen from the reactor. Next, the sealed reactor was purged three times under H2 (30 bar) conditions. After purging was completed, the reactor was pressurized to H2 (30 bar), a pressure corresponding to the reaction conditions. The pressurized reactor was placed in a heater and heated to the reaction temperature (200 ℃–300 ℃). The reaction temperature was monitored by a thermocouple inserted into the reactor. When the temperature reached 150 °C, stirring was started at a speed of 500 rpm for the target reaction time. To prevent overshooting, the temperature was raised using an OMEGA PID controller under the following detailed conditions: 16 minutes to 160 °C, 14 minutes to 239 °C, 22 minutes to 250 °C, and the reaction proceeded from 250 °C for the reaction time (typically 3 hours). After the reaction, the reactor was cooled to room temperature in an ice bath. The gaseous and liquid products were transferred to a 2 L PVC gas bag and a 50 mL centrifuge tube, respectively. Mesitylene solution (125 mmol / L) was used as the internal standard, and toluene was used as the wash solvent for liquid collection. After separating the unreacted reactants and catalyst, they were dried in an oven set to 60 °C for 48 hours. The centrifuge tubes containing the reaction products and catalyst were weighed after drying. The exact amount of unreacted reactants was calculated by subtracting the weight of the initial empty tube and the added catalyst from the measurement.The products were analyzed using a gas chromatograph (Agilent 8890 GC System) equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD). A GS-Carbon PLOT (Agilent) column was used for the gas phase, and an HP-1 column (Agilent) was used for the liquid phase. Gas product analysis was performed using the Agile-nt 8890 GC System from 38 °C to 325 °C at a heating rate of 20 °C / min and held for 10 minutes. The corresponding retention times for C1-C6 were for CH4, C2H4, C2H6, C3H8, and n-C4H in Ar. 10 The FID region signal was verified and corrected using a reference gas mixture purchased from Union Gas containing [subject]. The TCD region signal was corrected with high-purity hydrogen (99.999%) purchased from Union Gas. The liquid product of the analysis was also heated from 50 °C to 325 °C at a heating rate of 15 °C / min using an Agilent 8890 GC system and held for 45 minutes. C5-C 40 The corresponding retention times were identified, and the FID region signals were obtained from Sigma-Aldrich n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-dodecane, n-octadecane, n-dococane, and alkane standard solutions C8-C 20 and C 21 - C 40 It was corrected.

[0111]

[0112] Reusability test

[0113] The catalyst used was collected 12 hours after the reaction to be completely converted into an extractable state. After the reaction mixture was dried, the spent catalyst underwent a two-step process. First, it was calcined at a temperature of 300 °C under an air flow (80 mL / min). Subsequently, the catalyst was pretreated at 400 °C under a 10% H2 / Ar flow (50 mL / min). Since the catalyst recovery rate was approximately 95% and about 5% was lost, the preceding reaction was repeated two or more times to secure the amount of catalyst required for the subsequent reaction.

[0114]

[0115] Reactivity mechanism map

[0116] The reactivity mechanism map is displayed with the sum of the normalized mean carbon number ratio and the metal-acid balance on the x-axis and the corresponding transformation on the y-axis. To treat the MAB and mean carbon number ratio as equivalent ratios, the lowest value was standardized to 0 and the highest value to 5, respectively, and their sum was expressed on a scale from 0 to 10. 0 to 3.3 represents hydrocracking, 3.3 to 6.7 represents difunctional depolymerization, and 6.7 to 10 represents hydrogenolysis. The formula is as follows.

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123] Here v m The volume occupied by atoms in bulk Ru metal, a m The area occupied by silver surface atoms, d VA is the average particle size determined by STEM.

[0124]

[0125] Pyridine poisoning

[0126] The catalyst was subjected to ex-situ reduction at a ramping rate of 5 °C / min for 1.5 hours while maintaining a temperature of 400 °C under a 10% H2 / Ar flow (50 mL / min). To ensure sufficient poisoning, pyridine (100 mg, 1.27 mmol) was added dropwise using a pipette to poison 50 mg of 5% Ru / zeolite-Y (40 times the acid site density estimated by NH3-TPD). The mixture was dried in a vacuum desiccator at room temperature for 12 hours and then used immediately in the reaction.

[0127]

[0128] Data analysis

[0129] The BAS / LAS ratio was calculated as follows.

[0130]

[0131] Here, IBAS and ILAS are the combined absorbance of the BAS and LAS bands (cm²). -1 ) is. r is the radius of the sample disk (cm). m sample is the weight of the sample (mg). The molar extinction coefficients used were 1.8 cm / μmol for BAS and 1.5 cm / μmol for LAS.

[0132] The conversion rate and yield were calculated as follows.

[0133]

[0134]

[0135]

[0136] LDPE depolymerization

[0137] LDPE depolymerization reactions were carried out using various Ru catalysts supported on SiO2, SBA-15, γ-Al2O3, TiO2, and zeolite-Y. In most cases, the addition of water resulted in lower or similar activity, consistent with previous research findings. However, Ru / zeolite-Y showed a noticeable increase in conversion rate by 16.3 percentage points, rising from 80.6% to 96.9% after the addition of water. This increase in conversion rate is desirable for the intermediate range (C5-C) for liquid fuel production. 22 ) accompanied a shift in product distribution toward alkanes. To further understand the promoting effect of water on Ru / zeolite-Y, experiments were conducted by changing the reaction conditions.

[0138] FIGS. 1a to 1c are drawings showing the conversion rate under various reaction conditions and the results of reusability using 5% Ru / zeolite-Y according to an embodiment of the present invention.

[0139] As shown in Fig. 1a, the addition of water resulted in an improvement in the conversion rate over time. Additionally, the conversion rate exhibited a bell-shaped curve as a function of the water / catalyst ratio, reaching a peak at a water / catalyst ratio of 1.0 (Fig. 1b). This observation suggests that as the water / catalyst ratio increases, the presence of water gradually enhances LDPE conversion, but beyond this optimal ratio, reactivity decreases due to the dilution effect.

[0140] As shown in Fig. 1c, a reusability test was performed to investigate the effect of coke precipitation on the reactivity of Ru / zeolite-Y in LDPE depolymerization. When Ru / zeolite-Y was reused with water, the initial conversion rate was 96.9%, and subsequent first and second regenerations showed conversion rates of 94.5% and 90.1%, respectively. These results suggest that the reactivity of the catalyst remained almost unchanged.

[0141] Figure 1a shows the conversion rate according to reaction time, and Figure 1b shows the conversion rate according to the water / catalyst ratio. Unless otherwise noted, reaction conditions are as follows: 250 °C for 1.5 h, 30 bar H2 pressure (at 25 °C), 1.70 g LDPE (Mn: ~1,700, Mw: ~4,000), 50 mg Ru / zeolite-Y (metal: 5 wt%), 50 mg water (if required). (c) Results on the reusability of Ru / zeolite-Y. Reaction conditions: 250 °C, 3 h, 30 bar H2 pressure (at 25 °C), 1.70 g LDPE (Mn: ~1,700, Mw: ~4,000), 50 mg waste Ru / zeolite-Y (metal: 5 wt%), 50 mg water (if required). Error bars: standard deviation.

[0142]

[0143] To understand the role of the acidic site and how water enhances reactivity and reusability, control experiments were performed using pyridine. The Ru / zeolite-Y catalyst poisoned with pyridine exhibited a negligible effect with water, unlike the fresh catalyst (Table 1, Entries 1, 2).

[0144] Entry Catalyst Ru Content (mg) Catalyst / Water Weight Conversion Rate (%) a Yield (%) Gas Gasoline Jet Fuel Diesel Lubricant 15% Ru / zeolite-Y-pyridine 2.50 47.7 ± 1.2 0.4 48.6 17.8 26.8 22.5 147.4 ± 1.3 0.5 4.4 8.9 18 26.5 31% Ru / zeolite-Y 0.50 34.3 ± 0.6 0 1.4 38.1 20.9 40.5 135.3 ± 0.4 0 1.5 3.6 9.3 21.85 b1% Ru / zeolite-Y+ Zeolite-Y0.5050.7 ± 0.30.15.99.816.725.460.5147.2 ± 1.00.13.97.113.327.871% Ru / zeolite-Y2.5056.8 ± 0.30.611.613.121.42682.5194.5 ± 0.11.513.227.145.244.290.2% Ru / zeolite-Y2.5054.5 ± 0.75.340.62925.72.6102.5182.8 ± 0.30.32.510.829.651.411 c 5% Ru / SiO2+ Zeolite-Y2.5065.6 ± 1.20.14.610.722.937.9122.5148.1 ± 0.70.12.15.614.429.8

[0145] Reaction conditions: 250 ℃, 3 hours, 30 bar H2 (at 25 ℃), LDPE 1.70 g (Mn: ~1,700, Mw: ~4,000), catalyst 50 mg, water 50 mg (if necessary). a The products were classified according to carbon number. Gas: C1-C4, Gasoline: C5-C 12 , Jet Fuel: C8-C 16 , Diesel: C9- C 22 , Lubricant: C 20 - C 35 , b 50 mg of a physical mixture of 1% Ru / zeolite-Y and 200 mg of Zeolite-Y, c A physical mixture of 50 mg of 5% Ru / SiO2 and 50 mg of Zeolite-Y.

[0146]

[0147] FIGS. 2a and 2b are diagrams illustrating the role of the acid site in the LDPE depolymerization according to an embodiment of the present invention.

[0148] Referring to Fig. 2a, unlike the new catalyst, the product distribution of the poisoned catalyst remained similar regardless of water. This finding strongly suggests that acidic sites are involved in the depolymerization of LDPE for the facilitating effect of water. Given that pyridine poisons both Lewis and Brønsted acid sites, pyridine-IR analysis of the Ru / zeolite-Y used was performed to identify the role of Brønsted acid sites. At 1450 cm⁻¹ in Ru / zeolite-Y before and after reaction with water -1 (LAS) and 1540 cm -1 A peak of (BAS) appeared (Fig. 2b). However, after reaction without water, the pyridine-IR spectrum of the catalyst was at 1540 cm⁻¹. -1It shows a noticeable decrease in the peak. Indeed, the BAS / LAS ratio of the catalyst decreased from 0.410 before the reaction to 0.100 after the water-free reaction. The substantial decrease in the BAS peak after the water-free reaction may be due to the precipitation of coke at the Brønsted acid sites during the water-free reaction. This also implies that the reaction occurs primarily at the Brønsted acid sites rather than the Lewis acid sites. To determine whether the decrease in Brønsted acid sites is caused by coke precipitation during the LDPE depolymerization reaction or by catalyst structural deformation at the reaction temperature, additional control experiments were performed without LDPE under the same reaction conditions. The pyridine-IR spectra of the control experiments with and without water (Fig. 2b) remained similar to the spectrum of the new catalyst, indicating that the loss of Brønsted acid sites in the absence of water is associated with coke formation occurring during LDPE. Therefore, it can be concluded that the loss of Brønsted acid sites is consistent with the occurrence of coking during LDPE depolymerization. To further evaluate reactivity according to acid strength, catalysts with Si / Al ratios of 30 and 80, distinct from the reference (Si / Al ratio of 60), were synthesized and tested. Both catalysts exhibited a conversion enhancement similar to that of the reference catalyst, but differences in selectivity according to the concentration of Brønsted acid sites were observed only in the absence of water. This behavior is attributed to the ability to undergo water-promoted protonation / deprotonation and the increased influence of metal sites in the presence of water.

[0149]

[0150] Metal-acid interactions in the presence of water

[0151] Considering that Brønsted acid is involved in LDPE depolymerization, additional experiments were conducted by varying the MAB to investigate how water affects the LDPE depolymerization process.

[0152] FIGS. 3a to 3f are drawings showing the product distribution after the LDPE depolymerization reaction according to an embodiment of the present invention.

[0153] As shown in Fig. 3a, 5% Ru / zeolite Y exhibited an improved conversion rate of 96.9% in the presence of water compared to 80.6% in the absence of water after 3 hours of reaction. Conversely, Fig. 3b shows that 1% Ru / zeolite-Y exhibited negligible differences in conversion rates of 34.3% and 35.3% in the presence and absence of water, respectively, indicating that there was no promoting effect from water. To understand varying degrees of promoting effects, the number of acidic sites was increased by adding zeolite-Y. However, despite this addition, no observable water-promoting effect occurred in the case of 1% Ru / zeolite-Y (Fig. 3c). As the number of metal sites remained constant and the number of acidic sites increased, the amount of 1% Ru / zeolite-Y was adjusted to match that of Ru / zeolite-Y with a Ru content of 5%. This adjustment significantly increased the conversion rate in the presence of water from 56.8% to 94.5% (Fig. 3d). A similar trend was observed in 0.2% Ru / zeolite-Y, which increased the conversion rate by water from 54.5% to 82.8% (Fig. 3e). These findings highlight the importance of MAB in the water-promoting effect. To investigate the effect of proximity between the metal and the acidic site, experiments were conducted using a physical mixture of 5% Ru / SiO2 and zeolite-Y (Fig. 3f). The physical mixture exhibited a minimal promoting effect, which strongly suggests that metal-acid proximity plays a pivotal role in inducing the water-promoting effect through metal-acid interactions in LDPE depolymerization.

[0154] In addition, noticeable changes in product distribution depending on the presence or absence of water were observed (Figs. 3a, 3d, and 3e). While the product distribution remains relatively consistent with water, significant changes depending on Ru loading are observed without water, particularly in catalysts with low Ru loading. For example, 0.2% Ru / zeolite-Y showed yields of 40.6% for gasoline and 2.6% for lubricating oil without water, whereas these changed to 2.5% and 51.4%, respectively, upon the addition of water. In contrast, 5% Ru / zeolite-Y exhibited yields of 9.8% and 41.5% for gasoline and lubricating oil, respectively, without the addition of water, and changed to 18.5% and 41.7%, respectively, upon the addition of water. Hydrocracking reactions generally produce shorter alkanes (C3-C4) when a dominant acid group is present, and longer alkanes (C3-C4) when a dominant metal group is present. 21+ Considering that it produces ) or methane, it can be seen that regardless of the Ru weight loading, the reaction mainly occurs at the Ru sites rather than the zeolite sites with water.

[0155]

[0156] Insights into reaction mechanisms

[0157] Deuterium water (D2O) was used instead of ordinary water (H2O) to elucidate the effect of water on the reaction mechanism.

[0158] FIGS. 4a to 4f are drawings showing the results of a depolymerization reaction using a substitute according to an embodiment of the present invention.

[0159] Referring to Figure 4a, similar product distributions were observed in both H2O and D2O. Further analysis using mass spectrometry (MS) revealed that there were no HDO or D2O peaks in the catalyst after the reaction without water, whereas the appearance of an HDO peak in the catalyst after the reaction with D2O indicated the inclusion of deuterium atoms. Additionally, isotopic analysis of the gas products (Figures 4b and 4c) showed a selectivity of 0.3% for deuterium atoms substituted without water, which increased to 4.1% when D2O was used, suggesting that some hydrogen atoms were replaced by deuterium. These results support the hypothesis that water acts as a proton donor in the reaction. Furthermore, MS and GC-MS analyses were performed to investigate the effect of water on the extent of the isomerization reaction. The goal was to elucidate the role of the acid site, which is important for isomerization, by using n-dodecane as a substitute. Comparing the reactions with and without Ru / zeolite-Y catalysts of 0.2% and 5% or more (Figs. 4d-4f), significant differences in isomer selectivity were observed. In particular, the selectivity for isomers exceeding 0.2% Ru / zeolite-Y decreased from 72.1% in the absence of water to 1.6% in the presence of water (Figs. 4e, 4f). This indicates that there is a significant change in the reaction pathway in the presence of water, especially when the metal content is low. Conversely, reactions with 5% Ru / zeolite-Y or more exhibited isomer selectivity of 1.2% in the absence of water and 3.0% in the presence of water, indicating a dominant role of the metal site under these conditions regardless of the presence of water (Figs. 4d, 4f). This suggests that water alters the LDPE depolymerization reaction pathway by potentially promoting the protonation of carbocations rather than skeletal rearrangement, thereby inducing the dominant production of linear alkanes.

[0160]

[0161] Relationship between Metal Acid Balance (MAB) and Reaction Pathways

[0162] Considering that MAB is widely recognized as a critical factor in short alkane hydrocracking, MAB has been integrated as a classification criterion. While acid-catalyzed reactions tend to slow down at high MABs, at low MABs, the rate-determining step shifts to hydrogenation / dehydrogenation reactions. Reflecting the change in the rate-determining step, C 21+ / C 4-6 The selectivity ratio of was reported to increase with increasing MAB. To explain this, C was used with Ru / zeolite-Y along with various Ru loadings. 21+ / C 4-6 Plotted the molar ratio of.

[0163] FIGS. 5a to 5e are drawings showing PE depolymerization results as a function of metal acid balance (MAB) according to an embodiment of the present invention.

[0164] Referring to Fig. 5a, C is consistent with previous research results. 21+ / C 4-6 The molar ratio increases with increasing MAB in the absence of water. However, the results for water show noticeable differences in product distribution, implying a mechanism different from hydrogenolithism and hydrocracking. For example, the yield of gasoline is highest in the absence of water, whereas the yields of diesel and lubricating oil peak in the presence of water greater than 0.2% Ru / zeolite-Y (Fig. 3e). C 21+ / C 4-6 In addition to the ratio, the average carbon number ratio between the gaseous and liquid phases was influenced by MAB.

[0165] Referring to Fig. 5b, C of the average carbon number without water, similar to previous research results liq / C gas The ratio increases as MAB increases. However, even if MAB levels are similar, the distribution varies significantly depending on the water, so C liq / C gasIt changes. Therefore, to classify the depolymerization of polyolefins into three groups, both MAB and all product distributions are considered.

[0166] Considering both MAB and the corresponding ratio, MAB is low and C liq / C gas The lower the value, the closer the reaction is to hydrocracking (see Methods for details).

[0167] Conversely, the higher the MAB, the more C liq / C gas The reaction is similar to hydrogenolysis and is classified as a difunctional depolymerization reaction in the intermediate case (Fig. 5c). The mechanism of each reaction classified in Fig. 5c will be explained in Figs. 6a and 6b.

[0168] FIGS. 6a and 6b are diagrams illustrating an LDPE depolymerization mechanism according to an embodiment of the present invention.

[0169] FIG. 6a is a diagram showing the overall reaction mechanism of a PE depolymerization reaction according to an embodiment of the present invention, and FIG. 6b is a diagram showing a simplified reaction mechanism for high, medium, and low metal acid balances (MAB).

[0170] The distribution shown in Fig. 5d represents the average of all reaction results. When the Ru content is high and the acid site concentration is low, hydrogenolysis is the dominant reaction. This reaction proceeds through the dehydrogenation of the reactants and the cleavage of CC bonds at the metal sites, as described in pathway (II) of Fig. 6a. Although the introduction of water can promote the protonation of the intermediate (Fig. 6a, II-ii), β-cleavage does not occur because there are no or almost no acid sites even in the presence of water (Fig. 5(c)). Consequently, the hydrogenolysis reaction for the Ru catalyst mainly produces methane (Scheme 1b and Fig. 5d). The Ru / zeolite-Y catalyst exposed to pyridine poisoning is classified as undergoing the hydrogenolysis reaction because there are no acid sites. This is because CC bond dissociation occurs only at Ru.

[0171] When the Ru content is low and the acid site concentration is high, a hydrocracking reaction occurs. This process involves dehydrogenation at the metal site followed by protonation at the acid site, inducing a skeletal rearrangement for isomerization. The protonated intermediate then undergoes β-cleavage to cleave the CC bond at the acid site (Fig. 6a, Pathway (I)). In particular, the β-cleavage rate of the reaction intermediate depends on the skeletal structure; deep skeletal rearrangements exhibit the fastest rate, whereas unbranched reactions are slow or do not proceed (Fig. 6a, I-iv). As illustrated in Figs. 4d and 4e, iso-C 12 The amount of iso-C is relatively higher than other Cn (<12) products in both 0.2% and 5% Ru / zeolite-Y, regardless of water. This is primarily related to β-cleavage, which is the rate-determining step of LDPE depolymerization (Figs. 6a and 6b). Alkanes undergo dehydrogenation followed by protonation, isomerization via skeletal rearrangement, and subsequent conversion to short alkanes via β-cleavage. In this series of steps, the β-cleavage reaction acts as the rate-determining step. Therefore, a larger amount of iso-C is present in the preceding skeletal rearrangement step.12 A is produced. Interestingly, the product obtained by hydrocracking exhibits a yellow tint, indicating the formation of isomer products as previously reported (Fig. 5e).

[0172] When the MAB falls within the intermediate range, it is classified as difunctional depolymerization (Fig. 5c). Although the roles of the metal and acid sites are well-defined in hydrogenolithosis and hydrocracking reactions, hydrogenolithosis and hydrocracking occur simultaneously in difunctional depolymerization. Essentially, the cleavage of CC bonds occurs simultaneously at both the metal and acid sites, exhibiting superior activity compared to other mechanisms (Fig. 5c). For example, catalysts with relatively low MAB, such as 0.2% and 1% Ru / zeolite-Y, exhibited enhanced reactivity in the presence of water compared to the absence of water due to their difunctionality.

[0173]

[0174] Applicable to various types of plastic waste

[0175] We understood the influence of water on the reaction mechanism and performed depolymerization reactions using materials with varying degrees of branching.

[0176] FIGS. 7a to 7d are drawings showing the results of a depolymerization reaction using various types of plastic according to an embodiment of the present invention.

[0177] The product distribution showed a significant difference between the highly branched material (PP) and the less branched material (HDPE) (Figs. 7a, 7b). In more branched materials like PP, β-cleavage occurs more rapidly due to stabilization provided by neighboring carbons, allowing it to occur without skeletal rearrangement. Conversely, in less branched materials like HDPE, skeletal rearrangement is essential for β-cleavage. Additionally, water plays a crucial role by promoting the protonation or deprotonation of carbocations to achieve a more stable state (Fig. 7a). In the presence of water, HDPE produced methane primarily due to the dissociation of terminal CC bonds at the Ru site without undergoing skeletal rearrangement. Conversely, PP exhibits a more stable carbocation skeleton in the presence of water, leading to the dissociation of internal CC bonds rather than terminal bonds. This results in C 3-6 Compared to short alkanes, the yield of high-value materials in the gasoline and jet fuel range has increased.

[0178] The promoting effect of water was also clearly observed in depolymerization reactions using commercially available LDPE and LDPE bottles. For commercial LDPE, the gas yield decreased from 32.2% in the absence of water to 2.5% in the presence of water, while the diesel yield increased from 0.7% in the absence of water to 34.3% in the presence of water (Fig. 7c). Similarly, for LDPE bottles, the gasoline yield decreased from 34.1% in the absence of water to 8.8% in the presence of water, while the diesel yield increased from 9.2% in the absence of water to 21.1% in the presence of water, indicating a noticeable change in product distribution (Fig. 7d). These changes in selectivity highlight the practical feasibility of guiding the depolymerization pathway toward a desired carbon range product, representing a significant advancement in plastic waste upcycling. The embodiments of the present invention have revealed a promising path for the development of sustainable and efficient methodologies in plastic waste upcycling by successfully demonstrating intentional control over the plastic waste depolymerization reaction products.

[0179]

[0180] conclusion

[0181] Catalytic depolymerization of polyolefins presents a promising pathway for plastic waste recycling that surpasses existing methods, such as mechanical recycling and landfilling, in terms of sustainability. In the embodiments of the present invention, it was discovered that the addition of water significantly influences plastic depolymerization, increasing the yield of valuable liquid fuel from 41.8% to 71.0% and effectively suppressing coke formation to preserve catalytic activity. Through an investigation into the reaction mechanism with water, the reactions were classified into three groups based on catalytic properties and product distribution, including hydrogenolithosis, hydrocracking, and difunctional depolymerization. Among these, the proposed difunctional depolymerization reaction exhibited the highest activity, with the cleavage of CC bonds occurring simultaneously at both the metal and acid sites. This water-promoting effect is expected to extend across various types of waste plastics and be applicable to plastic waste recycling. This opens up the possibility of advancing the overall chemical recycling of plastic waste while simultaneously addressing environmental pollution caused by plastic waste.

[0182]

[0183] Although the embodiments have been described above with reference to limited examples and drawings, those skilled in the art can make various modifications and variations from the description above. For example, suitable results can be achieved even if the described techniques are performed in a different order than described, and / or the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents.

[0184] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below.

Claims

Step of preparing the catalyst; A step of forming a mixture by stirring the catalyst, water, and waste plastic material in a stirrer; and Step of placing the above mixture into a reactor and decomposing waste plastic; including, Process for producing liquid fuel from waste plastics. In paragraph 1, The step of preparing the above catalyst is, A step of forming a suspension by adding a stirring rod, a metal precursor, water, and a support in sequence and stirring in a stirrer at 100 rpm to 800 rpm for 60 minutes to 300 minutes; A step of evaporating water from the above suspension in a constant temperature water bath at a temperature range of 40 ℃ to 80 ℃; A step of drying the above-mentioned water-evaporated suspension in an oven at a temperature range of 80°C to 150°C for 6 to 24 hours; and A step of pre-treating the above dried suspension in a tube furnace under a 10% H2 / Ar flow (50 mL / min) at a heating rate of 2 ℃ / min to 10 ℃ / min for 30 to 300 minutes to increase the temperature from room temperature to a range of 300 ℃ to 800 ℃, and maintaining it for 30 to 300 minutes to synthesize a catalyst; including, Process for producing liquid fuel from waste plastics. In paragraph 2, The above metal precursor is, Comprising at least one selected from the group consisting of ruthenium (Ru), platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W), rhodium (Rh), and palladium (Pd), Process for producing liquid fuel from waste plastics. In paragraph 2, The above support is a zeolite catalyst having Brønsted acid sites, Process for producing liquid fuel from waste plastics. In paragraph 4, The above zeolite catalyst comprises at least one selected from the group consisting of zeolite Y, zeolite Socony Mobil-5 (ZSM-5), beta zeolites (BEA), and mordenite zeolite (MOR). Process for producing liquid fuel from waste plastics. In paragraph 2, After the above preprocessing step, The above-mentioned synthesized catalyst is heated using a heating furnace under a 10% H2 / Ar flow at a heating rate of 2 ℃ / min to 10 ℃ / min from room temperature to a temperature range of 200 ℃ to 600 ℃ for 30 minutes to 300 minutes, and then ex-situ reduced at the said temperature for 30 minutes to 300 minutes. Process for producing liquid fuel from waste plastics. In paragraph 1, The above waste plastic comprises at least one selected from the group consisting of High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Polypropylene (PP), Polyamide (PA), Polystyrene (PS), Polyvinyl Chloride (PVC), and Ethylene Vinyl Acetate (EVA). Process for producing liquid fuel from waste plastics. In paragraph 1, The step of forming the above mixture is, The above catalyst, water, and waste plastic material are sequentially placed into a stirrer and stirred to form a mixture. Process for producing liquid fuel from waste plastics. In paragraph 1, In the step of forming the above mixture, The mass ratio of the catalyst to water is 1:0.5 to 1:2, Process for producing liquid fuel from waste plastics. In paragraph 1, The step of decomposing the waste plastic is performed in a temperature range of 200 ℃ to 700 ℃ and a pressure range of 0.01 MPa to 10 MPa, Process for producing liquid fuel from waste plastics.

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