WO2025038327A1 - Conversion of polymers in mixtures of organic compounds at supercritical conditions - Google Patents

Abstract

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

Description

CONVERSION OF POLYMERS IN MIXTURES OF ORGANIC COMPOUNDS AT

SUPERCRITICAL CONDITIONS

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63/532,156 filed on August 11, 2023, the entire contents of which are incorporated in its entirety.

FIELD OF INVENTION

[0002] The present disclosure generally relates to the field of catalytic methods for the continuous conversion of polyolefins and/or pyrolysis oil into smaller chain products. More specifically, the method may be operated under supercritical conditions to enable a high level of control of product distribution and yield.

BACKGROUND

[0003] Every year, up to 75% of all plastics including polymers in the United States are discarded into landfills, which may be an irremediable loss of materials and cause a severe threat to the environment. However, plastics, which include polymers, may be utilized as fuels or reprocessed to produce low-quality materials. Thus, there is a need to utilize any plastic or polymer as a source of carbon for refinery' feedstocks and chemical productions.

[0004] Unfortunately, current recycling practices have not been able to efficiently utilize these plastics, in particular polyolefins and polystyrene, which are chemically stable. Existing chemical routes to convert polymers into smaller molecules rely on elevated temperatures of above 400 °C, which is associated with a low degree of control of product distribution and a low yield of useful molecules. Methods reported in the 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 not be practical in a continuous process. Other methods rely on the addition of external solvents, such as water, that may be chemically incompatible with polymers. In view of this, the current methods are costly and low yielding.

[0005] Therefore, there is a need in the art to develop a method with a high level of control to converting plastics for use in a recycled product or a refinery feedstock.

SUMMARY

[0006] In an embodiment of the present disclosure, a method for converting polymers and/or pyrolysis oil into a light hydrocarbon chain product is provided. In some embodiments, the method may operate under supercritical conditions. That is, the method may operate under temperature and pressure combinations that are sufficient to induce supercritical fluid conditions for the reaction mixture. The method may include supplying a feed of polymer and light hydrocarbon solvent to a mixer, wherein the light hydrocarbon solvent may include a linear or branched Cs to Cio. or a mixture thereof, applying hydrogen gas in the mixer, feeding the polymer, the light hydrocarbon solvent, and the hydrogen mixture into a 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 including a heterogeneous catalyst suitable for the hydrogenolysis (mono-, bi- or multi-metallic). In some embodiments, the heterogenous catalyst suitable for hydrogenolysis may be a catalyst including a platinum group metal C’pgm"). In other embodiments, the heterogenous catalyst suitable for hydrogenolysis may be a catalyst including a transition metal group, wherein the transition metal includes a pgm, a non-pgm, or a combination thereof.

[00010] In some embodiments, the method may operate at a supercritical fluid condition.

[00011] In some embodiments, the feed of polymer may include a polyolefin.

[00012] In some embodiments, the polyolefin may include polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, medium range hydrocarbons, polyethylene waxes, or a combination thereof; and wherein the polyolefin is linear, branched or a combination thereof.

[00013] In some embodiments, the polypropylene may have a molecular weight of about 30,000 g/mol to about 5,000,000 g/mol.

[00014] In some embodiments, the polyethylene may have a molecular weight of about 300 g/mol to about 6,000,000 g/mol.

[00015] In some embodiments, the feed may have a concentration of polymer that reaches the saturation limit of the solvent under supercritical fluid conditions. In certain embodiments, the feed may have a concentration of about 4 g/L to about 80 g/L.

[00016] In some embodiments, the reactor may be held at a temperature of about 150 °C to 400 °C.

[00017] In some embodiments, the process may operate at a temperature between about 190 °C and about 230 °C.

[00018] In some embodiments, hydrogenolysis may be performed on the feed of polymer and light hydrocarbon solvent. [00019] In some embodiments, the reactor may have a pressure of about 20 to about 100 bar.

[00020] In some embodiments, the method may further include forming a light hydrocarbon vapor and a liquid hydrocarbon product after the first separator.

[00021] In some embodiments, the method may further include recycling any remaining liquid hydrocarbon solvent to the mixer.

[00022] In some embodiments, the method may further include feeding the light hydrocarbon vapor and a liquid hydrocarbon product from the first separator to a second separator.

[00023] In some embodiments, after feeding the light hydrocarbon vapor and the liquid hydrocarbon product to the second separator, the light hydrocarbon vapor is recycled to the mixer. [00024] In some embodiments, after feeding to the second separator, a light hydrocarbon product may be collected.

[00025] In another embodiment of the present disclosure, a system for converting a polymer oligomer, and/or pyrolysis oil into a light hydrocarbon chain product is provided. The system may include a polymer feed, a mixer that may be configured to receive the polymer feed, a reactor, a first separator that may be configured to receive a first effluent from the reactor, and a second separator that may be configured to receive a second effluent from the first separator.

[00026] In some embodiments, the polymer feed may be contacted with a light hydrocarbon solvent to produce a dissolved polymer stream.

[00027] In some embodiments, the dissolved polymer stream may be contacted with hydrogen gas to form the first effluent.

[00028] In some embodiments, the first effluent may be separated into a light hydrocarbon vapor, or a combination thereof in the first separator.

[00029] In some embodiments, the first effluent may be separated into a liquid hydrocarbon product.

[00030] In some embodiments, the mixer may be configured to receive the light hydrocarbon vapor from the first separator and any remaining light hydrocarbon solvent from the first separator. [00031] In some embodiments, the reactor may include a slurry of a supported catalyst.

[00032] In some embodiments, the supported catalyst may include a catalyst and a support.

[00033] In some embodiments, the catalyst may include a metal containing catalyst, a heterogenous catalyst that may include a platinum group metal, a heterogenous catalyst that may include a transition metal, or a combination thereof.

[00034] In some embodiments, the support may include a metal oxide. In some embodiments, the support may include titania, AI2O3, silica-alumina, titania, SiCh, ZrCh, carbon or a combination thereof. [00035] In some embodiments, the second separator may be configured to remove a light hydrocarbon vapor and recycle the light hydrocarbon vapor into the mixer.

[00036] In some embodiments, the second separator may be configured to remove a liquid hydrocarbon product from the second effluent.

[00037] In some embodiments, the reactor may be held at a constant temperature and pressure. [00038] In some embodiments, the polymer feed may include a polyolefin.

[00039] In some embodiments, the polyolefin may include polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, medium range hydrocarbons, polyethylene waxes, or a combination thereof; and wherein the polyolefin is linear, branched or a combination thereof.

BRIEF DESCRIPTION OF DRAWINGS

[00040] The disclosure described herein is illustrated by way of example and not by way of limitation in the accompanying figures.

[00041] FIG. 1 illustrates a process for converting polyolefins according to an embodiment of the present disclosure.

[00042] FIG. 2a-c illustrates the carbon fraction in gas, liquid and solid residue after PE hydrogenolysis on several transition metal catalysts and/or different supports.

[00043] FIG. 3a-c illustrates the pressure-temperature projection of phase diagram (phase envelope) for the mixture of hexadecane and a solvent.

[00044] FIG. 4a-d illustrates the results of PE hydrogenolysis with different solvents at different reaction conditions.

[00045] FIG. 5 illustrates the carbon fraction in gas, liquid and solid residue after Ru/C- catalyzed PE hydrogenolysis with n-hexane.

[00046] FIG. 6a-c illustrates a proposed reaction network for the hydrogenolysis of PE and its products on Ru/C in the presence of isopentane as a solvent.

[00047] FIG. 7 illustrates the PE conversion of a reaction according to an embodiment of the present disclosure.

[00048] FIG. 8a-f illustrates carbon yield of gas and liquid products at different PE conversion upon hydrogenolysis.

[00049] FIG. 9a, b illustrates how reaction parameters effect PE consumption rate and product distribution.

[00050] FIG. 10a, b illustrates the kinetics of PE hydrogenolysis of an Example. [00051] FIG. l la-d illustrates the carbon yield of gas and liquid products from PE hydrogenolysis under the kinetic regime at different temperatures varying the amount of catalyst and reaction time of the Example.

[00052] FIG. 12a-d illustrates the reaction results of hexadecane conversion.

[00053] FIG. 13 illustrates the GC-FID chromatogram of Cio products after squalane hydrogenolysis.

[00054] FIG. 14a-d shows the results of dehydrogenation and hydrogenation of hexadecane upon hydrogenolysis.

[00055] FIG. 15a,b shows results of GC-MS mass spectra of i-Cs solvent during hexadecane hydrogenolysis.

[00056] FIG. 16a,b shows methane formation upon Ru/C-catalyzed hydrogenolysis.

[00057] FIG. 17a,b shows MNR spectra results of PE at 100°C

DETAILED DESCRIPTION

[00058] The present disclosure relates to a system and method for converting polyolefins into a small hydrocarbon product. In some embodiments, the system and method may be used for converting polymers, oligomer, and/or pyrolysis oil. Pyrolysis oil may be produced from a pyrolysis process. Pyrolysis is a thermal degradation of plastic waste in an inert atmosphere and yields value added pyrolysis gas, liquid pyrolysis oil and char (residue), wherein pyrolysis oil is the major product. The method and system as described herein is a continuous system that enables a high level of control and high product yield of small hydrocarbon products. As used herein, the term "‘small hydrocarbon product” refers to a hydrocarbon including Ci to C?o, wherein the chain may be linear, branched or a combination thereof.

[00059] Reference throughout this specification to ’‘one embodiment” or '‘an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. In addition, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.”

[00060] As used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly indicates otherwise. Thus, for example, reference to “a sample” includes a single sample as well as more than one sample.

[00061] As used herein, the term “about” or “approximately” in connection with a measured quantity refers to the normal variations in that measured quantity as expected by one of ordinary' skill in the art in making the measurement and exercising a level of care commensurate with the objective of measurement and the precision of the measuring equipment. In certain embodiments, the term ‘'about” includes the recited number ±10%, such that “about 10” would include from 9 to 11.

[00062] As used herein, the term “polyolefins” refers to, but is not limited to, a medium range hydrocarbon. polypropylene, polyethylene, polyethylene waxes, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, 1 -hexene, 1 -octene, medium range hydrocarbons, polyethylene waxes, or a combination thereof. In some embodiments, the polyethylene may include a low molecular weight polyethylene (LMWPE), a high molecular weight polyethylene (HMWPE), a ultra-high molecular weight polyethylene (UHMWPE), or a combination thereof.

[00063] As used herein, the term “supercritical” refers to conditions of temperature and pressure where distinct liquid and gas phases of the solvent do not exist.

[00064] As used herein, the term '‘pyrolysis” relates to a thermal decomposition or degradation of a feedstock such as plastic waste under inert conditions and results in a gas. a liquid, and a solid char fraction. During the pyrolysis, the feedstock is converted in a pyrolysis unit into a great variety of chemicals including gases such as H2, Cl - to C4-alkanes, C2- to C4-alkenes, ethyne, propyne, 1 -butyne, pyrolysis oil having a boiling temperature of 25 °C to 500 °C or more and char. The direct products from such a pyrolysis are “pyrolysis gas” and solid products. The liquid product ■‘pyrolysis oil” is then separated by condensation from the '‘pyrolysis gas”. In addition, water is formed during the pyrolysis which may be partially dispersed in the pyrolysis oil and may be partially contacted with the pyrolysis oil in a separate phase. The water formed during pyrolysis comprises various organic compounds and/or salts thereof which were also formed during the pyrolysis. The term “pyrolysis” includes slow pyrolysis, fast pyrolysis, flash pyrolysis and catalytic pyrolysis. These pyrolysis types differ regarding process temperature, heating rate, residence time, feed particle size, etc. resulting in different product quality⁷. The pyrolysis unit may be operated adiabatically, isothermally, nonadiabatically, non-isothermally, or combinations thereof. The pyrolysis reactions of this disclosure may be carried out in a single stage or in multiple stages. For example, the pyrolysis unit can comprise two reactor vessels fluidly connected in series.

[00065] As used herein, the term “pyrolysis oil” is understood to mean any oil originating from the pyrolysis of plastic waste. The term “plastic waste” includes rubber waste such as end-of-life tires and feedstocks comprising plastic waste. The pyrolysis oil is obtained and/or obtainable from pyrolysis of such plastic waste As used herein, the term “plastic waste” refers to any plastic material discarded after use, i.e., the plastic material has reached the end of its useful life and is considered post-consumer waste. The plastic waste can be pure polymeric plastic waste, mixed plastic waste or film waste, including soiling, adhesive materials, fillers, residues etc. The plastic waste may have an oxygen content, a nitrogen content, sulfur content, halogen content and optionally also a heavy' metal content. The plastic waste can originate from any plastic material containing source. Typically, plastic waste is a mixture of different plastic materials, including hydrocarbon plastics, e.g., polyolefins such as polyethylene (HDPE. LDPE) and polypropylene, polystyrene, and copolymers thereof, etc., and polymers composed of carbon, hydrogen, and other elements such as chlorine, fluorine, oxygen, nitrogen, sulfur, silicone, etc., for example chlorinated plastics, such as polyvinylchloride (PVC), polyvinylidene chloride (PVDC). etc., nitrogencontaining plastics, such as polyamides (PA), polyurethanes (PU), acrylonitrile butadiene styrene (ABS). etc., oxygen-containing plastics such as polyesters, e.g.. polyethylene terephthalate (PET), polycarbonate (PC), etc., silicones and/or sulfur bridges crosslinked rubbers.

[00066] Typically, the plastic material comprises additives, such as processing aids, plasticizers, flame retardants, pigments, light stabilizers, lubricants, impact modifiers, antistatic agents, antioxidants, etc. These additives may comprise elements other than carbon and hydrogen. For example, bromine is mainly found in connection to flame retardants. Heavy metal compounds may be used as lightfast pigments and/or stabilizers in plastics. Cadmium, zinc, and lead may be present in heat stabilizers and slip agents used in plastics manufacturing. The plastic waste can also contain residues. Residues in the sense of the invention are contaminants adhering to the plastic waste. The additives and residues are usually present in an amount of less than 50 wt.-%, preferably less than 30 wt.-%, more preferably less than 20 wt.-%, even more preferably less than based on the total weight of the dry weight plastic.

[00067] To obtain a pyrolysis oil according to the present disclosure, the plastic waste is inserted into a pyrolysis reactor using a dosing unit such as a screw or an extruder or a rotary valve or a pneumatic conveyor or a liquid injector. The plastic is optionally pre-heated in e.g., a heat exchanger prior to insertion into the pyrolysis reactor and/or subjected to a pre-pyrolysis at a temperature in the range of, for example, from about 200 °C to about 360 °C. Next, the plastic waste is heated in the pyrolysis reactor to a temperature in the range of from about 350 °C to about 900 °C, more preferably in the range of from 400 °C to about 550 °C, and a pressure in the range of from about 0.5 bar to about 2 bar(abs), more preferably in the range of from 0.9 bar to about 1.5 bar(abs). The pyrolysis reactor is preferably selected from the group comprising fluidized bed reactors, moving bed reactors, entrained flow reactors, screw reactors, extruders, stirred tank reactors and rotary kiln reactor. Preferably, the pyrolysis is performed in the pyrolysis reactor under an inert atmosphere exempt of oxygen or air.

[00068] Pyrolysis processes as such are known. They are described, e.g., in EP 0713906 Al and WO 95/03375 Al. Suitable pyrolysis oils are also commercially available. The pyrolysis oil is typically a liquid at 15 °C or a wax at said temperature. "Liquid at 15 °C” in the terms of the present invention means that the pyrolysis oil has a density of at most 1.3 g/ml, e g., a density in the range from 0.65 to 0.98 g/ml, at 15 °C and 1013 mbar, as determined according to DIN EN ISO 12185.

[00069] Optionally, the pyrolysis oil or mixture of pyrolysis oils is subjected to one or more methods selected from filtration, centrifugation, adsorption, washing, extraction before used as e.g., a feedstock for a steam cracking process. Such optional pre-treatment methods are for example described in WO 2021/224287 Al, WO 2023/061834 Al, EP 0713906 Al and WO 95/03375 Al which are incorporated herein by reference. A skilled person knows how and in which cases to use pre-treatment methods disclosed in said documents and comparable pretreatment methods disclosed elsewhere.

[00070] In an embodiment of the present disclosure, a method has been developed for the conversion of polymers into smaller hydrocarbon chain products. The method of the present disclosure includes applying a light hydrocarbon solvent and a hydrogen gas to a polymer feed in a mixer at supercritical conditions to convert the polymer into a small hydrocarbon chain product. It has been found that by operating the system and performing the method at supercritical conditions was able to produce a high yield of small hydrocarbon products from the polymer feed. In some embodiments, the light hydrocarbon solvent may include a linear or branched C3 to C10, linear or branched C3 to Cs, linear or branched C3 to Ce or linear or branched C4 to Ce. In some embodiments, the light hydrocarbon may have a weight based content of branched hydrocarbons is in the range of about 30% to about 99%, about 40% to about 95%, or about 50% to about 90%. [00071] In an embodiment, the method includes supplying a feed of a polymer and light hydrocarbon solvent to a mixer. The polymer may include a mixture of polyolefins that may include polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, polyisoprene, medium range hydrocarbons, polyethylene waxes, 1 -hexene, 1- octene, or a combination thereof. In some embodiments, the feed of polymer may include a polyolefin in combination with an additional polymer. The additional polymer may include, but is not limited to, a polyurethane, polyamide, polyester, polyether, poly vinylacetate/ alcohol, polyacrylonitrile, polystyrene, polyvinylchloride, or a combination thereof. In some embodiments, the polyolefin and additional polymer may be present in the feed of polymer in a weight ratio of about 50:50, about 80: 10, or about 99: 1. In some embodiments, the feed may also include a polymer, olefins, pyrolysis oil. or a combination thereof.

[00072] In some embodiments, the feed of polymer may be a mixture that stems from polymer waste from an industry⁷ or household wasteform. For example, the feed of polymer may be a polymer waste from a marine source, a terrestrial collection, or from an extraction from a landfill site. In another example, the feed of polymer may stem from plastic waste.

[00073] In some embodiments, the polymer may include polypropylene, polyethylene or a combination thereof. In some embodiments, the light hydrocarbon solvent may include a linear or branch C3 to C10, or a mixture thereof. The method may further include applying hydrogen gas into the mixer. The method further includes feeding the polymer, light hydrocarbon solvent and/or hydrogen gas mixture into a reactor to form a first effluent, and directing the first effluent from the reactor to a first separator.

[00074] In some embodiments, the polypropylene may have a molecular weight of about 30,000 g/mol to about 5.000,000 g/mol. In other embodiments, the 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.

[00075] In some embodiments, the polyethylene may have a molecular weight of about 300 g/mol to about 6,000,000 g/mol. In some embodiments, the polyethylene may have a molecular weight 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, about 65,000 g/mol to about 1,000,000 g/mol, 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 sub-range herein.

[00076] In some embodiments, the feed may have a concentration of polymer that reaches the saturation limit of the solvent under supercritical fluid conditions In some embodiments, the feed of polymer, such as LDPE, may have a concentration of about 4 g/L to about 80 g/L. In some embodiments, the concentration of the feed of polymer, 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.

[00077] In some embodiments, the reactor may include a fixed bed reactor, a semi-bath reactor, a si urn reactor, or a mixed bed reactor. In some embodiments, the reactor may include a metal containing catalyst. In another embodiment, the reactor may include a heterogeneous catalyst including a platinum group metal (“pgm”). In yet another embodiment, the reactor may include a heterogeneous catalyst including at least a transition metal.

[00078] In some embodiments, the reactor may include a bimetallic or multimetallic catalyst including, a platinum group metal. In another embodiment, the reactor may include a heterogenous catalyst that may include a transition metal, or a combination thereof.

[00079] In some embodiments, the reactor may be held at constant temperature and pressure, which create a supercritical fluid condition. In certain embodiments, the method of the present disclosure may operate at supercritical conditions.

[00080] In some embodiments, the reactor may be held at a temperature above the critical point, where distinct liquid and gas phases do not exist 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.

[00081] In some embodiments, the method may operate at a temperature of about 190 °C to about 230 °C, about 195 °C to about 225 °C, of about 200 °C to about 220 °C, or about 205 °C to about 215 °C.

[00082] 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.

[00083] In some embodiments, the method may further include performing hydrogenolysis on the feed of polymer and light hydrocarbon solvent. The hydrogenolysis may be performed within the reactor. As understood herein, “hydrogenolysis” may include performing a reaction at elevated pressure under a hydrogen gas atmosphere, and/or performing the reaction at elevated temperatures under a hydrogen gas atmosphere. In some embodiments, liquid phase n-paraffins may be formed after hydrogenolysis. In some embodiments, liquid phase branched hydrocarbons may be formed as products after hydrogenolysis.

[00084] In some embodiments, the method may further include forming a second effluent comprising a light hydrocarbon vapor and a liquid hydrocarbon product after the first separator. After forming the second effluent, any remaining liquid hydrocarbon solvent after the reactor may be recycled to the mixer.

[00085] In some embodiments, the light hydrocarbon solvent may include a linear or branch C3 to C10, or a mixture thereof. [00086] In some embodiments, the second effluent including the light hydrocarbon vapor and the liquid hydrocarbon product may be fed to a second separator. In some embodiments, after feeding the second effluent to the second separator, the light hydrocarbon vapor may be recycled to the mixer.

[00087] In an embodiment, after feeding the second effluent to the second separator, a light hydrocarbon product may be collected.

[00088] In some embodiments, the light hydrocarbon vapor may include gaseous alkanes with between 1 and 4 carbon atoms.

[00089] In some embodiments, the light hydrocarbon product may include linear and/or branched liquid alkanes with between 6 and 40 carbon atoms.

[00090] 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.

[00091] In some embodiments the polymer feed may include a mixture of polyolefins. In some embodiments, the mixture of polyolefins may include polypropylene, polyethylene, poly isobutylene, polymethylpentene, poly butene, poly butadiene, poly isoprene. 1- medium range hydrocarbons, polyethylene waxes, hexene, 1 -octene, or a combination thereof. In some embodiments, the mixture of polyolefins may include polypropylene, polyethylene, or a combination thereof. In some embodiments, the feed may also include a polymer, olefins, pyrolysis oil, or a combination thereof.

[00092] In some embodiments, the 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.

[00093] In some embodiments, the polyethylene may have a molecular weight of about 300 g/mol to about 6.000,000 g/mol. In some embodiments, the polyethylene may have a molecular weight 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, about 65.000 g/mol to about 1.000,000 g/mol. 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 sub-range herein.

[00094] 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 concentration of polymer that reaches the saturation limit of the solvent under supercritical fluid conditions.

[00095] 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 gas to be incorporated into the first effluent. In an embodiment, the first effluent may be separated into a light hydrocarbon vapor, liquid hydrocarbon product, or a combination thereof in the first separator.

[00096] In some embodiments, the light hydrocarbon solvent may include a linear and/or branch C3 to C10, or a mixture thereof.

[00097] In some embodiments, the reactor of the sy stem 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.

[00098] In some embodiments, the mixer may form a dissolved polymer stream. In some embodiments, the reactor may be configured to receive the dissolved polymer stream. In some embodiments, the reactor may be configured to perform hydrogenolysis on a dissolved polymer feed. In some embodiments, the reactor may create a first effluent.

[00099] The first separator of the system may be configured to receive the first effluent. In some embodiments, the first separator may separate the first effluent in a stream of hydrogen gas and gas products. In some embodiments, the gas products may include methane. In some embodiments the first separator may separate the first effluent into a second effluent, where the second effluent may include a light hydrocarbon vapor, a 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 the second effluent including a light hydrocarbon vapor, a light hydrocarbon product, or a combination thereof. In some embodiments, the second separator may create a light hydrocarbon vapor. In some embodiments, the second separator may create a light hydrocarbon product.

[000100] In some embodiments, the light hydrocarbon vapor may include gaseous alkanes with between 1 and 4 carbon atoms. [000101] In some embodiments, the liquid hydrocarbon product may include linear and branched liquid alkanes with between 6 and 40 carbon atoms.

[000102] In some embodiments, the light hydrocarbon vapor may be recycled to the mixer.

[000103] In some embodiments, after the second separator a light hydrocarbon product may collected.

[000104] In some embodiments, hydrogenolysis may be performed on the mixture of polymer feed, hydrogen gas, light hydrocarbon solvent, or combination thereof. As understood herein, “hydrogenolysis” may include a reactor at elevated pressure under a hydrogen gas atmosphere. Hydrogenolysis may also include a reactor at elevated temperatures, where the reactor is under a hydrogen gas atmosphere. In some embodiments, liquid phase ^-paraffins may be formed after hydrogenolysis. In some embodiments, liquid phase branched hydrocarbons may be formed as products after hydrogenolysis.

[000105] In some embodiments, the reactor may be held at constant temperature and pressure, which create a supercritical fluid condition. In some embodiments, the reactor may operate at supercritical conditions.

[000106] In some embodiments, the reactor may be held at a temperature 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.

[000107] In some embodiments, the process may operate at a temperature of about 190 °C to about 230 °C, about 195 °C to about 225 °C, of about 200 °C to about 220 °C. or about 205 °C to about 215 °C.

[000108] 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.

[000109] In some embodiments, the reactor may include a heterogeneous catalyst including a transition metal group, wherein the transition metal may include at least one platinum group metal or a combination thereof.

[000110] In some embodiments, the reactor may include a slurry of a supported catalyst. In some embodiments, a supported catalyst may include a catalyst and a support.

[000111] In some embodiments, the catalyst may include a metal containing catalyst, a heterogenous catalyst including a platinum group metal, a heterogenous catalyst including a transition metal, or a combination thereof. [000112] In some embodiments, the metal containing catalysts may include zinc, nickel, cobalt magnesium, molybdenum, tungsten titanium, tantalum, chromium, iron, gallium, other similarly catalytically active metals, or a combination thereof.

[000113] In some embodiments, the support may include AlCh, silica-alumina. titania, SiCh, ZrO2. carbon, or a combination thereof.

[000114] In some embodiments, catalyst binders may be used. In some embodiments, catalyst binders may include silica, alumina, silica-alumina, silica-titania, silica-thoria, silica-magnesia, silica-zirconia, silica-beryllia, ternary compositions of silica with other refractory oxides, and the like. In some embodiments, other matrices may include clays, such as naturally occurring clays illustrated by montmorillonites, kaolines, bentonites, halloysites, dickites, nacrites and anauxites. [000115] Referring to FIG. 1, FIG. 1 illustrates a schematic of the process for the conversion of polyolefins in organic environments at supercritical conditions 100 according to an embodiment of the present disclosure. As can be seen in FIG. 1. a polymer feed 105 is fed into a mixer 110. The polymer feed 105 may include any of the polymer species that have been described herein, including but not limited to, polypropylene, polyethylene, polyisobutylene, polymethylpentene, polybutene, polybutadiene, poly isoprene, medium range hydrocarbons, polyethylene waxes, 1- hexene. 1 -octene, or a combination thereof.

[000116] When the polymer feed 105 enters the mixer 110, it may be mixed with a light hydrocarbon vapor 155 to form a dissolved polymer stream 120. As can be seen in FIG. 1 the dissolved polymer stream may then be contacted with hydrogen gas 115. The hydrogen gas is provided such that a hydrogenolysis reaction may be performed in the reactor. The dissolved polymer stream 120 may then be fed into the reactor 125. Hydrogenolysis may then be performed on the dissolved polymer stream 120 in the reactor 125. After hydrogenolysis is performed in the reactor 125, a first effluent 130 may be formed. The first effluent 130 may then leave the reactor 125 as shown in FIG. 1.

[000117] As illustrated in FIG. 1. the first effluent 130 is received by the first separator 135. The first separator 135 then separates the first effluent into a mixture of hydrogen gas and gas products 140. In some embodiments, the gas products may include methane. The first separator 135 may also separate the first effluent into a second effluent 145 that may contain a mixture of light hydrocarbon vapor and light hydrocarbon products.

[000118] The second effluent 145 may be fed to the second separator 150. The second separator 150 may then separate the second effluent 145 into a stream of light hydrocarbon vapor 155. The light hydrocarbon vapor 155 may then be recycled to the mixer 1 10 as shown in FIG. 1. The second separator 150 also separates the second effluent 145 into a stream of light hydrocarbon products 160. The stream of light hydrocarbon product 160 may then be collected and further processed. [000119] Claims or descriptions that include "‘or” or "and/or" between at least one members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context. The disclosure includes embodiments in which exactly one member of the group is present in, employed in, or otherwise relevant to a given product or process. The disclosure includes embodiments in which more than one, or all the group members are present in, employed in, or otherwise relevant to a given product or process.

[000120] Furthermore, the disclosure encompasses 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 that is dependent on another claim can be modified to include at least one limitation found in any other claim that is dependent on the same base claim. Where elements are presented as lists, such as, e.g., in Markush group format, each subgroup of the elements is also disclosed, and any element(s) can be removed from the group. It should be understood that, in general, where the disclosure, or aspects of the disclosure, is/are referred to as comprising particular elements and/or features, embodiments of the disclosure or aspects of the disclosure consist, or consist essentially of, such elements and/or features. For purposes of simplicity, those embodiments have not been specifically set forth in haec verba herein. Where ranges are given (such as, e.g.. from [X] to [Y]), endpoints (such as. e.g., [X] and [Y] in the phrase '‘from [X] to [Y]”) are included unless otherwise indicated. Furthermore, unless otherwise indicated or otherwise evident from the context and understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value or sub-range within the stated ranges in different embodiments of the disclosure, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise.

[000121] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. EXAMPLES

[000122] The following examples are intended to be illustrative and are not meant in any way to limit the scope of the disclosure.

[000123] Several experiments were conducted to provide better insight into the polyethylene (PE) hydrogenolysis process according to an embodiment of the present disclosure. In particular, a Ru/C-catalyzed PE hydrogenolysis in the presence of a light hydrocarbon (with isopentane as model compound) as a solvent under supercritical conditions. The choice of model compound was based on an advantage in polymer solubility under supercritical conditions and because Ru is the most active and selective among noble metals as can be seen in FIG. 2. Preliminarymeasurements showed that the depolymerization under supercritical conditions of longer-chain hydrocarbons lead to selective hydrogenolysis of PE, minimizing methane formation and negligible solvent conversion. The consecutive C-C cleavage of the polyolefin upon primary and secondary- hydrogenolysis reactions, gradually changes the selectivity- from heavy oils (C20-40) to gasoline-ranged hydrocarbon (Ce-io) with a preference for linear over branched products. Ru- catalyzed hydrogenolysis of model compounds of hexadecane and squalane in this work show that C-C cleavage also favors primary and secondary- carbons, i.e. ²C-'C or ²C-²C compared to tertiary ³C-^XC, controlling hydrogenolysis reactivity as well as product selectivity.

Chemicals

[000124] Polyethylene (PE) was purchased from Sigma-Aldrich as powder, with Mw and Mn of -4000 g/mol and -1700, respectively. Activated carbon-supported Ru, Rh, Pd, Ir and Ni catalysts at 5 wt.% were purchased from Sigma-Aldrich. 2-Methylbutane, n-butane, n-hexane. n- butylcyclohexane, and ethyl acetate for solvent and external standard were also purchased from Sigma-Aldrich. These chemicals were used in the studies described herein.

Characterization

[000125] Elemental analysis: The metal contents in the catalysts were determined using a Perkin Elmer Optima 7300DV ICP-OES instrument equipped with a cyclonic spray chamber and a Meinhard nebulizer. Prior to analysis, the samples (50-60 mg) were digested with HNOs (3 ml)/HCl (2 ml)/HF (0.5 miyFhO (0.5 ml) in a sealed vessel at 210 °C for 30 min. After cooling to room temperature, 1.5 ml of saturated boric acid solution was added and then heated at 180 °C for 20 min.

[000126] X-ray diffraction (XRD): The diffractograms were collected using a Rigaku Mini Flex II bench top X-ray diffractometer operated at 30 kV and 15 mA using Cu-Ka radiation (0.154056 nm). Measurements were conducted on a rotating powder sample holder in the 20 range of 10-90 ° with 0.02 7s of step size.

[000127] Nitrogen physisorption: The porosity was measured by N2-physisorption at -196 °C using Micrometrics ASAP 2020. Prior to N2 adsorption, each sample was degassed at 300 °C for 5 h under vacuum (10^-3 mbar). The Brunauer-Emmett-Teller, Barrett-Joyner-Halenda and t-plot methods were employed to determine the specific surface area, mesopore volume and micropore volume, respectively.

[000128] Solid-state

and ¹³C magic-angle spinning (MAS) NMR: Solid-state MAS NMR measurements were carried out using a Varian Inova wide-bore 300 MHz NMR spectrometer equipped with a 7.5 mm commercial Vespel MAS NMR probe and a commercial heating stack for variable temperature experiments. The corresponding Larmor frequencies for 'H and ¹³C were 299.97 and 75.43 MHz, respectively. The samples were stored in a nitrogen-filled glovebox, in which a MAS NMR rotor with 300 pL volume was packed. For single pulse 'H and ¹³C MAS NMR experiments, the MAS frequency was 4 kHz, and 128-2000 spectrum were acquired at 20- 150 °C depending on ¹ H or ¹³C MAS NMR experiment with a 45 degree angle pulse, 2 ps of pulse width, and 20 s of recycle delay of 20 s. All the spectra were referenced to TMS (0 ppm) by using adamantane as a second reference (38.48 ppm for its downfield ¹³C peak and 1.82 ppm for the center band of ^XH).

[000129] Hydrogen chemisorption: H2 chemisorption was conducted with Micromeritics ASAP 2020, in chemisorption mode. The catalyst was outgassed under vacuum (10‘³ mbar) at room temperature, followed by reduction under H2 (50 mL/min) at 350 °C. The first adsorption isotherm was recorded at room temperature from 0. 1 mbar to 600 mbar at 50 °C. After evacuation at 50 °C under vacuum (10‘³ mbar) for 1 h, the second isotherm was measured. The chemisorbed H2 was then quantified by the difference between the first and second isotherms, which was then followed by extrapolated to zero H2 pressure. The stoichiometry factor between dissociated H2 and the active metal was assumed to be 1.0 (H/Ru).

Conditions for performing catalytic hydrogenolysis of PE of the study

[000130] Catalytic hydrogenolysis of PE was performed at 170-230 °C using a 100 ml Hastelloy PARR reactor. In a typical reaction, 40 ml of solvent, 1-3 g of PE, and 20-150 mg of catalyst were loaded into the autoclave reactor. The reactor was sealed, and air was removed bypressurizing with H2 and venting it at least five successive cycles. On the final cycle, the reactor was pressurized with H2 to the desired pressure at room temperature and then heated to reaction temperature (170-230 °C) under vigorous stirring at 700 rpm. After the reaction, the reactor was immediately quenched below 20 °C with an ice/water mixture. The gas products in the headspace were transferred directly to a 5 L gas sampling bag (Tedlar®) and analyzed by gas chromatography -thermal conductivity detection (GC-TCD) (Inficon Micro GC Fusion gas analyzer with a four-module chassis). When the pressure vessel was completely vented, it was disassembled and the remaining liquid and solids were transferred together via pipette to a preweighed 40 mL glass vial. The liquids were separated from the solids by filtration and analyzed by gas chromatography-flame ionization detection (GC-FID) (Agilent 7890A GC, DB-5 column, Agilent 7693 autosampler), where the liquid products were quantified with external standard of n- butylcyclohexane. To determine the mass of reacted LDPE, all remaining solids were collected, dried overnight at 80 °C, and weighed. The amount of catalyst was subtracted from the final weight.

Selection of solvent and reaction conditions for polyethylene conversion

[000131] The physicochemical and thermodynamic properties of the hydrocarbon solvent critically impact PE hydrogenolysis. With hydrocarbons being formed during hydrogenolysis, several lighter hydrocarbons were investigated as potential solvents, i.e., n-pentane (n-Cs), isopentane (i-Cs), and n-hexane (n-Ce). The reaction temperature of 210 °C was chosen because it is above the critical temperature of the pure solvents n-Cs (196 ± 1 °C) and i-Cs (191 ± 5 °C). The inventors surmised that PE is effectively solvated under these conditions facilitating PE mobility and interaction with the Ru surface. They noted that the phase envelope predicted by the Soave- Redlich-Kwong equation of state estimated the critical temperature to decrease by 1 °C, i.e., 195 and 190 °C for n-Cs and i-Cs, respectively, when mixed with n-hexadecane (Figure 3), which was regarded as a model compound of long-chain hydrocarbon. The rates of PE conversion in n-Cs and i-Cs were similar, i.e., (18% and 20% conversion after 2 hours at 210 °C), while the rate was 6- fold lower with n-hexane (3% of PE conversion, Figure 4a). PE conversion increased with the reaction time and reacted to 21% at the critical temperature of n-hexane and n-hexadecane mixture of 245 °C (Figure 5). This suggests that the PE conversion rate is enhanced in the supercritical phase, likely due to effective solvation, increased diffusivity and enhanced mass transport at the reactive surface of the catalyst.

[000132] To better understand the reactivity of the potential solvents, the reactivity of Ru/C- catalyzed hydrogenolysis of n-Cs and i-Cs. n-Cs and i-Cs conversions after respective 4 h and 60 h of reaction time at 210 °C reached ca. 18% was studied, which implied normalized solvent consumption rates of 2.4 and 0.15 molsoivent/molRu/s. The observation that the hydrogenolysis rate of n-Cs is an order of magnitude higher than that of i-Cs aligns well with the understanding that the hydrogenolysis rate decreases with an increasing number of substituted carbon atoms in the C- C bond. The inventors mostly attribute this to increased activation enthalpies and entropies of ³C- ^XC bonds compared to ²C-²C or ²C-'C bond cleavage. The ease of C-C cleavage also influences product selectivity from the solvent hydrogenolysis. Ru/C catalyzed n-Cs hydrogenolysis to linear Ci-4 hydrocarbon (Figure 4c). The equivalent molar selectivity' of Ci (30 %) and Cr (29 %), as well as C2 (21%) and C3 (20%), at 5-10 % of n-Cs conversion, describes primary terminal (²C-’C) and central (²C-²C) C-C cleavages, respectively. The comparable central and terminal C-C cleavage indicates a stochastic C-C cleavage on the Ru surface. With increased n-Cs conversion, the inventors observed that the Ci and C4 formation increased to 33% and 31%, but C2 (21%) and C3 (15%) decreased. This indicated secondary terminal C-C cleavage of C2-4, which enhanced Ci formation. On the other hand, for i-Cs. predominant selectivity to Ci and i-C4 was observed (Figure 4d). This can be linked to the significantly lower reactivity of ³C-^XC bonds than C²-^ in the 1-C5 molecule. These findings suggested that the C-C cleavage reactivity on Ru/C follows the order ²C-^lC > ²C-²C » ³C-¹C or ³C-²C. It should be highlighted, however, that the Ru/C -catalyzed hydrogenolysis of n-Cs and i-Cs becomes negligible in the presence of PE or n-hexadecane. This was most likely attributed to the stronger adsorption of longer chain hydrocarbons on the Ru surface.

General Conversion path for PE hydrogenolysis

[000133] To obtain better insight into PE hydrogenolysis on Ru/C, we further examined the kinetics and product distributions at varying PE conversions. The PE conversion was manipulated by varying the reaction time and the amount of catalyst. PE conversion linearly increased with reaction time at 170-230 °C (Figure 6a and Figure 7). The constant PE consumption rate regardless of the extent of PE hydrogenolysis features zero-order kinetics, which further suggested that the Ru surface was saturated by strongly adsorbed PE molecules. Statistical mechanics and transition state theory for hydrocarbon hydrogenolysis indicated that the rate constants increase with the length of alkanes due to Van der Waals interactions with metal surfaces as well as a substantial increase of activation entropy. This supported the finding of selective PE hydrogenolysis even in the presence of the solvent as a result of the strong adhesion of PE to Ru surface. This finding was in line with the preferred adsorption of polymers over small alkanes during hydrocracking and hydrogenolysis.

[000134] The carbon fractions of gas (C1-4) and liquid (C6-40) products along with PE conversion are shown in Figures 6b and 8. In these representations the Cs carbon fraction was not included, as a Cs solvent was used. The liquid products were sorted by the carbon numbers of Ce-io, C11-20. and C21-40, representing gasoline, diesel, and lubricant-ranged hydrocarbons. Upon PE hydrogenolysis, the inventors observed the predominant selectivity to longer-chain hydrocarbons C21-40 (~ 50-55% at up to 45% of PE conversion). However. C21-40 selectivity decreased with increasing PE conversion to 90%. while a considerable increase in Ce-io (50%) and C 11-20 (24%) occurred. The product distribution changes along with PE conversion indicate Ru/C catalyzes PE hydrogenolysis by C-C cleavage leading to C 11-20 and C21-40 product formation, which prevents the re-adsorption of products upon primary' C-C cleavage. Higher carbon selectivity' for liquid alkanes over methane was attributed to the multiple contact points within the polymer chain for C-C cleavage, resulting in the production of liquid products.

[000135] The primary products subsequently undergo secondary C-C cleavage to Ce-io with the increase of PE conversion, i.e., the extent of PE hydrogenolysis. Moreover, shorter chain hydrocarbon formation through subsequent primary and secondary C-C cleavage of PE can be explained by the adsorption preference of longer chain hydrocarbon on Ru surface, whereas the adsorption of solvent on the surface can be restricted. However, excessive reaction times of >20 h (Figure 8c), after complete PE conversion, showed a significant increase in production of gaseous products together with a carbon yield above 100% relative to the initial amount of PE. This was attributed to the conversion of the solvent, which contributes to product pool during the secondary C-C cleavage.

[000136] Therefore, a simplified reaction network can be derived from the observations described above (Figure 8c). Central and terminal C-C cleavage are primary routes. These two routes dominate the reaction below 50% PE conversion. Those products undergo secondary C-C cleavage with the saturation of the primary longer chain hydrocarbon products, yielding methane and smaller liquid products. As the extent of the reaction results in the depletion of PE and the primary products, the secondary' products and solvent can undergo further C-C cleavage and turn into small molecules, such as methane.

[000137] In the next step it was explored, how reaction parameters affect PE consumption rate and product distribution under a kinetic regime below 20% of PE conversion observing only primary PE hydrogenolysis. In a series of experiments at varying temperatures and initial amounts of PE (Figure 9a), saturation kinetics were observed at 170-230 °C, i.e., the PE consumption rates plateau regardless of the amount of initial PE. This finding was in line with the observation of the linear correlation between the amount PE converted and reaction time, indicative of zero-order kinetics for PE hydrogenolysis. Interestingly, the saturation kinetics remained even under supercritical conditions above 210 °C, while the activation decreased from 127 kJ/mol to 80 kJ/mol (Figure 9b). Thus, the inventors hypothesize that supercritical condition allows to enhance the mobility' of PE to the active surface sites, whereas intermolecular interaction, i.e., solvation in the supercritical condition, reduces the activation energy.

[000138] The variations of the product yields with temperature, and the corresponding Arrhenius-type plots, are exhibited in Figure 10a and 10b. The mol-based product formation rates normalized to accessible Ru sites increase with increasing reaction temperature, which allows to determine the apparent activation energies. Identical activation energy changes for the formation of gas and liquid alkanes from 127 ± 9 kJ/mol to 88 ± 10 kJ/mol were observed above 210 °C, which shows good agreement with the activation energy changes in PE consumption rate. This indicates that selectivity is not affected by temperature. This finding is in line with the indistinguishable product distribution at ca. 20% PE conversion regardless of reaction temperature (Figure 11).

Mechanism of PE and alkane hydrogenolysis

[000139] Additional studies were conducted using a defined linear model compound with limited carbon chain length, i.e., n-hexadecane and squalane, to study the recti on mechanism in detail. Ru/C -catalyzed hexadecane hydrogenolysis from its reaction characteristics closely resembled PE hydrogenolysis. The linear correlation between hexadecane conversion with reaction time indicated zero-order kinetic for hydrogenolysis, attributed to strong hexadecane adsorption on Ru (Figure 12a). Hexadecane hydrogenolysis exclusively yielded C1-15 linear alkanes through stochastic central and internal C-C cleavage. At hexadecane conversion below 20%, the equivalent carbon fraction of Ce-is liquid products (Figure 12c and 12d) was observed, but it was higher than the fraction of Ci-4 gas products (Figure 12b). The uniformly distributed carbon fraction in liquid products implies a stochastic central and internal C-C cleavage during hexadecane hydrogenolysis. On the other hand, with the increase of hexadecane conversion, we observed a continuous shift of the product distribution toward shorter-chain hydrocarbon due to subsequent decreasing carbon yield of longer-chain alkane as following the order of Cis, Ci4, and Ci3. Moreover, the carbon yields C13-15 decreased after maximum carbon yield at 80% hexadecane conversion. Those findings could be understood as resulting from secondary C-C cleavage and C- C cleavage preference of longer-chain alkanes even in the secondary C-C cleavage.

[000140] Investigating the hydrogenolysis of squalane (2,6,10,15.19,23- hexamethyltetracosane) as example of branched alkanes hydrogenolysis, its consumption rate was found to be 0.15 mol/molRu/min below 20% conversion, which was an order of magnitude lower than that of hexadecane hydrogenolysis (2.7 mol/molRu/min). In analogy to the hydrogenolysis of n-Cs and i-Cs, the lower reactivity was attributed to the significantly lower hy drogenolysis rate of branched ³C-²C or ³C-'C bonds compared to ²C-²C or ²C-^XC bonds. When considering the primary C-C cleavage, the distribution of C10 products from squalane hydrogenolysis further demonstrated the C-C cleavage preference, which showed selectively dimetyloctane (Figure 13). Dimethyloctane was produced solely by ²C-²C cleavage, whereas the combination of ³C-²C and ²C-²C cleavages or the ³C-¹C cleavage was required to produce methylnonane. Negligible concentrations of n-decane, which required secondary ³C-¹C cleavage to form, and subsequent methane formation also reflected the preference of ²C-²C cleavage over ³C-²C or ³C-¹C cleavage. [000141] In the next step, the kinetic H/D isotope effects (KIEs) were investigated to probe the C-H cleavage and re-hydrogenation after C-C cleavage products during hydrogenolysis (Figure 14a). The difference in the normalized consumption rate of n-hexadecane, (C16H34), under H2 and D2 was 2.7 and 2.6 mol/molRu/min, respectively, i.e., no KIE between H2 and D2 (kn/kn ~ 1.1). This was attributed to facile hydrogen addition by surface H and D from H2 and D2 after C-H and C-C cleavage on Ru surface, as depicted in Figure 14b. Notably, the hydrogenolysis rate of deuterated hexadecane (C16D34) in H2 was 5-fold reduced kci6H34/kci6D34 ~ 5) compared to n- C16H34 hydrogenolysis in H2. This strongly suggests that for hydrogenolysis, the cleavage of C- H/C-D, but not the (re)hydrogenation, is rate determining.

[000142] Analyzing the mass spectra of unreacted hexadecane and products after hydrogenolysis provided an estimate of the degree of hydrogenation and dehydrogenation via the H-D exchange. For the parent C16H34 and C16D34 molecules, the primary mass fragments (before the hydrogenolysis) corresponded to the molecular weights of 226 and 260 g/mol, respectively, with the naturally abundant amount of ¹³C in the molecules (Figure 14c). The hexadecane conversion in D2 (C16H34-D2) at 0.1 h reaction time was less than 1% with no detectable gas and liquid products indicating minimal C-C cleavage through hydrogenolysis. The mass spectra of hexadecane showed a broad m/z distribution of 228-240 with the maximum abundance at 230 m/z (Figure 14d), i.e., 2-14 H-D exchanges per hexadecane molecule. This indicated that adsorption, desorption, and the reactions of dehydrogenation and hydrogenation can be regarded as quasiequilibrated. This finding was then used to quantify the H-D exchange rate of hexadecane with the deuteration rate as 3.2x10² mmoln^/mo s. On the other hand, for the counterpart C16D34 in H2, a comparable hexadecane conversion was observed at 0.6 h, where 23-33 D were exchanged with an 8-fold lower H-D exchange (40 mmolu-D/molRu/s). Taking into account the substantial hydrogenation rate, C-D cleavage in the dehydrogenation of C16D34 was concluded to limit the hydrogenolysis rate, probably because of the higher C-D dissociation energy of 341 kJ/mol in comparison to the C-H bond dissociation energy of 338 kJ/mol. Interestingly, with the extent of hexadecane conversion, the fraction of deuterium per hexadecane molecule for both C16H34 in D2 and C16D34 in H2 was continuously reduced (Figure 14d), while the m/z=72 of i-Cs solvent increased (Figure 15). This finding suggests the deuterium of hexadecane can be substituted by H from the solvent during hydrogenolysis. This is in agreement with H-D exchange observed between deuterated polymer and hydrogen-containing solvents. Considering the negligible conversion of i-Cs during hexadecane hydrogenolysis, it can be concluded that the solvent in the presence of hexadecane (or other longer-chain alkanes) can only undergo C-H cleavage and H-D exchange by dehydrogenation and (re)hydrogenation, but will experience minimal or no C-C cleavage.

[000143] The partial pressure of hydrogen significantly impacted the alkane hydrogenolysis rates. Figure 16 shows PE conversion and methane selectivity as functions of hydrogen pressure. PE conversion was negligible in the absence of hydrogen (Figure 6a) and greatly increased as the hydrogen pressure increased from 2.5 bar to 30 bar. However, the conversion decreased as hydrogen pressure exceeded 30 bar. The decrease in PE conversion is attributed to excess hydrogen coverage of the surface, in consequence hydrogen covered sites compete for adsorption sites with PE. This finding is also in good agreement with the negative reaction order of hydrogen for transition metal-catalyzed alkane hydrogenolysis due to competitive adsorption between hydrogen and alkanes.

[000144] The partial pressure of hydrogen significantly impacted the alkane hydrogenolysis rates. Figure 16 shows PE conversion and methane selectivity as functions of hydrogen pressure. PE conversion was negligible in the absence of hydrogen (Figure 6a) and greatly increased as the hydrogen pressure increased from 2.5 bar to 30 bar. However, the conversion decreased as hydrogen pressure exceeded 30 bar. The decrease in PE conversion is attributed to excess hydrogen coverage of the surface, in consequence hydrogen covered sites compete for adsorption sites with PE. This finding is also in good agreement with the negative reaction order of hydrogen for transition metal-catalyzed alkane hydrogenolysis due to competitive adsorption between hydrogen and alkanes.

[000145] From a mechanistic point of view, hydrogenolysis proceeds through the following elementary reactions: (i) stepwise (full) dehydrogenation forming a strong C-metal bond on the surface, (ii) C-C bond cleavage, and (iii) (re)hydrogenation followed by desorption. To bind dissociated hydrogen upon C-H bond cleavage, free adjacent metal sites are beneficial (the surface bound hydrogen is likely mobile on the surface). In absence of H2, the dehydrogenation of the adsorbed alkane led to the formation of unreactive surface intermediates and desorption of H2. Thus, initially the presence of H2 increases the reaction rate by facilitating the (re)hydrogenation of the reacted partners of the first two elementary reaction sequences. Increasing H2 pressure, however, led to the increase of H* coverage on the surface, and ultimately lowers the PE conversion. Interestingly, methane selectivity was substantially reduced with increasing hydrogen pressure, reflecting the low requirement of available binding sites for ²C-²C cleavage.

[000146] It is worth noting that methane selectivity is relatively invariable along the PE conversion degree (Figure 16b). At the comparable PE conversion of 45% the methane formation rate was reduced by 4-fold from 0.53 molcm/molRu/min to 0.13 molcm/molRu/min as the hydrogen pressure increased from 15 bar to 56 bar. By considering *CH-CH* intermediate for hydrogenolysis, terminal ¹C-²C cleavage results in a 1.5-fold higher amount of dissociated hydrogen formation compared to central ²C-²C bond cleavage. Those findings, indicated that higher hydrogen pressure leads to preferential hydrogenolysis of central C-C bonds, consequently minimizing the terminal C-C bond cleavage.

[000147] Exploring the methane formation further using linear and branched model compounds. Figure 16b compares methane formation rate during hydrogenolysis of PE, n- hexadecane (n-CieH?^). octacosane (n-C28Hs6), and squalane as a function of primary carbon fraction. The fraction of primary' l'C). secondary (²C) and tertiary (³C) carbon atoms in PE was determined by solid-state NMR as shown in Figure 17. The methane formation rate at comparable conversion (~ 20%) showed a linear correlation with the pnmary carbon fraction, i.e., the concentration of terminal carbon in the reacting substrate. Even though higher fraction of primary carbon was present in squalane (0.27) among the compounds studied, the methane formation rate of 0.91 molcH4/molRu/min was lower than in the hydrogenolysis of linear hydrocarbons, hexadecane (1.64 molcm/molRu/min) and octacosane (1.28 molcm/molRu/min). This reflects well the previously noted lower reactivity of ¹C-³C bonds that dominate in squalane.

Conclusion

[000148] The studies presented herein support that there is a path to deconstruct polyolefins via hydrogenolysis under supercritical conditions, while minimizing methane formation. Ru- catalyzed hydrogenolysis of polyethylene and alkanes, such as hexadecane and squalane, in the presence of isopentane as a solvent occurs with satisfying rates above 150°C. The supercritical condition of the solvents at 190-210 °C leads to enhanced polyethylene mobility to the active sites, while reducing the apparent activation energy' of polymer conversion. Alkanes of intermediate chain length were used as model compounds and showed that C-C bond cleabage occurs stochastically, where the cleavage of C-C bonds between primary and secondary' carbon atoms occurs preferentially to the cleavage of C-C bonds involving tertiary carbon atoms. Therefore, a lightly branched hydrocarbon (isobutane is predicted to be ideal) as a solvent allows for the selective C-C cleavage of polyethylene and hexadecane, minimizing solvent conversion. H-D exchange and the kinetic isotope effect upon hydrogenolysis of deuterated hexadecane in H2 and n-hexadecane in D2 show that the reaction was started by extensive C-H cleavage (local dehydrogenation), followed by the C-C cleavage, and hydrogenation of the surface fraction. C-C cleavage can primarily be the kinetically rate determining step, while C-D cleavage further reduced the rate. Furthermore, increasing H2 chemical potential (realized through higher partial pressure) and diluting the longer-chain hydrocarbon will reduce methane formation, as hydrogenolysis at terminal C-C bonds requires a larger available surface spot to break the C-C bond. The findings offer a mechanistic understanding of stochastic C-C cleavage in polyolefin hydrogenolysis particularly under supercritical conditions, allowing to significantly reduce methane production and advancing the development of new technologies for converting plastic waste to recyclates.

Claims

What is claimed is:

1. A method for converting a polymer and/or pyrolysis oil, into a light hydrocarbon chain product, wherein the method comprises: supplying a feed of polymer and light hydrocarbon solvent to a mixer, wherein the light hydrocarbon solvent comprises a linear or branched C? to Cio, or a mixture thereof; applying hydrogen gas in the mixer; feeding the polymer, the light hydrocarbon solvent, and the hydrogen mixture into a reactor to form an effluent, and directing the effluent from the reactor to a first separator.

2. The method of claim 1, wherein the reactor comprises a fixed bed reactor, a semi -batch reactor, a slurry reactor, or a mixed bed reactor.

3. The method of claim 1, wherein the reactor comprises a metal containing catalyst.

4. The method of claim 1 , wherein the reactor comprises a heterogeneous catalyst suitable for the hydrogenolysis (mono-, bi- or multi-metallic).

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

6. The method according to any one of claims 1-5, wherein the converting occurs at supercritical fluid conditions.

7. The method according to any one of claims 1-6. wherein the feed comprises a polyolefin, oligomer, or a combination thereof, and/or pyrolysis oil.

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

9. The method according to 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 according to 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 concentration of about 4 g/L to about 80 g/L of polymer.

12. The method according to claim 1, wherein the feed comprises pyrolysis oil.

13. The method according to any one of claims 1-1 1, wherein the reactor is held at a temperature of about 150 °C to 400 °C.

14. The method according to any one of claims 1-11, wherein the process operates at a temperature between about 190 °C and about 230 °C.

15. The method according to any one of claims 1 -14, wherein hydrogenolysis is performed on the feed of polymer and light hydrocarbon solvent.

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

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

18. The method according to claim 17, further comprising recycling any remaining liquid hydrocarbon solvent to the mixer.

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

20. The method according to claim 19. wherein after feeding the light hydrocarbon vapor and the liquid hydrocarbon product to the second separator, the light hydrocarbon vapor is recycled to the mixer.

21. The method according to claim 19 or 20, wherein after feeding to the second separator, a light hydrocarbon product is collected.

22. A system for converting a polymer into a light hydrocarbon chain product comprising: a feed comprising a polymer, pyrolysis oil. or a combination thereof, a mixer configured to receive the 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.

23. The system of claim 22, wherein the feed comprises 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 contacted with hydrogen gas to form the first effluent.

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

26. The system of any one of claims 22-25, wherein the first effluent is separated into a liquid hydrocarbon product.

27. The system according to 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 according to any one of claims 22-27, wherein the reactor comprises a slurry of a supported catalyst.

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

30. The system of claim 29, wherein the catalyst comprises a metal containing catalyst, a heterogenous catalyst comprising a platinum group metal, a heterogenous catalyst comprising a transition metal, or a combination thereof.

31. The system of claim 29, wherein the support comprises AIO2, silica-alumina, titania, SiCh, ZrO2, carbon or a combination thereof.

32. The system according to claim 22, wherein the second separator is configured to remove a light hydrocarbon vapor and recycle the light hydrocarbon vapor into the mixer.

33. The system according to claim 22, wherein the second separator is configured to remove a liquid hydrocarbon product from the second effluent.

34. The system according to claim 22, wherein the reactor is held at constant temperature and pressure.

35. The system according to claim 22, wherein the feed comprises a polyolefin.

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

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

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

40. The system according to claim 22, wherein the reactor is held at a temperature of about 150 °C to 400 °C.

41. The system according to claim 22. wherein the reactor is held at a pressure of about 20 to about 100 bar.

42. The system according to claim 22, wherein the feed comprises pyrolysis oil.