Conversion of polymers in mixtures of organic compounds under supercritical conditions

Abstract

Disclosed herein is a process for converting a polymer to a light hydrocarbon chain product. The process involves supplying a polymer, a light hydrocarbon solvent, and a hydrogen feed into a mixer to form a dissolved polymer feed. The process further includes recycling the light hydrocarbon vapor formed in the process back to the mixer.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 532,156, filed August 11, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure generally relates to the field of catalytic methods for the continuous conversion of polyolefins and / or pyrolysis oils into smaller chain products. More specifically, these methods can be operated under supercritical conditions to achieve a high degree of control over product distribution and yield. Background Technology

[0003] Every year in the United States, up to 75% of all plastics (including polymers) end up in landfills, representing potentially irreparable material loss and posing a serious threat to the environment. However, plastics (including polymers) can be used as fuel or reprocessed to produce lower-quality materials. Therefore, there is a need to utilize any plastic or polymer as a carbon source for refinery feedstocks and chemical production.

[0004] Unfortunately, current recycling practices do not efficiently utilize these chemically stable plastics, particularly polyolefins and polystyrene. Existing chemical pathways for converting polymers into smaller molecules rely on elevated temperatures above 400°C, which is associated with low control over product distribution and low yields of useful molecules. Methods reported in this art describe thermal gasification and pyrolysis or catalytic hydrocracking using zeolites or combinations of zeolites with supported metal catalysts. Some methods utilize noble metals supported on perovskites, but rely on the use of melts, which may be impractical in continuous processes. Other methods rely on the addition of external solvents (such as water), which may be incompatible with the polymer chemistry. Therefore, current methods are expensive and yield low amounts.

[0005] Therefore, there is a need in the field to develop a method with a high level of control for converting plastics for use in recycled products or as feedstock in refineries. Summary of the Invention

[0006] In one embodiment of this disclosure, a method is provided for converting a polymer and / or pyrolysis oil into a light hydrocarbon chain product. In some embodiments, the method can be operated under supercritical conditions. That is, the method can be operated at a temperature and pressure combination sufficient to induce supercritical fluid conditions in the reaction mixture. The method may include feeding a polymer and a light hydrocarbon solvent into a mixer, wherein the light hydrocarbon solvent may comprise straight-chain or branched C3 to C4 chains. 10 The polymer, or a mixture thereof, is fed into a reactor to form a first effluent by applying hydrogen gas in a mixer, feeding the polymer, light hydrocarbon solvent and hydrogen mixture into the reactor to form a first effluent, and directing the effluent from the reactor to a first separator.

[0007] In some embodiments of the method, the reactor may include a fixed-bed reactor, a semi-batch reactor, a slurry reactor, a mixed-bed reactor, or a combination thereof.

[0008] In some embodiments, the reactor may contain a metal-containing catalyst.

[0009] In some embodiments, the reactor may contain a heterogeneous catalyst, which includes a heterogeneous catalyst (monometallic, bimetallic, or multimetallic) suitable for hydrogenolysis. In some embodiments, the heterogeneous catalyst suitable for hydrogenolysis may be a catalyst comprising platinum group metals (“pgm”). In other embodiments, the heterogeneous catalyst suitable for hydrogenolysis may be a catalyst comprising transition metal groups, wherein the transition metals include pgm, non-pgm, or combinations thereof.

[0010] In some embodiments, the method can be operated under supercritical fluid conditions.

[0011] In some embodiments, the polymer feed may include polyolefins.

[0012] In some embodiments, the polyolefin may include polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, medium-range hydrocarbons, polyethylene wax, or combinations thereof; and wherein the polyolefin is linear, branched, or a combination thereof.

[0013] In some embodiments, polypropylene may have a molecular weight of about 30,000 g / mol to about 5,000,000 g / mol.

[0014] In some embodiments, polyethylene may have a molecular weight of about 300 g / mol to about 6,000,000 g / mol.

[0015] In some embodiments, the feed may have a polymer concentration that reaches the solvent saturation limit under supercritical fluid conditions. In some embodiments, the feed may have a concentration of about 4 g / L to about 80 g / L.

[0016] In some embodiments, the reactor may be maintained at a temperature of about 150°C to 400°C.

[0017] In some embodiments, the method can be operated at a temperature between about 190°C and about 230°C.

[0018] In some embodiments, hydrogenolysis can be performed on polymer and light hydrocarbon solvent feedstocks.

[0019] In some embodiments, the reactor may have a pressure of about 20 to about 100 bar.

[0020] In some embodiments, the method may further include forming light hydrocarbon vapor and liquid hydrocarbon products after the first separator.

[0021] In some embodiments, the method may further include recycling any remaining liquid hydrocarbon solvent back into the mixer.

[0022] In some embodiments, the method may further include feeding light hydrocarbon vapor and liquid hydrocarbon products from a first separator to a second separator.

[0023] In some embodiments, after the light hydrocarbon vapor and liquid hydrocarbon product are fed into the second separator, the light hydrocarbon vapor is recycled back into the mixer.

[0024] In some embodiments, light hydrocarbon products can be collected after the feed is introduced into the second separator.

[0025] In another embodiment of this disclosure, a system for converting polymer oligomers and / or pyrolysis oil into light hydrocarbon chain products is provided. The system may include a polymer feed, a mixer configured to receive the polymer feed, a reactor, a first separator configured to receive a first effluent from the reactor, and a second separator configured to receive a second effluent from the first separator.

[0026] In some embodiments, the polymer feed may be contacted with a light hydrocarbon solvent to produce a dissolved polymer stream.

[0027] In some embodiments, the dissolved polymer stream may be contacted with hydrogen to form a first effluent.

[0028] In some embodiments, the first effluent may be separated into light hydrocarbon vapor or a combination thereof in a first separator.

[0029] In some embodiments, the first effluent can be separated into liquid hydrocarbon products.

[0030] In some embodiments, the mixer may be configured to receive light hydrocarbon vapor from the first separator and any remaining light hydrocarbon solvent from the first separator.

[0031] In some embodiments, the reactor may include a slurry of a supported catalyst.

[0032] In some embodiments, a supported catalyst may include a catalyst and a support.

[0033] In some embodiments, the catalyst may include a metal-containing catalyst, a heterogeneous catalyst that may include platinum group metals, a heterogeneous catalyst that may include transition metals, or a combination thereof.

[0034] In some embodiments, the support may include a metal oxide. In some embodiments, the support may include titanium dioxide, Al2O3, silicon dioxide-alumina, titanium dioxide, SiO2, ZrO2, carbon, or a combination thereof.

[0035] In some embodiments, the second separator may be configured to remove light hydrocarbon vapor and recycle the light hydrocarbon vapor back to the mixer.

[0036] In some embodiments, the second separator may be configured to remove liquid hydrocarbon products from the second effluent.

[0037] In some embodiments, the reactor can be maintained at a constant temperature and pressure.

[0038] In some embodiments, the polymer feed may include polyolefins.

[0039] In some embodiments, the polyolefin may include polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, medium-range hydrocarbons, polyethylene wax, or combinations thereof; and wherein the polyolefin is linear, branched, or a combination thereof. Attached Figure Description

[0040] The disclosures described herein are illustrated in the accompanying figures by way of example rather than limitation.

[0041] Figure 1 A method for converting polyolefins according to embodiments of this disclosure is illustrated.

[0042] Figure 2 ac shows the carbon fraction in gaseous, liquid, and solid residues after PE hydrogenolysis on several transition metal catalysts and / or different supports.

[0043] Figure 3 ac shows the pressure-temperature projection of the phase diagram (phase envelope) of the mixture of hexadecane and solvent.

[0044] Figure 4 ad shows the results of PE hydrogenolysis under different reaction conditions and with different solvents.

[0045] Figure 5 The carbon fraction in the gaseous, liquid, and solid residues following Ru / C catalytic hydrogenolysis of PE with n-hexane is shown.

[0046] Figure 6 ac demonstrates a proposed reaction network for the hydrogenolysis of PE and its products on Ru / C in the presence of isopentane as a solvent.

[0047] Figure 7 The PE conversion rate of the reaction according to an embodiment of this disclosure is shown.

[0048] Figure 8 af shows the carbon yield of gaseous and liquid products at different PE conversion rates during hydrogenolysis.

[0049] Figure 9 a and 9b demonstrate how reaction parameters affect the PE consumption rate and product distribution.

[0050] Figure 10 a and 10b illustrate the kinetics of hydrogenolysis of PE in one example.

[0051] Figure 11 ad shows the carbon yield of gaseous and liquid products from the hydrogenolysis of PE under kinetic conditions, with varying amounts of catalyst and reaction times in examples at different temperatures.

[0052] Figure 12 ad shows the reaction results for hexadecane conversion.

[0053] Figure 13 It shows C after the hydrogenolysis of squalane 10 GC-FID chromatogram of the product.

[0054] Figure 14 The diagram shows the dehydrogenation and hydrogenation results of hexadecane during hydrolysis.

[0055] Figure 15 a and 15b show the GC-MS mass spectrometry results of the i-C5 solvent during the hexadecane hydrogenolysis process.

[0056] Figure 16 a and 16b show methane formation following Ru / C-catalyzed hydrogenolysis.

[0057] Figure 17 a and 17b show the MNR spectra of PE at 100°C. Detailed Implementation

[0058] This disclosure relates to a system and method for converting polyolefins into minor hydrocarbon products. In some embodiments, the system and method can be used to convert polymers, oligomers, and / or pyrolysis oils. Pyrolysis oils can be produced by a pyrolysis method. Pyrolysis is the thermal degradation of plastic waste in an inert atmosphere to produce value-added pyrolysis gas, liquid pyrolysis oil, and char (residue), wherein the pyrolysis oil is the major product. The methods and systems described herein are continuous systems that enable a high level of control and high product yield of minor hydrocarbon products. As used herein, the term "minor hydrocarbon product" refers to products including C1 to C2. 30 Hydrocarbons, wherein the chain can be straight, branched, or a combination thereof.

[0059] Throughout this specification, references to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, the phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment. Furthermore, the term "or" is intended to mean an inclusive "or," not an exclusive "or."

[0060] As used herein, the singular forms “a / an” and “the” include plural indicators unless the context explicitly indicates otherwise. Thus, for example, a reference to “sample” includes a single sample as well as more than one sample.

[0061] As used herein, the term “about” or “approximately” in conjunction with the quantity being measured refers to a standard variation of the quantity being measured, as would be expected by one of ordinary skill in the art when performing the measurement and implementing a level of caution commensurate with the accuracy of the measurement target and the measuring equipment. In some embodiments, the term “about” includes the listed number ±10%, such that “about 10” would include numbers from 9 to 11.

[0062] As used herein, the term "polyolefin" refers to, but is not limited to, medium-range hydrocarbons, polypropylene, polyethylene, polyethylene wax, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, 1-hexene, 1-octene, medium-range hydrocarbons, polyethylene wax, or combinations thereof. In some embodiments, polyethylene may include low molecular weight polyethylene (LMWPE), high molecular weight polyethylene (HMWPE), ultra-high molecular weight polyethylene (UHMWPE), or combinations thereof.

[0063] As used in this article, the term “supercritical” refers to the temperature and pressure conditions of different liquid and gas phases in the absence of a solvent.

[0064] As used herein, the term "pyrolysis" refers to the thermal decomposition or degradation of a feedstock, such as plastic waste, under inert conditions, producing gaseous, liquid, and solid char components. During pyrolysis, the feedstock is converted in a pyrolysis unit into a wide variety of chemicals, including gases such as H2, C1- to C4-alkanes, C2- to C4-olefins, acetylene, propyne, 1-butyne, pyrolysis oil with a boiling temperature of 25°C to 500°C or higher, and char. The direct products from this pyrolysis are "pyrolysis gases" and solid products. The liquid product, "pyrolysis oil," is then separated from the "pyrolysis gases" by condensation. Additionally, water is formed during pyrolysis, which may be partially dispersed in the pyrolysis oil and may be partially in contact with the oil as a separate phase. The water formed during pyrolysis contains various organic compounds and / or their salts that are also formed during pyrolysis. The term "pyrolysis" includes slow pyrolysis, fast pyrolysis, flash pyrolysis, and catalytic pyrolysis. These pyrolysis types differ in process temperature, heating rate, residence time, feed particle size, etc., resulting in varying product qualities. Pyrolysis units can operate adiabatic, isothermal, non-adiabatic, non-isothermal, or combinations thereof. The pyrolysis reaction disclosed herein can be carried out in a single stage or in multiple stages. For example, a pyrolysis unit may comprise two reactor vessels connected in series with fluid connection.

[0065] As used herein, the term "pyrolysis oil" should be understood to mean any oil derived from the pyrolysis of plastic waste. The term "plastic waste" includes rubber waste such as end-of-life tires and raw materials containing plastic waste. Pyrolysis oil is obtained and / or is available from the pyrolysis of such plastic waste. As used herein, the term "plastic waste" refers to any plastic material discarded after use, i.e., plastic material that has reached the end of its service life and is considered post-consumer waste. Plastic waste can be pure polymer plastic waste, mixed plastic waste, or membrane waste, including sludge, adhesive materials, fillers, residues, etc. Plastic waste may have oxygen, nitrogen, sulfur, halogen, and optionally heavy metal content. Plastic waste can originate from any source containing plastic materials. Typically, plastic waste is a mixture of different plastic materials, including hydrocarbon plastics such as polyolefins such as polyethylene (HDPE, LDPE) and polypropylene, polystyrene and their copolymers, and polymers composed of carbon, hydrogen and other elements such as chlorine, fluorine, oxygen, nitrogen, sulfur, silicon, etc., such as chlorinated plastics such as polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), nitrogen-containing plastics such as polyamide (PA), polyurethane (PU), acrylonitrile butadiene styrene (ABS), oxygen-containing plastics such as polyesters such as polyethylene terephthalate (PET), polycarbonate (PC), silicone and / or sulfur-bridged crosslinked rubber.

[0066] Typically, plastic materials contain additives such as processing aids, plasticizers, flame retardants, pigments, light stabilizers, lubricants, impact modifiers, antistatic agents, antioxidants, etc. These additives may contain elements other than carbon and hydrogen. For example, the presence of bromine is primarily associated with flame retardants. Heavy metal compounds can be used as light-resistant pigments and / or stabilizers in plastics. Cadmium, zinc, and lead may be present in heat stabilizers and slip agents used in plastic manufacturing. Plastic waste may also contain residues. In the context of this invention, residues are contaminants that adhere to plastic waste. Additives and residues are generally present in amounts of less than 50 wt.-%, preferably less than 30 wt.-%, more preferably less than 20 wt.-%, and even more preferably less than 10 wt.-%, based on the total dry weight of the plastic.

[0067] To obtain the pyrolysis oil according to this disclosure, plastic waste is inserted into a pyrolysis reactor using a metering unit such as a screw or extruder, a rotary valve, a pneumatic conveyor, or a liquid injector. The plastic is optionally preheated in, for example, a heat exchanger and / or pre-pyrolyzed at a temperature, for example, in the range of about 200°C to about 360°C, before being inserted into the pyrolysis reactor. The plastic waste is then heated in the pyrolysis reactor to a temperature in the range of about 350°C to about 900°C, more preferably in the range of about 400°C to about 550°C, and a pressure in the range of about 0.5 bar to about 2 bar (absolute value), more preferably in the range of about 0.9 bar to about 1.5 bar (absolute value). The pyrolysis reactor is preferably selected from the group consisting of fluidized bed reactors, moving bed reactors, entrained flow reactors, screw reactors, extruders, stirred tank reactors, and rotary kiln reactors. Preferably, the pyrolysis is carried out in the pyrolysis reactor under an inert atmosphere free of oxygen or air.

[0068] Pyrolysis methods are known in themselves. They are described, for example, in EP 0713906 A1 and WO 95 / 03375 A1. Suitable pyrolysis oils are also commercially available. Pyrolysis oils are typically liquid at 15°C or waxy at said temperature. In the terminology of this invention, "liquid at 15°C" means that the pyrolysis oil has a density of up to 1.3 g / ml at 15°C and 1013 mbar, as determined according to DIN EN ISO 12185, for example, a density in the range of 0.65 to 0.98 g / ml.

[0069] Optionally, the pyrolysis oil or mixture of pyrolysis oils may be subjected to one or more methods selected from filtration, centrifugation, adsorption, washing, and extraction before being used as feedstock for processes such as steam cracking. Such alternative pretreatment methods are described, for example, in WO2021 / 224287 A1, WO 2023 / 061834 A1, EP 0713906 A1, and WO 95 / 03375 A1, which are incorporated herein by reference. Those skilled in the art will understand how and in what circumstances to use the pretreatment methods disclosed in the aforementioned documents and comparable pretreatment methods disclosed elsewhere.

[0070] In one embodiment of this disclosure, a method for converting a polymer into a smaller hydrocarbon chain product has been developed. The method includes applying a light hydrocarbon solvent and hydrogen to a polymer feed in a mixer under supercritical conditions to convert the polymer into a smaller hydrocarbon chain product. It has been found that operating the system and performing the method under supercritical conditions enables the production of small hydrocarbon products from the polymer feed in high yields. In some embodiments, the light hydrocarbon solvent may include straight-chain or branched C3 to C4 hydrocarbons. 10 The light hydrocarbons may be straight-chain or branched C3 to C8, straight-chain or branched C3 to C6, or straight-chain or branched C4 to C6. In some embodiments, the light hydrocarbons may have a weight-based branched hydrocarbon content in the range of about 30% to about 99%, about 40% to about 95%, or about 50% to about 90%.

[0071] In one embodiment, the method includes feeding a polymer and a light hydrocarbon solvent feed into a mixer. The polymer may include a mixture of polyolefins, such as polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, medium-range hydrocarbons, polyethylene wax, 1-hexene, 1-octene, or combinations thereof. In some embodiments, the polymer feed may include a polyolefin in combination with other polymers. These other polymers may include, but are not limited to, polyurethanes, polyamides, polyesters, polyethers, polyvinyl acetate / alcohol, polyacrylonitrile, polystyrene, polyvinyl chloride, or combinations thereof. In some embodiments, the polyolefin and other polymers may be present in the polymer feed at a weight ratio of about 50:50, about 80:10, or about 99:1. In some embodiments, the feed may also include a polymer, an olefin, pyrolysis oil, or a combination thereof.

[0072] In some embodiments, the polymer feed can be a mixture of polymer waste derived from industrial or household waste. For example, the polymer feed can be polymer waste from marine sources, terrestrial collections, or extracts from landfills. In another instance, the polymer feed can be derived from plastic waste.

[0073] In some embodiments, the polymer may include polypropylene, polyethylene, or combinations thereof. In some embodiments, the light hydrocarbon solvent may include straight-chain or branched C3 to C4 hydrocarbons. 10 The method may further include applying hydrogen to a mixer. The method further includes feeding a mixture of polymer, light hydrocarbon solvent, and / or hydrogen into a reactor to form a first effluent, and directing the first effluent from the reactor to a first separator.

[0074] In some embodiments, polypropylene may have a molecular weight of about 30,000 g / mol to about 5,000,000 g / mol. In other embodiments, polypropylene may have a molecular weight of about 100,000 g / mol to about 4,500,000 g / mol, about 500,000 g / mol to about 4,000,000 g / mol, about 1,000,000 g / mol to about 3,500,000 g / mol, about 1,500,000 g / mol to about 3,000,000 g / mol, about 2,000,000 g / mol to about 2,500,000 g / mol.

[0075] In some embodiments, polyethylene may have a molecular weight of about 300 g / mol to about 6,000,000 g / mol. In some embodiments, polyethylene may have a concentration of about 500 g / mol to about 5,500,000 g / mol, about 1,000 g / mol to about 5,000,000 g / mol, about 5,000 g / mol to about 4,500,000 g / mol, about 10,000 g / mol to about 4,000,000 g / mol, about 15,000 g / mol to about 3,500,000 g / mol, about 25,000 g / mol to about 3,000,000 g / mol, about 35,000 g / mol to about 2,500,000 g / mol, about 45,000 g / mol to about 2,000,000 g / mol, about 55,000 g / mol to about 1,500,000 g / mol, or about 65,000 g / mol to about 1,000,000 g / mol. Molecular weight of about 75,000 g / mol to about 500,000 g / mol, about 85,000 g / mol to about 450,000 g / mol, about 95,000 g / mol to about 400,000 g / mol, about 100,000 g / mol to about 350,000 g / mol, about 125,000 g / mol to about 300,000 g / mol, or about 150,000 g / mol to about 250,000 g / mol, or any value or subrange thereof herein.

[0076] In some embodiments, the feed may have a polymer concentration that reaches the solvent saturation limit under supercritical fluid conditions. In some embodiments, the polymer (e.g., LDPE) feed may have a concentration of about 4 g / L to about 80 g / L. In some embodiments, the concentration of the polymer (e.g., LDPE) feed may be about 8 g / L to about 76 g / L, about 12 g / L to about 72 g / L, about 16 g / L to about 68 g / L, about 20 g / L to about 64 g / L, about 24 g / L to about 60 g / L, about 28 g / L to about 56 g / L, about 32 g / L to about 52 g / L, about 36 g / L to about 48 g / L, or about 40 g / L to about 44 g / L.

[0077] In some embodiments, the reactor may include a fixed-bed reactor, a semi-batch reactor, a slurry reactor, or a mixed-bed reactor. In some embodiments, the reactor may include a metal-containing catalyst. In another embodiment, the reactor may contain a heterogeneous catalyst comprising platinum group metals (“pgm”). In yet another embodiment, the reactor may contain a heterogeneous catalyst comprising at least a transition metal.

[0078] In some embodiments, the reactor may contain a bimetallic or multimetallic catalyst comprising platinum group metals. In another embodiment, the reactor may contain a heterogeneous catalyst, which may include transition metals or combinations thereof.

[0079] In some embodiments, the reactor can be maintained at a constant temperature and pressure, which produces supercritical fluid conditions. In some embodiments, the methods disclosed herein can be operated under supercritical conditions.

[0080] In some embodiments, the reactor may be maintained at temperatures above the critical point of about 150°C to about 900°C, about 175°C to about 875°C, about 200°C to about 850°C, about 250°C to about 825°C, about 275°C to about 800°C, about 325°C to about 750°C, about 350°C to about 700°C, about 375°C to about 675°C, about 400°C to about 650°C, about 425°C to about 625°C, about 450°C to about 600°C, about 475°C to about 575°C, or about 550°C to about 550°C, wherein there are no distinct liquid and gas phases.

[0081] In some embodiments, the method can be operated at temperatures of about 190°C to about 230°C, about 195°C to about 225°C, about 200°C to about 220°C, or about 205°C to about 215°C.

[0082] In some embodiments, the reactor may have a pressure of about 20 bar to about 100 bar, about 25 bar to about 95 bar, about 30 bar to about 90 bar, about 35 bar to about 85 bar, about 40 bar to about 80 bar, about 45 bar to about 75 bar, about 50 bar to about 70 bar, or about 55 bar to about 65 bar.

[0083] In some embodiments, the method may further include hydrogenolysis of the polymer and light hydrocarbon solvent feedstock. Hydrogenolysis may be carried out in a reactor. As understood herein, “hydrogenolysis” may include a reaction carried out in a hydrogen atmosphere at elevated pressure and / or a reaction carried out in a hydrogen atmosphere at elevated temperature. In some embodiments, liquid-phase n-chain alkanes may be formed after hydrogenolysis. In some embodiments, liquid-phase branched hydrocarbons may be formed as products after hydrogenolysis.

[0084] In some embodiments, the method may further include forming a second effluent comprising light hydrocarbon vapor and liquid hydrocarbon products after the first separator. After forming the second effluent, any remaining liquid hydrocarbon solvent after the reactor may be recycled back to the mixer.

[0085] In some embodiments, the light hydrocarbon solvent may include straight-chain or branched C3 to C4 solvents. 10 Or a mixture thereof.

[0086] In some embodiments, a second effluent comprising light hydrocarbon vapor and liquid hydrocarbon product may be fed into a second separator. In some embodiments, after the second effluent is fed into the second separator, the light hydrocarbon vapor may be recycled back into the mixer.

[0087] In one embodiment, after the second effluent is fed into the second separator, the light hydrocarbon product can be collected.

[0088] In some embodiments, light hydrocarbon vapors may include gaseous alkanes having between 1 and 4 carbon atoms.

[0089] In some embodiments, the light hydrocarbon product may include straight-chain and / or branched liquid alkanes having between 6 and 40 carbon atoms.

[0090] In another embodiment, a system is provided. The system may include a polymer feed; a mixer configured to receive the polymer feed; a reactor; a first separator configured to receive a first effluent from the reactor; and a second separator configured to receive a second effluent from the first separator.

[0091] In some embodiments, the polymer feed may include a mixture of polyolefins. In some embodiments, the mixture of polyolefins may include polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, 1-medium-range hydrocarbons, polyethylene wax, hexene, 1-octene, or combinations thereof. In some embodiments, the mixture of polyolefins may include polypropylene, polyethylene, or combinations thereof. In some embodiments, the feed may also include a polymer, olefin, pyrolysis oil, or combinations thereof.

[0092] In some embodiments, polypropylene may have a molecular weight of about 30,000 g / mol to about 5,000,000 g / mol, about 100,000 g / mol to about 4,500,000 g / mol, about 500,000 g / mol to about 4,000,000 g / mol, about 1,000,000 g / mol to about 3,500,000 g / mol, about 1,500,000 g / mol to about 3,000,000 g / mol, about 2,000,000 g / mol to about 2,500,000 g / mol.

[0093] In some embodiments, polyethylene may have a molecular weight of about 300 g / mol to about 6,000,000 g / mol. In some embodiments, polyethylene may have a concentration of about 500 g / mol to about 5,500,000 g / mol, about 1,000 g / mol to about 5,000,000 g / mol, about 5,000 g / mol to about 4,500,000 g / mol, about 10,000 g / mol to about 4,000,000 g / mol, about 15,000 g / mol to about 3,500,000 g / mol, about 25,000 g / mol to about 3,000,000 g / mol, about 35,000 g / mol to about 2,500,000 g / mol, about 45,000 g / mol to about 2,000,000 g / mol, about 55,000 g / mol to about 1,500,000 g / mol, or about 65,000 g / mol to about 1,000,000 g / mol. Molecular weight of about 75,000 g / mol to about 500,000 g / mol, about 85,000 g / mol to about 450,000 g / mol, about 95,000 g / mol to about 400,000 g / mol, about 100,000 g / mol to about 350,000 g / mol, about 125,000 g / mol to about 300,000 g / mol, or about 150,000 g / mol to about 250,000 g / mol, or any value or subrange thereof herein.

[0094] In some embodiments, the polymer feed may include a polymer such as LDPE and may have a concentration of about 4 g / L to about 80 g / L. In some embodiments, the concentration of the polymer feed (such as LDPE) may be about 8 g / L to about 76 g / L, about 12 g / L to about 72 g / L, about 16 g / L to about 68 g / L, about 20 g / L to about 64 g / L, about 24 g / L to about 60 g / L, about 28 g / L to about 56 g / L, about 32 g / L to about 52 g / L, about 36 g / L to about 48 g / L, or about 40 g / L to about 44 g / L. In some embodiments, the polymer feed may have a polymer concentration that reaches the solvent saturation limit under supercritical fluid conditions.

[0095] In some embodiments, the polymer feed may be contacted with a recycled light hydrocarbon solvent to produce a dissolved polymer stream. In some embodiments, the dissolved polymer stream may be contacted with hydrogen to incorporate into a first effluent. In one embodiment, the first effluent may be separated in a first separator into light hydrocarbon vapor, liquid hydrocarbon products, or a combination thereof.

[0096] In some embodiments, the light hydrocarbon solvent may include straight-chain and / or branched C3 to C4 chains. 10 Or a mixture thereof.

[0097] In some embodiments, the system's reactor may include a fixed-bed reactor, a semi-batch reactor, a slurry reactor, or a mixed-bed reactor. In some embodiments, the reactor may include a slurry of a supported catalyst.

[0098] In some embodiments, the mixer may form a stream of dissolved polymer. In some embodiments, the reactor may be configured to receive the stream of dissolved polymer. In some embodiments, the reactor may be configured to hydrogenate the dissolved polymer feed. In some embodiments, the reactor may produce a first effluent.

[0099] A first separator of the system may be configured to receive a first effluent. In some embodiments, the first separator may separate the first effluent from a hydrogen and gaseous product stream. In some embodiments, the gaseous product may include methane. In some embodiments, the first separator may separate the first effluent into a second effluent, wherein the second effluent may include light hydrocarbon vapor, light hydrocarbon product, or a combination thereof. The system may further include a second separator. In some embodiments, the second separator may be configured to receive a second effluent comprising light hydrocarbon vapor, light hydrocarbon product, or a combination thereof. In some embodiments, the second separator may generate light hydrocarbon vapor. In some embodiments, the second separator may generate light hydrocarbon product.

[0100] In some embodiments, light hydrocarbon vapors may include gaseous alkanes having between 1 and 4 carbon atoms.

[0101] In some embodiments, the liquid hydrocarbon product may include straight-chain and branched liquid alkanes having between 6 and 40 carbon atoms.

[0102] In some embodiments, light hydrocarbon vapors can be recycled back to the mixer.

[0103] In some embodiments, light hydrocarbon products may be collected after the second separator.

[0104] In some embodiments, hydrogenolysis can be performed on a polymer feed, hydrogen, a light hydrocarbon solvent, or a mixture thereof. As understood herein, “hydrolysis” can include a reactor under elevated pressure in a hydrogen atmosphere. Hydrolysis can also include a reactor at elevated temperature, wherein the reactor is in a hydrogen atmosphere. In some embodiments, liquid-phase n-alkanes can be formed after hydrogenolysis. In some embodiments, liquid-phase branched hydrocarbons can be formed as products after hydrogenolysis.

[0105] In some embodiments, the reactor can be maintained at a constant temperature and pressure, which produces supercritical fluid conditions. In some embodiments, the reactor can be operated under supercritical conditions.

[0106] In some embodiments, the reactor may be maintained at temperatures of about 150°C to about 400°C, about 160°C to about 390°C, about 170°C to about 380°C, about 180°C to about 370°C, about 190°C to about 360°C, about 200°C to about 350°C, about 210°C to about 340°C, about 220°C to about 330°C, about 230°C to about 320°C, about 240°C to about 310°C, about 250°C to about 300°C, about 260°C to about 290°C, or about 270°C to about 280°C.

[0107] In some embodiments, the method can be operated at temperatures of about 190°C to about 230°C, about 195°C to about 225°C, about 200°C to about 220°C, or about 205°C to about 215°C.

[0108] In some embodiments, the reactor may have a pressure of about 20 bar to about 100 bar, about 25 bar to about 95 bar, about 30 bar to about 90 bar, about 35 bar to about 85 bar, about 40 bar to about 80 bar, about 45 bar to about 75 bar, about 50 bar to about 70 bar, or about 55 bar to about 65 bar.

[0109] In some embodiments, the reactor may contain a heterogeneous catalyst comprising a transition metal group, wherein the transition metal may include at least one platinum group metal or a combination thereof.

[0110] In some embodiments, the reactor may include a slurry of a supported catalyst. In some embodiments, the supported catalyst may include a catalyst and a support.

[0111] In some embodiments, the catalyst may include a metal-containing catalyst, a heterogeneous catalyst including platinum group metals, a heterogeneous catalyst including transition metals, or a combination thereof.

[0112] In some embodiments, the metal catalyst may include zinc, nickel, cobalt, magnesium, molybdenum, tungsten, titanium, tantalum, chromium, iron, gallium, other similar catalytically active metals, or combinations thereof.

[0113] In some embodiments, the carrier may include AlO2, silicon dioxide-alumina, titanium dioxide, SiO2, ZrO2, carbon, or a combination thereof.

[0114] In some embodiments, a catalyst binder may be used. In some embodiments, the catalyst binder may include silica, alumina, silica-alumina, silica-titanium dioxide, silica-thorium oxide, silica-magnesium oxide, silica-zirconium oxide, silica-beryllium oxide, ternary compositions of silica and other refractory oxides, etc. In some embodiments, other matrices may include clays, such as naturally occurring clays represented by montmorillonite, kaolin, bentonite, hydrous kaolin, dikaolin, perlite, and vermicular clay.

[0115] refer to Figure 1 , Figure 1 A schematic diagram of a method 100 for converting polyolefins in an organic environment under supercritical conditions, according to an embodiment of this disclosure, is shown. Figure 1 As can be seen, polymer feed 105 is fed into mixer 110. Polymer feed 105 may include any polymer species described herein, including but not limited to polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, medium-range hydrocarbons, polyethylene wax, 1-hexene, 1-octene, or combinations thereof.

[0116] When polymer feed 105 enters mixer 110, it can mix with light hydrocarbon vapor 155 to form a dissolved polymer stream 120. For example... Figure 1 As can be seen, the dissolved polymer stream can then be contacted with hydrogen gas 115. Providing hydrogen gas allows the hydrogenolysis reaction to take place in the reactor. The dissolved polymer stream 120 can then be fed into reactor 125. Hydrogenolysis of the dissolved polymer stream 120 can then be performed in reactor 125. After hydrogenolysis in reactor 125, a first effluent 130 can be formed. The first effluent 130 can then exit reactor 125, as... Figure 1 As shown.

[0117] like Figure 1 As shown, the first effluent 130 is received by the first separator 135. The first separator 135 then separates the first effluent into a mixture 140 of hydrogen and gaseous products. In some embodiments, the gaseous products may include methane. The first separator 135 may also separate the first effluent into a second effluent 145, which may contain a mixture of light hydrocarbon vapor and light hydrocarbon products.

[0118] The second effluent 145 can be fed into the second separator 150. The second separator 150 then separates the second effluent 145 into a light hydrocarbon vapor stream 155. The light hydrocarbon vapor 155 can then be recycled back to the mixer 110, such as... Figure 1As shown. The second separator 150 also separates the second effluent 145 into a light hydrocarbon product stream 160. The light hydrocarbon product stream 160 can then be collected and further processed.

[0119] If one, more than one, or all of the group members are present, used in, or otherwise related to the given product or method, then the inclusion of "or" or "and / or" in the claims or descriptions among at least one member of that group is considered satisfactory, unless otherwise stated or otherwise clearly apparent from the context. This disclosure includes embodiments in which exactly one member of the group is present, used in, or otherwise related to the given product or method. This disclosure includes embodiments in which more than one or all of the group members are present, used in, or otherwise related to the given product or method.

[0120] Furthermore, this disclosure covers all variations, combinations, and permutations in which at least one limitation, element, clause, and descriptive term from at least one of the listed claims is introduced into another claim. For example, any claim dependent on another claim may be modified to include at least one limitation seen in any other claim dependent on the same basic claim. Where elements are presented in a list (e.g., in the form of a Markush group), each subgroup of elements is also disclosed, and any element may be removed from that group. It should be understood that, generally, where an aspect of this disclosure is referred to as containing a particular element and / or feature, an embodiment of this disclosure or an aspect of this disclosure consists of or is substantially composed of such elements and / or features. For the purpose of brevity, these embodiments are not specifically described in words herein. When a range is given (e.g., from [X] to [Y]), endpoints are included (e.g., [X] and [Y] in the phrase “from [X] to [Y]”), unless otherwise specified. Furthermore, unless otherwise stated or otherwise clearly apparent from the context and as understood by one of ordinary skill in the art, values ​​represented as ranges in the various embodiments of this disclosure may take any specific value or subrange within the range, up to one-tenth of the lower limit unit of the range, unless the context otherwise explicitly indicates otherwise.

[0121] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms (such as those defined in common dictionaries) shall be interpreted as having the same meaning as they have in the relevant field and in the context of this disclosure, and shall not be interpreted as having an idealized or overly formal meaning unless expressly defined herein. Example

[0122] The following examples are intended to be illustrative and are not intended to limit the scope of this disclosure in any way.

[0123] Several experiments were conducted to provide better insight into a polyethylene (PE) hydrogenolysis method according to one embodiment of this disclosure. Specifically, Ru / C catalytic PE hydrogenolysis was carried out under supercritical conditions in the presence of a light hydrocarbon (with isopentane as a model compound) as a solvent. The model compound was chosen based on the advantage of polymer solubility under supercritical conditions and because Ru is the most active and selective among noble metals, such as... Figure 2 As can be seen from the data, preliminary measurements indicate that the depolymerization of long-chain hydrocarbons under supercritical conditions leads to the selective hydrogenolysis of PE, minimizing methane formation and negligible solvent conversion. In both primary and secondary hydrogenolysis reactions, the continuous CC cleavage of polyolefins gradually alters the process from heavy oil (CC) 20-40 From gasoline-grade hydrocarbons (C) 6-10 The selectivity of the product is such that straight-chain products are preferred over branched products. In this work, Ru-catalyzed hydrogenolysis of model compounds of hexadecane and squalane shows that C / C cleavage also favors primary and secondary carbons, i.e., tertiary carbons. 3 C- x Compared to C, 2 C- 1 C or 2 C- 2 C, thereby controlling the hydrogenolysis reactivity and product selectivity.

[0124] chemicals

[0125] Polyethylene (PE) was purchased as powder from Sigma-Aldrich, with Mw and Mn at approximately 4000 g / mol and 1700 g / mol, respectively. Activated carbon-supported Ru, Rh, Pd, Ir, and Ni catalysts were also purchased from Sigma-Aldrich. 2-Methylbutane, n-butane, n-hexane, n-butylcyclohexane, and ethyl acetate, used as solvents and external standards, were also purchased from Sigma-Aldrich. These chemicals were used in the studies described herein.

[0126] Characterization

[0127] Elemental analysis: The metal content in the catalyst was determined using a Perkin Elmer Optima 7300DV ICP-OES instrument equipped with a cyclone spray chamber and a Meinhard nebulizer. Prior to analysis, samples (50–60 mg) were digested in sealed containers at 210°C for 30 min using HNO3 (3 ml) / HCl (2 ml) / HF (0.5 ml) / H2O (0.5 ml). After cooling to room temperature, 1.5 ml of saturated boric acid solution was added, and the mixture was then heated at 180°C for 20 min.

[0128] X-ray diffraction (XRD): Diffraction patterns were collected using a Rigaku Mini Flex II benchtop X-ray diffractometer (operated at 30 kV and 15 mA using Cu-Kα radiation (0.154056 nm)). Measurements were performed on a rotating powder sample holder in 2θ steps of 0.02° / s over a range of 10°–90°.

[0129] Nitrogen physisorption: Porosity was measured using Micrometrics ASAP 2020 via N2 physisorption at -196°C. Each sample was subjected to vacuum (10...) prior to N2 adsorption. -3 The gas was degassed at 300°C for 5 h at a temperature of 1 mbar. The specific surface area, mesopore volume, and micropore volume were determined using the Brunauer-Emmett-Teller, Barrett-Joyner-Halenda, and t-plot methods, respectively.

[0130] solid state 1 H and 13 C Magic Angle Rotation (MAS) NMR: Solid-state MAS NMR measurements were performed using a Varian Inova wide-aperture 300 MHz NMR spectrometer equipped with a 7.5 mm commercial Vespel MAS NMR probe and a commercial heated stack for variable temperature experiments. 1 H and 13 The corresponding Larmor frequencies for C were 299.97 and 75.43 MHz, respectively. The samples were stored in a nitrogen-filled glove box containing a 300 µL volume of MAS NMR rotor. For single-pulse... 1 H and 13 The CMOS NMR experiment used a MAS frequency of 4 kHz, and based on... 1 H or 13¹²C MAS NMR experiments were performed at 20°C–150°C using 45° angle pulses, 2 µs pulse widths, and a 20 s cycle delay to acquire spectra from 128 to 2000 nm. Adamantane was used as a second reference (its lower field strength...). 13 The C peak was 38.48 ppm and 1 The center band of H is 1.82 ppm), and all spectra are referenced to TMS (0 ppm).

[0131] Hydrogen chemisorption: H2 chemisorption was performed in chemisorption mode using Micromeritics ASAP 2020. The catalyst was placed under vacuum (10) at room temperature. -3 Degassing was performed at 0.1 mbar (mbar) followed by reduction at 350°C with H2 (50 mL / min). The first adsorption isotherm was recorded at 50°C from 0.1 mbar to 600 mbar. Adsorption isotherms were also recorded at 50°C under vacuum (10 mbar). -3 After evacuation for 1 hour at a pressure of (mbar), the second isotherm was measured. The chemisorbed H2 was then quantified by the difference between the first and second isotherms, and subsequently extrapolated to zero H2 pressure. The stoichiometric factor between the dissociated H2 and the active metal was assumed to be 1.0 (H / Ru).

[0132] Conditions for the catalytic hydrogenolysis of PE used in the study

[0133] Catalytic hydrogenolysis of PE was carried out in a 100 ml Hastelloy Parr (PARR) reactor at 170°C–230°C. In a typical reaction, 40 ml of solvent, 1–3 g of PE, and 20–150 mg of catalyst were charged into an autoclave reactor. The reactor was sealed, and air was removed by pressurizing with H2 and venting it for at least five consecutive cycles. In the last cycle, the reactor was pressurized with H2 to the desired pressure at room temperature and then heated to the reaction temperature (170°C–230°C) with vigorous stirring at 700 rpm. After the reaction, the reactor was immediately quenched to below 20°C with an ice / water mixture. The gaseous products in the headspace were directly transferred to a 5 L gas sampling bag (Tedlar®) and analyzed by gas chromatography-thermal conductivity detection (GC-TCD) using an Inficon Micro GC Fusion gas analyzer with a four-module chassis. Once the pressure vessel was completely vented, it was disassembled, and the remaining liquid and solids were transferred together via pipette to pre-weighed 40 mL glass vials. The liquid and solids were separated by filtration and analyzed by gas chromatography-flame ionization detection (GC-FID) (Agilent 7890A GC, DB-5 column, Agilent 7693 autosampler), where the liquid product was quantified using an external standard of n-butylcyclohexane. To determine the mass of LDPE from the reaction, all remaining solids were collected, dried overnight at 80°C, and weighed. The amount of catalyst was subtracted from the final weight.

[0134] Selection of solvents and reaction conditions for polyethylene conversion

[0135] The physicochemical and thermodynamic properties of hydrocarbon solvents significantly influence the hydrogenolysis of PE. Several lighter hydrocarbons were investigated as potential solvents in cases where hydrocarbons are formed during hydrogenolysis, namely n-pentane (n-C5), isopentane (i-C5), and n-hexane (n-C6). The reaction temperature of 210°C was chosen because it is higher than the critical temperatures of the pure solvents n-C5 (196°C ± 1°C) and i-C5 (191°C ± 5°C). The inventors hypothesize that PE is effectively solvated under these conditions, which promote PE mobility and interaction with the Ru surface. They note that the phase envelope predicted by the Soave-Redlich-Kwong equation of state estimates that when mixed with n-hexadecane, considered a model compound of long-chain hydrocarbons, the critical temperatures of n-C5 and i-C5 decrease by 1°C, respectively, to 195°C and 190°C. Figure 3 The PE conversion rates in n-C5 and i-C5 are similar (18% and 20% conversion after 2 hours at 210°C, respectively), while the conversion rate of n-hexane is 6 times lower (3% PE conversion). Figure 4a). PE conversion increased with reaction time and reached 21% at the critical temperature of the hexane and hexadecane mixture at 245°C. Figure 5 This indicates that PE conversion is enhanced in the supercritical phase, which may be due to effective solvation, increased diffusivity, and enhanced mass transport at the reactive surface of the catalyst.

[0136] To better understand the reactivity of the potential solvents, the reactivity of Ru / C catalytic hydrogenolysis of n-C5 and i-C5 fractions was investigated. After reaction times of 4 h and 60 h at 210°C, respectively, the conversions of n-C5 and i-C5 fractions reached approximately 18%, implying normalized solvent consumption rates of 2.4 and 0.15 mol, respectively. 溶剂 / mol Ru The observation that the hydrogenolysis rate of n-C5 is an order of magnitude higher than that of i-C5 is well consistent with the understanding that the hydrogenolysis rate decreases with increasing number of substituted carbon atoms in the C-C bond. The inventors primarily attribute this to... 2 C- 2 C or 2 C- 1 Compared to C-bond breaking, 3 C- x The activation enthalpy and entropy of the C bond increase. The ease of C-C cleavage also affects the product selectivity of solvent hydrogenolysis. Ru / C-catalyzed n-C5 hydrogenolysis to straight-chain C bonds... 1-4 hydrocarbon( Figure 4 c). At n-C5 conversion rates of 5%–10%, the equivalent molar selectivity of C1 (30%) and C4 (29%), and C2 (21%) and C3 (20%), respectively described the primary terminal ( 2 C- 1 C) and the center ( 2 C- 2 C) CC fracture. Comparable central and terminal CC fractures indicate random CC fractures on the Ru surface. With increasing n-C5 conversion, the inventors observed that C1 and C4 formation increased to 33% and 31%, respectively, but C2 (21%) and C3 (15%) decreased. This indicates that C... 2-4 The secondary terminal CC fracture enhances C1 formation. On the other hand, for i-C5, a major selectivity for C1 and i-C4 was observed. Figure 4 d). This may be related to the i-C5 molecule. 3 C- x The reactivity of the C bond is significantly lower than that of the C bond. 2 - 1 C is relevant. These findings indicate that the CC fracture reactivity on Ru / C follows... 2 C- 1 C ≥ 2 C-2 C 3 C- 1 C or 3 C- 2 The order of C. However, it should be emphasized that in the presence of PE or n-hexadecane, the Ru / C catalytic hydrogenolysis of n-C5 and i-C5 hydrocarbons becomes negligible. This is likely due to the stronger adsorption of long-chain hydrocarbons on the Ru surface.

[0137] General conversion pathway of PE hydrogenolysis

[0138] To gain a better understanding of the hydrogenolysis of PE on Ru / C, we further investigated the kinetics and product distribution at different PE conversions. PE conversion was manipulated by varying the reaction time and the amount of catalyst. Within the range of 170°C–230°C, the PE conversion increased linearly with reaction time. Figure 6 a and Figure 7 Regardless of the extent of PE hydrolysis, the constant PE consumption rate is characterized by zero-order kinetics, further indicating that the Ru surface is saturated with strongly adsorbed PE molecules. Statistical mechanics and transition state theory of hydrocarbon hydrolysis show that the rate constant increases with increasing alkane length due to van der Waals interactions with the metal surface and a significant increase in activation entropy. This supports the discovery of selective PE hydrolysis, even in the presence of a solvent, due to the strong adhesion of PE to the Ru surface. This finding is consistent with the preferred adsorption of polymers relative to smaller alkanes during hydrocracking and hydrolysis.

[0139] Gas (C) 1-4 ) and liquid (C 6-40 The carbon fraction of the product and the PE conversion rate are as follows: Figure 6 b and Figure 8 As shown. In these representations, the C5 carbon fraction is not included because a C5 solvent is used. Liquid products are expressed according to C... 6-10 C 11-20 and C 21-40 The carbon number classification represents gasoline, diesel, and lubricant grade hydrocarbons. After PE hydrogenolysis, the inventors observed an effect on the carbon content of longer-chain hydrocarbons. 21-40 The main selectivity (approximately 50%-55% at PE conversion rates up to 45%). However, C 21-40 Selectivity decreases as PE conversion rate increases to 90%, while C... 6-10 (50%) and C 11-20 A significant increase of (24%). The change in product distribution, along with the PE conversion rate, indicates that Ru / C catalyzes the hydrogenolysis of PE through CC cleavage, leading to a significant increase in C. 11-20 and C 21-40Product formation prevents re-adsorption of the product after a single CC breakage. The higher carbon selectivity of liquid alkanes relative to methane is attributed to multiple contact points within the polymer chain for CC breakage, resulting in liquid products.

[0140] The primary product then undergoes secondary C-C fracture to form C. 6-10 This is accompanied by an increase in PE conversion rate (i.e., the degree of PE hydrogenolysis). Furthermore, the formation of shorter-chain hydrocarbons through subsequent primary and secondary CC cleavage of PE can be explained by the adsorption preference of longer-chain hydrocarbons on the Ru surface, while solvent adsorption on the surface can be limited. However, after complete PE conversion, excessive reaction time > 20 h ( Figure 8 c) shows a significant increase in the production of gaseous products, along with a carbon yield exceeding 100% relative to the initial amount of PE. This is attributed to solvent conversion, which contributes to the formation of a product pool during secondary CC fracture.

[0141] Therefore, a simplified reaction network can be derived from the above observations. Figure 8 c). Central and terminal CC cleavage are the primary pathways. These two pathways dominate reactions below 50% PE conversion. These products undergo secondary CC cleavage, in which the primary longer-chain hydrocarbon product is saturated, producing methane and smaller liquid products. Due to the extent of the reaction leading to the depletion of PE and primary products, secondary products and solvents can undergo further CC cleavage and transform into smaller molecules, such as methane.

[0142] In the next step, the effects of reaction parameters on the PE consumption rate and product distribution under kinetic conditions with PE conversion below 20% were explored, with only one instance of PE hydrogenolysis observed. This was investigated in a series of experiments at different temperatures and initial PE amounts. Figure 9 (a) Saturated kinetics were observed in the range of 170°C–230°C, indicating that the PE consumption rate remained stable regardless of the initial PE amount. This finding is consistent with the observed linear correlation between the amount of PE converted and the reaction time, suggesting zero-order kinetics of PE hydrogenolysis. Interestingly, even under supercritical conditions above 210°C, the saturated kinetics remained intact, while the activation decreased from 127 kJ / mol to 80 kJ / mol. Figure 9 b). Therefore, the inventors hypothesize that supercritical conditions allow for increased migration of PE to active surface sites, while intermolecular interactions (i.e., solvation under supercritical conditions) reduce the activation energy.

[0143] The product yield as a function of temperature and the corresponding Arrhenius curve are shown in the figure. Figure 10 a and Figure 10In b, the mol-based product formation rate, normalized to accessible Ru sites, increases with increasing reaction temperature, allowing for the determination of the apparent activation energy. For both gaseous and liquid alkanes, the same activation energy change was observed above 210°C from 127 ± 9 kJ / mol to 88 ± 10 kJ / mol, showing good agreement with the activation energy change for PE consumption rates. This indicates that selectivity is not affected by temperature. This finding is consistent with the indistinguishable product distribution at approximately 20% PE conversion, regardless of reaction temperature. Figure 11 ).

[0144] Mechanism of hydrogenolysis of PE and alkanes

[0145] Further studies were conducted using defined linear model compounds with specific carbon chain lengths (i.e., n-hexadecane and squalane) to investigate the reaction mechanism in detail. Ru / C-catalyzed hexadecane hydrogenolysis closely resembles PE hydrogenolysis in its reaction characteristics. The linear correlation between hexadecane conversion and reaction time indicates zero-order kinetics of hydrogenolysis, attributed to strong hexadecane adsorption on Ru. Figure 12 a). Hexadecane hydrogenolysis produces only C2C ... 1-15 Straight-chain alkanes. At hexadecane conversion rates below 20%, C1 was observed. 6-15 Equal carbon fraction of liquid products ( Figure 12 c and Figure 12 d), but it is higher than C. 1-4 Fraction of gaseous products ( Figure 12 (b) A uniform carbon fraction distribution in the liquid product implies random centers and internal C-C breakage during hexadecane hydrogenolysis. On the other hand, with increasing hexadecane conversion, we observed a continuous shift in the product distribution towards shorter-chain hydrocarbons, due to the subsequent decrease in carbon yield of longer-chain alkanes, following a C-C ratio. 15 C 14 and C 13 The order. Furthermore, after reaching maximum carbon yield at 80% hexadecane conversion, the carbon yield C... 13-15 The decrease. These findings can be interpreted as being caused by secondary CC cleavage and CC cleavage preference in longer-chain alkanes, even in secondary CC cleavage.

[0146] The hydrogenolysis of squalane (2,6,10,15,19,23-hexamethyltetracosane) was studied as an example of hydrogenolysis of branched alkanes, and its consumption rate was found to be 0.15 mol / mol when the conversion rate was below 20%. Ru / min, which is higher than the consumption rate of hexadecane hydrogenolysis (2.7 mol / mol). Ru ( / min) is an order of magnitude lower. Similar to the hydrogenolysis of n-C5 and i-C5, the lower reactivity is attributed to the...2 C- 2 C or 2 C- 1 C-bonds compared to branches 3 C- 2 C or 3 C- 1 The rate of hydrogenolysis of the C bond is significantly lower. When considering a single C-C breakage, the C-C bond from the hydrogenolysis of squalane... 10 The product distribution further confirms the CC fragmentation preference, which selectively exhibits the characteristics of dimethyloctane (CMC). Figure 13 Dimethyl octane only through 2 C- 2 C fracture occurs, and therefore requires 3 C- 2 C and 2 C- 2 C fracture combination or 3 C- 1 C-cleavage yields methylnonane. n-Decane (which requires secondary cleavage) 3 C- 1 The negligible concentration of methane (formed through C-fracture) and subsequent methane formation also reflect the relative... 3 C- 2 C or 3 C- 1 C fracture preferred 2 C- 2 C fracture.

[0147] In the next step, the kinetic H / D isotope effect (KIE) will be investigated to explore CH fragmentation and rehydrogenation following CC fragmentation products during hydrogenolysis. Figure 14 a). Under H2 and D2, n-hexadecane (C 16 H 34 The differences in normalized consumption rates were 2.7 and 2.6 mol / mol, respectively. Ru / min, meaning there is no KIE (k) between H2 and D2. H / k D Approximately 1.1). This is attributed to the ease with which hydrogen is added from H2 and D2 via surface H and D after the CH and CC fractures on the Ru surface, as... Figure 14 As depicted by b. It is noteworthy that, compared to nC in H2... 16 H 34 Compared to hydrogenolysis, deuterated hexadecane (C636) in H2 16 D 34 The hydrogenolysis rate of ) decreased by 5 times (k C16H34 / k C16D34 (Approximately 5). This strongly suggests that, for hydrogenolysis, the breakup of CH / CD, rather than (re)hydrogenation, is rate-determined.

[0148] Mass spectrometry analysis of unreacted hexadecane and products after hydrogenolysis provides an estimate of the degree of hydrogenation and dehydrogenation via HD exchange. For the parent C... 16 H 34 and C 16 D 34 The molecules, with primary mass fractions (before hydrogenolysis) corresponding to molecular weights of 226 and 260 g / mol respectively, contain naturally abundant amounts of [missing information]. 13 C ( Figure 14 c). At a reaction time of 0.1 h, in D2(C 16 H 34 The conversion of hexadecane in -D2) was less than 1%, with no detectable gaseous or liquid products indicating minimal CC cleavage via hydrogenolysis. The mass spectra of hexadecane showed a broad m / z distribution of 228–240, with maximum abundance at 230 m / z. Figure 14 d), namely, 2–14 HD exchanges per hexadecane molecule. This indicates that adsorption, desorption, and dehydrogenation and hydrogenation reactions can be considered quasi-equilibrium. This finding was then used to quantify the HD exchange rate of hexadecane, where the deuteration rate is 3.2 × 10⁻⁶. 2 mmol H-D / mol Ru / s. On the other hand, for the counterpart C in H2 16 D 34 Comparable hexadecane conversion was observed at 0.6 h, where 23–33 D was exchanged with 8-fold lower HD (40 mmol). H-D / mol Ru The exchange occurs at a rate of / s. Considering the substantial hydrogenation rate, it is concluded that C 16 D 34 The CD cleavage during dehydrogenation limits the hydrogenolysis rate, likely due to the higher CD dissociation energy of 341 kJ / mol compared to the CH bond dissociation energy of 338 kJ / mol. Interestingly, with increasing hexadecane conversion, the C in D2... 16 H 34 And C in H2 16 D 34 The deuterium fraction per hexadecane molecule decreases continuously ( Figure 14 d), while the m / z = 72 of the i-C5 solvent increases ( Figure 15This finding indicates that the deuterium in hexadecane can be replaced by H from the solvent during hydrogenolysis. This is consistent with the HD exchange observed between deuterated polymers and hydrogen-containing solvents. Considering the negligible i-C5 conversion during hexadecane hydrogenolysis, it can be concluded that solvents in the presence of hexadecane (or other longer-chain alkanes) undergo CH cleavage and HD exchange only through dehydrogenation and (re)hydrogenation, but will experience minimal or no C-C cleavage.

[0149] The partial pressure of hydrogen significantly affects the hydrogenolysis rate of alkanes. Figure 16 The PE conversion and methane selectivity as a function of hydrogen pressure are shown. The PE conversion is negligible in the absence of hydrogen. Figure 6 a) and increases significantly with increasing hydrogen pressure from 2.5 bar to 30 bar. However, the conversion decreases as the hydrogen pressure exceeds 30 bar. The decrease in PE conversion is attributed to excess hydrogen coverage on the surface, resulting in hydrogen-covered sites competing with PE for adsorption sites. This finding is also well consistent with the negative reaction order of hydrogen in the hydrogenolysis of alkanes using transition metal catalysis, due to competitive adsorption between hydrogen and alkanes.

[0150] The partial pressure of hydrogen significantly affects the hydrogenolysis rate of alkanes. Figure 16 The PE conversion and methane selectivity as a function of hydrogen pressure are shown. The PE conversion is negligible in the absence of hydrogen. Figure 6 a) and increases significantly with increasing hydrogen pressure from 2.5 bar to 30 bar. However, the conversion decreases as the hydrogen pressure exceeds 30 bar. The decrease in PE conversion is attributed to excess hydrogen coverage on the surface, resulting in hydrogen-covered sites competing with PE for adsorption sites. This finding is also well consistent with the negative reaction order of hydrogen in the hydrogenolysis of alkanes using transition metal catalysis, due to competitive adsorption between hydrogen and alkanes.

[0151] From a mechanistic perspective, hydrogenolysis proceeds through the following basic reactions: (i) stepwise (complete) dehydrogenation, forming strong C-metallic bonds on the surface; (ii) C-C bond cleavage; and (iii) (re)hydrogenation, followed by desorption. Free adjacent metal sites are beneficial for binding the dissociated hydrogen during C-C bond cleavage (surface-bound hydrogen may migrate on the surface). In the absence of H2, dehydrogenation of the adsorbed alkane leads to the formation of a non-reactive surface intermediate and the desorption of H2. Therefore, the initial presence of H2 increases the reaction rate by promoting the (re)hydrogenation of the reaction coupler in the first two basic reaction sequences. However, increasing H2 pressure leads to H2 adsorption on the surface. Increased coverage ultimately reduces PE conversion. Interestingly, methane selectivity decreases significantly with increasing hydrogen pressure, reflecting the effect of increased coverage. 2 C- 2The requirements for available binding sites for C-fracture are low.

[0152] It is worth noting that the methane selectivity remains relatively constant along the degree of PE conversion. Figure 16 b). At a comparable PE conversion rate of 45%, the methane formation rate increased from 0.53 mol / L to 56 bar as the hydrogen pressure increased from 15 bar to 56 bar. CH4 / mol Ru / min to 0.13mol CH4 / mol Ru / min decreased by a factor of 4. This was achieved by considering the use of hydrogenolysis. CH-CH intermediate, and center 2 C- 2 Compared to C-bond breakage, the end 1 C- 2 C-bond breakage resulted in 1.5 times more dissociated hydrogen formation. These findings suggest that higher hydrogen pressure leads to preferential hydrogen dissociation of the central C-bond, thereby minimizing the breakage of the terminal C-bond.

[0153] Further exploration of methane formation was conducted using straight-chain and branched-chain model compounds. Figure 16 b compared the changes in primary carbon fraction in PE and n-hexadecane (nC) 16 H 34 ), octadecane (nC) 28 H 56 ) and the methane formation rate during squalane hydrogenolysis. Primary (PE) 1 C), Zhong ( 2 C) and Uncle ( 3 C) The fraction of carbon atoms is determined by solid-state NMR, such as... Figure 17 As shown. The methane formation rate at comparable conversions (approximately 20%) exhibited a linear correlation with the primary carbon fraction (i.e., the concentration of terminal carbons in the reaction substrate). Although a high primary carbon fraction (0.27) was observed in squalane among the compounds studied, 0.91 mol... CH4 / mol Ru The methane formation rate per minute is lower than that of straight-chain hydrocarbons, such as hexadecane (1.64 mol / min). CH4 / mol Ru / min) and octadecane (1.28 mol) CH4 / mol Ru In the hydrogenolysis ( / min), this well reflects the previously noted dominance of squalane. 1 C- 3 The lower reactivity of C bonds.

[0154] in conclusion

[0155] The study presented in this paper supports the existence of a pathway for the decomposition of polyolefins via hydrogenolysis under supercritical conditions, while minimizing methane formation. In the presence of isopentane as a solvent, Ru-catalyzed hydrogenolysis of polyethylene and alkanes (such as hexadecane and squalane) occurs at satisfactory rates above 150°C. Supercritical conditions in the solvent at 190°C–210°C lead to increased migration of polyethylene to the active sites while lowering the apparent activation energy of polymer conversion. Medium-chain alkanes were used as model compounds and showed random C / C bond breaking, with C / C bond breaking between primary and secondary carbon atoms preferentially occurring over C / C bond breaking involving tertiary carbon atoms. Therefore, mildly branched hydrocarbons (isobutane was predicted as ideal) as solvents allow selective C / C breaking of polyethylene and hexadecane, thereby minimizing solvent conversion. The kinetic isotope effects during HD exchange and the hydrogenolysis of deuterated hexadecane in H2 and n-hexadecane in D2 suggest that the reaction initiates via extensive CH breaking (local dehydrogenation), followed by C / C breaking and hydrogenation of the surface fraction. CC-C breakage can be primarily a kinetically rate-determining step, while CD-C breakage further reduces the rate. Furthermore, increasing the H2 chemical potential (achieved through higher partial pressure) and diluting longer-chain hydrocarbons will reduce methane formation because hydrogenolysis at the terminal CC bonds requires a larger available surface area to break them. These findings provide a mechanistic understanding of stochastic CC-C breakage, particularly in the hydrogenolysis of polyolefins under supercritical conditions, allowing for significant reductions in methane production and advancing the development of new technologies for converting plastic waste into recyclables.

Claims

1. A method for converting polymers and / or pyrolysis oils into light hydrocarbon chain products, wherein the method comprises: The polymer and light hydrocarbon solvent are fed into the mixer, wherein the light hydrocarbon solvent comprises straight-chain or branched C3 to C4 chains. 10 or mixtures thereof; Hydrogen gas is applied to the mixer; The polymer, the light hydrocarbon solvent, and the hydrogen mixture are fed into the reactor to form an effluent, and The effluent from the reactor is directed to the first separator.

2. The method as described in claim 1, wherein, The reactor may be a fixed-bed reactor, a semi-batch reactor, a slurry reactor, or a mixed-bed reactor.

3. The method as described in claim 1, wherein, The reactor contains a metal catalyst.

4. The method of claim 1, wherein, The reactor contains heterogeneous catalysts (monometallic, bimetallic, or multimetallic) suitable for hydrogenolysis.

5. The method of claim 1, wherein, The reactor contains a heterogeneous catalyst comprising at least a transition metal group, wherein the transition metal comprises platinum group metals, non-platinum group metals, or combinations thereof.

6. The method according to any one of claims 1-5, wherein, This transformation occurs under supercritical fluid conditions.

7. The method according to any one of claims 1-6, wherein, The feed contains polyolefins, oligomers, or combinations thereof, and / or pyrolysis oil.

8. The method of claim 7, wherein, The polyolefin comprises polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, medium-range hydrocarbons, polyethylene wax, or combinations thereof; and wherein the polyolefin is linear, branched, or a combination thereof.

9. The method of claim 8, wherein, The polypropylene has a molecular weight of about 30,000 g / mol to about 5,000,000 g / mol.

10. The method of claim 8, wherein, The polyethylene has a molecular weight of about 300 g / mol to about 6,000,000 g / mol.

11. The method according to any one of claims 1-10, wherein, The feed has a polymer concentration of approximately 4 g / L to approximately 80 g / L.

12. The method of claim 1, wherein, The feed contains pyrolysis oil.

13. The method according to any one of claims 1-11, wherein, The reactor is kept at a temperature of approximately 150°C to 400°C.

14. The method according to any one of claims 1-11, wherein, The method operates at temperatures between approximately 190°C and approximately 230°C.

15. The method according to any one of claims 1-14, wherein, Hydrogenolysis is carried out on the polymer and light hydrocarbon solvent feedstock.

16. The method according to any one of claims 1-15, wherein, The reactor has a pressure of approximately 20 to approximately 100 bar.

17. The method according to any one of claims 1-16, further comprising forming light hydrocarbon vapor and liquid hydrocarbon products after the first separator.

18. The method of claim 17, further comprising recycling any remaining liquid hydrocarbon solvent back into the mixer.

19. The method of claim 17, further comprising feeding the effluent and the light hydrocarbon vapor and the liquid hydrocarbon product from the first separator to the second separator.

20. The method of claim 19, wherein, After the light hydrocarbon vapor and the liquid hydrocarbon product are fed into the second separator, the light hydrocarbon vapor is recycled back to the mixer.

21. The method of claim 19 or 20, wherein, After the feed is introduced into the second separator, the light hydrocarbon products are collected.

22. A system for converting a polymer into a light hydrocarbon chain product, the system comprising: Feeds containing polymers, pyrolysis oils, or combinations thereof, The mixer is configured to receive this feed. reactor, A first separator configured to receive the first effluent from the reactor, and A second separator configured to receive a second effluent from the first separator.

23. The system of claim 22, wherein, The feed contains the polymer and is contacted with a light hydrocarbon solvent to produce a dissolved polymer stream.

24. The system of claim 23, wherein, The dissolved polymer stream is brought into contact with hydrogen gas to form the first effluent.

25. The system as claimed in any one of claims 22-24, wherein, The first effluent is separated into light hydrocarbon vapor in the first separator.

26. The system as claimed in any one of claims 22-25, wherein, The first effluent was separated into liquid hydrocarbon products.

27. The system of claim 25, wherein, The mixer is configured to receive the light hydrocarbon vapor from the first separator and any remaining light hydrocarbon solvent from the first separator.

28. The system as claimed in any one of claims 22-27, wherein, The reactor contains a slurry of supported catalysts.

29. The system of claim 28, wherein, This supported catalyst comprises a catalyst and a support.

30. The system of claim 29, wherein, The catalyst includes metal catalysts, heterogeneous catalysts containing platinum group metals, heterogeneous catalysts containing transition metals, or combinations thereof.

31. The system of claim 29, wherein, The carrier comprises AlO2, silica-alumina, titanium dioxide, SiO2, ZrO2, carbon, or a combination thereof.

32. The system of claim 22, wherein, The second separator is configured to remove light hydrocarbon vapor and recycle it back to the mixer.

33. The system of claim 22, wherein, The second separator is configured to remove liquid hydrocarbon products from the second effluent.

34. The system of claim 22, wherein, The reactor is kept at a constant temperature and pressure.

35. The system of claim 22, wherein, The feed contains polyolefins.

36. The system of claim 35, wherein, The polyolefin comprises polypropylene, polyethylene, or combinations thereof; and wherein the polyolefin is linear, branched, or a combination thereof.

37. The system of claim 36, wherein, The polypropylene has a molecular weight of about 30,000 g / mol to about 5,000,000 g / mol.

38. The system of claim 36, wherein, The polyethylene has a molecular weight of about 300 g / mol to about 6,000,000 g / mol.

39. The system of claim 22, wherein, The feed has a polymer concentration of approximately 4 g / L to approximately 80 g / L.

40. The system of claim 22, wherein, The reactor is kept at a temperature of approximately 150°C to 400°C.

41. The system of claim 22, wherein, The reactor is maintained at a pressure of approximately 20 to approximately 100 bar.

42. The system of claim 22, wherein, The feed contains pyrolysis oil.

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