Methods of depolymerization of single- and multi-layer plastics

Abstract

The disclosure relates to a method for depolymerizing a polyolefin or other polymer. A mixture including a polymer such as a polyolefin and a metal catalyst is heated to a temperature above a melting temperature of the polymer, thereby partially or completely depolymerizing the polymer. The metal catalyst can include a metal salt alone or in combination with a metal oxide, an elemental metal, and / or a metal alloy. Depolymerization of the polymer can form one or more of a corresponding gas hydrocarbon product, a liquid hydrocarbon product, and a solid or waxy hydrocarbon product. Reaction parameters, such as heating time, heating temperature, catalyst concentration, etc. can be selected or otherwise controlled for a given polymer feed to adjust the distribution between gas, liquid, and solid hydrocarbon products, for example providing a reaction product that primarily contains a gas, liquid, or solid hydrocarbon product.

Description

METHODS OF DEPOLYMERIZATION OF SINGLE- AND MULTI-LAYER PLASTICS CROSS REFERENCE TO RELATED APPLICATION

[0001] Priority is claimed to U.S. Provisional Application No. 63 / 469,618 filed on May 30, 2023 and U.S. Provisional Application No. 63 / 536,789 filed on September 6, 2023, each of which is incorporated herein by reference in its entirety.STATEMENT OF GOVERNMENT INTEREST

[0002] None.BACKGROUND OF THE DISCLOSUREField of the Disclosure

[0003] The disclosure relates to a method for depolymerizing a polyolefin or other polymer. A mixture including a polymer such as a polyolefin and a metal catalyst such as a metal salt is heated to a temperature above a melting temperature of the polymer, thereby partially or completely depolymerizing the polymer. Depolymerization of the polymer can form one or more of a corresponding gas hydrocarbon product, a liquid hydrocarbon product, and a solid or waxy hydrocarbon product.Brief Description of Related Technology

[0004] Plastics have become an indispensable part of modern life, but their poor disposal management has created an environmental crisis. The packaging industry consumes nearly 34% of all plastics due to their excellent properties. Plastics upon leakage into environment break down into persistent microplastics (plastic particles with diameters < 5 mm). Incineration for energy and landfilling are widely used to handle plastic waste. For example, globally, in 2019, 19% of plastic waste was incinerated and 50% was sent to sanitary landfills. However, neither of these approaches are sustainable. For example, both incineration and landfilling are open loop practices, as carbon does not stay in the loop. Incineration leads to air pollution and landfilling, in the long run, leads to water contamination. The EU’s latest legislation calls for a circular plastic economy, which essentially demands mechanical and chemical recycling of plastics. Mechanical recycling and chemical recycling are complementary approaches. Although mechanical recycling is an economical approach, this approach has its shortcomings when it comes to handling contaminated plastics, mixed plastics, metallized plastics, films, and so forth. The compatibilization approach can be used for mixed clean plastics, but it is only applicable to high quality clean plastic waste, is costly, and is ineffective for inhomogeneous post-consumer plastics streams. Also, even mechanically recycled plastics must eventually undergo chemical recycling after one or more cycles of use.

[0005] Chemical and molecular recycling approaches enable plastics to be part of the circular economy as it can cope with contaminated as well as mixed plastics waste. In addition, solvent-based separation (molecular recycling) is being developed but it has its own limitations such as the need for costly and time-consuming purification processes to remove organic solvent impurities. The chemical recycling approaches include depolymerization into monomers, oil and gas, and chemicals.

[0006] The chemical recycling of plastics into their monomers, gas, and oil offers solutions for contaminated, mixed, and metalized plastics. However, more than 60% of plastic waste is comprised of polymers with carbon-carbon backbones such as high-density polyethylene (HDPE), low-density PE (LDPE), linear low-density PE (LLDPE), and polypropylene (PP).11 The chemical recycling of these materials demands high temperatures as well as large amounts of prohibitively expensive and harmful catalysts. Extensive research has been conducted on the pyrolysis of a single type of polyolefin-based plastic waste and commodity polymers. However, the recycling of mixed waste plastic waste comprised of metalized films and mixed plastics has received only scant attention. For example, PP / LDPE / HDPE mixtures were subjected to pyrolysis with the help of a Ziegler-Natta catalyst to promote the thermal catalytic cracking of a mixture of polyolefins at different temperatures resulting in a ratio of gas :liqu id :solid weight fractions of 6.5:89.0:4.5 at 500°C. However, such catalysts are expensive, require high temperatures, and are prone to thermal degradation. Also, such methods have not been tested for metallized plastics.

[0007] Waxes have numerous applications such as paper and cardboard coatings, rheology modifiers, feedstocks for surfactants, cosmetics, additives for asphalt, candles, food, pharmaceuticals, lubricants, rubber production, and so forth. Polyethylene waxes are important hydrocarbons with many recognized properties, including high thermal stability, dispersibility, and fluidity as well as low cost. Waxes increase the workability of rubber and polymer-modified asphalt, and improve moisture and crack resistance of asphalt. Waxes are widely used in paper coating and cardboard applications. Although wax is a value-added product, it has rarely been a focus for pyrolysis processes as it is difficult to obtain wax in high yield. For example, about 30 wt% wax is obtained from the pyrolysis of HDPE at 645°C using a conventional pyrolysis reactor.SUMMARY

[0008] In an aspect, the disclosure relates to a method for depolymerizing a polyolefin, the method comprising: heating a mixture comprising (i) at least one polyolefin and (ii) a metal catalyst comprising a metal salt to a temperature above a melting temperature of the at least one polyolefin, thereby at least partially depolymerizing the at least one polyolefin and forming at least one of a corresponding gas hydrocarbon product, a liquid hydrocarbon product, and a solid hydrocarbon product.

[0009] In another aspect, the disclosure relates to a method for depolymerizing a polymer, the method comprising: heating a mixture comprising (i) at least one polymer and (ii) a metal catalyst having (A) a heat capacity in a range of 0.4 to 100 J / (g*K) and (B) a thermal conductivity in a range of 0.2 to 60 W / (m»K) to a temperature above a melting temperature of the polymer, thereby at least partially depolymerizing the polymer and forming at least one of a corresponding gas hydrocarbon product, a liquid hydrocarbon product, and a solid hydrocarbon product. In embodiments, the heat capacity can be in a range of 10 to 100 J / (g*K); and / or the thermal conductivity can be in a range of 2 to 60 W / (m»K). In embodiments, the metal catalyst can comprise a first metal catalyst and a second metal catalyst; the first metal catalyst can have a first heat capacity in a range of 30 to 100 J / (g*K) and a first thermal conductivity in a range of 0.2 to 60 W / (m»K); and / or the second metal catalyst can have a second heat capacity in a range of 0.4 to 100 J / (g*K) and a second thermal conductivity in a range of 10 to 60 W / (m»K).

[0010] Various refinements of the disclosed methods are possible.

[0011] In a refinement, the method comprises depolymerizing the at least one polyolefin by heating the mixture to a temperature in a range of 350°C to 500°C or 415°C to 460°C.

[0012] In a refinement, the method comprises depolymerizing the at least one polyolefin by heating the mixture to: (i) a temperature at least 10°C above a melting temperature of the at least one polyolefin; and / or (ii) a temperature at least 50°C below a decomposition temperature of the at least one polyolefin, wherein heating to the decomposition temperature would result in one or more of combustion, burning, and charring of the at least one polyolefin.

[0013] In a refinement, the method comprises depolymerizing the at least one polyolefin by heating the mixture for a time in a range of 0.5 hr to 20 hr or 1 .5 hr to 5 hr (e.g., reaction / heating time in a batch reactor, (mean) residence time in a continuous reactor).

[0014] In a refinement, the method comprises heating the mixture in a batch process.

[0015] In a refinement, the method comprises heating the mixture in a continuous process.

[0016] In a refinement, the method comprises heating the mixture in an inert atmosphere.

[0017] In a refinement, the method comprises heating the heating the mixture in the presence of oxygen.

[0018] In a refinement, the at least one polyolefin is present in the mixture in an amount of 70 wt.% to 99 wt.%.

[0019] In a refinement, a combined amount of the at least one polyolefin and the metal catalyst in the mixture is in a range of 70 wt.% to 100 wt.%.

[0020] In a refinement, the mixture further comprises one or more additives or impurities in a (combined) amount up to 30 wt.%.

[0021] In a refinement, the mixture further comprises one or more free radical inhibitors or suppressors in a (combined) amount up to 5 wt.% (e.g., at least 0.01 , 0.1 , 1 , or 2 wt.% and / or up to 0.5, 1 , 2, 3, 4, or 5 wt.%).

[0022] In a refinement, the at least one polyolefin comprises high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP). In a further refinement, the HDPE is present in the mixture in an amount of 1 wt.% to 95 wt.% or 25 wt.% to 45 wt.% relative to total polyolefins in the mixture; the LDPE is present in the mixture in an amount of 1 wt.% to 95 wt.% or 10 wt.% to 25 wt.% relative to total polyolefins in the mixture; the LLDPE is present in the mixture in an amount of 1 wt.% to 95 wt.% or 10 wt.% to 25 wt.% relative to total polyolefins in the mixture; and / or the PP is present in the mixture in an amount of 1 wt.% to 95 wt.% or 20 wt.% to 35 wt.% relative to total polyolefins in the mixture. The weight ranges also can be relative to the mixture as a whole and / or total polymer content of the mixture.

[0023] In a refinement, the mixture further comprises one or more oxygenated polymers selected from the groups consisting of polyesters, co-polyesters, polyvinyl alcohol, polyethylene vinyl alcohol, polyvinyl acetate, and combinations thereof.

[0024] In a refinement, the mixture comprises at least one metallized polymer (e.g., metallized film such as a metallized polyolefin film or other polymer film). The metallized polymer can include one or more metals (e.g., aluminum alone or in combination with other metals) in an amount of at least 1 -10 wt.% or 3-7 wt.%, for example at least 1 , 2, 3, 4 or 5 wt.% and / or 5, 6, 7, 8, 9, or 10 wt.% relative to the polymer.

[0025] In a refinement, the mixture is free from vinyl polymers comprising one or more vinyl monomer units comprising at least one of a pendant aromatic group and a pendant ester group (e.g., polystyrene). In an alternative refinement, the mixture can include one or more such polymers as impurities, for example polystyrene and / or polyethylene terephthalate.

[0026] In a refinement, the metal catalyst is present in the mixture in an amount of 2 wt.% to 20 wt.% (e.g., relative to mixture as a whole or relative to total polyolefin / total polymer).

[0027] In a refinement, the metal catalyst comprises sodium chloride.

[0028] In a refinement, the metal catalyst comprises an alkali metal halide salt catalyst comprising: at least one of a lithium cation, a sodium cation, and a potassium cation; and at least one of a fluoride anion, chloride anion, bromide anion, and iodide anion.

[0029] In a refinement, the metal catalyst comprises an alkaline earth metal halide salt catalyst comprising: at least one of a beryllium cation, a magnesium cation, a calcium cation, and a barium cation; and at least one of a fluoride anion, chloride anion, bromide anion, and iodide anion.

[0030] In a refinement, the metal catalyst further comprises one or more of a metal oxide, an elemental metal, a metal alloy, and combinations thereof.

[0031] In a refinement, the metal catalyst further comprises a metal oxide (e.g., alumina; alkali metal oxides; alkaline earth metal oxides).

[0032] In a refinement, the metal catalyst has a particle size in a range of 10 nm to 2 mm (e.g., 1 pm to 500 pm, and 10 pm to 100 pm).

[0033] In a refinement, the metal catalyst is in solid form in the mixture at the temperature to which the mixture is heated (e.g., catalyst also in solid form as initially added to the mixture; no melting or formation of a liquid catalyst medium at depolymerization heating temperature).

[0034] In a refinement, the mixture is substantially free from Ziegler-Natta and platinum- containing catalysts (e.g., or other precious metal-containing (or transition metal-containing) catalysts).

[0035] In a refinement, the mixture contains not more than 0.1 wt.% of transition metal catalysts (or not more than 0.1 wt.% of transition metals).

[0036] In a refinement, the mixture contains not more than 0.1 wt.% of metal catalysts other than alkali metal-containing catalysts and alkaline earth metal-containing catalysts (or not more than 0.1 wt.% of metals other than alkali and alkaline earth metals).

[0037] In a refinement, the method comprises depolymerizing the at least one polyolefin with a conversion of at least 70 wt.% (e.g., can apply to conversion of individual polyolefins in the mixture and / or all polyolefins in the mixture combined; also can apply to other nonpolyolefin polymers in the mixture).

[0038] In a refinement, the method comprises depolymerizing the at least one polyolefin with a yield of at least 70 wt.% for the gas hydrocarbon product, the liquid hydrocarbon product, or the solid hydrocarbon product (e.g., also can apply to other non-polyolefin polymers in the mixture for overall product yield).

[0039] In a refinement, depolymerizing the at least one polyolefin comprises forming the gas hydrocarbon product.

[0040] In a further refinement, the gas hydrocarbon product is formed in an amount of at least 40 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed (e.g., more generally any amount from 1-100 wt.% relative to total hydrocarbon product).

[0041] In a further refinement, the gas hydrocarbon product comprises hydrocarbons having 1 to 4 carbon atoms (e.g., linear or branched, saturated or unsaturated, unsubstituted (only C and H atoms) or substituted / oxygenated (C, H, and O or other substituting atoms; generally a gas at ambient temperature, but oxygenates can be liquids at ambient temperature).

[0042] In a further refinement, the gas hydrocarbon product comprises hydrocarbons having a molecular weight in a range of 16-60 g / mol.

[0043] In a refinement, depolymerizing the at least one polyolefin comprises forming the liquid hydrocarbon product.

[0044] In a further refinement, the liquid hydrocarbon product is formed in an amount of at least 80 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed (e.g., more generally any amount from 1-100 wt.% relative to total hydrocarbon product).

[0045] In a further refinement, the liquid hydrocarbon product comprises hydrocarbons having 5 to 30 (or 5 to 25) carbon atoms.

[0046] In a further refinement, the liquid hydrocarbon product comprises hydrocarbons having a molecular weight in a range of 60-500 g / mol.

[0047] In a further refinement, the liquid hydrocarbon product contains 5-100 wt.% saturated hydrocarbons (e.g., alkanes) and 0-95 wt.% unsaturated hydrocarbons (e.g., alkanes alone or in combinations with one or more terminal or internal alkenes with one, two, three, or more C=C double bonds).

[0048] In a further refinement, the liquid hydrocarbon product comprises saturated hydrocarbons and unsaturated hydrocarbons; and a ratio of saturated hydrocarbons:unsaturated hydrocarbons is in a range of 100:1 to 1 :100 (or 10:1 to 1 :10) (e.g., weight basis or molar basis).

[0049] In a refinement, depolymerizing the at least one polyolefin comprises forming the solid hydrocarbon product. As used herein, a solid hydrocarbon product is generally free from char, ash, etc. that would result from combustion, burning, etc. of the polyolefin.

[0050] In a further refinement, the solid hydrocarbon product is formed in an amount of at least 90 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed (e.g., more generally any amount from 1-100 wt.% relative to total hydrocarbon product).

[0051] In a further refinement, the solid hydrocarbon product comprises hydrocarbons having 24 to 200 carbon atoms.

[0052] In a further refinement, the solid hydrocarbon product has at least one of the following properties: a number-average molecular weight (Mn) in a range of 400-2000 (or 400-1500) g / mol; a weight-average molecular weight (Mw) in a range of 600-10000 (or 600- 3000) g / mol; and / or a polydispersity index (Mw / Mn) in a range of 1-5.

[0053] In a further refinement, the solid hydrocarbon product has at least one of the following properties: a melting temperature (Tm) a range of 25-130°C (or 80-120°C or 80- 150°C); a crystallization temperature (Tc) a range of 80-120°C (or 60-140°C); a temperature difference (Tm-Tc) a range of 1-50°C (or 5-20°C); and / or a decomposition temperature (Td) a range of 350-450°C.

[0054] In a refinement, the method comprises depolymerizing the at least one polyolefin by heating the mixture in an inert atmosphere (i) to a temperature in a range of 415°C to 460°C, (ii) for a time in a range of 1 .5 hr to 5 hr, (iii) with a conversion of at least 70 wt.% for the at least one polyolefin, and (iv) with a yield of at least 70 wt.% for the gas hydrocarbon product, the liquid hydrocarbon product, or the solid hydrocarbon product; wherein: the atleast one polyolefin is present in the mixture in an amount of 80 wt.% to 98 wt.%; the metal catalyst comprises an alkali metal halide salt and is present in the mixture in an amount of 2 wt.% to 20 wt.%; a combined amount of the at least one polyolefin and the metal catalyst in the mixture is in a range of 80 wt.% to 100 wt.%; the at least one polyolefin comprises high-density polyethylene (HDPE) present in the mixture in an amount of 25 wt.% to 45 wt.% relative to total polyolefins in the mixture, low-density polyethylene (LDPE) present in the mixture in an amount of 10 wt.% to 25 wt.% relative to total polyolefins in the mixture, linear low-density polyethylene (LLDPE) present in the mixture in an amount of 10 wt.% to 25 wt.% relative to total polyolefins in the mixture, and polypropylene (PP) present in the mixture in an amount of 20 wt.% to 35 wt.% relative to total polyolefins in the mixture.

[0055] In a further refinement, depolymerizing the at least one polyolefin comprises forming the gas hydrocarbon product; and / or the gas hydrocarbon product comprises hydrocarbons having 1 to 4 carbon atoms and having a molecular weight in a range of I860 g / mol.

[0056] In a further refinement, depolymerizing the at least one polyolefin comprises forming the liquid hydrocarbon product; and / or the liquid hydrocarbon product comprises hydrocarbons having 5 to 30 carbon atoms and having a molecular weight in a range of 60- 500 g / mol.

[0057] In a further refinement, depolymerizing the at least one polyolefin comprises forming the solid hydrocarbon product; the solid hydrocarbon product comprises hydrocarbons having 24 to 200 carbon atoms; the solid hydrocarbon product has a numberaverage molecular weight (Mn) in a range of 400-1500 g / mol, a weight-average molecular weight (Mw) in a range of 600-3000 g / mol, and a polydispersity index (Mw / Mn) in a range of 1 -5; and / or the solid hydrocarbon product has a melting temperature (Tm) a range of 80- 150°C, a crystallization temperature (Tc) a range of 80-120°C, a temperature difference (Tm- Tc) a range of 1 -50°C, and a decomposition temperature (Td) a range of 350-450°C.

[0058] In an aspect, the disclosure relates to a gas hydrocarbon product formed according to the disclosed methods in any of its various aspects, refinements, embodiments, etc.

[0059] In an aspect, the disclosure relates to a liquid hydrocarbon product formed according to the disclosed methods in any of its various aspects, refinements, embodiments, etc.

[0060] In an aspect, the disclosure relates to a solid hydrocarbon product formed according to the disclosed methods in any of its various aspects, refinements, embodiments, etc.

[0061] In an aspect, the disclosure relates to a coated article comprising: the solid hydrocarbon product according to the disclosure coated on a substrate (e.g., paper).

[0062] In an aspect, the disclosure relates to a hot-melt adhesive comprising: 30-50 wt.% of ethylene-vinyl acetate (EVA); 20-40 wt.% of gum rosin; and 20-40 wt.% of the solid hydrocarbon product according to the disclosure.

[0063] In an aspect, the disclosure relates to an asphalt binder comprising: 70-99.5 wt.% of asphalt binder; 0.5-20 wt.% of the solid hydrocarbon product according to the disclosure; and up to 20 wt.% of additives selected from the group consisting of cellulose fibers, compatibilizers, surfactants, lignin, and combinations thereof. Cold mix asphalt (CMA) and warm mix asphalt (WMA) have lower CO2 emissions than hot mix asphalt (HMA) by about 70% and -10-15% reductions, respectively. However, their durability is typically lower, limiting their applicability and impact. An asphalt binder composition according to the disclosure uses low-cost recycled waxes obtained from waste / discarded polyolefins as flow enhancers for the mixing temperature of the binders.

[0064] In an aspect, the disclosure relates to a polymer blend comprising: 80-98 wt.% of at least one polyolefin; and 2-20 wt.% of the solid hydrocarbon product according to the disclosure (e.g., as a rheology modifier for the polymer).

[0065] In an aspect, the disclosure relates to a heat exchange article for cooling and heating via solid-liquid phase transformations, the article comprising: a reservoir; the solid hydrocarbon product according to the disclosure (e.g., as a phase change material) contained in the reservoir, wherein the solid hydrocarbon product has a melting temperature in a range of 15°C-40°C (e.g., at least 15, 20, or 25°C and / or up to 25, 30, 35, or 40°C; alternatively at least 60, or 70°F and / or up to 80, 90, or 100°F); and optionally, one or more thermally conducting fillers dispersed throughout the solid hydrocarbon product.

[0066] While the disclosed articles, apparatus, methods, and compositions are susceptible of embodiments in various forms, specific embodiments of the disclosure are illustrated (and will hereafter be described) with the understanding that the disclosure is intended to be illustrative, and is not intended to limit the claims to the specific embodiments described and illustrated herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0067] For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawings wherein:

[0068] Figure 1 is a schematic of a coated article including a solid hydrocarbon product (wax) coating according to the disclosure.

[0069] Figure 2 includes total ion chromatograms (TICs) for GC / MS analysis of hydrocarbons resulting from pyrolysis of a polyolefin mixture without a metal catalyst (panel a) and with sodium chloride as a metal catalyst (panel b). The vertical (y-axis) scale (counts) and horizontal (x-axis) scale (retention time) are the same for both chromatograms.

[0070] Figure 3 presents a comparison of high-temperature, medium-temperature, and sodium chloride-assisted medium-temperature pyrolysis. (A) High-temperature (500-600°C) pyrolysis leads to minimal wax formation. (B) Medium-temperature (425-450°C) pyrolysis leads to no wax at all. (C) Salt-assisted pyrolysis at medium temperature provides an excellent yield of wax. The degree of polymerization (n) is based on GC-MS and GPC data.DETAILED DESCRIPTION

[0071] In an aspect, the disclosure relates to a method for depolymerizing plastics via a pyrolysis process to provide a high yield of ambient-temperature liquid hydrocarbons and gas (e.g., gas hydrocarbons). Metal catalysts such as alkali salts can be used in large amounts (e.g., 2-20 wt.%) for pyrolysis of plastics in an inert environment such as nitrogen. The alkali salts can be salts formed from alkali metals, which include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). The most common salts are often composed of alkali metal cations and various anions such as halogens (CI-,Br-). Examples of alkali salts include NaCI, KCI, etc. The plastics can include one or more polyolefins such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP); virgin or recycled polyolefins, single or multilayer plastics, metallized and non-metalized materials, mixed plastics where polyolefin is a major component along some oxygenated polymer impurities such as polyester, co-polyesters, polyvinyl alcohol, polyethylene vinyl alcohol, polyvinyl acetate, etc. The pyrolysis / depolymerization products include a distribution of gas, liquid, and / or wax components, and the distribution of the components can be controlled by duration of the reaction, temperature, and the amount of catalyst. For example, at 420°C for 4 hrs, gas and liquid are the major products. The alkali salt is optionally recyclable byseparating it from the pyrolyzed product by extraction with water for re-use. Metal catalysts such as the alkali salts in large amounts (e.g., 2-20 wt.%) can also be used for oxidative degradation (i.e., pyrolysis at high temp in the presence of oxygen) to make oxygenated hydrocarbons with polar groups such as hydroxyl, carbonyl, carboxyl, etc. These can be enzymatically / microorganism converted into chemicals such as dicarboxylic acid (short or long chain), polymers like polyhydroxy alkanoates, etc. The chemistry for pyrolysis can be a batch or continuous process, where the depolymerized, low-boiling point products (e.g., boiling point below 400°C) can stay in the reactor at high temperature during the reaction or can be separated or distilled during the reaction using a condensation / collection system.

[0072] In an aspect, the disclosure relates to a method for depolymerizing plastics via a pyrolysis process to provide a high yield of wax (e.g., wax hydrocarbons; up to 100% conversion / yield). Metal catalysts such as alkali salts can be used in large amounts (e.g., 2- 20 wt.%) for pyrolysis of plastics in an inert environment such as nitrogen. The alkali salts can be as described above. The plastics can be as described above. The pyrolysis / depolymerization products include a distribution of gas, liquid, and / or wax components, and the distribution of the components can be controlled by duration of the reaction, temperature, and the amount of catalyst. For example, the wax yield as well as the wax melting temperature can be controlled by duration of the reaction, temperature, and the amount of catalyst. The melting temperature of the wax can be in the range of 25-130°C or 80-120°C. Waxes are optionally recyclable by separating by extraction with water or solvent. The chemistry for pyrolysis can be a batch or continuous process, where the waxes and other depolymerized high-boiling point products (e.g., boiling point above 450°C or 500°C) can stay in the reactor at high temperature during the reaction or can be separated or distilled from low-boiling products during the reaction using a condensation / collection system (e.g., where the waxes remain in the reaction vessel while low-boiling products are distilled off). The formed waxes have performance comparable to those of commercial rheology modifiers. Paper coated with the formed waxes exhibit excellent water- and oil-resistance. The formed waxes can be used as surfactant by grafting with unsaturated anhydrides and subsequent hydrolysis and neutralization. The formed waxes can be further reacted with catalyst to create functional waxes.

[0073] More generally, the disclosure relates to a method for depolymerizing a polyolefin or other polymer. A mixture including a polymer such as a polyolefin and a metal catalyst is heated to a temperature above a melting temperature of the polymer, thereby partially or completely depolymerizing the polymer. The metal catalyst can include a metal salt alone or in combination with a metal oxide, an elemental metal, and / or a metal alloy. Alternatively oradditionally, the metal catalyst can be selected to have a heat capacity in a range of 0.4 to 100 J / (g*K) and (B) a thermal conductivity in a range of 0.2 to 60 W / (m»K).Depolymerization of the polymer can form one or more of a corresponding gas hydrocarbon product, a liquid hydrocarbon product, and a solid hydrocarbon product (e.g., wax, not char). Reaction parameters, such as heating time, heating temperature, catalyst concentration, etc. can be selected or otherwise controlled for a given polyolefin or other polymer to adjust the distribution between gas, liquid, and solid hydrocarbon products, for example providing a reaction product that primarily or preferentially contains a gas, liquid, or solid hydrocarbon product.Polymers

[0074] The polymer can include one or more polyolefins or other polymers containing olefinic backbone units (e.g., substituted or unsubstituted -C-C- units) with or without pendant groups. Alternatively or additionally, the polymer can include polymers other than polyolefins, such as oxygenated polymers with backbone and / or pendant oxygen atoms, for example including polyesters, co-polyesters, polyvinyl alcohol, polyethylene vinyl alcohol, and / or polyvinyl acetate.

[0075] The polyolefin is not particularly limited and can include one or more of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very-low-density polyethylene (VLDPE), ultra-low-density polyethylene (LILDPE), medium-density polyethylene (MDPE), polypropylene (PP), polymethylpentene (PMP), polybutene-1 (PB-1 ), ethylene-octene copolymers, stereo-block PP, olefin block copolymers, propylene-butane copolymers; polyisobutylene (PIB), poly(alpha-olefins), ethylene-propylene rubber (EPR), and ethylene propylene diene monomer rubber (EPDM rubber). The polyolefins can be present in any desired amount or proportion, depending on the particular source of the polyolefin material (e.g., a waste polyolefin to be recycled) and / or a particular depolymerization product to be formed (e.g., selected polyolefin(s) favoring production of a gas, liquid, or solid product as desired). For example, a given polyolefin can be present in an amount of 0.1 to100 wt.% or 1 to 95 wt.%, such as at least 0.1 , 1 , 2, 5, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 98, or 99 wt.% and / or up to 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 98, 99, 99.9 or 100 wt.%. The foregoing amounts and ranges can be relative to total polyolefin in the mixture, total polymer in the mixture, or the mixture as a whole (e.g., also including catalyst amounts, etc.). Different polyolefin can amounts and ranges independently selected from the foregoing.

[0076] In embodiments, the polyolefin can include high-density polyethylene (HDPE), low- density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP). Such combinations are common for mixed plastic waste (MPW) that might otherwise be sent to a landfill, but which can be converted to one or more useful depolymerization products using the disclosed methods. In embodiments, the HDPE can be present in the mixture in an amount of 25 wt.% to 45 wt.% or 30 wt.% to 40 wt.% In embodiments, the LDPE can be present in the mixture in an amount of 10 wt.% to 25 wt.% or 12 wt.% to 20 wt.%. In embodiments, the LLDPE can be present in the mixture in an amount of 10 wt.% to 25 wt.% or 12 wt.% to 20 wt.%. In embodiments, the PP can present in the mixture in an amount of 20 wt.% to 35 wt.% or 25 wt.% to 30 wt.%. The foregoing amounts and ranges can be relative to total polyolefin in the mixture, total polymer in the mixture, or the mixture as a whole (e.g., also including catalyst amounts, etc.). More generally, the HDPE, LDPE, LLDPE, and / or PP can be present in any broader ranges above. Alternatively or additionally, the HDPE, LDPE, LLDPE, and / or PP can be present in relative amounts 4:2:2:3 for HDPE:LDPE:LLDPE:PP (w / w), + / - 0%, 5%, 10%, 15%, 20%, or 25% for any of the foregoing ratios. For example, an LDPE:LLDPE ratio can be 1 .8-2.2:2 (i.e., 2 + / - 10% for LDPE, and 2 + / - 0% for LLDPE). Similarly, an HDPE:LDPE ratio can be 3.8-4.2:1 .8-2.2 (i.e., 4 + / - 5% for HDPE, and 2 + / - 10% for LDPE).

[0077] The amount of the polymer in the mixture or feedstock to be depolymerized is not particularly limited, and it can vary widely depending on the desired catalyst loading, the potential presence of impurities, the potential inclusion of processing aids or additives, etc. In embodiments, the polyolefin(s) or other polymer(s) can be present in the mixture in an amount of 50-99 wt.%, 70-99 wt.%, 80-99 wt.%, or 90-99 wt.%, for example based on the total weight / amount of mixture (e.g., combined amount of polymer, catalyst, impurities, additives, etc.). For example, the polymer can be present in the mixture in an amount of at least 50, 60, 70, 80, 82, 84, 86, 88, 90, 92, 94, or 96 wt.% and / or up to 65, 80, 90, 92, 94, 95, 96, 97, 98, or 99 wt.%. Alternatively or additionally, a combined amount of the polymer(s) and the metal catalyst(s) in the mixture can be present in the mixture in an amount of 70-100 wt.%, 80-100 wt.%, or 90-100 wt.%, similarly based on the total weight / amount of mixture (e.g., combined amount of polymer, catalyst, impurities, additives, etc.). For example, the polymer(s) and the catalyst(s) can be present in the mixture in a combined amount of at least 70, 75, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, or 99 wt.% and / or up to 90, 92, 94, 95, 96, 97, 98, 99, 99.5, or 100 wt.%, for example including all polymer reactants and all catalysts combined when there is more than one species of polymer and / or catalyst components in the initial reaction mixture.

[0078] In some embodiments, the mixture to be depolymerized initially contains substantially only polymer and catalyst (e.g., as initially fed to a continuous reactor or as initially charged to a batch reactor), for example containing not more than 0.1 , 1 , 2, 3, or 5 wt.% based on the mixture of components other than the polymer and catalyst. In some embodiments, the mixture to be depolymerized can initially contain one or more additional components such as additives, impurities, other polymers (e.g., non-polyolefin polymers when the primary feed is one or more polyolefins), and / or free-radical initiators, which can be present in a polymer waste stream to be recycled or intentionally added for a processing benefit.

[0079] In embodiments, the mixture can include one or more additives and / or impurities in a (combined) amount up to 30 wt.% based on the mixture as a whole, such as at least 0.01 , 0.1 , 1 , 2, or 5 wt.% and / or up to 0.5, 1 , 2, 3, 5, 8, 12, 15, 20, 25, or 30 wt.%. Such additional components can include one or more of salts, metal residues, organic impurities or additives, inorganic impurities or additives, moisture, plastic additives, polymers other than polyolefins, etc. that might be present in a recycled feed as impurities and / or added to the feed mixture as a processing aid.

[0080] In embodiments, the mixture can include one or more free radical inhibitors or suppressors in a (combined) amount up to 5 wt.% based on the mixture as a whole, such as at least 0.01 , 0.1 , 1 , or 2 wt.% and / or up to 0.5, 1 , 2, 3, 4, or 5 wt.%. Free radical suppressors are generally known in the art and can include compounds such as TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl, 2,2,6,6-tetramethyl-1-piperidinyloxy), N- hydroxysuccinimide, etc.Catalysts

[0081] The primary catalyst in the mixture to be heated includes at least one metal catalyst (or metal-containing catalyst) to promote depolymerization of the polyolefin and / or other polymers into one or more of the corresponding depolymerization gas hydrocarbon product, the liquid hydrocarbon product, and the solid hydrocarbon product.

[0082] Examples of metal catalysts include metal salts, metal oxides, elemental metals, metal alloys, and combinations or mixtures thereof. Such metals in the various forms can include one or more alkali metals such as Li, Na, K; alkaline earth metals such as Be, Ca, Mg, Ba; other metals such as Al; salts thereof such as halide salts, acetate or ester salts; oxides thereof; and alloys thereof such as steel or stainless steel. The metal catalyst is generally in a solid form such as powder, mesh, wire, etc.

[0083] In embodiments, the metal catalyst can include an alkali metal halide salt, for example including at least one of a lithium cation, a sodium cation, and a potassium cation; and at least one of a fluoride anion, chloride anion, bromide anion, and iodide anion. In particular embodiments, the metal catalyst can include sodium chloride and / or potassium chloride. In embodiments, the metal catalyst can include an alkaline earth metal halide salt, for example including at least one of a beryllium cation, a magnesium cation, a calcium cation, and a barium cation; and at least one of a fluoride anion, chloride anion, bromide anion, and iodide anion.

[0084] In embodiments, the metal catalyst can include one or more of a metal oxide, an elemental metal, and a metal alloy (e.g., in addition to or instead of a metal salt). Examples of suitable metal oxides include alumina; alkali metal oxides; alkaline earth metal oxides.

[0085] The metal catalyst can be present in the mixture during heating and depolymerization in relatively wide ranges, although it can be particularly effective in terms of relatively high depolymerization conversion or yield even at relatively low concentrations. In embodiments, the catalyst can be present in the mixture in an amount of 2 wt.% to 20 wt.% or 0.5 wt.% to 40 wt.% relative to the (total) polyolefin and / or other polymer originally present in the mixture. For example, the catalyst (e.g., all metal catalysts) can be present in amount of at least 0.5, 1 , 2, 3, 4, 5, 7, 10, 15, or 20 wt.% and / or up to 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, or 40 wt.% relative to the (total) polyolefin and / or other polymer in the mixture. The foregoing ranges and amounts can similarly apply to the (total) polyolefin and / or other polymer relative to the mixture as a whole.

[0086] In embodiments, the metal catalyst can be in a powder or particulate form. In embodiments, the metal catalyst can have a particle size (e.g., average size or diameter; size or diameter distribution) selected to provide a desired specific surface area of the metal catalyst, which in turn can be selected to control or adjust a relative rate and / or homogeneity of heat transfer between the metal catalyst and the bulk polymer being depolymerized during heating. In embodiments, the metal catalyst can have a particle size in a range of 10 nm to 2 mm (e.g., 1 pm to 500 pm, and 10 pm to 100 pm). A particle size or size range can represent an average size or diameter of a particle size distribution, for example a number-, weight-, or volume-average size or diameter. A particle size or size range can alternatively or additionally represent lower and upper boundaries of a size particle size distribution, for example minimum / maximum particles sizes resulting from sieve cuts, 1 % / 99% sizes from a cumulative size distribution, 5% / 95% sizes from a cumulative size distribution, etc. For example, the particle size of the metal catalyst powder or particles can be at least 0.01 , 0.02,0.05, 1 , 2, 5, 10, 15, 20, 30, 40, 50, or 60 |im and / or up to 0.5, 1 , 2, 5, 10, 20, 30, 40, 50, 60, 80, 100, 120, 150, 200, 300, 400, 500, 800, 1000, or 2000 |im.

[0087] In embodiments, the mixture being heated can be free or substantially free from Ziegler-Natta and platinum-containing catalysts. More generally, the mixture can be free or substantially free from precious metal-containing (or transition metal-containing) catalysts such as those containing one or more of ruthenium, rhodium, palladium, osmium, iridium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, platinum, gold, and / or silver. For example, the mixture can contain up to (or not more than) 0.0001 , 0.001 , 0.01 , or 0.1 wt.% of such catalysts. Alternatively or additionally, the mixture can contain not more than 0.1 wt.% of transition metal catalysts (or not more than 0.1 wt.% of transition metals). Alternatively or additionally, the mixture can contain not more than 0.1 wt.% of metal catalysts other than alkali metal-containing catalysts and alkaline earth metal-containing catalysts (or not more than 0.1 wt.% of metals other than alkali and alkaline earth metals). In some alternative embodiments, the mixture can include such catalysts in addition to the metal salt catalyst, for example when desired to further drive the depolymerization reaction toward a higher proportion of gas hydrocarbon products. When present, the precious or transition metal-containing catalyst can be present in amount of at least 0.01 , 0.1 , 0.2, or 0.3 wt.% and / or up to 1 , 2, 3, 4, or 5 wt.% relative to the mixture or relative to total polymer being depolymerized.

[0088] In embodiments, the metal catalyst can be selected such that it has favorable heat capacity and thermal conductivity properties to promote one or more of efficient heat transfer and heating, and depolymerization of the polymer as sufficiently low temperatures to avoid polymer degradation (e.g., burning, charring, etc.). The metal catalyst can include any metal-containing material, such as a metal salt, a metal oxide, an elemental metal, and a metal alloy as generally described above. In some embodiments, the mixture to be heated can include multiple metal catalysts, for example a first metal catalyst such as a metal salt and a second metal catalyst such as a metal oxide. In embodiments, the metal catalyst (or one of the metal catalysts) can have a heat capacity in a range of 0.4 to 100 J / (g*K) or 10 to 100 J / (g*K), for example a heat capacity of at least 0.4, 1 , 2, 3, 5, 7, 10, 15, 20, 25, 30, 40, or 50 J / (g*K) and / or up to 1 , 2, 3, 6, 10, 20, 40, 60, 70, 80, 90, or 100 J / (g*K). In embodiments, the metal catalyst (or one of the metal catalysts) can have a thermal conductivity in a range of 0.2 to 60 W / (m»K) or 2 to 60 W / (m»K), for example a thermal conductivity of at least 0.2, 0.5, 1 , 2, 3, 5, 7, 10, 15, 20, 25, or 30 W / (m»K) and / or up to 1 , 2, 3, 4, 5, 6, 8, 10, 20, 30, 40, 50, or 60 W / (m*K).Depolymerization and Products

[0089] Heating of the mixture to effect depolymerization can be performed in any suitable reaction vessel (e.g., batch, continuous, etc.) up to or at a temperature suitably selected for the particular polyolefin(s) and / or other polymer(s) being depolymerized and the particular catalyst(s) being incorporated into the mixture. For example, the depolymerization reaction can be performed in a batch or continuous distillation apparatus such that such that the high mixture temperature required to melt the polymer and effect depolymerization will also vaporize formed gas hydrocarbon product and / or other low-boiling liquid hydrocarbon products, which in turn can be separated from the reaction mixture (i.e., as a separate phase) that includes a molten solid hydrocarbon product that solidifies upon cooling to ambient temperature (e.g., 20-30°C). The gas and / or liquid hydrocarbon products can be recovered and separated after condensation or other cooling. As described above, the heating or depolymerization temperature is above the melting temperature of the polymer(s) in the mixture, for example being above the highest melting temperature in a mixture with multiple different polymers, thereby providing a bulk liquid / polymer melt reaction medium for depolymerization. Additionally, the heating or depolymerization temperature is low enough such that the catalyst (e.g., metal catalyst such as a metal salt) remains in solid form (e.g., powder, particulate, etc.) in the mixture, for example being below the lowest melting and / or decomposition temperature in a mixture with one or more different catalysts (e.g., single catalyst, mixture of catalysts, eutectic mixture of catalysts), such that the catalyst can be a discrete or separate solid phase in the bulk liquid / polymer melt reaction medium for depolymerization. During depolymerization, suitable reaction pressures can be ambient pressure or approximately atmospheric pressure, for example 0.2-5 bar, 0.5-1 .5 bar, 0.8- 1 .2 bar, or 0.9-1 .1 bar, which can represent a pressure in one or more of the reaction vessel where depolymerization occurs, a product vessel where gas and / or liquid hydrocarbon product is collected (e.g., a receiving flask or other vessel to collect depolymerization product condensate as a liquid), etc. Suitable reaction times can be selected as appropriate based on desired conversion the reactant, selectivity of the desired product (e.g., gas, liquid, and solid hydrocarbon product(s) vs. other byproducts), etc. for example 0.05-20 hr, 0.5- 20 hr, 1 .5-5 hr, 0.2-2 hr, 0.5-1 .5 hr, or 0.8-1 .2 hr, such as at least 0.05, 0.2, 0.5, 0.8, 1 , 1 .2, 1 .5, 2, or 3 hr and / or up to 1 , 1 .2, 1 .5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 10, 15, 20 hr.

[0090] In embodiments, heating of the mixture to effect depolymerization can be performed up to or at a temperature in a range of 350°C-500°C, 415°C-460°C, or 250°C- 600°C, for example representing an essentially constant depolymerization temperature in the range or a variable-temperature profile in which the maximum temperature is within therange. More generally, the depolymerization temperature can be at least 250, 300, 350, 380, 400, 410, 415, 420, 425, 430, 435, 440, 445, 450, 455, 460, 465, 475, 480, 500, or 550°C and / or up to 400, 410, 415, 420, 425, 430, 435, 440, 445, 450, 455, 460, 465, 475, 480, 500, 550, or 600°C, depending on the particular polymer(s) in the mixture. In the particular case of polyolefin polymers, particularly suitable depolymerization temperatures can be in a range of 400°C to 480°C, 415°C to 460°C, or 425°C to 450°C.

[0091] In embodiments, heating of the mixture to effect depolymerization can be performed up to or at a temperature that is at least 10°C above a melting temperature of the polymer(s), and / or a temperature that is at least 50°C below a decomposition temperature of the polymer(s). For example, the depolymerization temperature can be at least 10, 20, 30, or 50°C above the melting temperature of the polymer, such as above the highest melting temperature in a mixture with multiple different polyolefins or other polymers. Alternatively or additionally, the depolymerization temperature can be at least 10, 20, 30, 40, 50, 70, or 100°C below the decomposition temperature of the polymer, such as below the lowest decomposition temperature in a mixture with multiple different polyolefins or other polymers. The decomposition temperature of the polymer can represent the lower of the temperature at which the polymer would depolymerize in the absence of a catalyst or other additive (and the temperature at which the polymer would combust, burn, char, etc. to form a carbon-based product (e.g., ash) instead of a gas, liquid, or solid hydrocarbon product.

[0092] In embodiments, heating of the mixture can be performed an inert atmosphere. An inert atmosphere is free or substantially free form oxygen (O2 or other materials containing oxygen atoms), for example atmosphere / reaction headspace containing not more than 0.0001 , 0.001 , 0.01 , 0.1 or 1 wt.% or mol.% oxygen. Examples of suitable inert atmospheres include nitrogen (e.g., N2), argon, etc. The inert atmosphere limits or prevents the formation oxygenated depolymerization products, for example forming gas, liquid, and / or solid hydrocarbon products that contain only carbon and hydrogen atoms (e.g., when the starting polymer(s) also has only carbon and hydrogen atoms, such as in a polyolefin).

[0093] In embodiments, heating of the mixture can be performed in the presence of oxygen. For example, heating can be performed in air or other oxygen (O2or other materials containing oxygen atoms)-containing atmosphere to produce one or more oxygenated gas, liquid, and / or solid hydrocarbon product, even when the starting polymer(s) has only carbon and hydrogen atoms. Examples of such oxygenated products can include alcohols, ketones, aldehydes, carboxylates, carboxylic acids, etc. The relative amount of oxygen in the heating atmosphere can be selected to control the degree of oxygenation ofthe product. Similar oxygenated products can be formed when the starting polymer contains oxygen atoms (e.g., polyesters, polyvinyl alcohol), even when the mixture is heated in an inert or otherwise oxygen-free atmosphere.

[0094] The depolymerization method according to the disclosure is particularly effective in that it can achieve relatively high levels of conversion of the original polymer feed into desired gas, liquid, and / or solid hydrocarbon products corresponding to the original vinyl polymer. Similarly, the depolymerization method can achieve relatively high selectivity values or yields for the desired depolymerization product, whether gas, liquid, and / or solid hydrocarbon products, for example by selecting or controlling one or more of reaction temperature, reaction time, and reaction pressure. Further, the amount of catalyst can be selected to control reaction selectivity.

[0095] In embodiments, the polyolefin or other polymer initially in the reaction mixture is depolymerized with a conversion of at least 70 wt.%. For example, at least 70, 75, 80, 82, 85, 87, 90, 92, 94, 96, 98, or 99 wt.% and / or up to 85, 88, 90, 92, 95, 98, 99, 99.5, or 100 wt.% of original polymer is converted to and / or recovered as the corresponding gas, liquid, and / or solid hydrocarbon products combined, such as in gas, liquid, and / or solid product phase(s) in the reaction vessel (e.g., at ambient temperatures of 5-50°C, 15-35°C, or 20-30°C after cooling from the high reaction temperature). The foregoing conversion values can reflect the conversion of an individual polymer (e.g., when multiple different polymers are initially present in the mixture). Alternatively or additionally, the foregoing conversion values can reflect the collective conversion of all polymers initially present in the mixture. The remainder of unconverted polymer can be present after reaction as a solid phase, such as unreacted polymer (e.g., solidifying or precipitating after cooling to ambient temperatures) or other residue.

[0096] In embodiments, the depolymerization method provides or otherwise results in a yield of at least 70 wt.% for the gas hydrocarbon product, the liquid hydrocarbon product, or the solid hydrocarbon product, relative to total (or initial) polyolefin or other polymer being depolymerized. For example, depending on whether the reaction conditions are selected to favor a gas, liquid, or solid (wax) hydrocarbon product, the yield of the gas, liquid, or solid hydrocarbon product can be at least 70, 75, 77, 80, 82, 85, 87, 90, 92, 94, 96, 98, or 99 wt.% and / or up to 85, 88, 90, 92, 95, 98, 99, or 100 wt.% relative to total polymer. More generally, the yield of a given hydrocarbon product phase can be at least 0.1 , 1 , 2, 5, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 98, or 99 wt.% and / or up to 1 , 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 98, 99, 99.9 or100 wt.% (i.e., considering that one product phase can be the primary product, and the other two product phases can be minor products or essentially absent). Alternatively or additionally, the foregoing amounts and ranges can represent the relative amount of a given hydrocarbon product phase (i.e., gas, liquid, or solid hydrocarbon product) relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed.

[0097] In embodiments, a given or primary hydrocarbon product phase (i.e., gas, liquid, or solid hydrocarbon product) can be formed with a selectivity of at least 2 relative to either or both of the other product phases. For example, the primary hydrocarbon product phase can be formed with a selectivity of at least 2, 4, 6, 8, 10, 12, 15, 20, 30, or 40 and / or up to 15, 20, 30, 50, 100, 200, 300, or 500 on a weight / weight basis.

[0098] The gas hydrocarbon product generally includes hydrocarbons that are in gaseous form at ambient or near-ambient temperatures (e.g., in gas phase at a temperature in a range of 5-50°C, 15-35°C, or 20-30°C). In embodiments, the gas hydrocarbon product can include or contain one or more hydrocarbons having 1 to 4 carbon atoms, for example 1 , 2, 3, or 4 carbon atoms. The gas hydrocarbon product can include linear or branched, saturated or unsaturated hydrocarbons, such as alkanes (e.g., methane, ethane, propane, butane, and isomers thereof) and alkenes. The gas hydrocarbon product can include unsubstituted hydrocarbons (e.g., containing only C and H atoms) or substituted / oxygenated hydrocarbons (e.g., containing C, H, and O or other substituting atoms). While the gas hydrocarbon product is generally a gas at ambient temperature, it can include low molecular weight oxygenates that can be liquids at ambient temperature (e.g., methanol, ethanol, propanol, butanol, and isomers thereof). In embodiments, the gas hydrocarbon product can be formed in an amount of at least 40 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed, or more generally any amount from 1-100 wt.% relative to total hydrocarbon product.

[0099] In embodiments, the gas hydrocarbon product can include one or more hydrocarbons having a molecular weight in a range of 16-60 g / mol or 16-74 g / mol, for example at least 16, 24, 32, or 40 g / mol and / or up to 28, 36, 42, 50, 60, or 74 g / mol. The foregoing ranges can represent an average molecular weight of a molecular weight distribution (e.g., a number-, or weight-average molecular weight) or lower / upper boundaries of the molecular weight distribution (e.g., 1 % / 99%, 5% / 95%, or 10% / 90% cut points in a cumulative molecular weight distribution).

[0100] The liquid hydrocarbon product generally includes hydrocarbons that are in liquid form at ambient or near-ambient temperatures (e.g., in liquid phase at a temperature in a range of 5-50°C, 15-35°C, or 20-30°C), although some of the liquid hydrocarbon products can include some high-melting hydrocarbon chains solvated in a mixture of liquid / low-melting chains for an overall liquid-phase product. In embodiments, the liquid hydrocarbon product can include or contain one or more hydrocarbons having 5 to 25 or 5 to 30 carbon atoms, for example at least 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, or 20 carbon atoms and / or up to 8, 10, 12, 15, 20, 25, or 30 carbon atoms. The liquid hydrocarbon product can include linear or branched, saturated or unsaturated hydrocarbons, such as alkanes (e.g., methane, ethane, propane, butane, and isomers thereof) and alkenes. The liquid hydrocarbon product can include unsubstituted hydrocarbons (e.g., containing only C and H atoms) or substituted / oxygenated hydrocarbons (e.g., containing C, H, and O or other substituting atoms). In embodiments, the liquid hydrocarbon product can be formed in an amount of at least 80 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed, or more generally any amount from 1 -100 wt.% relative to total hydrocarbon product.

[0101] In embodiments, the liquid hydrocarbon product can include saturated hydrocarbons (e.g., alkanes) alone or in combination with unsaturated hydrocarbons (e.g., terminal or internal alkenes with one, two, three, or more C=C double bonds). For example, the liquid hydrocarbon product can include 5-100 wt.% saturated hydrocarbons relative to total liquid hydrocarbon product, such as at least 5, 10, 20, 30, 40, 50, 60, 70, or 80 wt.% and / or up to 20, 30, 40, 50, 60, 70, 80, 90, or 100 wt.% saturated hydrocarbons. Likewise, the liquid hydrocarbon product can include 0-95 wt.% unsaturated hydrocarbons relative to total liquid hydrocarbon product, such as at least 5, 10, 20, 30, 40, 50, 60, 70, or 80 wt.% and / or up to 20, 30, 40, 50, 60, 70, 80, 90, or 95 wt.% unsaturated hydrocarbons. Alternatively or additionally, a ratio of saturated hydrocarbons:unsaturated hydrocarbons in the liquid hydrocarbon product can be in a range of 100:1 to 1 :100, 10:1 to 1 :10, 2:1 to 1 :2, 1 .2:1 to 1 :1 .2 on a molar basis or a weight basis.

[0102] In embodiments, the liquid hydrocarbon product can include one or more hydrocarbons having a molecular weight in a range of 60-500 g / mol or 50-600 g / mol, for example at least 50, 60, 70, 80, 100, 120, 140, 160, 200, or 250 g / mol and / or up to 100, 150, 200, 250, 300, 350, 400, 450, 500, or 600 g / mol. The foregoing ranges can represent an average molecular weight of a molecular weight distribution (e.g., a number-, or weightaverage molecular weight) or lower / upper boundaries of the molecular weight distribution(e.g., 1 % / 99%, 5% / 95%, or 10% / 90% cut points in a cumulative molecular weight distribution).

[0103] The solid hydrocarbon product generally includes hydrocarbons that are in solid form at ambient or near-ambient temperatures (e.g., in solid phase at a temperature in a range of 5-50°C, 15-35°C, or 20-30°C). The solid hydrocarbon product is generally waxy material and is free from char, ash, etc. that would result from combustion, burning, etc. of the polyolefin or other polymer. In embodiments, the solid hydrocarbon product can include or contain one or more hydrocarbons having 20 to 300 or 24 to 200 carbon atoms, for example at least 20, 24, 30, 40, 50, 60, 80, 100, 120, or 150 carbon atoms and / or up to 40, 50, 60, 80, 100, 120, 150, 200, 250, or 300 carbon atoms. The solid hydrocarbon product can include linear or branched, saturated or unsaturated hydrocarbons, such as alkanes (e.g., methane, ethane, propane, butane, and isomers thereof) and alkenes. The solid hydrocarbon product can include unsubstituted hydrocarbons (e.g., containing only C and H atoms) or substituted / oxygenated hydrocarbons (e.g., containing C, H, and O or other substituting atoms). In embodiments, the solid hydrocarbon product can be formed in an amount of at least 90 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed, or more generally any amount from 1- 100 wt.% relative to total hydrocarbon product.

[0104] In embodiments, the solid hydrocarbon product can include one or more hydrocarbons having a number-average molecular weight (Mn) in a range of 400-2000 or 400-1500 g / mol, for example at least 400, 500, 600, 700, 800, or 1000 g / mol and / or up to 700, 1000, 1200, 1500, or 2000 g / mol. In embodiments, the solid hydrocarbon product can include one or more hydrocarbons having a weight-average molecular weight (Mw) in a range of 600-10000 or 600-3000 g / mol, for example at least 600, 700, 800, 1000, 1200, 1500, or 2000 g / mol and / or up to 800, 1000, 1500, 2000, 3000, 4000, 6000, 8000, or 10000 g / mol. The foregoing ranges can represent an average molecular weight of a molecular weight distribution (e.g., a number-, or weight-average molecular weight) or lower / upper boundaries of the molecular weight distribution (e.g., 1 % / 99%, 5% / 95%, or 10% / 90% cut points in a cumulative molecular weight distribution). In embodiments, the solid hydrocarbon product can include include one or more hydrocarbons having a polydispersity index (Mw / Mn) in a range of 1 to 5, for example at least 1 , 1.1 , 1 ,2, 1.3, 1.4, 1 .5, 1 .7, 2, or 2.5 and / or up to 1 .2, 1 .5, 2, 2.5, 3, 3.5, 4, or 5.

[0105] In embodiments, the solid hydrocarbon product can be characterized by one or more temperature properties. The solid hydrocarbon product can have a meltingtemperature (Tm) a range of 25-130°C (or 80-120°C or 80-150°C), for example at least 25, 40, 60, 70, 80, 90, 100 or 110°C and / or up to 60, 80, 90, 100, 110, 120, 130, 140, or 150°C. The solid hydrocarbon product can have a crystallization temperature (Tc) a range of 80- 120°C (or 60-140°C), for example at least 60, 70, 80, 90, 100 or 110°C and / or up to 90, 100, 110, 120, 130, or 140°C. The solid hydrocarbon product can have a temperature difference (Tm-Tc) a range of 1-50°C (or 5-20°C), for example at least 1 , 2, 3, 5, 7, 10, or 15°C and / or up to 10, 12, 15, 20, 30, 40, or 50°C. The solid hydrocarbon product can have a decomposition temperature (Td) a range of 350-450°C, for example at least 350, 370, 390, or 410°C and / or up to 390, 410, 430, or 450°C.

[0106] The gas hydrocarbon product, the liquid hydrocarbon product, and the solid (waxy) hydrocarbon product that are produced according to the disclosed methods can be used in various other compositions and articles. The liquid and gas fractions can be used as is or converted into useful forms after further modification. This modification can be obtained via catalytic, non-catalytic, enzymatic, or electrochemical reactions. Portions can be used as fuel and / or as feedstock to produce chemicals, surfactants, monomers, etc. The gas can also be utilized as fuel and / or as feedstock for chemicals and monomers. In embodiments, the disclosed depolymerization methods can be extended with additional step(s) to form one or more end-use articles, compositions, products, etc. using the gas, liquid, and / or solid hydrocarbon product(s) formed by the depolymerization method.

[0107] In embodiments, the solid hydrocarbon product can be used as a coating on a substrate such as paper or other cellulosic substrate, for example to impart water- and / or oilresistance to the substrate. As illustrated in Figure 1 , a coated article 300 can include a substrate 310 and a coating 320 on or adjacent to the substrate. The coating 320 can include the solid (or wax) hydrocarbon product. The coating can be applied by any suitable method, for example from an aqueous dispersion or emulsion of the wax (e.g., solvent casting). In other embodiments, the coating can be applied in the form of a melt coating of the wax (e.g., extrusion and non-extrusion melt-coating). In other embodiments, the coating can be applied by compression molding the wax (e.g., application of heat and pressure to a synthetic wax in contact with a substrate to be coated). The substrate 310 is suitably a cellulosic substrate such as a paper substrate. The wax can be used as a coating directly on a cellulosic substrate, or as a top layer on an already-coated cellulosic substrate (e.g., with a first coating on the substrate such as a polymer like starch, and then a top or second coating of the wax). The wax can also be applied as a coating on other materials such as plastic films / bottles; water repellent fabrics; automotive polishes, as mold release agents in mold making, and other non-packaging applications. Typical coating 320 thicknesses canbe 1 pm to 1000 pm or 20 pm to 50 pm. For example, the coating 320 can have thickness of at least 1 , 2, 5, 10, 20, 30, 50, 100, 200, or 300 pm and / or up to 30, 50, 70, 100, 200, 500, 700, or 1000 pm. Typical cast coatings can have thicknesses of 10 pm to 100 pm. As described herein, multiple coating layers can be applied to substrate 310 to form even thicker layers of the coating 320 (e.g., above 1000 pm, 2000 pm, or otherwise) if desired. Various iterations are possible, for example, wax coating on uncoated or precoated paper, cardboard, corrugated boxes, etc.

[0108] The cellulosic substrate is not particularly limited, and can be formed from any cellulosic material desired for protection with a wax coating. For example, the substrate can be a molded fiber containers, paper, paperboard, wood, or fabric (or textile). Examples of paper substrates can include, but are not limited to, generally thinner, flexible papers, for example useful as wrapping materials, as well as generally thicker, rigid papers or cardboard (e.g., corrugated paper cardboard, paperboards), for example useful as box, container, plate, cup, or other storage or food-service items. Suitable wood materials can be any type of wood commonly used in home, office, and outdoor settings. Suitable fabric or textile materials can include any cellulosic materials commonly used in garments or otherwise, such as cotton, jute, flax, hemp, etc.

[0109] In embodiments, the coated article 300 can have a kit rating in a range of 4 to 12; and / or the coated article has a. For example, the kit rating can be at least 4, 5, 6, 7, 8, 9, 10, or 11 and / or up to 8, 9, 10, 11 , or 12. Suitable methods for determining the kit rating include TAPPI methods T599 pm-96 and UM 557. In embodiments, the coated article 300 can have a cobb (or cobb1800) rating of 20 g / m2or less. For example, the cobb rating (or cobb1800 rating) can be at least 0.1 , 0.2, 0.5, 1 , 2, 3, 6, 8, 10, 12, or 15 g / m2and / or up to 3, 5, 7, 10, 15, or 20 g / m2. A suitable methods for determining the cobb rating includes TAPPI method T441 om-09.

[0110] In embodiments, the solid hydrocarbon product can be used as an additive in a hot-melt adhesive composition. For example, a hot-melt adhesive composition can include 30-50 wt.% of ethylene-vinyl acetate (EVA), 20-40 wt.% of gum rosin, and 20-40 wt.% of the solid hydrocarbon product.

[0111] In embodiments, the solid hydrocarbon product can be used as an additive in an asphalt binder composition. Cold mix asphalt (CMA) and warm mix asphalt (WMA) have lower carbon dioxide emissions than hot mix asphalt (HMA) by about 70% and -10-15% reductions, respectively. However, their durability is typically lower, limiting their applicability and impact. An asphalt binder composition according to the disclosure uses low-costrecycled waxes obtained from waste / discarded polyolefins as flow enhancers for the mixing temperature of the binders. For example, an asphalt binder composition can include 70-99.5 wt.% of asphalt binder, 0.5-20 wt.% of the solid hydrocarbon product, and up to 20 wt.% of additives such as cellulose fibers, compatibilizers, surfactants, and / or lignin.

[0112] In embodiments, the solid hydrocarbon product can be used as a rheology modifier when blended with another polymer. For example, a polymer blend including the solid hydrocarbon product as a rheology modifier can include 80-98 wt.% of at least one polyolefin (or other polymer), and 2-20 wt.% of the solid hydrocarbon product.

[0113] In embodiments, the solid hydrocarbon product can be used as a phase change material. For example, a heat exchange article for cooling and heating via solid-liquid phase transformation can include a reservoir, the solid hydrocarbon product (e.g., as a phase change material (PCM)) contained in the reservoir, and optionally, one or more thermally conducting fillers dispersed throughout the solid hydrocarbon product. The solid hydrocarbon product can have a melting temperature in a range of 15°C-40°C., such as at least 15, 20, or 25°C and / or up to 25, 30, 35, or 40°C (alternatively at least 60, or 70°F and / or up to 80, 90, or 100°F). The solid hydrocarbon product can be used to enhance building cooling efficiency. The waxy hydrocarbons store and release heat during their phase transitions, usually from solid to liquid, thereby helping to regulate indoor temperatures and reduce air conditioning dependency. Waxes, which are hydrocarbons that typically possess 20-40 carbon atoms, are colorless, soft solids derived from coal or oil. Their melting temperature and heat storage capacities increase with chain length. The obtained waxes with melting temperatures that are suitable for buildings, typically ranging from 70-90°F. The obtained solid hydrocarbon waxes serve as effective PCMs for energy storage and cooling applications, and their performance can be further enhanced by incorporating thermally conducting fillers. Utilizing wax from plastic waste as a PCM addresses plastic waste problems and also contributes to more efficient and sustainable building solutions.EXAMPLES

[0114] The following examples illustrate the disclosed methods, but are not intended to limit the scope of any claims thereto.

[0115] Thermogravimetric analysis (TGA): Thermogravimetric analysis of the reference and obtained materials were performed using a thermogravimetric analyzer (TA Instruments, Q50) by taking a sample with a weight of approximately 7-15 mg and placing it in airflow of 40 mL / min from room temperature up to 600°C using a heating rate of 10°C / min.

[0116] Differential scanning calorimetry (DSC) analysis: Differential scanning calorimetry (DSC) tests were performed with a TA Instruments (DSC Q100 model) calorimeter.Typically, samples with a mass of about 10 mg were placed under an N2 flow of 100 mL / min. Heating cycles were recorded between the range of 0 and 300°C at a rate of 10°C / min.

[0117] GC-MS analysis: Gas chromatography-mass spectrometry (GC-MS) analysis was performed using an Agilent 7890A GC / single quadrupole mass spectrometer that was equipped with an Agilent 5975C inert XL MSD quadrupole. The derivatized sample was injected in a split mode (1 :10) with a 1 .0 mL / min flow rate using helium as a carrier gas with an injector temperature of 275°C. Separation of the individual monomers or components was achieved via an Agilent J&W VF-5ms column (30 m x 0.25 mm x 0.25 pm). A peak at a retention time of 2.73 min was recorded for dichloromethane, 2.88 min for ethyl acetate, S4 and 3.25 min for cyclohexene are not taken into % area calculations, as these peaks were already present in the dichloromethane blank.

[0118] Size exclusion chromatography (SEC): The molecular weights of waxes were measured using a size exclusion chromatography (SEC) system (Massachusetts, USA). The SEC system was connected to a refractive index detector (Waters 2414), an isocratic pump (Waters 1515), an autosampler (Waters 717), and a series of HR STYRAGEL HR4, HR3, HR2 (300 mm x 7.8 mm I.D.) columns with a controlled temperature of 35 °C and tetrahydrofuran (THF) was employed as an eluent at a flow rate of 1 mL / min. Approximately 2 mg of each wax sample was dissolved in 2 mL of THF and kept overnight before being filtered using a polytetrafluoroethylene-glass fiber (PTFE-GF) syringe filter (pore size = 0.45 pm and diameter = 13 mm). Polystyrene standard-SHODEX SM-105 supplied by Waters was used for the calibration (three replications).

[0119] MFI measurements: The melt flow index (MFI) of the L-PO / wax blends was determined by inserting the pellets into a Ray Ran melt flow indexer at a temperature of 230 °C using a weight of 2.16 kg. The MFI value was taken from an average of five samples.

[0120] Paper coating with upcycled waxes: Wax (1.1 g) was dissolved in 2.2 mL of chloroform by heating at 60 °C until a clear solution was obtained. Paper that was precoated with starch (5%) was trimmed to dimensions of 20 x 15 cm2and wax solution was applied onto it. The coated paper was subsequently dried in an oven at 65°C for 30 min. The samples were cooled down after they had been removed from the oven and they were then kept at room temperature for 24 h prior to other testing.

[0121] Water resistance: The standard TAPPI protocol, T441 , was used to record the water resistance of paper samples against liquid deionized water via Cobb Test for 1800 s.The weighed paper sample was placed in the Cobb sizing tester (Buchel BV Inc. Utrecht, Netherlands) and 100 mL of deionized water was added to it. The sample was weighed again after the test and difference in weight was related to the Cobbl 800 value and the results were expressed in units of grams per square meter (g / m2). To investigate water droplet behavior on the coated paper, a water droplet was placed on the surface of a paper sample and the results (e.g., contact angles) were recorded by capturing images after a time interval of 5 min had elapsed.

[0122] Oil Resistance: The oil resistance of developed coated papers was evaluated via kit tests which were performed according to the TAPPI T559 method. A series of kit solutions with kit ratings in the range of 1-12 was prepared using different ratios of n-heptane, toluene, and castor oil. A 0.1 mL droplet of test solution was placed onto a piece of paper for 15 s to check for the appearance of any dark spots which would indicate that the paper was unable to repel that kit solution. If no spot appeared for a test solution, the paper was considered to have passed the test. The highest number of kit solutions (in the range of 1 -12) which the sample can sustain corresponds to the kit number of that specimen. To evaluate the oil resistance, an oil droplet test following a similar method to that used for the water droplet test.Example 1 : Pyrolysis of Polyolefin Blends

[0123] Chemical recycling enables plastics to be a part of the circular economy as it can cope with contaminated as well as mixed plastics waste. Carbon-carbon backbone plastics such as polyethylene (PE) and polypropylene (PP) are the most widely used polymers, but high temperatures and large amounts of expensive and often toxic catalysts are needed to break down these polymers. This example illustrates the use of table salt (NaCI) as a metal catalyst to facilitate the low temperature pyrolysis of polyolefins comprised of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP) at the ratio of (4:2:2:3), respectively, thus enabling the efficient recycling of these mixed plastics. The 4:2:2:3 ratio for the different polyolefins was selected because it has a similar composition to plastics in municipal solid waste (MSW) in the United States. For comparative analysis, two different Pt catalysts as well as a control were investigated. Compared to the control, the use of table salt at 10 wt% increased both the oil and gas contents by 80% and enabled 100% conversion to gas and oil without producing any undesirable wax. The obtained oil fraction was further characterized using gas chromatography-mass spectrometry (GC-MS). In addition, the re-use of salt, the effect of salt particle size and effect of the wt% were explored. The thermal properties of the wax(solid) were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Economic estimation revealed a 3.5-fold increase in revenue could be generated using this method as compared to pyrolysis without any salt. In contrast, pyrolysis with a conventional Pt / alumina system incurs huge losses. The results indicate that table salt can provide an inexpensive (4 cents / kg) and efficient pyrolysis methodology for the conversion of mixed plastics waste to useful hydrocarbon products.

[0124] Materials: Polymers, including high density polyethylene (HDPE, MFI - 9 g / 10 min, DOWLEX IP-10262), low density polyethylene (LDPE, MFI - 25 g / 10 min, Sigma Aldrich, CAS-9002-88-4), linear low-density polyethylene (LLDPE, MFI - 1 g / 10 min, DOWLEX 2056G), and polypropylene (PP, MFI - 3 g / 10 min, Sabie), were used as received. Sodium chloride (Fisher Chemical, LOT 207695) was used as received. The platinum catalysts used included Pt / carbon (205931 , Sigma Aldrich, 5 wt% loading) and Pt / alumina (205974, Sigma Aldrich, 5 wt% loading).

[0125] Several screening experiments were initially carried out at different temperatures, using different reactor types (glass versus metal), pyrolysis with and without NaCI, as well as pyrolysis with selected Pt catalysts, as well as pyrolysis in the presence of NaCI / Pt catalyst. Pyrolysis was carried out in the presence of NaCI, Pt / carbon, and Pt / alumina, and a control pyrolysis process was carried out without any catalysts.

[0126] Polyolefin blends pyrolysis: HDPE / LDPE / LLDPE / PP were mixed at a weight ratio of 4:2:2:3, respectively. These blends were fed into an autoclave reactor wrapped in aluminum foil and then heated to 425 ± 5 °C for 4 h. All conditions were kept the same. After the reaction, oil and wax fractions were separated and weighed. The gas fraction was obtained by subtracting the weight of oil and wax from the initial load of plastic. The obtained oil fraction was analyzed via gas chromatography-mass spectrometry (GC-MS). The wax fraction was characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The gas fraction was not analyzed. The data obtained are listed in Table 1 .

[0127] Very low pressure was observed during the P-Control pyrolysis reaction. Overall, the product composition by weight was 18% liquid oil, 64% solid wax, and 18% gas as shown in Table 1 . The TGA analysis showed that the resultant wax lost 31.1% of its weight at 400 °C and had similar thermal properties to that of solid paraffin wax. Moreover, the DSC data confirmed that the melting point of the obtained wax was 58 °C. The pressure increased dramatically during the pyrolysis reaction of polyolefins with table salt, suggesting a very successful pyrolysis reaction. A remarkable increase in the liquid product fraction was obtained in comparison with that produced without table salt. For example, 86% of the product was liquid oil, -14% was gas, and nearly 0% was wax (Table 1).

[0128] The Pt catalyst used in the pyrolysis reaction has two different supporting materials, carbon and alumina. The reaction conducted at 425 ± 5 °C for 4 h and information regarding the obtained pyrolysis products is summarized in Table 1 . The use of Pt / carbon catalyst (>9000 $ / kg) with the mixed polyolefins did not affect the amount of the resulting oilbut increased the released gas content to 28% and caused the obtained solid product to decrease to 54% (Table 1 ). These results reflect the role of the Pt / carbon catalyst along the overall process, which began with facilitating the decomposition of the polymer from long chain waxes to small fragments and then continued with facilitating the conversion into gaseous materials. In contrast, the Pt / alumina catalyst (>9000 $ / kg) did not help to decrease the amount of wax obtained from the pyrolysis reaction, which still accounted for 62 wt% of the net product, and the amount of resultant oil was reduced to 14 wt% compared with the blank test. These results reflect the effect of the Pt / alumina catalyst in promoting the decomposition of the oil product to gaseous products; the content of gas had increased to 24% (Table 1 ).

[0129] In general, the addition of sodium chloride resulted in significant increases in the obtained oil which was 73% and 64% in case of P-Pt / C / NaCI and P-Pt / AI / NaCI, respectively. Meanwhile, the remaining wax obtained with P-Pt / C / NaCI dropped to 2%. The TGA analysis confirmed that dramatic loss of wax amount and showed that almost 84 wt% of the remaining solid was the recovered NaCI. The gas contents were 25% and 35% in the case of Pt / C / NaCI and Pt / AI / NaCI, respectively (Table 1). The Pt / alumina catalyst is well-known for the reforming of liquid hydrocarbons. Accordingly, a huge difference in the gas contents was observed, thus confirming the capability of Pt / AI / NaCI to facilitate the decomposition of short hydrocarbons to gaseous compounds. The resulting wax obtained with the P-Pt / C and P-Pt / AI catalysts have similar thermal properties. In particular, they lost 35.5% and 33.6% of their weights at 400 °C, respectively. The DSC curves showed melting temperatures at 78 and 75 °C, for the P-Pt / C and P-Pt / AI waxes, respectively.

[0130] GC-MS analysis was also performed on the oil fractions of various samples, including P-control, P-NaCI, P-Pt / C, P-Pt / C / NaCI, P-Pt / AI / NaCI, and P-Pt / AI / NaCI. Prior to the GC-MS analysis, the oil fraction was diluted by 1 :1000-fold in dichloromethane (DCM). GC-MS analysis suggests that a regular series of hydrocarbon peaks was obtained. The GC-MS of condensed oil obtained from the blank mixture pyrolysis showed a hydrocarbon distribution range (C11 -C25, where n in Cn denotes the number of carbon atoms in the respective hydrocarbon chain) with a high content of (C15-C20) hydrocarbon fractions, which is close to the range found in diesel fuel (Figure 2, panel a). All the obtained hydrocarbon compounds are normal hydrocarbon chains, and very few of them are unsaturated compounds.

[0131] For the P-NaCI sample, the GC-MS spectrum showed a broad hydrocarbon distribution (C8-C28) with a significant increase of hydrocarbon chains in the gasoline range(C8-C12), and most hydrocarbon products have the same intensity inside the product sample (Figure 2, panel b). Consequently, many compounds with C=C bonds, as shown by the presence of high intensity alkenes (C8, C9 and C11 ) in the obtained pyrolysis oil, are found in the gasoline range. The formation of many different hydrocarbon species provides some insights into the role of NaCI. The presence of low molecular weight hydrocarbons suggests that beta-scission is one of the pathways through which the pyrolysis reaction proceeds. Beta-scission often requires higher energy but produces shorter products than those obtained via random scission in thermal pyrolysis. It is possible that the presence of NaCI may affect the process via two modes. First, NaCI offers better thermal mixing thanks to the good heat transfer properties of the salt. Second, salt may absorb too much heat, which would lead to the formation of presumably ‘hot temperature sites’ around the NaCI particle.

[0132] The effect of varying wt% of NaCI with mixed plastics during pyrolysis and its effect on the gas and oil fractions was evaluated. Reduction of the NaCI load led to a gradual decrease in the oil and gas contents in parallel with an increase in the wax content. For example, for pyrolysis with 5.0 and 2.5 wt% of NaCI, the obtained oil / gas / wax weight ratios were 38 / 7 / 55 wt% and 18 / 4 / 78 wt%, respectively (P-NaCI(5) and P-NaCI(2.5) in Table 1 ).

[0133] The effect of salt particle size on the gas and oil fractions obtained from the pyrolysis process was evaluated. For these purposes, powder NaCI was used instead of its crystalline counterpart (P-(p)NaCI in Table 1). The use of powder NaCI led to complete pyrolysis of the polymer mixture, and the obtained oil and gas contents were 73 and 27 wt%, respectively. On the other hand, the crystalline P-NaCI system yielded oil and gas contents of 86 and 14 wt%, respectively (Table 1 ). It is evident that powder NaCI produced more gas than oil and the possible reason for this observation is that the smaller size of the NaCI particles enhanced the surface area for a given amount of NaCI that improved both the heat transfer properties and the number of hot temperature sites.

[0134] The reusability of NaCI (powder) was evaluated as a catalyst / additive and its impact on the pyrolysis product. In the first cycle of NaCI use, the obtained oil and gas contents were 73 and 27 wt%, respectively (P-(p)NaCI in Table 1). In the second cycle, the obtained oil and gas contents were 71 and 24 wt%, respectively, while the wax content was 5 wt% (P-INaCI in Table 1). The recovered NaCI was able to promote the second pyrolysis cycle with negligible activity losses when compared with the fresh NaCI, thus validating the reusability of table salt for pyrolysis.

[0135] GC-MS patterns of the oil obtained from the Pt / carbon catalyzed pyrolysis were evaluated for reactions performed without NaCI and with NaCI. The presence of the Pt catalyst enhanced the formation of unsaturated hydrocarbons, especially in the range of (C9- C12), owing to the Pt-catalyzed dehydrogenation reaction. Highly intense hydrocarbon peaks (C13-C21 ) were observed within the diesel range. The addition of NaCI caused the hydrocarbon distribution to become much broader (C8-C28) and enhanced the formation of unsaturated hydrocarbons with the aid of the Pt / carbon catalyst as well. The GC-MS chromatogram of the oil obtained from this reaction displayed peaks corresponding to hydrocarbons in the gasoline range (C8-C12), and highly intense peaks were observed which corresponded to hydrocarbons in the range of C10 to C17.

[0136] The Pt / alumina catalyst exhibited similar performance to that of the Pt / carbon catalyst but offered a slight increase in the obtained hydrocarbon distribution which extended to the formation of C29. As was the case with the Pt / carbon catalyst, the formation of unsaturated alkenes was observed when we used the Pt / carbon catalyst. The addition of table salt to the Pt / AI yielded hydrocarbons with lengths reaching up to C31 while also promoting the formation of gasoline range hydrocarbons.Example 2: Pyrolysis of Metallized Films

[0137] This example illustrates that metallized plastics were successfully pyrolyzed with table salt with excellent conversion efficiencies. Pyrolysis was carried out in the presence of NaCI, Pt / carbon, and Pt / alumina, and a control pyrolysis process was carried out without any catalysts.

[0138] Materials: Metallized plastic packaging films for potting roasted sauce were collected from CONAGRA Brands and they were used after grinding to amorphous powder using a single speed mini cutting mill. Sodium chloride (Fisher Chemical, LOT 207695) was used as received. The platinum catalysts used included Pt / carbon (205931 , Sigma Aldrich, 5 wt% loading) and Pt / alumina (205974, Sigma Aldrich, 5 wt% loading).

[0139] Metalized films (MF) are widely used in industry, but they are very difficult to recycle. In addition, metallized films contain aluminum, which has good heat dissipation. This example evaluates whether aluminum also had an influence on the oil and gas fractions that were produced during the pyrolysis reaction. Commercially available metalized films were obtained, ground, and then subjected them to pyrolysis. Typically, these samples were run at a 5 g scale in an autoclave reactor. The TGA analysis showed that the ground metallized films had a metal content of 5 wt%. Conditions for the pyrolysis of these metallized films and the results obtained from these reactions are summarized in Table 2.

[0140] For the MF-Control, the oil / gas / wax contents obtained from the pyrolysis reaction were 25, 27, and 48 wt%, respectively. Meanwhile, for the MF-NaCI sample, the oil / gas / wax weight ratios were 42, 42, and 16 wt%, respectively. Following the pyrolysis of the metallized film in the presence of NaCI, the residual wax content was reduced dramatically from 48 to 16 wt% (Table 2). Again, NaCI greatly improved the efficiency of the pyrolysis reaction. The composition of the remaining solid and the thermal properties of the obtained wax were estimated by TGA and DSC analysis. The wax obtained from the MF-NaCI lost 75% of its weight upon heating up to 400 °C and its DSC curve showed a sharp low melting point at 53 °C. In contrast, the wax obtained from the MF-control sample melted at 66 °C.

[0141] The Pt / carbon catalyst was also used to promote the pyrolysis of the metallized films (this system was denoted as MF-Pt / C). Based on the obtained products, this catalyst had no significant effect, except that the fraction of low molecular weight hydrocarbons was increased when the Pt / carbon catalyst was employed as compared to the fraction obtained with the MF-Control sample. For example, for the MF-Control, the oil / gas / wax weight ratios were 25, 27, and 48 wt%, respectively, while those obtained for the MF-Pt / C sample were 21 , 32, and 47 wt%. This slight increase in the gas fraction corresponds to an increase in the catalytic dehydrogenation reaction rate in the presence of the Pt / carbon catalyst. For the MF-Pt / C / NaCI system, the resultant oil / gas / wax weight ratios were 42, 49, and 9 wt%,respectively. Thus, again a great increase was observed in the oil and gas fractions with the use of table salt.

[0142] The GC / MS chromatograms obtained from the MF-control and MF-NaCI samples are almost identical. This finding suggests that there is no significant difference in the composition of the oil produced via pyrolysis either without or with the addition of NaCI, rather than a slight decrease in the formation of unsaturated hydrocarbons. In both cases the resulting oil hydrocarbons are found to be in the range (C9-C29) which is falls in the diesel range. Therefore, the addition of NaCI improved the pyrolysis product yields but it did not significantly affect the chemical composition of the obtained oils.

[0143] Compared to the oil composition of the pyrolyzed MF-control sample, the use of Pt / C catalyst did not show any significant effect on the hydrocarbon composition of the resulting oil, except for the enhancement of the unsaturated hydrocarbon content, reflecting an increase of the catalytic dehydrogenation reaction rate. In contrast, the use of MF- Pt / C / NaCI led to a significant drop in the unsaturated hydrocarbon content in the obtained oil, reflecting the ability of table salt to accelerate the degradation reaction rate of polyolefins, which took place faster than the dehydrogenation reaction. The highest hydrocarbon content in the obtained oil was found to be in the ranges of C14-C21 and C15-C20 for MF-Pt / C and MF-Pt / C / NaCI, respectively.

[0144] The GC-MS analysis of oil obtained following the pyrolysis of the MF-Pt / AI sample showed that the hydrocarbons in the gasoline range (C13-C18) had the highest concentration, and they were combined with small amounts of unsaturated hydrocarbons. As mentioned earlier, the use of Pt / alumina with NaCI leads to a lower yield of oil from the pyrolysis reaction. From the GC-MS chromatogram of the oil obtained from the MF- Pt / AI / NaCI system, it is evident that the addition of NaCI increased the unsaturated hydrocarbon content due to the enhancement of Pt / alumina dehydrogenation reactivity compared with that observed with MF-Pt / AI. In addition, the high intensity hydrocarbon content was extended to the range of C12-C21 . The chromatogram of the oil product obtained from MF-Pt / AI / NaCI is almost identical to that obtained from MF-Control.

[0145] An economic analysis was performed to measure the impact of the pyrolysis method. The value of the oil obtained was considered to be similar to that of gasoline, and the cost of gasoline was taken to be identical to that of natural gas. Meanwhile, wax was treated as a waste product with no economic value. The cost of highly pure NaCI was obtained from Statista. Also, the costs of the catalyst and salts were assumed to be for single use. Bearing the above assumptions in mind, a reactor was selected with an annualpyrolysis capacity of 8,400 tons, which is equivalent to 24 tons per day for 350 days per year. Using this reactor, an annual revenue of 2.18 million USD for the control pyrolysis is projected. Meanwhile, pyrolysis process driven by NaCI yields a revenue of 9.8 million USD, after accounting for the NaCI expenses. This marks a 3.5-fold increase in output by the disclosed method in yearly revenue as compared to the control pyrolysis without an alkali metal salt catalyst. On the other hand, Pt / alumina system leads to an annual net loss of 258 million USD, due to the high cost of this catalyst.Example 3: Pyrolysis of High-Density Polyethylene

[0146] Chemical upcycling of plastic waste from landfills to value-added products offers both economic and environmental benefits. This example illustrates a method to convert high-density polyethylene (HDPE) into upcycled waxes in a very high yield (up to 93%). This selectivity is achieved by reducing the degradation temperature of HDPE via the addition of an inexpensive and reusable sodium chloride as a metal catalyst. These upcycled waxes had performance comparable to those of commercial rheology modifiers. In addition, kraft paper coated with these upcycled waxes exhibited excellent water- and oil resistance. A revenue analysis showed that this method allows plastic-to-wax to conversion with a threefold revenue benefit over traditional ways of producing pyrolysis waxes from plastics. The method can be extended to major plastics by reducing the degradation temperatures of plastics, thereby obtaining even better control over the pyrolysis products.

[0147] Materials: HDPE was supplied by Nova Chemicals, LLDPE (DOWLEX 2056G, MFI - 9 g / 10 min) was purchased from Dow Chemicals, and polypropylene (PP, PD-1428) was supplied by Formosa Plastics Corp. The commercial Fischer-Tropsch wax SASOL B52 was supplied by SASOL Chemicals, South Africa. The waste plastics were obtained from Michigan State University (MSU) Surplus and Recycling Center, Michigan, United States. One-gallon HDPE milk bottles were obtained from a local store. These bottles were then washed with detergents to remove any fats. These cleaned HDPE bottles were cut into flakes and subsequently dried at room temperature. Finally, they were ground into a powder to thus obtain the waste plastic (WP), which would be used for subsequent pyrolysis experiments.

[0148] Pyrolysis Procedure: An autoclave reactor was filled with 10.0 g of HDPE (virgin or waste) and 1 .0 g of NaCI (10 parts per hundred resins, referred to here and onward as 10 wt%). The autoclave reactor was completely wrapped with aluminum foil to maintain the pyrolysis temperature inside the reactor and the reactor was placed in a pre-heating heating mantle at 425 °C (virgin HDPE) and 450 °C (waste HDPE) (Table 3). The wax wasrecovered using three different approaches including: 1 ) dissolution in and evaporation of an organic solvent, such as chloroform; 2) cooling down and scraping out salt from the bottom of the solidified wax; and 3) hot-water dispersion followed by cooling, with the solid wax collected from top of the water surface.

[0149] Results: Both virgin and waste HDPE were used as feedstocks for upcycled waxes. As a general strategy, virgin HDPE (denoted as V) was pyrolyzed with 10 wt% sodium chloride for different durations such as 2.0, 2.5, 3.0, and 5.0 h, and the obtained pyrolyzed products are listed in Table 3. After pyrolysis, waxes were recovered by different methods such as dissolution-evaporation or scraping of salt from the bottom of solidified wax (salt settles at the bottom during cooling), or by a hot-water dispersion approach. This hot- water dispersion approach is simple and very effective as the salt can be easily separated from wax, and both recovered wax and salt were ready for further use.Table 3. HDPE pyrolysis conditions, pyrolytic waxes yield, and characterization

[0150] Pyrolysis of Virgin HDPE: The Tm and Tc of the obtained waxes were determined by DSC (Table 3). The DSC analysis showed that the V / 3h recovered wax has a Tm and Tc of 108 and 95 °C, respectively, which almost match those of the commercial SASOLWAX B52 which are 110 and 99 °C. Both V / 2.5h and V / 2h have similar thermal properties. For example, V / 2.5h and V / 2h have Tm values of 125 and 127 °C, respectively, and Tc values of 107 and 112 °C while the HDPE (polymer) showed a Tm at 132 °C and Tc at 116 °C. The decrease in Tm clearly indicated the successful formation of wax from virgin HDPE. To obtain highly viscous wax (Wv), virgin HDPE was heated with 10 wt% sodium chloride for 5 h (Table 3, labelled as V / 5h). When pyrolysis was conducted for virgin HDPE in the absence of NaCI, no wax was produced under these conditions (see V / 3h Blank shown in Table 3). This confirms that NaCI facilitates production of large amounts of wax at moderate temperatures.

[0151] The number average molecular weight (Mn), weight average molecular weight (Mw), and polydispersity (PDI) of the recovered waxes were determined by size exclusion chromatography (SEC) in tetrahydrofuran (THF). SEC analysis shows that the Mn of the recovered waxes (soluble portion) was 657, 523, and 589 g / mol corresponding to samples V / 3h, V / 2.5h, and V / 2h with PDI values of 2.02, 1 .98, and 1 .24, respectively. The partial solubility of the pyrolytic solid in THF is further evidence for wax formation because HDPE could not dissolve in THF and thus its Mn, Mw, and PDI could not be determined. Based on the 1 H-NMR analysis, the obtained hard waxes V / 3h, V / 2.5h, and V / 2h are mainly saturated hydrocarbon chains. The ratio of unsaturated chains is in the range of 1-2% assigned with the presence of alkene protons at 4.9, 5.4, and 5.8 ppm, representing both terminal and internal (-C=C-) bonds, and there are no aromatic protons visible in the spectra of the hard waxes. The aromatic protons are found at 7.0-7.3 ppm, confirming the presence of a small content of aromatics, but only in viscous wax (V / 5h) with a ratio of ~1%. Due to the poor solubility / volatilization of hard waxes V / 3h, V / 2.5h, and V / 2h, the GC-MS analysis did provide useful information, for V / 5h shows regular series of light hydrocarbon peaks from C15 to C35. Overall, the obtained waxes are alkanes, especially the hard waxes.

[0152] The TGA analysis confirmed the thermal stability of the obtained waxes. It has been reported that the pure paraffin wax showed a one-step thermal decomposition profile which started at 208 + 2°C. Therefore, to determine the actual recovered wax yield, 210°C was set as a reference point. The losses prior to these points were considered as liquid volatile products and the losses observed above this temperature of 210 °C were taken as solid wax. In general, the waxes recovered after 2 and 2.5 h (V / 2h and V / 2.5h) from thevirgin HDPE showed high thermal stability compared with SASOLWAX B52. At 210 °C, the V / 3h recovered solid underwent an 8% loss of volatile materials reflecting the actual wt% of the recovered wax, which was 82% (Table 3), while only less than 1% loss of volatile materials were observed the cases of the V / 2h and V / 2.5 samples. The V / 3h recovered wax showed the same thermal stability as that of SASOLWAX B52 at 377 °C by losing 32% of its analyzed weight, while V / 2h and V / 2.5h still exhibited high thermal stability and underwent modest weight losses of 2% and 4%, respectively.

[0153] Pyrolysis of Waste HDPE: The pyrolysis method using a metal salt catalyst was also applied to waste HDPE (WP). This WP was obtained from milk bottles which were ground into a powder. WP pyrolysis was initially performed in the presence of 10 wt% salt in a sealed autoclave reactor at 425 °C for 2 h, but no wax was recovered. Then the pyrolysis time was increased to 4 h and there was still no change in the WP. It is believed that this was due to the presence of stabilizer in the WP and / or a very high molecular weight of the WP that had prevented wax formation. Therefore, the pyrolysis temperature for WP was raised to 450 °C. At this higher temperature, viscous wax (Wr) was recovered after four hours (Table 3, WP / 4h). To obtain hard waxes (with a high Tm), WP was subjected to pyrolysis for 1 .5, 2.0, and 2.5 h, with the resultant yields of the crude waxes being 95%, 92%, and 90%, respectively, corresponding to WP / 1.5h, WP / 2h, and WP / 2.5h (Table 3). The wax yield was lower with longer pyrolysis time because of the further depolymerization of wax into oil. When pyrolysis was conducted for WP in the absence of NaCI, no wax was produced under these conditions (WP / 2.5h Blank in Table 3).

[0154] The Tm and Tc of the resulting waxes were determined by DSC analysis. Overall, 1 .5 h of heating at 450 °C was enough to depolymerize WP and reduce its Tm and Tc from 136 and 118 °C, respectively, to 121 and 108 °C corresponding to the WP / 1 ,5h wax (T able 3). Extending the pyrolysis time to 2 h led to a further reduction in the Tm and Tc of the WP / 2h obtained wax to 117 and 103 °C, respectively. A further increase in the pyrolysis time by 30 min afforded a soft wax (WP / 2.5h) and caused the Tm and Tc to decrease to 92 and 79 °C, respectively (Table 3). SEC analysis for the soluble portion revealed that the Mn of the resultant waxes gradually decreased as the pyrolysis time was extended and was found to be 955, 638, and 517 g / mol, respectively, for the WP / 1 ,5h, WP / 2h, and WP / 2.5h samples. In addition, a gradual broadening of the PDI was observed for the resultant waxes when the pyrolysis time was extended from 1 .5 to 2.5 h. The 1 H-NMR analysis confirms the saturated hydrocarbon nature of the resulting waxes with gradual increasing degrees of unsaturation as the pyrolysis time progresses from 1 .5 to 2.5 h. The ratio of unsaturated hydrocarbon is 1 - 2 mol%, assigned at 5.8, 5.4, and 4.9 ppm and they are mostly terminal alkenes, without anyaromatic content. Due to the low solubility of hard waxes such as WP / 1 ,5h and WP / 2h GC- MS did not give meaningful data. However, WP / 2.5h wax shows the presence of light hydrocarbons up to C35 (limited to the standard alkane) similar to R / 4h viscous wax but with higher C16-26 content. Overall, the obtained waxes are alkanes, especially the hard waxes.

[0155] The thermal stability and presence of any volatile oil in the recovered crude waxes was observed via TGA analysis. Assuming that the decomposition of wax started after 210°C, the respective losses of 2%, 7%, and 14% of their initial weights for the WP / 1 ,5h, WP / 2h, and WP / 2.5h samples at temperatures up to 210 °C can be attributed to volatile contaminant materials. Consequently, after deducting volatile components, 93, 85, and 76 wt% are the actual wax contents for WP / 1 ,5h, WP / 2h, and WP / 2.5h, respectively (Table 3). WP / 2.5h produced a soft wax which was less thermally stable than the other recovered waxes and SASOLWAX B52, while the waxes recovered from WP2h and WP / 1 ,5h showed significant thermal stability. At 400 °C, the recovered waxes from WP / 2h and WP / 1 ,5h lost 18% and 21% of their initial weight and showed higher thermal stability than the commercial SASOLWAX B52 (which lost 46 wt%), thus giving the recovered waxes an advantage for applications as rheology modifiers for high-temperature processing methodologies. WP / 2h and WP / 1 ,5h recovered waxes have the same thermal stability as SASOLWAX B52 at 344 and 308 °C, respectively.

[0156] Effect of Temperature and Salt: A comparison between high-temperature, medium-temperature, and sodium chloride-assisted medium-temperature pyrolysis is shown in Figure 3. High-temperature pyrolysis at 500-600°C using a fixed-bed reactor system for 3 h pyrolysis time results in minimal wax formation (only 32%) and a broad range of products, due to the further degradation of waxes into oil / gas at high temperature. This example shows that medium-temperature pyrolysis without salt for virgin HDPE (425 °C) and for waste HDPE (450 °C) yields no wax (Table 3 for pyrolysis without salt). However, performing salt-assisted pyrolysis at these relatively low temperatures in an autoclave reactor for produces an excellent yield of waxes from both virgin and recycled waste HDPE (at least 95%; Table 3). As the waste HDPE used here was milk-grade (used for milk containers), and milk-grade HDPE has a molecular weight of 42,000-50,000 g / mol, the degree of polymerization (n) before pyrolysis is 1 ,500 (i.e., 42,000 g / mol divided by 28 g / mol).

[0157] The presence of sodium chloride facilitated the depolymerization of HDPE into waxes at a lower temperature (425-450°C). Without salt, HDPE remained mostly in its original texture under the same conditions. TGA analysis further confirms this by indicatingthat NaCI significantly lowers the degradation temperature of HDPE. It is believed that NaCI promotes uniform heat distribution, enabling a uniform breakdown of plastics throughout the sealed reactor. In addition, the high heat capacity of NaCI, which is notably double that of aluminum, means it stores more energy and conducts it faster to the surrounding plastic melt, which effectively initiates HDPE breakdown at a relatively lower overall temperature. Also, plastic could serve as a solvent for some salts, leading to the liberation of free ions with strong heat transfer capabilities. It is important to highlight that the rate of byproduct formation accelerates with increasing temperature. Therefore, the NaCI-enabled reduction of HDPE’s degradation temperature permits desired waxes to be obtained.

[0158] Use of upcycled waxes as rheology modifiers: Laboratory-controlled polyolefins (L-PO) were made up of three types of PE (HDPE, LDPE, and LLDPE) and PP. The PE / PP composition was chosen to be 62.5 / 37.5 wt / wt to mimic the PE and PP present in U.S. municipal solid waste (MSW). L-PO pellets were prepared from the mentioned PE / PP blends by a single screw extruder (SSE) at a temperature profile of 190, 180, 170, and 160 °C utilizing a screw speed of 20 rpm. The bulk polymer strands were then pelletized into small pellets. These pellets were then mixed with different concentrations of the wax and subsequently processed via a laboratory-sized DSM micro-compounder at a temperature of 180 °C for 10 min to ensure effective mixing of the polyolefins and the waxes. The L-PO / wax polymer strands were then cut into small pellets for melt flow evaluation.

[0159] The effect of the waxes on the melt flow properties was evaluated with a melt flow indexer. The neat L-PO was used as a reference to compare the effectiveness of the waxes in altering the melt flow index (MFI) values of the samples. The L-PO sample containing the commercial SASOLWAX B52 showed a higher MFI at 5 and 10 wt% compared to the neat L- PO sample. At 10 wt% loading, the waxes derived from waste HDPE (Wr), WP / 1 ,5h, WP / 2h, and W / 2.5h significantly increased the MFI of the L-PO compared to the neat sample. Overall, V / 2.5h, WP / 2h, and WP / 2.5h showed good rheological enhancement behavior.

[0160] Paper coating application: The water resistance of the coated paper samples was evaluated via Cobb1800 tests using deionized water as the test liquid. The results obtained from these tests were compared to those obtained with uncoated kraft paper (blank), starch-coated papers (SCP), and two commercial benchmarks (i.e., carnauba wax- coated paper and paraffin wax-coated paper), which were used as a control. The blank was unmodified with a highly porous surface, and thus it exhibited a very high Cobb1800 value of 164.05 ± 5.44 g / m2. The Cobbl 800 value was reduced to 86.50 ± 6.36 g / m2 for SCP afterthe application of only starch onto kraft paper because the pores were thoroughly masked by starch. Although the surface of the SCP was well-covered by the starch, its Cobb1800 value was still rather high due to the hydrophilic nature of starch. The application of the wax sample V / 5h onto SCP caused its Cobb1800 value to decrease up to 29.15 ± 3.88 g / m2. A significant reduction in the Cobbl 800 value to 2.70 ± 0.84 g / m2 was observed when the wax sample WP / 4h was applied onto blank paper. The result shows that the water resistance of recycled waxes is comparable with commercial benchmarks. The Cobbl 800 value of sample V / 5h is comparable to that of paraffin-coated paper (22.09 ± 2.41 g / m2) and lower than that of carnauba wax-coated paper (43.65 ± 0.77 g / m2). Meanwhile, sample WP / 4h showed a Cobb1800 value that was significantly lower than both commercial benchmarks. Paper coated with WP / 4h had better performance than that coated with V / 5h, because the former wax gave a smooth and homogeneous coating, leading to enhanced water resistance. This smoothness is attributed to the presence of a larger ratio of low-molecular-weight waxes that act as plasticizers, thus resulting in a superior coating compared to that of V / 5h. This result indicates that paper samples obtained by coating with waxes have excellent water resistance and can be used in the paper coating industry to prepare hydrophobic packaging.

[0161] A water droplet test was also performed by placing a droplet of deionized water on the surface of a paper sample while comparing the results observed with uncoated kraft paper and starch-coated paper. The penetration effect was noted by recording the photographs of the water droplet after five minutes had elapsed since its placement on each coated paper. Similarly, the images were recorded once the droplet was wiped off (after it had been present for 5 min) to determine whether any stains remained from the droplet. The droplet left a dark scar behind on the blank sample. Meanwhile, water droplets remained in place on the paper samples that were coated with V / 5h, WP / 4h and commercial benchmarks, and no stains were observed after the water droplets had been wiped away, indicating that these samples had good water resistance.

[0162] Oil Resistance: A kit test was carried out to analyze the oil repellency of the coated paper samples. The kit values were in the range between 0-12, with a higher value corresponding to better oil resistance. When there was no stain visible after the application of a particular kit solution, paper was considered to have passed the kit rating test for that liquid. The kit rating corresponded to the liquid with the highest kit rating that could be applied onto the paper without leaving a stain. The blank sample showed a kit value of 0, as stains were observed for the kit 1 solution. The failure of a kit test means that a dark stain appears following the application of the kit solution. The SCP showed a kit rating of 8, which indicates that the starch-coated paper is oleophobic in nature. The kit rating of the papersamples that were coated with V / 5h and WP / 4h was further increased to 12 in both cases, indicating that these samples had excellent oil resistance, with the highest possible rating that can be achieved via this test.

[0163] The resistance against oil was recorded using a castor oil droplet following a similar method to that used for the water droplet test. The results revealed that the castor oil was quickly taken up by the blank sample, leaving a dark stain behind while there was no spot visible on the surfaces of the SCP and wax-coated paper samples (V / 5h, WP / 4h and commercial benchmarks), suggesting that they had high oil repellency. These results showed that all these wax-coated papers can be used as highly oil repellent packaging.Example 4: Depolymerization of Polymers at Low Temperatures

[0164] Polymer depolymerization or pyrolysis can be performed at a relatively lower temperature by using additives that have higher heat capacity and thermal conductivity (e.g., compared to thermal pyrolysis without a catalyst or other additive). A decrease in pyrolysis temperature helps to control selectivity in the pyrolysis products. For example, HDPE pyrolysis without a catalyst or other additive at 500°C will give all kinds of products such as gas, oil, and gas from the very beginning, especially at large-scale reactions where the products are difficult to diffuse from the plastic melt. However, if such reactions are performed at lower temperatures, one can obtain wax, oil, or gas in quantitative yield by controlling the duration of the reaction. This is because, under milder temperatures, degradation is milder. A lower polymer degradation temperature can be achieved using additives with high heat capacity and thermal conductivity (e.g., at 2-20 wt.% loading relative to polymer as general described for metal / salt catalysts herein). This additive can be water soluble, like table salt, water-insoluble, alumina, etc. This approach can be applied to all major plastics (solo or mixed). Salts and other inorganic materials can be designed to reduce the degradation temperatures of plastics further, thereby providing even better control over the pyrolysis products.

[0165] Degradation temperature is affected by multiple factors, including the scale of the process, reaction conditions, the physical texture (size and shape) of the plastic, and the manner in which samples are heated. As shown above, HDPE can be converted into waxes at 425-450°C in the presence of salt. Without salt, HDPE remains unchanged. TGA analysis above confirms this, which suggests that NaCI lowered the degradation temperature of HDPE by a significant degree.

[0166] Physical Texture: A TGA analysis was performed with both HDPE pellets and powder. A distinct shift in degradation temperature (Td ) was observed. HDPE pelletsdegrade at higher temperatures than HDPE powder. A further decrease in Td for HDPE powder was observed with the addition of NaCI to the system.

[0167] Thermal conductivity: It is believed that the uniform heat distribution provided by sodium chloride promotes a consistent breakdown process throughout the reactor system. Additionally, the granularity of the salt (i.e., correlating to specific surface area of the salt) affects the pyrolysis reaction. The thermal conductivity of HDPE is approximately 0.4 W / (m-K). Meanwhile, the thermal conductivity of NaCI is significantly higher than that of HDPE, at 3.13-3.87 W / (m-K). It is believed that metal catalysts like NaCI facilitate the transfer of heat more readily than would be the case if only HDPE were heated, thereby enabling the use of a lower temperature to achieve HDPE degradation.

[0168] Heat capacity: It is believed that the significantly high heat capacity of sodium chloride, which is double that of aluminum metal, could potentially create localized regions of elevated temperatures, effectively initiating HDPE’s breakdown even when the reactor’s overall temperature is comparatively low. For example, the molar heat capacity of sodium chloride crystals is 50.5 J / (mol-K)). Meanwhile, the specific heat capacity of aluminum is 0.897 J / (g-K) and its molar heat capacity is 24.20 J / (mol-K) at 25 °C and 100 kPa. Silica (SiC>2) was also evaluated for its effect on the degradation temperature of HDPE. Silica has a specific heat capacity of 0.745 J / g-K and a low thermal conductivity of 1 .38 W / m-K (fused silica). The degradation temperature of HDPE remained unchanged, likely due to silica’s low thermal conductivity.

[0169] Alumina (Aluminum Oxide (AI2O3)): Alumina has a Specific Heat Capacity of 0.765 J / g-K and a thermal conductivity 30 W / m-K. By adding table salt to alumina in equal weight ratio, the thermal conductivity and heat capacities will be the average of the NaCI and alumina, which in turn decreased the impact of alumina on the degradation temperature of HDPE.

[0170] Doping / blends: Several combinations are possible to design new catalysts for controlling the degradation temperature. For example, doping / blending table salt or other metal catalyst with different mineral conductors can help to achieve desirable degradation temperatures. This approach can be extended to many different plastics, especially those with a C-C backbone. The concept can be used to create to gas, oil, or wax as selective products.

[0171] The role of sodium chloride (NaCI) in the pyrolysis of HDPE was evaluated with and without several heat transfer materials different in their thermal transfer properties andheat capacities, and the resultant yields of the crude waxes were at least 92%. The results and reaction conditions are shown in Table 4.Table 4. Pyrolysis conditions for HDPE using (20 wt%) additives at 450 ± 5 °C

[0172] Lower Temperature Depolymerization: A striking observation was the ability of HDPE to become converted into waxes at 425-450 °C in the presence of salt. Without salt, HDPE remains unchanged. This is also confirmed by the TGA analysis, which suggests that NaCI lowered the degradation temperature of HDPE by a significant degree. The degradation temperature (Td) of the blank residue is 421 °C, while the wax formed with the addition of table salt showed Td at 384°C. Mixing the table salt with alumina (high heat transfer materials) in 50 / 50 ratio also decreased the Td to 388°C. However, doping table salt with 20% weight ratio of alumina formed high thermally stable wax with a Td at 420 °C. The pyrolysis with the addition of 20wt% alumina showed an extreme decrease in the Td which reduced to 355°C, confirming the role of the super high heat transfer property of alumina, while there is no recognized difference in the Td values of the solid recovered from blank sample and the solid obtained after the use of silica which have very low thermal conductivity. The pyrolysis conditions and the thermal properties of the recovered materials are summarized in Table 4. Supposing that wax decomposition started after 210°C, there is no any weight loss in case of blank and silica used samples confirming there is no waxformation, but in case of alumina, about 12% wight loss is observed and in case of NaCI and mixed additive the pyrolytic waxes lost about 4%-6% of their initial weights.

[0173] The Tm and Tc of the resulting solids (high Mw PE) and waxes were determined by DSC analysis. The highest Tm and Tc are (128, 110 °C) and (126, 111 °C) corresponding to the solid recovered from blank and silica addition trials, respectively. The wax recovered by using alumina showed the lowest Tm and Tc values at (98, 84 °C) confirmed the extreme effect of alumina in the degradation process during pyrolysis. With the addition of NaCI, the recovered wax has Tm and Tc (118, 104 °C), respectively. Using mixed table salt and alumina has a slight effect on the thermal properties of the recovered waxes compared with the wax recovered by table salt only.

[0174] Salt grain size: The granularity (or particle size) of the salt appears to affect pyrolysis as a surface area effect in the reaction process. It is believed that uniform heat distribution enabled by sodium chloride promotes a consistent breakdown process throughout the reactor system.Example 5: Selective Pyrolysis of Mixed Polyethylene Waste

[0175] Advanced recycling offers a unique opportunity for the circular economy, especially for mixed and contaminated plastics that are difficult to recycle mechanically. However, advanced recycling has barriers such as poor selectivity, contaminant sensitivity, and the need for expensive catalysts. This examples illustrates yet scalable methodology for converting mixed polyethylene (high-density and low-density polyethylene recycled polyethylene) into upcycled waxes with up to 94% yield. This high yield was possible by performing the reaction at a mild temperature and was enabled by using inexpensive and reusable table salt. Without table salt, in otherwise identical conditions, the plastic remained essentially undegraded. These upcycled waxes were used as prototypes for applications such as water- and oil-resistant paper, as well as rheology modifiers for plastics. Their performance is similar to that of commercial wax as well as rheology modifiers. An economic analysis shows that the upcycled waxes obtained by this table salt-catalyzed approach offer three times more revenue than those reported in the literature.

[0176] Materials: HDPE and LDPE were supplied by Nova Chemicals (Pellets form, the average size of the pellet is 0.12-0.13 inch), LLDPE (DOWLEX 2056G, MFI - 9 g / 10 min) was purchased from Dow Chemicals, and polypropylene (PP, PD-1428) was supplied by Formosa Plastics Corp. The commercial Fischer-Tropsch wax SASOBIT B52 was supplied by SASOL Chemicals, South Africa. The waste plastics were obtained from Michigan State University (MSU) Surplus and Recycling Center, Michigan, United States. The waste plasticsunder study were separated to HDPE waste and LDPE wastes based on the number in the recycling symbol. The waste plastics were washed with detergent then rinsed by tab water and dried at room temperature for 24h. The waste plastics were used after grinding to amorphous powder using a single speed mini cutting mill (20 MESH Screen).

[0177] Pyrolysis Process: An autoclave reactor was filled with 10.0 g of HDPE / LDPE mixture (virgin or waste) in different ratios (10-50% LDPE) and 1.0 g of NaCI (10 parts per hundred resins, referred to here and onward as 10 wt%). The autoclave reactor was completely wrapped with aluminum foil to maintain the pyrolysis temperature inside the reactor, and the reactor was placed in a pre-heating heating mantle at 425 °C (virgin HDPE / LDPE mixture) and 450 °C (waste HDPE / LDPE mixture). The wax was recovered using three different approaches including: 1) dissolution in and evaporation of an organic solvent, such as chloroform; 2) cooling down and scraping out salt from the bottom of the solidified wax; and 3) hot-water dispersion followed by cooling, with the solid wax being collected from the top of the water surface.

[0178] Selectivity: Branched PE (LDPE) is thermally less stable than linear PE (HDPE), and the conditions required to obtain wax from mixed PE are likely to be different than those needed for HDPE alone. A thermogravimetric analysis (TGA) of HDPE and LDPE blends was performed, including a comparative TGA analysis of HDPE / LDPE blends both in the presence and absence of table salt (a good thermal conductor and high heat capacity) and silica (a low thermal conductor with a low heat capacity). It is believed that table salt reduces the degradation temperature thanks to its high heat capacity and good thermal conductivity. For example, the thermal conductivity of PE is nearly 0.4 W / (m K), while that of sodium chloride it is almost 3.5 W / (m-K); therefore, sodium chloride facilitates the transfer of heat more readily. In addition, the high heat capacity of sodium chloride leads it to absorb more heat that is then transferred to the plastic. These high heat spots trigger degradation while allowing a low overall plastic melt temperature to be maintained, and this leads to milder conditions for pyrolysis. As a result, pyrolysis can be performed at lower temperatures with more control over product selectivity. In contrast, no real decrease in the Td was observed when silicon dioxide was added to the HDPE / LDPE blends.

[0179] Virgin HDPE / LDPE mixture chemical upcycling into wax: Virgin HDPE / LDPE mixtures where the LDPE content was varied from 10, 20, 30, 40, and 50 by wt% were used as feedstocks to produce upcycled waxes. Unless specified otherwise, the pyrolysis was performed in the presence of 10 wt% of table salt. The detailed composition and the physical properties of the obtained upcycled waxes are listed in Table 5. Waxes were recoveredusing various techniques, including hot-water dispersion, solvent dissolution-evaporation, or scratching salt off the bottom of solidified wax. The latter of these three methods was particularly efficient because the salt and wax could be simply separated, and both recovered wax and salt were ready for further use.Table 5. Pyrolysis conditions for HDPE / LDPE virgin mixture using (10 wt%) NaCI at 450 ± 5 °C

[0180] As shown in Table 5, high yields of waxes were recovered (at least 90%). To obtain viscous waxes (V3-V5), virgin HDPE / LDPE mixtures were heated with 10 wt% table salt for three h in the case of the 70 / 30 mixture (Table 5, labeled as V3) and for two h for the 60 / 40 and 50 / 50 HDPE / LDPE mixtures (Table 5, labeled as V4 and V5). The virgin HDPE / LDPE (50:50) mixture did not produce wax products under the blank pyrolysis methodology (without adding NaCI). The thermal characteristics of the recovered product (V / 50% blank) show that it is not wax but rather, a moderately degraded HDPE. 1 H-NMR analysis of the soft waxes reveals that they are primarily saturated hydrocarbon chainscontaminated with about 1 -2% alkene content assigned by the presence of unsaturated protons at 4.9, 5.4, and 5.8 ppm and there are no aromatic protons found. The viscous waxes contaminated with 1 mol% of aromatic content assigned at 7.0-7.3 ppm.

[0181] The thermal properties of the recovered waxes were determined using both differential scanning calorimetry (DSC) and TGA analysis, and the data are summarized in Table 5. In general, all obtained waxes possessed melting points I over 100 °C, with a temperature range of 101-118 °C. The DSC analysis showed that the thermal properties of the V / 10%, V / 20%, and V / 30% recovered waxes match those of the commercial SASOLWAX B52, considering that the V / 20% and V / 30% waxes are contaminated with a high wt% of volatile materials, 17 and 13%, respectively. Heating the HDPE / LDPE mixture (50:50) at the optimized temperature for just 1 h yielded the recovered V / 50% wax which showed the highest Tm and crystallization temperature (Tc) values at 118 °C and 103 °C, respectively. It is worth mentioning that the V / 40% wax almost has the same Tm and Tc of its V / 50% counterpart, thus confirming that the simple change in the mixture ratio to (60:40), does not affect the thermal properties of the resulting wax under the same pyrolysis conditions. The decrease in the Tm and Tc of the recovered solids clearly indicated the successful formation of waxes from virgin HDPE / LDPE mixtures.

[0182] From the TGA analysis, it is evident that the obtained waxes are more thermally stable compared with the commercial SASOLWAX B52. All recovered waxes possessed thermal degradation temperature (Td) over 415°C while the referenced SASOLWAX B52 decomposed at 313°C. The most thermally stable waxes are V / 40% and V / 50%, which decomposed at 433°C and 438°C, respectively, considering the short pyrolysis time (1 h). As reported, the pure paraffin wax has a one-step thermal decomposition profile which occurred at 208 (±2) °C. Consequently, 210 °C was chosen as a reference point to determine the actual recovered wax yield and the ratio of contaminated volatile materials, so the losses observed prior to these points were considered as liquid volatile products and the losses observed above this temperature of 210 °C were taken as solid wax. As mentioned above, at 210 °C, the V / 20% and V / 30% waxes were contaminated with high wt% of volatile materials, 17 and 13%, respectively. Meanwhile, the amounts of volatiles in the V / 10%, V40%, and V50% waxes are 6%, 6%, and 5%, respectively. It is worth mentioning that, at 400 °C the V / 30% wax has identical thermal stability to that of SASOLWAX B52 by losing 46% of its analyzed weight, while other waxes such as V40% and V50% still showed high thermal stability and underwent modest weight losses of 18% and 12%, respectively. Gas chromatography-mass spectrometry (GC-MS) analyses were performed but did not provide any useful information for the hard waxes (V / 10%- V / 50%) that had low solubility and vaporpressure. However, soft waxes (V3-5) displayed a consistent series of saturated hydrocarbon peaks from C15 to C35. It is evident from the NMR and GC-MS analysis that the upcycled waxes are primarily saturated alkanes.

[0183] Upcycled wax from waste HDPE / LDPE mixed plastics: The pyrolysis of waste HDPE / LDPE mixture (labeled R) with different mixing ratios (from 10% to 50% of waste LDPE) was performed in the presence of 10 wt% salts in an autoclave at 450 °C for the optimized pyrolysis operating time as shown in Table 6. The upcycled waxes (with a high Tm) R / 10%, R / 20%, R / 30%, R / 40%, and R / 50%, which had been obtained from waste mixtures, were recovered after heating for periods in the range of 1 .00 -2.00 h, and the resultant yields of the crude waxes were at least 94%. The wax yield was lower with a longer pyrolysis time because of the further degradation of the wax into oil. To obtain viscous waxes, the pyrolysis time was increased to 4 h which was longer than the reaction time employed for virgin mixtures, but it is presumably due to the high molecular weights of recycled LDPE / HDPE. The yields of the recovered viscous waxes were 79%, 72%, and 50% for R3, R4 and R5, corresponding to 70 / 30, 60 / 40, and 50 / 50 waste HDPE / LDPE mixtures, respectively. Under the blank pyrolysis methodology (in the absence of NaCI), the waste HDPE / LDPE (50:50) mixture did not create wax product.Table 6. Pyrolysis conditions for waste HDPE / LDPE mixture using (10 wt%) NaCI at 450 ± 5 °C

[0184] The 1 H-NMR analysis confirmed that the upcycled wax from waste HDPE / LDPE mixed plastics are almost identical with the waxes recovered from the virgin HDPE / LDPE mixtures. For example, the 1 H-NMR charts of R / 50% and V / 50% as soft waxes as well as R5 and V5 as viscous waxes are completely identical. As indicated earlier, GC-MS was only effective for the viscous waxes (R3, R4 and R5), which exhibited light hydrocarbons up to C35 (based on standard alkane calibration).

[0185] The Tm and Tc of the resulting waxes were determined by DSC analysis. As mentioned earlier, 1 .00 - 2.00 h of heating at 450 °C was enough to depolymerize waste HDPE / LDPE mixtures I and R / 10% resulted waxes showed the lowest Tm and Tc values of 97 and 83 °C, respectively (Table 6). Meanwhile, the highest Tm and Tc are (116, 101 °C) and (119, 106 °C) corresponding to R / 20% and R / 50%, respectively, considering that the pyrolysis of R / 20% was run 30 min more than R / 50% mixture. The thermal properties of theR / 30% and R / 40% recovered waxes are similar to those of the SASOLWAX B52 commercial wax. The Tm of R / 30% and R / 40% recovered waxes are 107 and 111 °C, respectively, and is 110 °C for SASOLWAX B52. Similarly, The Tc of SASOLWAX B52 is in range of (92-99 °C) and for R / 30% and R / 40% recovered waxes are 94 and 97°C, respectively (Table 6).

[0186] TGA analysis was used to determine the thermal stability and whether any volatile oils were present in the recovered crude waxes. Supposing that wax decomposition started after 210 °C, it appears that the R / 10%, R / 20%, R / 30%, R / 40%, and R / 50% recovered waxes lost 13%, 9%, 6%, 5%, and 3%, respectively, of their initial weights. These losses can be attributable to volatile contaminant materials. As a result, the wax contents for R / 10%, R / 20%, R / 30%, R / 40%, and R / 50%, respectively, are 82, 93, 89, 92, and 94 wt% after the volatile components are subtracted. The R / 10% wax was less thermally stable compared with the other recovered waxes and SASOLWAX B52 as well, while the waxes recovered from R / 50% showed significant thermal stability considering the short duration of the pyrolysis process. The recovered waxes from R / 20%, R40%, and R / 50% possessed degradation temperatures (Td) over 400 °C which is significantly higher than the commercial SASOLWAX B52 (which is 313 C°), thus offering the recovered waxes an advantage for applications such as rheology modifiers at high-temperature processing methodologies. The waxes recovered from R / 30% and R / 40% waxes have the same degradation temperature as that of SASOLWAX B52 at 367 and 344 °C, respectively.

[0187] Paper coating application: The coated papers were screened for their water resistance via Cobb1800 tests. The paper samples, uncoated kraft paper (K-P), and 5% starch-coated paper and paraffin wax-coated paper (Paraffin) were used as controls. A very high Cobb1800 value (i.e., 164.05 ± 5.44 g / m2) was observed for the uncoated kraft paper due to the highly porous and hydrophilic nature of cellulose fibers. Although a starch layer covered this porous surface, The starch-coated paper still possessed a slightly higher Cobbl 800 value despite bearing a starch layer that covered its porous surface due to the hydrophilic nature of starch. The application of paraffin wax has reduced the water absorption, thus enhancing the water resistance up to a Cobb1800 value of 22.09 ± 2.41 g / m2 due to hydrophobic nature of paraffin wax. Water resistance was increased by applying the selected upcycled waxes (depending on their solubility in chloroform solvent) from the virgin and recycled series of samples. Among the virgin series, the best-performing sample was V3, which showed the lowest Cobbl 800 value of 4.75 ± 0.35 g / m2 and an almost equal value of 4.80 ± 0.56 g / m2 was exhibited by the R5 sample (the best performer) from the recycled-series. The highest Cobb1800 value among the wax-coated paper samples was 14.15 ± 0.35 g / m2 shown by sample V5 among tested samples which was still much lowerthan those of many commercial benchmarks, and paraffin-coated paper, suggesting its applicability as a paper coating. These results show that waxes obtained from recycled plastics have water resistance almost like waxes obtained from virgin polymers, thus suggesting that waxes obtained from waste recycled plastics do not lose their integrity.

[0188] The water resistance offered by coated paper samples was visualized by water droplet tests; the samples with the best Cobb1800 values were selected for this test (V3and R5). During each test a droplet of deionized water was placed on the surface of coated paper sample and images were recorded after five minutes and then the droplet was wiped off. Images were recorded again and compared with those taken before the application of the droplet. The photos of coated paper samples were evaluated based on compassion with uncoated kraft paper to find changes in water absorption. For uncoated paper (K-P) a dark stain began to appear quickly after the placing of the droplet. This stain was still visible after the droplet had been wiped away, indicating that the uncoated paper had poor water resistance. In contrast, the coated paper was able to support the droplet for 5 min (without it becoming absorbed into the paper) and there was no stain visible following the removal of these droplets (shown by sample V3 and R5), thus demonstrating that the water resistance was improved after application of the coating.

[0189] The oil resistance of coated paper samples was measured by a standard kit test. Uncoated paper exhibited a kit rating of zero because it failed the test performed with kit solution 1 , which left a stain behind. The kit value was improved with the application of starch layer on kraft paper (S-P) up to 8. There was further improvement in kit value with the wax-coated samples. All the wax-coated samples showed kit value of 12, which is equal to that exhibited by the paraffin-coated paper (used as a control), thus indicating these paper samples had highly oil resistant surfaces.

[0190] Like water resistance, oil resistance was visualized by recording castor oil droplet behavior on the surfaces of various coated paper samples. The same paper samples were chosen for testing which had been subjected to the water droplet tests. The oil droplet left a dark stain on uncoated paper. In contrast, no stains were visible on the wax-coated samples after an oil droplet had been placed on its surface and subsequently wiped away, thus suggesting that they have strong potential as oil repellent packaging products.

[0191] Application of wax as rheology modifiers: One of the challenges encountered in efficiently recycling mixed plastics is the issue of inconsistent MFI values. Usually, waste plastics include different types of polymers having varying MFI values. Plastics that are processed via injection molding usually require high MFI values and the opposite is the casefor plastics that are processed via extrusion. Rheological modifiers can be used to improve the processibility of waste plastics.

[0192] The effect of the wax derived from a stream of waste plastics in its ability to alter the rheological properties of laboratory-controlled polyolefins was investigated. An increase in the MFI values when the concentration of the waxes was increased was observed for all laboratory-controlled polyolefins (L-POs) samples. This increase in the MFI of L-POs in the presence of the waxes is due to the reduction in viscosity. MFI is inversely proportional to viscosity, and the wax acts as a plasticizer in disrupting the entanglements in the polyolefin polymer structure leading to a free flow of the polymer chains. The practical significance of MFI modifiers is that such flow modifiers are widely used for both virgin and recycled plastic processing, and upcycled waxes can be used for such purpose.Example 6: Upcycled Waxes in Hot-Melt Adhesive (HMA) Applications

[0193] Virgin paraffin waxes are filled with poly(ethylene-co-vinyl acetate) (EVA) to make hot-melt adhesives (HMAs). This example forms partially recycled HMAs that were prepared by blending EVA with upcycled waxes obtained from mix waste polyolefins. First, waste mixed polyolefins (such as high-density, low-density, and linear low-density polyethylene, and polypropylene) were converted into waxes in high yields reaching up to 92%. The obtained upcycled waxes were used as an additive for HMAs along with gum rosin. The thermal properties and seal strength obtained for the HMAs bearing upcycled waxes were compared with that of commercially available HMA. The HMA made from upcycled wax was found to be as efficient is seal strength as the commercially available HMA. This upcycling of plastic waste for use in HMA is yet another way of promoting circularity in single-use plastics.

[0194] Hot melt adhesives (HMAs) are thermoplastic adhesives that are applied as meltadhesives via heating, which gain strength upon cooling. HMAs are inexpensive, solvent- free, water-resistant, and are compatible with high-speed manufacturing processes, and thus they are widely employed in numerous industries. HMAs are comprised of copolymer poly(ethylene-co-vinyl acetate) (EVA), a plasticizer, as well as an adhesive, which is made up of tackifiers, waxes, and optionally inorganic fillers. Waxes comprise up to 30 wt% of the adhesive formulation. For HMAs, waxes are required to decrease the viscosity of the melt adhesive to offer better flow and uniform surface coverage during adhesive applications, as well as to reduce the application temperature. Waxes also enhance the hardening rate of the adhesives and improve the cohesive strength of the adhesives, thus speeding up the manufacturing process.

[0195] Materials: The waste plastics used in this investigation were obtained from the Michigan State University (MSU) Surplus and Recycling Center, Michigan, United States, East Lansing, Ml. Sodium chloride (NaCI) was purchased from Fisher Chemical. EVA and gum rosin natural resin were purchased from Sigma Aldrich.

[0196] Pyrolysis Process: An autoclave reactor was filled with mixed waste plastics (grinded) and 10 wt% of NaCI. The autoclave reactor was completely wrapped with aluminum foil to maintain the pyrolysis temperature inside the reactor, and the reactor was heated using a heating mantle at 450 °C for the selected operating time. The wax was upcycled using hot-water dispersion, followed by cooling, and then the solid wax was collected from the top of the water surface.

[0197] Adhesive Blend: Three ingredients were used to create a hot melt adhesive. The first ingredient was the polymer ethylene-vinyl acetate (EVA) 40 wt% with a melt index of 41- 63 dg / min and 190°C / 2.16kg from (Sigma Aldrich, St Louis, MO). The second ingredient was Gum rosin natural resin (Sigma Aldrich, St Louis, MO). The third ingredient was the wax created from mixed waste plastic by the pyrolysis process. The three components were blended in a 100 mL beaker at a temperature of 210°C for 60 min. This blend was then dried after proper mixing, thus yielding the adhesive. Blends were prepared in the ratio of (40 / 30 / 30) for EVA / Gum Rosin / Wax solution by dissolving the components in chloroform (at a concentration of 5% by volume) (Fisher Scientific, Hampton, NH). The blend was then vacuum-dried to remove solvent residue.

[0198] Glue Gun Stick: The adhesive blend was reheated and cast inside a hollow PTFE tube to form the shape of the glue gun stick. The molten glue was then kept in a refrigerator for 24 hours to attain the shape of the cylindrical glue stick.

[0199] Synthesis of Upcycled Waxes: Mixed plastic waste (MPW), which is commonly sent to landfills, was used as a feedstock for the upcycled waxes. As a general strategy, 10 grams of MPW was pyrolyzed with 10 wt% sodium chloride for different time periods, such as 2.0, 3.0, 4.0, and 5.0 h, as shown in Table 7. After pyrolysis, the resultant waxes were upcycled via a hot-water dispersion approach. This hot-water dispersion approach is simple and very effective, as the sodium chloride can be easily separated from wax. The obtained waxes are ready to use for HMA applications, and sodium chloride is for further use for pyrolysis after the necessary drying step. The upcycled waxes obtained from this process varied from hard to soft based on the pyrolysis reactor residence time. The obtained wax yields were 84%, 81%, 60%, and 30% (these waxes are respectively denoted as Wax A, Wax B, Wax C, and Wax D) corresponding to pyrolysis operation times of 2.0, 3.0, 4.0, and5.0 h, respectively. The gas and oil contents increased with the operation time, and the softness of the obtained wax increased as well. For 30 g of MPW was used, and the pyrolysis process was conducted for an operation time of 8 h at 450eC. During these experiments performed at the 30 g MPW scale, the yield of the upcycled wax was 93% (Wax E). In another trial conducted with 50 g of MPW and 12 h of pyrolysis time, the yield of the resultant wax (Wax F) was 82%.Table 7. Pyrolysis conditions, pyrolytic waxes yield, and characterization

[0200] The DSC analysis revealed the melting temperature I and the crystallization temperature (Tc) of the resulting waxes. Meanwhile, the MPW sample was found to have T m and T c values of 136 and 117eC, respectively.

[0201] In general, the Tm and Tc of the resulting waxes are decreased by increasing the pyrolysis operating time. For the 10 g scale experiments, the obtained Waxes A, B, and C exhibited Tm values of 109, 106 and 93eC, respectively, and Tc values of at 96, 91 , 77eC. Meanwhile, Wax D was viscous, and thus, it did not exhibit clear Tm and Tc temperatures. Wax E which was obtained from a larger-scale experiment using 30 g of MPW showed Tmand Tc at values of 118 and 106 °C, while the viscous Wax D did not show a clear Td temperature. Meanwhile, Wax F, which was obtained from the pyrolysis of 50 g of MPW for 12 h, exhibited Tm and Tc temperatures of 109 and 97eC, respectively, which are similar to those of Wax A.

[0202] The thermal stability of the resulting waxes was investigated with the TGA analysis. The MPW sample decomposed at 447eC, while after the pyrolysis the decomposition temperatures (Td) of the obtained waxes were found to be at 425, 422 and 413eC for Wax A, Wax B, and Wax C, respectively, while Wax D had a Td of 175 °C. Wax E obtained from the 30 g scale experiment showed high thermal stability with a Td value of 426eC.

[0203] As the obtained waxes also contained some volatile low molecular weight hydrocarbons. To quantify the actual waxes, we excluded volatile contents from them. This was done by calculating any loss in TGA before 210 °C as volatile. A temperature of 210 °C was selected because commercial paraffin waxes degrade at 210 and above.Consequently, 210 °C was used as the starting point to calculate the actual upcycled wax yield without any low molecular weight hydrocarbons. Losses detected above 210 °C were attributed to solid wax, while losses observed below these values were classified as liquid volatile compounds. Consequently, after deducting the volatile component contents, the actual wax contents for Wax A, Wax B, Wax C, and Wax D were found to be 81 .6, 79.4, 56.4, and 26.4 wt%, respectively.

[0204] Proton nuclear magnetic resonance (1 H-NMR) analysis revealed that the obtained waxes were mainly comprised of saturated hydrocarbon chains, with a signal corresponding to terminal methyl-protons observed at 0.89 ppm and a signal corresponding to the methylene protons of the backbone chain at 1 .26 ppm. The ratio of unsaturated protons (about 1%) is attributed to the presence of alkene protons at 4.6, 4.9, 5.4, and 5.8 ppm, representing both terminal and internal (-C=C-) bonds, and there are no aromatic protons visible in the spectra of the waxes.

[0205] GC-MS analysis was also performed on the dichloromethane (DCM) soluble fractions of pyrolytic waxes (Wax A - Wax E). Prior to the GC-MS analysis, the wax was dissolved in DCM and then diluted by 1000-fold with DCM. GC-MS analysis indicates that a normal series of hydrocarbon peaks was obtained. The GC-MS of Wax C- and Wax D- soluble fractions showed a hydrocarbon distribution range of C15-C34, which is the range found in diesel fuel. For Wax B, the hydrocarbon was saturated, lacking an carbon carbon double bonds, with a carbon distribution range of C18-C34. The hard waxes, such as Wax Aand Wax E, showed random hydrocarbon distributions and possessed both saturated and unsaturated chains.

[0206] Adhesive Blend: EVA was mixed with Gum rosin (a natural resin) and upcycled Wax E in the weight ratios of 40 / 30 / 30, respectively. To ensure a thorough mixing, hot mixing was performed at 210 °C for 1 h with stirring. To make a glue stick, the molten blend is cast into a PTFE tube to form a glue gun stick-like shape. The physical characteristics of the commercial HMA (CHMA) and lab-made HMA (LHMA) adhesive blend were visually compared. The shape and consistency of both CHMA and LHMAs are very similar, and both samples became viscous fluid when they were heated. The set time for both adhesives was approximately 3-7 seconds.

[0207] Thermal Characteristics of HMAs: DSC analysis shows that the thermal properties of LHMA resemble those of CHMA. For example, LHMA and CHMA have melting temperatures I at 118 and 108 °C, respectively. The crystallization temperature (Tc) of LHMA was found to be at 106 °C, while that of CHMA was observed at 95 °C. The Tm and Tc of LHMA are typically the same as that of the upcycled Wax E, which represents 30 wt% of the HMA composition. The difference in melting and crystallization temperatures between CHMA and LHMA came from the differences in compositions and types of wax blended with the adhesives. The higher Tm of the LHMA provides it with advantages for use in the packaging line of corrugated fiberboard (CFB) boxes and cartons, even during warm seasons of the year, as well as during storage in warehouses.

[0208] Efficacy and Sealing Strength of HMAs: To examine the peel strength of the adhesives made in this investigation, the force and tensile strength at the maximum weight were recorded for thermally sealed samples during different time intervals. The maximum required force for sealing peel-off (16.8 ± 1 .42 N) was observed after 48 h for the lab-made sample. The results show that an optimum composition was obtained when 30 wt% upcycled Wax E content was wused along with EVA and Gum Rosin. The tensile strength and sealing force were very similar for LHMA and CHMA. Except for 48 h, there was a gradual increase in the sealing strength and force required to peel off the sealing in both CHMA and LHMA. The similarity in the sealing strength of the adhesives at different periods indicates the adhesion stability even after one week. This indicates that the lab-made adhesive is equally effective in performance as a commercially available counterpart during storage.Example 7: Pyrolysis of HDPE, PP, and HDPE / PP Blends

[0209] This example illustrates the effect of polyolefin type on pyrolysis products. Pyrolysis was carried out in an autoclave reactor at 425°C in the presence of NaCI forHDPE, PP, and HDPE / PP blends. The products were characterized in terms of their gas, oil (or volatile), and wax component distributions, and the thermal properties of the wax (or solid) were analyzed by TGA and DSC. The results are summarized in Table 8.Table 8. Autoclave Pyrolysis of HDPE, HDPE / PP 50% and PP 425 ± 5 °C, pyrolytic waxes yields, and characterizationExample 8: Upcycled Waxes in Asphalt Applications

[0210] This example illustrates the use of upcycled waxes as a flow enhancer additive for asphalt compositions. Pyrolysis was carried out in an autoclave reactor filled with 10.0 g of recycled mixed polyolefin and 2.0 g of NaCI (20 parts per hundred resins). The autoclave reactor was completely wrapped with aluminum foil to maintain the pyrolysis temperature inside, and it was placed in a pre-heating heating mantle at 450°C for 4 hours. The wax was recovered from hot-water dispersion followed by cooling, with the solid wax being collected from the top of the water surface.

[0211] The formed wax was mixed with asphalt binders at various temperatures. It was found that with a 3wt% wax loading, there was a 7°F (3.9°C) decrease in the compaction temperature for waxes with a melting temperature of about 60°C. The viscosity decreases for 3 wt.% loading were 8.11% at 130°C, 17.8% at 150°C, and 13% at 170°C. It is believed that, by changing the nature of the waxes (e.g., chemistry and / or melting temperature) and by adjusting the wt.% wax loading, the compaction temperature of an asphalt binder can be significantly reduced, which will result in substantial energy savings and reduced carbon dioxide emissions.

[0212] Because other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the disclosure is not considered limited to the example chosen for purposes of illustration, and covers allchanges and modifications which do not constitute departures from the true spirit and scope of this disclosure.

[0213] Accordingly, the foregoing description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications within the scope of the disclosure may be apparent to those having ordinary skill in the art.

[0214] All patents, patent applications, government publications, government regulations, and literature references cited in this specification are hereby incorporated herein by reference in their entirety. In case of conflict, the present description, including definitions, will control.

[0215] Throughout the specification, where the compositions, processes, kits, or apparatus are described as including components, steps, or materials, it is contemplated that the compositions, processes, or apparatus can also comprise, consist essentially of, or consist of, any combination of the recited components or materials, unless described otherwise. Component concentrations can be expressed in terms of weight concentrations, unless specifically indicated otherwise. Combinations of components are contemplated to include homogeneous and / or heterogeneous mixtures, as would be understood by a person of ordinary skill in the art in view of the foregoing disclosure.

Claims

What is claimed is:

1. A method for depolymerizing a polyolefin, the method comprising: heating a mixture comprising (i) at least one polyolefin and (ii) a metal catalyst comprising a metal salt to a temperature above a melting temperature of the at least one polyolefin, thereby at least partially depolymerizing the at least one polyolefin and forming at least one of a corresponding gas hydrocarbon product, a liquid hydrocarbon product, and a solid hydrocarbon product.

2. The method of claim 1 , comprising depolymerizing the at least one polyolefin by heating the mixture to a temperature in a range of 350°C to 500°C.

3. The method of claim 1 , comprising depolymerizing the at least one polyolefin by heating the mixture to a temperature in a range of 415°C to 460°C.

4. The method of claim 1 , comprising depolymerizing the at least one polyolefin by heating the mixture to:(i) a temperature at least 10°C above a melting temperature of the at least one polyolefin; and(ii) a temperature at least 50°C below a decomposition temperature of the at least one polyolefin, wherein heating to the decomposition temperature would result in one or more of combustion, burning, and charring of the at least one polyolefin.

5. The method of claim 1 , comprising depolymerizing the at least one polyolefin by heating the mixture for a time in a range of 0.5 hr to 20 hr (e.g., reaction / heating time in a batch reactor, (mean) residence time in a continuous reactor)6. The method of claim 1 , comprising depolymerizing the at least one polyolefin by heating the mixture for a time in a range of 1 .5 hr to 5 hr.

7. The method of claim 1 , comprising heating the mixture in a batch process.

8. The method of claim 1 , comprising heating the mixture in a continuous process.

9. The method of claim 1 , comprising heating the mixture in an inert atmosphere.

10. The method of claim 1 , comprising heating the mixture in the presence of oxygen.

11. The method of claim 1 , wherein the at least one polyolefin is present in the mixture in an amount of 70 wt.% to 99 wt.%.

12. The method of claim 1 , wherein a combined amount of the at least one polyolefin and the metal catalyst in the mixture is in a range of 70 wt.% to 100 wt.%.

13. The method of claim 1 , wherein the mixture further comprises one or more additives or impurities in an amount up to 30 wt.%.

14. The method of claim 1 , wherein the mixture further comprises one or more free radical inhibitors or suppressors in an amount up to 5 wt.%.

15. The method of claim 1 , wherein the at least one polyolefin comprises high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP).

16. The method of claim 15, wherein : the HDPE is present in the mixture in an amount of 1 wt.% to 95 wt.% relative to total polyolefins in the mixture; the LDPE is present in the mixture in an amount of 1 wt.% to 95 wt.% relative to total polyolefins in the mixture; the LLDPE is present in the mixture in an amount of 1 wt.% to 95 wt.% relative to total polyolefins in the mixture; and the PP is present in the mixture in an amount of 1 wt.% to 95 wt.% relative to total polyolefins in the mixture.

17. The method of claim 15, wherein : the HDPE is present in the mixture in an amount of 25 wt.% to 45 wt.% relative to total polyolefins in the mixture; the LDPE is present in the mixture in an amount of 10 wt.% to 25 wt.% relative to total polyolefins in the mixture; the LLDPE is present in the mixture in an amount of 10 wt.% to 25 wt.% relative to total polyolefins in the mixture; and the PP is present in the mixture in an amount of 20 wt.% to 35 wt.% relative to total polyolefins in the mixture.

18. The method of claim 1 , wherein the mixture further comprises one or more oxygenated polymers selected from the groups consisting of polyesters, co-polyesters, polyvinyl alcohol, polyethylene vinyl alcohol, polyvinyl acetate, and combinations thereof.

19. The method of claim 1 , wherein the mixture comprises at least one metallized polymer.

20. The method of claim 1 , wherein the mixture is free from vinyl polymers comprising one or more vinyl monomer units comprising at least one of a pendant aromatic group and a pendant ester group.

21. The method of claim 1 , wherein the metal catalyst is present in the mixture in an amount of 2 wt.% to 20 wt.%.

22. The method of claim 1 , wherein the metal catalyst comprises sodium chloride.

23. The method of claim 1 , wherein the metal catalyst comprises an alkali metal halide salt catalyst comprising: at least one of a lithium cation, a sodium cation, and a potassium cation; and at least one of a fluoride anion, chloride anion, bromide anion, and iodide anion.

24. The method of claim 1 , wherein the metal catalyst comprises an alkaline earth metal halide salt catalyst comprising: at least one of a beryllium cation, a magnesium cation, a calcium cation, and a barium cation; and at least one of a fluoride anion, chloride anion, bromide anion, and iodide anion.

25. The method of claim 1 , wherein the metal catalyst further comprises one or more of a metal oxide, an elemental metal, a metal alloy, and combinations thereof.

26. The method of claim 1 , wherein the metal catalyst further comprises a metal oxide.

27. The method of claim 1 , wherein the metal catalyst has a particle size in a range of 10 nm to 2 mm.

28. The method of claim 1 , wherein the metal catalyst is in solid form in the mixture at the temperature to which the mixture is heated.

29. The method of claim 1 , wherein the mixture is substantially free from Ziegler- Natta and platinum-containing catalysts.

30. The method of claim 1 , wherein the mixture contains not more than 0.1 wt.% of transition metal catalysts.

31. The method of claim 1 , wherein the mixture contains not more than 0.1 wt.% of metal catalysts other than alkali metal-containing catalysts and alkaline earth metalcontaining catalysts.

32. The method of claim 1 , comprising depolymerizing the at least one polyolefin with a conversion of at least 70 wt.%.

33. The method of claim 1 , comprising depolymerizing the at least one polyolefin with a yield of at least 70 wt.% for the gas hydrocarbon product, the liquid hydrocarbon product, or the solid hydrocarbon product.

34. The method of claim 1 , wherein depolymerizing the at least one polyolefin comprises forming the gas hydrocarbon product.

35. The method of claim 34, wherein the gas hydrocarbon product is formed in an amount of at least 40 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed.

36. The method of claim 34, wherein the gas hydrocarbon product comprises hydrocarbons having 1 to 4 carbon atoms.

37. The method of claim 34, wherein the gas hydrocarbon product comprises hydrocarbons having a molecular weight in a range of 16-60 g / mol.

38. The method of claim 1 , wherein depolymerizing the at least one polyolefin comprises forming the liquid hydrocarbon product.

39. The method of claim 38, wherein the liquid hydrocarbon product is formed in an amount of at least 80 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed.

40. The method of claim 38, wherein the liquid hydrocarbon product comprises hydrocarbons having 5 to 30 carbon atoms.

41. The method of claim 38, wherein the liquid hydrocarbon product comprises hydrocarbons having a molecular weight in a range of 60-500 g / mol.

42. The method of claim 38, wherein the liquid hydrocarbon product contains 5- 100 wt.% saturated hydrocarbons and 0-95 wt.% unsaturated hydrocarbons.

43. The method of claim 38, wherein: the liquid hydrocarbon product comprises saturated hydrocarbons and unsaturated hydrocarbons; and a ratio of saturated hydrocarbons:unsaturated hydrocarbons is in a range of 100:1 to 1 :100 on a molar basis.

44. The method of claim 1 , wherein depolymerizing the at least one polyolefin comprises forming the solid hydrocarbon product.

45. The method of claim 44, wherein the solid hydrocarbon product is formed in an amount of at least 90 wt.% relative to total gas hydrocarbon product, liquid hydrocarbon product, and solid hydrocarbon product formed.

46. The method of claim 44, wherein the solid hydrocarbon product comprises hydrocarbons having 24 to 200 carbon atoms.

47. The method of claim 44, wherein the solid hydrocarbon product has at least one of the following properties: a number-average molecular weight (Mn) in a range of 400-2000 g / mol; a weight-average molecular weight (Mw) in a range of 600-10000 g / mol; and a polydispersity index (Mw / Mn) in a range of 1-5.

48. The method of claim 44, wherein the solid hydrocarbon product has at least one of the following properties: a melting temperature (Tm) a range of 25-130°C; a crystallization temperature (Tc) a range of 80-120°C; a temperature difference (Tm-Tc) a range of 1 -50°C; and a decomposition temperature (Td) a range of 350-450°C.

49. The method of claim 1 , comprising: depolymerizing the at least one polyolefin by heating the mixture in an inert atmosphere (i) to a temperature in a range of 415°C to 460°C, (ii) for a time in a range of 1 .5 hr to 5 hr, (iii) with a conversion of at least 70 wt.% for the at least one polyolefin, and (iv) with a yield of at least 70 wt.% for the gas hydrocarbon product, the liquid hydrocarbon product, or the solid hydrocarbon product; wherein: the at least one polyolefin is present in the mixture in an amount of 80 wt.% to98 wt.%; the metal catalyst comprises an alkali metal halide salt and is present in the mixture in an amount of 2 wt.% to 20 wt.%; a combined amount of the at least one polyolefin and the metal catalyst in the mixture is in a range of 80 wt.% to 100 wt.%; and the at least one polyolefin comprises high-density polyethylene (HDPE) present in the mixture in an amount of 25 wt.% to 45 wt.% relative to total polyolefins in the mixture, low-density polyethylene (LDPE) present in the mixture in an amount of 10 wt.% to 25 wt.% relative to total polyolefins in the mixture, linear low-density polyethylene (LLDPE) present in the mixture in an amount of 10 wt.% to 25 wt.% relative to total polyolefins in the mixture, and polypropylene (PP) present in the mixture in an amount of 20 wt.% to 35 wt.% relative to total polyolefins in the mixture.

50. The method of claim 49, wherein: depolymerizing the at least one polyolefin comprises forming the gas hydrocarbon product; and the gas hydrocarbon product comprises hydrocarbons having 1 to 4 carbon atoms and having a molecular weight in a range of 16-60 g / mol.

51. The method of claim 49, wherein: depolymerizing the at least one polyolefin comprises forming the liquid hydrocarbon product; and the liquid hydrocarbon product comprises hydrocarbons having 5 to 30 carbon atoms and having a molecular weight in a range of 60-500 g / mol.

52. The method of claim 49, wherein: depolymerizing the at least one polyolefin comprises forming the solid hydrocarbon product; the solid hydrocarbon product comprises hydrocarbons having 24 to 200 carbon atoms; the solid hydrocarbon product has a number-average molecular weight (Mn) in a range of 400-1500 g / mol, a weight-average molecular weight (Mw) in a range of 600- 3000 g / mol, and a polydispersity index (Mw / Mn) in a range of 1-5; and the solid hydrocarbon product has a melting temperature (Tm) a range of 80-150°C, a crystallization temperature (Tc) a range of 80-120°C, a temperature difference (Tm-Tc) a range of 1-50°C, and a decomposition temperature (Td) a range of 350-450°C.

53. A method for depolymerizing a polymer, the method comprising: heating a mixture comprising (i) at least one polymer and (ii) a metal catalyst having (A) a heat capacity in a range of 0.4 to 100 J / (g*K) and (B) a thermal conductivity in a range of 0.2 to 60 W / (m»K) to a temperature above a melting temperature of the polymer, thereby at least partially depolymerizing the polymer and forming at least one of a corresponding gas hydrocarbon product, a liquid hydrocarbon product, and a solid hydrocarbon product.

54. The method of claim 53, wherein: the heat capacity is in a range of 10 to 100 J / (g*K); and the thermal conductivity is in a range of 2 to 60 W / (m»K).

55. The method of claim 53, wherein: the metal catalyst comprises a first metal catalyst and a second metal catalyst; the first metal catalyst has a first heat capacity in a range of 30 to 100 J / (g*K) and a first thermal conductivity in a range of 0.2 to 60 W / (m»K); and the second metal catalyst has a second heat capacity in a range of 0.4 to 100 J / (g*K) and a second thermal conductivity in a range of 10 to 60 W / (m»K).

56. A solid hydrocarbon product formed according to any one of claims 1 to 33 or 44 to 55.

57. A coated article comprising: the solid hydrocarbon product of claim 56 coated on a substrate.

58. A hot-melt adhesive comprising:30-50 wt.% of ethylene-vinyl acetate (EVA);20-40 wt.% of gum rosin; and20-40 wt.% of the solid hydrocarbon product of claim 56.

59. An asphalt binder comprising:70-99.5 wt.% of asphalt binder;0.5-20 wt.% of the solid hydrocarbon product of claim 56; and up to 20 wt.% of additives selected from the group consisting of cellulose fibers, compatibilizers, surfactants, lignin, and combinations thereof.

60. A polymer blend comprising:80-98 wt.% of at least one polyolefin; and2-20 wt.% of the solid hydrocarbon product of claim 56.

61. A heat exchange article for cooling and heating via solid-liquid phase transformations, the article comprising: a reservoir; the solid hydrocarbon product of claim 56 contained in the reservoir, wherein the solid hydrocarbon product has a melting temperature in a range of 15°C-40°C; and optionally, one or more thermally conducting fillers dispersed throughout the solid hydrocarbon product.

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