Zeolitic materials in polyolefin decomposition via pyrolysis

Abstract

A process for decomposing polyolefins including contacting a polyolefin with a zeolite having an internal to a total specific surface area ratio of at least 40 percent to provide a mixture, and pyrolyzing the mixture to a temperature of 400°C or less. In the process, the polyolefin is thermally decomposed in the absence of oxygen to produce a pyrolysis product including one or more chemical-value products such as C2-C4 olefin and C4-C20+ hydrocarbons in high yields.

Description

ZEOLITIC MATERIALS IN POLYOLEFIN DECOMPOSITION VIA PYROLYSISINVENTORS: Sina Sartipi, Mariarosa Maimone, Scott J. Weigel, Emiel DeSmit, HelgeJaensch and Allen W. BurtonCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to US Provisional Application No. 63 / 581996 filed September 12, 2023, the disclosure of which is incorporated herein by reference.FIELD

[0002] The present disclosure relates to recycling of plastic wastes and particularly, decomposition of polyolefins contained in plastic wastes through pyrolysis processes.BACKGROUND

[0003] Solid plastic waste processing has evolved towards a circular economy to include use as a feedstock in various ty pes of processes. Recycling plastic waste with pyrolysis reactions through catalytic conversion has the potential to economically convert plastic wastes into usable monomers, fuels, and the like under sustainable conditions. These solutions include conversion of plastic waste to chemical-value products. Ongoing efforts to maximize the chemical-value products, however, require either high direct olefin yield or high liquid yields combined with a subsequent steam cracking conversion.SUMMARY

[0004] A process for decomposing polyolefins comprising contacting a polyolefin with a zeolite having an external to total specific surface area ratio of at least 40 percent to provide a mixture, and pyrolyzing the mixture to a temperature of 300°C or less to thermally decompose the polyolefins in the absence of oxygen and produce chemical-value product.

[0005] A process for decomposing polyolefin in a plastic waste comprising providing a plastic waste comprising one or more polyolefins; pyrolyzing the plastic waste to produce an effluent; separating the polyolefins from the effluent; contacting the polyolefins with a zeolite having an external to total specific surface area ratio of between 40 percent and 70 percent to provide a mixture; and pyrolyzing the mixture to a temperature 400°C or less, where the polyolefins are thermally decomposed to provide chemical-value product comprising an amount of gas phase olefin greater than 60 mole percent ('‘mol.%”); an amount of propylene greater than 30 mol.%; and a liquid yield greater than 50 wt.%.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] To assist those of ordinary skill in the relevant art in making and using the subjectmatter hereof, reference is made to the appended drawings, wherein:

[0007] FIG. 1 A is graph is a “constant temperature ramp"’ (conventional) TGA comparison between thermal pyrolysis and catalytic pyrolysis of low density’ polyethylene (LDPE, 1.6 g / 10 min Melt Index (“MI”) (190°C I 2.16 kg) and 0.929 g / cm3 density) in the presence of ultra-small crystal Beta (“USC zeolite Beta”), instead of the high resolution TGA method.

[0008] FIG. IB provides a graph of the thermogravimetric analy sis having a constant temperature ramp rate of the pyrolytic decomposition of the same low density polyethylene over about 20 wt.% to 30 wt.% of USC zeolite Beta and zeolite Beta having a larger crystal size.

[0009] FIG. 2A provides a GC chromatogram of the different effluents taken from the pyrolyzer where low density polyethylene (LDPE, 1.6 g / 10 min Melt Index (“MI”) (190°C / 2.16 kg) and 0.929 g / cm3 density) was pyrolyzed at 300°C over 20 wt.% of USC zeolite Beta, compared to thermal pyrolysis at 550°C.

[0010] FIG. 2B compares effluents of pyrolysis of the same LDPE at 300°C and 550°C with and without USC zeolite Beta as the catalyst, respectively.

[0011] FIG. 3 is a graph of the composition of condensates (pyrolysis products) collected from an overhead of a batch reactor with larger batch size of low density polyethylene (LDPE, 1.6 g / 10 min Melt Index (“MI”) (190°C / 2.16 kg) and 0.929 g / cm3 density) operated between 280°C and 300°C.

[0012] FIG. 4A is a graph of a constant temperature ramp TGA comparison between the thermal pyrolysis and pyrolysis in the presence of EMM-20 of low density polyethylene (LDPE, 1.6 g / 10 min Melt Index (“MI”) (190°C / 2.16 kg) and 0.929 g / cm3 density).

[0013] FIG. 4B is a graph of the TGA analysis of Example 2 with a constant temperature ramp rate of the pyrolytic decomposition of low-density polyethylene (LDPE, 1.6 g / 10 min Melt Index (“MI”) (190°C 1 2.16 kg) and 0.929 g / cm3 density) over EMM-20 (Sample 3), and ZSM-5 with progressively lower specific external surface area (Sample 4 and 5, respectively).

[0014] FIG. 5 provides an overview of the catalytic pyrolysis of low density polyethylene (LDPE, 1.6 g / 10 min Melt Index (“MI”) (190°C / 2.16 kg) and 0.929 g / cm3 density ) over the zeolite catalysts summarized in Table 1 and illustrates the performance of USC zeolite Beta and EMM-20 materials.

[0015] FIG. 6A provides an overview of the catalytic pyrolysis of low density polyethylene (LDPE, 0.75 g / 10 min Melt Index (190°C / 2.16 kg) and 0.923 g / cm3 density ) over various zeolite catalysts and amorphous solid acid catalysts and illustrates the outstanding performance of USC zeolite Beta and EMM-20 materials.

[0016] FIG. 6B provides a detail of the catalytic pyrolysis of the same LDPE sample over various commercial amorphous silica-alumina with different Si / Ah ratios, specific surface area and pore volume (Siral 10, Siral 40, Siral 40 HPV, all obtained from Sasol), showing that Siral 40 HPV performance in decomposing LDPE at low temperature.

[0017] FIG. 6C provides a detail of the catalytic pyrolysis of the same LDPE Sample, highlighting the performance of USC zeolite Beta (Sample 1) versus conventional Beta zeolite (Sample 2) for which larger scale pyrolysis experiments were performed.

[0018] FIG. 6D provides a detail of the catalytic pyrolysis of the same LDPE sample, highlighting the performance of EMM-20 (Sample 3) versus conventional ZSM-5 (Sample 4 and Sample 5), even for the case where relatively small crystals of ZSM-5 were used. Larger scale pyrolysis experiments were performed for EMM-20 and small crystal ZSM-5 (Sample 4).

[0019] FIG. 7 illustrates the carbon number distribution of liquid products obtained from thermal pyrolysis, and catalytic pyrolysis over USC zeolite Beta, EMM-20 and Siral HPV (Sample 1, 3 and 15, respectively) and conventional Beta and ZSM-5 zeolites (Sample 2 and 4, respectively). Together with Table 2, the data illustrates the performance of the ultra-small crystal zeolite catalysts over thermal pyrolysis and amorphous silica-alumina materials.

[0020] FIG. 8A provides an overview of the catalytic pyrolysis of polypropylene (PP, 0.83 g / 10 min Melt Index (230°C / 2.16 kg) and 0.900 g / cm3 density) over various zeolite catalysts and amorphous solid acid catalysts and illustrates the outstanding performance of USC zeolite Beta and EMM-20 (high external specific surface area versus total specific surface area) materials.

[0021] FIG. 8B provides a detail of the catalytic pyrolysis of the same PP sample over various commercial amorphous silica-alumina with different Si / Al ratios, specific surface area and pore volume (Siral 10, Siral 40, Siral 40 HPV, all obtained from Sasol), showing that Siral 40 and Siral 40 HPV show the best performance in decomposing PP at low temperature.DETAILED DESCRIPTION

[0022] Before the present compounds, components, compositions, and / or methods are disclosed and described, it is to be understood that unless otherwise indicated this disclosure is not limited to specific compounds, components, compositions, reactants, reaction conditions, ligands, catalyst structures, or the like, as such may vary, unless otherwise specified. It is also to be understood that the terminology used herein is for the purpose of describing different embodiments and is not intended to be limiting.

[0023] All numerical values within this detailed description and claims should be considered modified by "about” or "approximately” the indicated value to account forexperimental error and variations.

[0024] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. Thus, even’ point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0025] For the purposes of this disclosure, the following definitions will apply:

[0026] As used herein, the terms “a” and “the” as used herein are understood to encompass the plural as well as the singular.

[0027] The term "chemi cal -value product” means and includes pyrolysis products produced by pyrolysis of polyolefin as described herein.

[0028] The term “crystal” includes zeolites and zeolite precursors that are XRD amorphous.

[0029] Plastic waste and polymer materials as described herein may take the physical form of one or more of a chip, pellet, and / or bead, and the like.Thermal and Catalytic Cracking of Plastic Waste & Decomposition of Polyolefins

[0030] Pyrolysis reactions provide a solution to the conversion of plastic waste. Chemicalvalue products can be maximized in configurations that integrate the pyrolysis processing with subsequent oil upgrading. To this end, high liquid yields via pyrolysis are needed for feedstock / feed supply to units such as naphtha crackers and contaminant removal.

[0031] Thermal cracking of plastic waste can be carried out locally at waste collection and segregation points together with technologies that are environmentally friendly while yielding desirable materials. Thermal cracking, however, can yield a broad range of hydrocarbons with respect to the carbon number, making the large-scale production of renewable materials (the main goal of the circular economy), transportation-quality fuels (secondary products), and valuable chemicals difficult. For thermal cracking, prior art pyrolysis conditions utilize temperatures from about 400°C to about 700°C and generally from about 450°C to about 650°C. Conventional pyrolysis also utilizes operating conditions of above-atmospheric pressures. See e.g., U.S. Pat. No. 4,642,401. Additionally, if adjusting the pressure downward, the yield of a desired product can be controlled. See e.g., U.S. Pat. No. 6,150.577.Accordingly, where a yield of a desired product, pyrolysis pressures have been sub- atmospheric. See e.g., US Pub. App. No. 2022 / 0389327. Because product outcome depends on process conditions ( / . e., temperature) as well as the composition of the plastic waste, the production of low molecular weight material requires temperatures (T >500°C).

[0032] On the other hand, catalytic cracking provides a solution to these problems. Catalytic cracking is energetically favorable as catalysts are often economically desirable. Moreover, zeolitic materials are useful in chemical recycling via catalytic cracking processes and depolymerization (referred to herein as decomposition) of polyolefins to provide a circular economy.

[0033] Through activation of high-energy bonds within a polymer backbone, heterogeneous catalysts can convert plastic wastes into chemical-value products (also referred to as "high-value products’7) such as low molecular weight naphtha-like liquid hydrocarbons and C2-C4 olefins and aromatics. Having selective active sites that reduce random bond scission, a narrower carbon number product distribution can result. Because of the active sites on the catalyst that assist in controlling the reaction, catalytic cracking of plastic waste can be selective towards liquid products within a narrower carbon number distribution. These catalysts can also reduce cracking temperatures by inducing the carbenium ion mechanism. Carbenium ions are formed via hydride ion abstraction from a polymer by an acid site on the catalyst. The ions subsequently undergo chain reactions via [3-scission, isomerization, hydrogen transfer alkylation, and oligomerization, resulting in cleavage of the macromolecule to gaseous and liquid products.

[0034] In competition with chain propagation is chain termination (stabilization) which occurs through disproportionation or recombination of radicals or ions. Plastic w aste often undergoes random scission under thermal and catalytic pyrolysis due to the complex nature of the polymer and can result in the production of primary, secondary, and tertiary radicals, as discussed above for thermal pyrolysis.

[0035] While both thermal and catalytic plastic cracking typically follow these general mechanisms, the intricacies of the polymer degradation mechanism are dependent on the type of catalyst and plastic waste used. For example, branched plastics such as LDPE, LLDPE and PP will preferentially undergo chain scission at the side chains, and this will yield short-chain radicals that will abstract hydrogens to aid in alkene production. PVC will form hydrogen chloride, which is toxic and corrosive and can deactivate the catalyst, and hydrocarbon radicals during initiation and propagation during thermal cracking and can undergo Diels-Alder reactions to produce aromatics. Catalyst shape, size, and acidity affect the product outcome byinducing Diels-Alder reaction, cyclization, aromatization, hydrogen recovery, and recombination.

[0036] The implementation of heterogeneous catalysts in plastic waste conversion allows for production of desired liquid oils and gaseous hydrocarbons. Furthermore, as an option, through modulating catalyst acidity and pore structure, heterogeneous catalytic systems can aid in shifting selectivity7between and within the two fractions.

[0037] As provided herein, the present catalytic cracking processes utilize zeolitic materials (zeolites) having an external -to-total surface ratio of greater than 40%. The zeolitic materials have been shown to decompose polyolefin polymers at a reduced process temperature of at least 100°C when compared with a thermal cracking process that does not use the zeolitic material. The reduced temperature process referred to herein as a “low-temperature pyrolysis process’7or “low-temperature pyrolysis.” Pyrolysis is also referred to sometimes as “thermal cracking”.

[0038] For example, as described below, ultra-small crystals (“USC”) of zeolite Beta (referred to herein as “USC zeolite Beta”) having an extemal-to-total surface ratio of 53% were mixed with low-density polyethylene (“LDPE”) in batch operations. The process temperatures required for onset of polyolefin decomposition over USC zeolite Beta were decreased between about 50°C to about 100°C, or between about 250°C and about 300°C compared to both larger cry stal sizes as well as an uncatalyzed thermal pyrolysis process. Furthermore, low-density polyethylene decomposition was achieved with USC zeolite Beta at temperature between about 280°C to 300°C. USC zeolite Beta is described in US Pat. No. 11.180,430, Col. 5., Is. 25 to 67, incorporated herein by reference. The chemical-value products produced were naphtha olefins having less than 10 carbons and less than 1 weight percent (“wt.%”) of aromatic compounds were detected.

[0039] By comparison, an amorphous silica-alumina catalyst having 100 percent specific surface area did not provide the process feature of lowering process temperature and / or improved chemical-value product yields. Conversely, we have shown that as the specific external surface area to total specific surface area is increased, starting at 40 percent and up to at least about 70 percent, the pyrolysis temperature can be deceased at least 50°C to 100°C while increasing chemical-value product yield.Zeolites and Zeolitic Materials

[0040] Zeolites are classified by the Structure Commission of the International Zeolite Association according to the rules of the IUPAC Commission on Zeolite Nomenclature. A framework-type describes the topology and connectivity of the tetrahedrally-coordinated atomsconstituting the framework and makes an abstraction of the specific properties for those materials. Zeolites can possess an internal pore system that includes interconnected cage like voids or a system of one-, two- or three-dimensional channels. Zeolite adsorbents for which a structure has been established are assigned a three-letter code and are described in the Atlas of Zeolite Framework Types, 5thedition, Elsevier, London, England (2001), which is incorporated in its entirety by reference herein.

[0041] Molecular sieve materials, both natural and synthetic, can be used as adsorbents and have catalytic properties for hydrocarbon conversion reactions. Certain molecular sieves, such as zeolites, AlPOs, and mesoporous materials, are ordered, porous crystalline materials having a definite crystalline structure as determined by X-ray diffraction (“XRD”). Molecular sieves can be ordered and produce specific identifiable XRD patterns. Within certain molecular sieve materials are cavities interconnected by channels or pores. Within a particular type of molecular sieve, the pores are generally uniform in size. Pore size determines whether a molecule can travel within the molecular sieve and be adsorbed or rejected.

[0042] Molecular sieves are utilized in a variety7of industrial processes, e.g., cracking, hydrocracking, disproportionation, alkylation, oligomerization, and isomerization. Molecular sieves, including naturally occurring or the synthetic crystalline molecular sieves, can find application in catalysis and adsorption.

[0043] Zeolites and their isoty pes are classified by the Structure Commission of the International Zeolite Association according to the rules of the IUPAC Commission on Zeolite Nomenclature. According to this classification, framework type zeolites and other crystalline microporous molecular sieves, for which a structure has been established, are assigned a three- letter code and are described in the “Atlas of Zeolite Framework Types”, eds. Ch. Baerlocher, L.B. McCusker, and D.H. Olson, Elsevier, Sixth Edition, 2007, which is hereby incorporated by reference.

[0044] Certain zeolites comprise an inorganic framework type where the silicon tetrahedral atoms are connected by oxygen atoms with the four next-nearest tetrahedral atoms. The term “silicate”, as used herein, refers to a substance comprising silicon and oxygen atoms alternately bonded to each other (z.e., -O-Si-O-Si-), and optionally comprise other types of atoms within the inorganic framework type, including boron, gallium, aluminum, or other metals (e.g., transition metals, such as titanium, vanadium, or zinc). Atoms other than silicon and oxygen in the framework occupy a portion of the lattice sites that would be otherwise occupied by silicon atoms in an 'all-silica' framework (also referred to as “silicate”). Thus, the term “framework silicate” or “zeolite framework silicate” refers to an atomic lattice comprisingsilicate, borosilicate, gallosilicate, ferrisilicate, aluminosilicate, titanosilicate, zincosilicate, vanadosilicate, and the like. As noted above, the framework structure within a zeolite determines the size of the pores or channels. The pore or channel size determines the type of process for which a given zeolite is applicable. Currently, there are more than 200 known zeolite framework silicates recognized by the Structure Commission of the International Zeolite Association, providing a range of pore geometries and orientations defined.

[0045] The zeolite framework silicate is commonly characterized in terms of ring size, wherein the ring size refers to the number of silicon atoms (or alternative atoms, such as those listed above) that are tetrahedrally coordinated with oxygen atoms in a loop to define a pore or channel within the interior of the zeolite. For example, an “8-ring’‘ zeolite refers to a zeolite having pores or channels defined by 8 alternating tetrahedral atoms and 8 oxygen atoms in a loop. The pores or channels defined within a given zeolite are symmetrical or asymmetrical depending upon various structural constrains that are present in the framework silicate.

[0046] Zeolites can be classified as having small, medium, large, and extra-large pore structures for pore windows delimited by 8, 10, 12, and more than 12 T-atoms, respectively. Extra-large pore zeolites (>12R) include, for example. AET (14R, e.g, ALPO-8), SFN (14R, e.g, SSZ-59), VFI (18R, e.g, VPI-5), CLO (20R, e.g, cloverite), and ITV (30R, e.g, ITQ-37) framework type zeolites. Extra-large pore zeolites generally have a free pore diameter of larger than about 0.8 nm. Large pore zeolites (12R) include, for example, LTL, MAZ, FAU, EMT, OFF, MTW, *BEA, MOR, and SFS framework type zeolites, e.g, mazzite, offretite, zeolite L, zeolite Y, zeolite X, omega. ZSM-2, ZSM-12, zeolite T, Beta, and SSZ-56. Large pore zeolites generally have a free pore diameter of 0.6 nm to 0.8 nm. Medium (or intermediate) pore size zeolites (10R) include, for example, MFI, MEL, *MRE, EUO, MTT, MFS, AEL, AFO, HEU, FER, MWW, and TON framework type zeolites, e.g., ZSM-5, ZSM-11, ZSM-48, ZSM-22, ZSM-23, ZSM-35, MCM-22. silicalite-1. and silicalite-2. Medium pore size zeolites generally have a free pore diameter of 0.45 nm to 0.6 nm. Small pore size zeolites (8R) include, for example, CHA, RTH, ERI, KFI, LEV, and LTA framework type zeolites, e.g, ZK-4, SAPO- 34, SAPO-35, ZK-14, SAPO-42, ZK-21, ZK-22, ZK-5, ZK-20, zeolite A, chabazite, and ALPO-17. Small pore size zeolites generally have a free pore diameter of 0.3 nm to 0.45 nm.

[0047] Synthesis of molecular sieve materials (zeolites) typically involves hydrothermal crystallization from a synthesis mixture comprising sources of all the elements present in the molecular sieve (or zeolite) such as sources of silica but also of alumina etc. In many cases a structure directing agent (“SDA’') is also present. Structure directing agents are compounds which are believed to promote the formation of a molecular sieve and which are thought to actas templates around which certain molecular sieve structures can form and which thereby promote the formation of the desired molecular sieve. Various compounds have been used as structure directing agents including various types of quaternary ammonium cations. Typically, molecular sieve (zeolite) crystals form around structure directing agents with the structure directing agent occupying pores in the molecular sieve once crystallization is complete. The “as -synthesized” (or “as-made”) molecular sieve will therefore contain the structure directing agent in its pores so that, following crystallization, the “as-synthesized” molecular sieve is subjected to a treatment step such as a calcination step to remove the structure directing agent.

[0048] For instance, US 3,308,069 and J.B. Higgins et al., Zeolites, 8, 446-448 (1988) disclose the preparation and characterization of zeolite Beta, a large pore zeolite of *BEA framework type, which exhibits a three-dimensional pore system formed by 12-membered ring channels. Zeolite Beta was first crystallized from a reaction mixture containing the tetraethylammonium ion (US 3,308,069). US 1 1, 180,430 B2 discloses the preparation of zeolite Beta, in particular zeolite Beta having a high external specific surface area, using 1,1’ -(pentane- l,5-diyl)bis(l-pentylpiperidinium), and their use in olefin oligomerization processes.

[0049] Beta zeolite (also “[3-zeolite”) is an aluminosilicate that consists of two distinct polymorph structures consisting of a three-dimensional network of 12-ring pores. The polymorphs grow as two-dimensional sheets and the structure randomly alternates between the two types of sheets. As taught in the prior art. [3-zeolite has been found to increase gas fractions and reduce liquid oil, however strong secondary reactions can occur to form high quantities of residue and wax, dependent on the plastic feedstock. See Mark, L. et al. (2020) The Use of Heterogenous Catalysis in the Chemical Valorization of Plastic Waste ChemSusChem, v, 13, pp. 5808-5826 citing K. Li, S. et al., Energies (2016), v.9, pg. 431 & C. Ma, et al. (2017) Fuel Process. Technol., v.155, pp. 32-41. For example, [3-zeolite could somewhat improve selectivity towards gaseous products while drastically reducing liquid oil products for the pyrolysis of HIPS. However, most of the cracked products underwent severe cross-linking reactions following cracking to produce yellowish brown wax that coated the reactor walls. Id.

[0050] Another class of zeolites that are commonly used for plastic conversion are ZSM-5 catalysts. These zeolites are MFI structured porous aluminosilicate zeolites that have been reported to have increased cracking activity for polyolefins in particular polyethylene that results in a decrease in the heavy oil fraction, reduction in wax production, minimization in char production, and an increase in light hydrocarbon content in the liquid and gas produced. Id. at 5822.

[0051] EMM-20 is disclosed in WO2014 / 099261 and WO2014 / 099262.

[0052] Other types of materials that can be used in plastic conversion include amorphous (non-zeolite) solid acids (such as used in amorphous silica-alumina. See e.g., Busca. G. (2020) Silica-Alumina Catalytic Materials: A Critical Review, v.357, pp. 621-629.Pyrolysis Processing of Plastic Waste

[0053] Consumer waste plastics, referred to herein as “plastic waste” or in the plural “plastic wastes" can contain polyethylene terephthalate (plastics recycle classification type 1), high density polyethylene (plastics recycle classification type 2), polyvinyl chloride (plastics recycle classification type 3), low density polyethylene (plastics recycle classification type 4, polypropylene (plastics recycle classification type 5), polystyrene (plastics recycle classification type 6) and other polymers (plastics recycle classification type 7).

[0054] Generally, to process plastic wastes, a pyrolysis plastic wastes reactor is used. The pyrolysis plastics waste reactor can operate in a fluidized flow or in a transport or pneumatic conveyance flow having a dilute phase of heat carrier particles. For example, a stream of globs of heat carrier particles and molten plastic undergoing pyrolysis, gaseous pyrolyzed plastic and the diluent gas stream flow upwardly together and a quasi-dense bed of plastic and heat carrier particle globs will undergo pyrolysis at the bottom of the pyrolysis waste plastics reactor. Globs of plastic and heat carrier particles transport upwardly upon size reduction due to pyrolysis.

[0055] An effluent stream from the pyrolysis plastic wastes reactor can comprise the heat carrier particles, a diluent gas stream, a pyrolyzed product, and other products such as oil. The effluent stream can comprise simpler lighter hydrocarbon molecules, including ethylene and propylene, most notably often generated at significant fractions within the effluent stream from the pyrolysis plastic wastes reactor.Preparation of Plastic Wastes for Polyolefin Pyrolysis

[0056] As provided herein, plastic wastes can be prepared by first cutting the polyolefins into small particles and / or by dissolving polyolefins in a solvent. The prepared plastic wastes feedstock can then be fed into a suitable pyrolysis plastic wastes reactor, such as a fluidized bed thermal cracker and then heated to a temperature between 500°C and 900°C for a reaction time. The temperature can depend in part on the desired products. Higher temperatures can increase selectivity for ethylene, while lower temperatures can increase selectivity’ for propylene. The reaction time where the feedstock is maintained at or above 500°C can be limited to reduce or minimize formation of coke. In an embodiment, the reaction time can correspond to 0.1 seconds to 6.0 seconds, or 0.1 seconds to 5.0 seconds, or 0.1 seconds to 1.0seconds, or 1.0 seconds to 6.0 seconds, or 1.0 seconds to 5.0 seconds. The pyrolyzed feedstock is cooled to below 500°C at the end of the reaction time. Diluent steam can also be fed into the reactor to control olefin partial pressure and to improve ethylene and propylene yields. Steam can also serve as a fluidizing gas. The weight ratio of steam to prepared plastic wastes feedstock can be between 0.3: 1 to 10: 1.

[0057] The heating and cooling of the products produced in the pyrolysis plastic wastes reactor can be performed in any convenient manner that allows for rapid heating of the plastic wastes feedstock. For example, at least a portion of the heating of the plastic wastes feedstock to the pyrolysis temperature can be performed at a heating rate of 100°C per second or more, or 200°C per second or more, such as up to l,000°C per second or possibly still faster.

[0058] In an embodiment, where the pyrolysis waste plastics reactor corresponds to a fluidized bed. the heating of the feedstock can be performed by mixing the feedstock with heated fluidizing particles. Sand is an example of a suitable type of particle for the fluidized bed. During operation, sand (or another type of heat transfer particle) can be passed into a regenerator to bum off coke and heat the particles. Additional heat will have to be supplied in the regenerator to compensate for the low coke make in this process. The heated particles can then be mixed with the plastic wastes feedstock prior to entering the reactor. By heating the heat transfer particles to a temperature above the desired pyrolysis temperature, the heat transfer particles can provide at least a portion of the heat needed to achieve the pyrolysis temperature. For example, the heat transfer particles can be heated to a temperature that is greater than the desired pyrolysis temperature by 100°C or more. Optionally, if the feedstock, sand, and fluidizing steam does not provide sufficient material to form a fluidized bed, additional fluidizing gas can be added, such as additional nitrogen, but this also will cause a corresponding increase in the volume of gas flow that needs to be handled during product recovery’.

[0059] Upon exiting from the pyrolysis plastic wastes reactor, the heat transfer particles are separated from the vapor portions of the effluent using a cyclone or another solid / vapor separator. Such a separator can also remove any other solids present after pyrolysis. It is noted that separation using a cyclone separator can result in an increase in N2 in the steam cracker effluent, which can make product recovery more challenging. Optionally, in addition to a cyclone or other primary solid / vapor separator, one or more filters can be included at a location downstream from the cyclone to allow’ for removal of fine particles that become entrained.

[0060] As further provided herein, the pyrolysis plastic wastes reactor can be a continuous stirred tank reactor, a rotary kiln, an auger reactor, or as described above, the fluidized bedreactor. The pyrolysis plastic wastes reactor typically employs an agitator. In the reactor, the plastic wastes feedstock / feed stream is heated to a temperature that pyrolyzes the plastic wastes feedstock stream to a pyrolysis effluent stream. The feed stream is pyrolyzed using various pyrolysis methods including fast pyrolysis and other pyrolysis methods such as vacuum pyrolysis, slow pyrolysis, and others. Fast pyrolysis is an intense, short duration process that can be carried out in a variety of pyrolysis reactors such as fixed bed pyrolysis reactors, fluidized bed pyrolysis reactors, circulating fluidized bed reactors, or other pyrolysis reactors capable of fast pyrolysis. Fast pyrolysis includes rapidly imparting a relatively high temperature to feedstocks for a very short residence time, typically about 0.5 seconds to about 0.5 minutes, and then rapidly reducing the temperature of the pyrolysis effluent before chemical equilibrium can occur. By this approach, the structures of polymers are broken into reactive chemical fragments that are initially formed by depolymerization and volatilization reactions, but do not persist for any significant length of time.

[0061] Noteworthy, when processing plastic wastes, polyethylene waste and polypropylene waste are often individually sorted from the plastic waste and sometimes sorted together from the plastic waste. See e.g, US Pub. Pat. App. No. 2021 / 0332299.

[0042] , Undesirable plastic materials such as multilayer films or composites, and / or compounded wastes such as rubber tires can be mechanically sorted from the feed stream with near infrared spectroscopy (NIR), laser or x-ray technologies. Other undesirable materials can include stones, metals and other non-combustible hard materials which can be removed by mechanical means. For example, ferrous metals can be removed by a magnet.Pyrolysis of Polyolefins

[0062] To decompose polymers used in plastic waste, a pyrolysis process can be employed. In such processes, the pyrolysis feedstock can be the effluent from the pyrolysis plastic wastes reactor or the pyrolysis feedstock can be supplied from different sources. In an embodiment, the pyrolysis reactor is a pyrolysis unit comprising a pyrolyzer useful to decompose polymer to a pyrolysis product. In an embodiment, the pyrolysis feedstock is a polyolefin, a polymer or group of poly olefins or polymers such as polyethylene and / or polypropylene.

[0063] Polyolefins can be catalytically pyrolyzed under pyrolysis conditions using the zeolites having an external to total specific surface area ratio of at least 40 percent to form the pyrolysis product or “chemical-value products” that include olefin monomers (also referred to herein as “olefins”) as C2 to C4 and / or C5 to C20+ olefin. In an embodiment of the present processes, zeolite (having an external to total specific surface area of 40% or more) is mixed with polyolefin feedstock in an amount of less than or equal to 1 wt.% or less than or equal to2 wt.%, less than or equal to 3 wt.%, less than or equal to 4 wt.%, or less than or equal to 5 wt.%.

[0064] Although the pyrolysis conditions can modify selectivity for the olefin monomers, the pyrolysis reaction generates a mixture of olefin monomers. For example, the present process that utilizes a zeolite having an external to total specific surface area ratio between about 40 percent and 70 percent produces chemical-value products such as a mixture of C2-C4 (■‘C2-C4”) olefins, a mixture including C2-C3 olefins, or a mixture including C2 olefins, C3 olefins and optionally C4 olefins. The C2-C4 olefins produced are primarily in a gas phase. Further, as described herein, the pyrolysis process that comprises a zeolite having an external to total specific surface area ratio of at least 40 percent can produce C5 to C20+ (“C5 to C20+ ”) olefins. The chemical-value products of C5 to C20+ olefins are produced in a liquid phase. The chemical-value products in the liquid phase can be less than or equal to 80 wt.%, or 75 wt.% or 70 wt.%, 60 wt.%, 50 wt.% or 45 wt.% of the total weight of chemical-value products produced. Similarly, chemical-value products in the gas phase can be less than or equal to 60 wt.%, 55 wt.%, 50 wt.%, 45 wt.%, 35 wt.%, 30 wt.% or 25 wt.% of the total weight of chemical-value products produced.

[0065] As described below, the pyrolysis process can include in the pyrolysis feed less than or equal to 1 weight percent zeolite having an external to total specific surface area ratio greater than 40% and producing more than 75 wt.% olefins and less than 25 wt.% of paraffin or less than 20 wt.%, 15 wt.% or 10 wt.% paraffin. The onset of decomposition of polyolefins in a pyrolysis process has been shown to occur at 300°C or less. As shown in the examples, chemical-value products comprise gas phase olefin in an amount greater than 60 mole percent C‘mol.%”); propylene in an amount greater than 30 mol.% and yield greater than 50 wt.% liquid (“liquid yield”).

[0066] The chemical-value products further comprise certain fuel components which can be upgraded in refinery units under chemical conversion processes, with final transportation fuels of higher quality and meeting the fuels quality requirements. See e.g, US Pub. App. No. 2021 / 033229

[0031] , For example, in an embodiment, a pyrolysis product can be a long chain, linear hydrocarbons, and / or can be waxy’ (i.e., able to form paraffinic wax upon cooling to ambient temperature). If w ax, wax can be separated, producing a heavy fraction that is sold to the wax markets. Also, the pyrolysis product from the pyrolysis unit can be used as fuel to operate the pyrolysis unit.

[0067] In an embodiment, the present process includes a step of selecting plastic wastescontaining polyolefins such as polyethylene and / or polypropylene. Plastic wastes are passed through the pyrolysis plastic wastes reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent can be separated into off gas, pyrolysis product, (z.e., comprising polyolefin, naphtha, diesel, and heavy fractions) and char. The pyrolyzed effluent can be used as the pyrolysis feedstock to the pyrolysis unit. In an embodiment, the pyrolysis unit further comprises a distillation unit to separate the pyrolysis product into a naphtha and diesel product streams which can be sold to fuel markets. If desired, the pyrolysis product in the form of a heavy pyrolysis oil fraction can be returned and recycled to the pyrolysis unit to maximize the fuel yield. Char can be removed from the pyrolysis unit.

[0068] In an embodiment, the present processes can optionally include a step of upgrading the pyrolysis product (chemical-value product) prior to use in a refinery unit. The pyrolysis unit might produce pyrolysis products containing contaminants, such as calcium, magnesium, chlorides, nitrogen, sulfur, phosphorus, silicon, dienes, and heavy components, which products cannot be used in large quantity for blending in transportation fuels. The contaminants, however, can be captured in one of many pre-treating units to diminish negative impacts. For example, pyrolysis product such as oil and wax which contain contaminants cannot be fed in a large quantity to refinery units, such as a fluid catalytic cracker (“FCC”) unit, because the contaminants deactivate refining catalysts, cause plugging or corrosion in the FCC unit or other processing units. Therefore, a filtration step followed by other treatments can be used to upgrade the pyrolysis products for safely processing in refinery units.

[0069] In an embodiment, the present process is integrated as a continuous process for converting plastic wastes comprising polyethylene into a recycle stream used in polyethylene polymerization. This process comprises the step of selecting plastic wastes containing polyethylene and / or polypropylene and then passing the plastic wastes through the pyrolysis plastic wastes reactor to thermally crack at least a portion of the plastic wastes and produce the pyrolyzed effluent which is further processed.

[0070] In an embodiment, the present processes can be incorporated into an oil refinery where a single use waste plastic such as polyethylene or polypropylene is in fluidic communication with a steam cracker for ethylene production allowing for a “circular economy / ’ Also, in an integrated process, the pyrolysis product in the form of a naphtha stream can be used as a steam cracker feedstock for ethylene generation and subsequent polyethylene production.Polyethylene & Other Polyolefins

[0071] Polyethylene is used widely in various consumer and industrial products including bags, films, geomembranes, and bottles. Polyethylene can be produced as high-density’ polyethylene (HDPE, approximately 0.940 to approximately 0.965 g / cm3), linear low-density polyethylene (LLDPE, approximately 0.915 to approximately 0.940 g / cm3) and low-density polyethylene (LDPE, <0.930 g / cm3), each having a chemical formula of (C2H4)nwhere n is a number one or greater, but with different molecular structure. HDPE has a low degree of branching with short side chains while LDPE has a very high degree of branching with long side chains. LLDPE is a substantially linear polymer with significant numbers of short branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins. US Pub. App. No. 2021 / 0332299 ^1

[0021] ,

[0072] Low density7polyethylene (“LDPE”) is produced via radical polymerization at a temperature between 150°C and 300°C and pressure of 1,000-3,000 atm (101-304 MPa). The process uses a small amount of oxygen and / or organic peroxide initiator to produce polymer with about 4.000-40.000 carbon atoms per the average polymer molecule, and with many branches. High density polyethylene (“HDPE”) is manufactured at relatively low pressure (10- 80 atm, 1-8 MPa) and 80°C-150°C temperature in the presence of a catalyst. Id. at

[0023] ,

[0073] The present process of decomposing polyolefin was performed by contacting one or more polyolefins (referred to sometimes as the “polyolefin feedstock”) with at least one heterogenous catalyst (zeolite) having an external surface area to a total specific surface area (or an external to total surface area) of at least 40 percent at pyrolysis conditions that include temperatures of 375°C, 350°C, 325°C or less or between about 200°C and 325°C, or between about 225°C and about 300°C, or at about 325°C, 320°C, 315°C, 310°C, 305°C, 300°C, 295°C, 290°C, 285°C, 280°C, 275°C, 270°C, 265°C, 260°C. 255°C. 250°C. 245°C, 240°C, 235°C, 230°C, 225°C, 220°C, 215°C, 210°C, 205°C, 200°C. The external to total surface specific area of the zeolite can be as high as 70 percent or between about 40 percent and about 70 percent, about 45 percent and about 65 percent, about 50 percent and about 60 percent, or at about 40 percent, about 45 percent, about 50 percent, about 55 percent, about 60 percent, about 65 percent, or about 70 percent.

[0074] As shown in the examples below, utilizing a zeolite having an external to total specific surface area ratio of at least 40 percent to produce high yield of chemical-value product, i.e., high amount of gas phase olefin (greater than 60 mol.%), greater than 30 mol.% propylene and yield greater than 50 wt.% liquid at low pyrolysis temperatures was unexpected. By way' of comparison, an amorphous silica-alumina has 100 percent of specific externalsurface area. Therefore, amorphous silica-alumina has ions which are more accessible for conversion of the polyolefin in the feedstock. Without any significant amounts of pores and having nearly 100 percent specific external surface area, our expectation was that a high yield of chemical-value product (both liquid and gas) might be produced and produced at lower temperatures. Yet, as shown in Example 3 below, the amorphous silica-alumina having an external to total surface of nearly 100 percent, required temperatures of over 400°C for the onset of decomposition. Furthermore, at 400°C plus, the amorphous silica-alumina yielded less than 80 percent chemical-value product. Therefore, the result of lowering process temperature and higher yield of chemical-value products when the ratio of specific external surface area to total surface area of the zeolite is between 40 percent and 70 percent was not expected.

[0075] During the pyrolysis of polyolefins, at least a portion of the feedstock is cracked, thus forming a pyrolysis effluent. As described in the examples, conversion yields can exceed 95 percent. The pyrolysis effluent comprises the pyrolysis product. The polyolefin feedstock comprises a polyolefin, a polyolefin blend or mixture thereof.

[0076] As provided herein, the polyolefin feedstock can be high-density polyethylene (“HDPE”), low-density polyethylene (“LDPE”), polyethylene (“PE”), polyethylene terephthalate (“PET”), polypropylene (“PP”), polystyrene (“PS”) and mixtures thereof. In another embodiment, the plastic material is substantially HDPE, linear low-density polyethylene (“LLDPE”). LDPE, PE or a mixture thereof.

[0077] In an embodiment, the polyolefin feedstock might include polyvinyl chloride (“PVC”) or poly vinylidenechloride (“PVDC”). PVDC is used, for example, in blister packaging. In a further embodiment, the polyolefin feedstock does not include more than 10 percent PVC or PVDC. In a further embodiment, the polyolefin feedstock does not include more than about 5 percent PVC or PVDC. In a further embodiment, the polyolefin feedstock is no more than about two percent PVC or PVDC. In another embodiment, the polyolefin feedstock can include no more than ten percent of a condensation polymer such as a polyester, a poly amide, poly ethylene terephthalate, polyamide or polyurethane.

[0078] As provided herein, a feedstock of polyolefin (referred to sometimes as “polyolefin polymer”) is injected into the pyrolyzer or other pyrolysis reactor and contacted with one or more heterogeneous catalysts (zeolites). Optionally, a diluent gas stream, which is typically inert, but can be hydrocarbon, hydrogen, or other gas, is added. Steam can be a diluent gas stream. The diluent gas stream separates reactive olefin products from each other to preserve the selectivity to light olefins thus avoiding oligomerization of light olefins to higher olefins orover cracking to light gas. The absence of oxygen, however, is critical. The feedstock can be preheated to high temperature before it is fed to the pyrolysis reactor but is typically heated to pyrolysis temperature after entering the pyrolysis reactor.

[0079] Polyolefin polymers are commonly used in a wide variety of industrial and consumer applications. In some instances, substantial quantities of plastic waste is available that correspond to a single ty pe of polyolefin, but more ty pically polyolefin waste corresponds to a mixture of polyethylene, polypropylene, and / or other polymer chains based on small olefins.

[0080] Polyolefins can be pyrolyzed under pyrolysis conditions to form the pyrolysis product (chemical-value product) that includes liquid phase and gas phase olefin monomers. Although the pyrolysis conditions can modify the selectivity for the olefin monomers, the pyrolysis reaction generates a mixture of olefin monomers. This can correspond to a mixture including C2-C4 C2-C4”) olefins, a mixture including C2-C3 (‘‘C2-C3”) olefins, or a mixture including C2 olefins, C3 olefins, optionally C4 olefins, and one or more additional olefins (such as C5 or Cg olefins).

[0081] As provided herein, a reference to a ‘Cx” fraction, stream, portion, feed, or other quantity7is defined as a fraction (or other quantity) where 50 wt.% or more of the fraction corresponds to hydrocarbons having “x” number of carbons. When a range is specified, such as “Cx-Cv”. 50 wt.% or more of the fraction corresponds to hydrocarbons having a number of carbons between “x” and “y”. A specification of ‘ Cx+” (or “Cx-”) corresponds to a fraction where 50 wt.% or more of the fraction corresponds to hydrocarbons having the specified number of carbons or more (or the specified number of carbons or less).

[0082] The present processes are not limited to processing a type of polyolefin, a polymer or group of polymers. However, to optimize melting of plastic wastes and depending on the type of polymers in the plastic wastes, separate flows can be required for different polymers. For example, the condensation polymers PET are mechanically recycled and are removed from the plastic material prior to pyrolysis or chemically recycled by an alternative process such as hydrolysis. In another example, because PVC generates HC1 at pyrolysis, PVC is typically removed from the plastic material. However, a small presence of PVC in the plastic material is acceptable. Alternative processes include chemical recycling by different processes (i.e., hydrolysis) of other polymers such as polyesters and polyamides.The Polyolefin Feedstock

[0083] As provided herein, the polyolefin feedstock for pyrolysis can comprise or consistessentially of one or more polyolefins or polyolefin polymers. The processes described herein are suitable for processing plastic wastes corresponding to a single type of olefinic polymer. However, additional benefits can be realized when the plastic waste contains polymers including a plurality of monomer types. Also, it is desirable to form polymer-grade olefin fractions from the pyrolysis processing of plastic waste because the subsequent polyolefin pyrolysis will produce higher yields of ethylene and / or propylene monomer than steam cracking of a crude fraction. US Pub. App No. 2022 / 0195309.

[0084] In an embodiment, where the polyolefin feedstock largely comprises polyolefin polymers (z.e., low density polyethylene), the polyolefin feedstock can further comprise additives, modifiers, packaging dyes, and / or other components typically added to a polymer during and / or after formulation. The polyolefin feedstock can further include components typically found in plastic wastes. Finally, the feedstock can further include one or more solvents or carriers so that the polyolefin feedstock corresponds to a solution or slurry of the polyolefin polymers.

[0085] In an embodiment, the polyolefin feedstock includes at least one of polyethylene and / or polypropylene. Polyethylene can be any type of polyethylene of HDPE or LDPE. In addition to polyethylene and / or polypropylene, the polyolefin feedstock can optionally include one or more of polystyrene, polyvinylchloride, polyamide (e g., nylon), polyethylene terephthalate, and ethylene vinyl acetate. Still other polyolefins can correspond to polymers (including co-polymers) of butadiene, isoprene, and isobutylene. In an embodiment, the polyethylene and polypropylene can be present in the mixture as a co-polymer of ethylene and propylene. More generally, polyolefins include co-polymers of various olefins, such as ethylene, propylene, butene, hexenes, and / or any other olefins suitable for polymerization.

[0086] Unless otherwise specified, weight of polyolefin polymer in the polyolefin feedstock corresponds to weights relative to the total polymer content in the polyolefin feedstock. Any additives / modifiers / other components included in a formulated polymer are included in this weight. However, the weight percentages described herein exclude any solvents or carriers used so that the polyolefin feedstock corresponds to a solution or slurry of polymers. For compatibility with introducing the pyrolysis product in a steam cracking process train, the polyolefin feedstock can include limited amounts of polymers different from polyethylene and / or polypropylene. In various aspects, the polyolefin feedstock for pyrolysis can include 55 wt.% to 100 wt.% of polyethylene, polypropylene, copolymer of ethylene and propylene, other Cq-Cty olefins and / or dienes, or a combination thereof. In embodiments where the polyolefin feedstock corresponds to 95 wt.% or more of polymers derived from ethyleneand propylene, the polyolefin feedstock can include 10 wt.% of more of ethylene monomers and 10 wt.% or more of propylene monomers.

[0087] In embodiments where the polyolefin feedstock includes less than 100 wt.% of polyethylene and / or polypropylene, the feedstock can optionally include 0.1 wt.% or more of other polymers. For example, the polyolefin feedstock can include 0.1 wt.% to 35 wt.% of polystyrene, or 1.0 wt.% to 35 wt.%, or 0.1 wt.% to 20 wt.%, or 1.0 wt.% to 20 wt.%, or 10 wt.% to 35 wt.%, or 5 wt.% to 20 wt.%. Including polystyrene in the feed can increase the yield of aromatics, including the yield of styrene. In some aspects, styrene can be isolated and used for production of polystyrene. Additionally, or alternately, styrene can be blended with steam cracked naphtha that is generated by the steam cracking process. It is noted that as the amount of polystyrene is increased, the yield of ethylene and / or propylene monomers can decrease. Limiting the amount of polystyrene can allow for production of ethylene and / or propylene from the polyethylene / polypropylene in the polyolefin feedstock in amounts that are greater than conventional steam cracker yields. Additionally, polystyrene can potentially be recycled by processing at lower temperatures, such as around 450°C, to convert polystyrene into styrene monomers. Thus, limiting polystyrene content in the polyolefin feed can also be beneficial in order to allow polystyrene to be processed under more favorable conditions.

[0088] In embodiments, the polyolefin feedstock can optionally include 0.1 wt.% to 10 wt.%, or 0.1 wt.% to 2.0 wt.%, or 0.1 wt.% to 1.0 wt.% of polyvinyl chloride, poly vinylidene chloride, or a combination thereof; and / or 0. 1 wt.% to 1.0 wt.% polyamide. Poly vinyl chloride is roughly 65% chlorine by weight. As a result, pyrolysis of polyvinyl chloride (and / or polyvinylidene chloride) can result in formation of substantial amounts of hydrochloric acid relative to the initial weight of the polyvinyl chloride. In limited amounts, the hydrochloric acid that results from pyrolysis of polyvinyl chloride and / or polyvinylidene chloride can be removed using guard beds prior to allowing the pyrolysis product to enter the steam cracking process train. In other aspects, from 0.1 wt.% to 10 wt.% of polyvinyl chloride and / or polyvinylidene chloride can optionally be included in the feed by including additional chlorine removal stages prior to combining the polyolefin pyrolysis product with the steam cracking processing train.

[0089] In an embodiment, the polyolefin feedstock can optionally include 0.1 wt.% to 10 wt.% polyethylene terephthalate, or 1.0 wt.% to 10 wt.%. Additionally, or alternately, the polyolefin feedstock can optionally include 0.1 wt.% to 10 wt.% of ethylene vinyl acetate, or 1.0 wt.% to 10 wt.%. Both polyethylene terephthalate and ethylene vinyl acetate can depress yields of ethylene and / or propylene monomers, while potentially also increasing production ofCO, CO2, or a combination thereof. Limiting the amount of polyethylene terephthalate and / or ethylene vinyl acetate can allow for production of ethylene and / or propylene from the polyethylene / polypropylene in the polyolefin feedstock in amounts that are greater than conventional steam cracker yields.

[0090] Polyolefins can be prepared for incorporation into the polyolefin feedstock with methods for preparing the polyolefins can include reducing the particle size of the polyolefins and mixing the polyolefins with a solvent or carrier. Where the polymer waste / polyolefins are introduced into the pyrolysis reactor at least partially as solids, having a small particle size can facilitate transport of the solids into the pyrolysis reactor. Smaller particle size can potentially also contribute to achieving a desired level of conversion of the polymers / poly olefins under the short residence time conditions of the pyrolysis.

[0091] To prepare solids for pyrolysis, the solid polymers / polyolefins can be crushed, chopped, ground, or otherwise physically processed to reduce the median particle size to 3.0 cm or less, or 2.5 cm or less, or 2.0 cm or less, or 1.0 cm or less, such as down to 0.01 cm or possibly still smaller. For determining a median particle size, the particle size is defined as the diameter of the smallest bounding sphere that contains the particle.

[0092] Additionally, or alternately, a solvent or carrier can be added to the polyolefin feedstock. For introduction into the pyrolysis reactor, it can be convenient for the polyolefin / polymer produced from plastic waste to be in the form of a solution, slurry, or other fluid-type phase. If a solvent is used to at least partially solvate the polyolefins, any convenient solvent can be used. Examples of suitable solvents can include (but are not limited to) a wide range of petroleum or petrochemical products. For example, some suitable solvents include crude oil, naphtha, kerosene, diesel, and oils. Other potential solvents can correspond to naphthenic and / or aromatics solvents, such as toluene, benzene, methylnaphthalene, cyclohexane, methylcyclohexane, and mineral oil. Still other solvents can correspond to refiner. ■ fractions, such as a gas oil fraction or naphtha fraction from a steam cracker product. If a carrier is used, the carrier can correspond to a liquid or gas phase carrier, such as steam.

[0093] Aspects of the disclosure are described in greater detail by way of specific examples. The following examples are offered for illustrative purposes and are not intended to limit the disclosure in any manner. Those of skill in the relevant art will readily recognize a variety' of parameters can be changed or modified to yield essentially the same results.EXAMPLES

[0094] The features of the disclosure are described in the following non-limiting examples.Example 1Decomposition Temperature Effect of Ultra-Small Crystal (USC) Zeolite Beta

[0095] USC zeolite Beta is a zeolitic material employed as the heterogenous catalyst in the pyrolysis reaction and pyrolytic decomposition of low-density polyethylene (“LDPE”). To evaluate the USC zeolite Beta, thermogravimetric analysis ("‘TGA”) and gas chromatography (“GC”) analysis were conducted. The onset temperature for pyrolytic decomposition of the LDPE over USC zeolite Beta zeolite was determined by TGA.

[0096] Thermogravimetric Analysis (“TGA”) measures the absolute and rate of weight change in a material as a function of time and temperature in a controlled atmosphere. It can be used to characterize any material that exhibits a weight change and to detect changes due to e.g., decomposition, oxidation, or dehydration. TGA was performed on a High Resolution ThermoGravimetric Analyzer Q500 (TA Instruments). In a typical method, the sample was exposed to a flow of inert gas (Argon), equilibrated at 40°C and kept at this temperature for 10 min. After this the sample was subjected to a constant ramp rate of 5°C / min to 800°C and the weight loss (and rate) was measured as a function of temperature.

[0097] LDPE (ExxonMobil LD117.NM, 1.6 g / 10 min Melt Index (190°C / 2.16 kg and 0.929 g / cm3 density)) was mixed with 20 wt.% of USC zeolite Beta powder and weight loss was measured as a function of temperature using TGA methodology. LDPE was thermally cracked (thermal pyrolysis, i.e., without the use of catalyst) in to determine an onset temperature difference for decomposition of LDPE over USC zeolite Beta. The impact of crystal size on the onset temperature of the pyrolytic decomposition of LDPE was evaluated by comparing zeolite Beta and USC zeolite Beta. Zeolite Beta has a larger crystal size compared to USC zeolite Beta.

[0098] Material screening for catalytic pyrolysis was performed by TGA under inert atmosphere. In this experiment, pyrolysis processing using USC zeolite Beta (Sample 1) was compared to uncatalyzed thermal pyrolysis (referred to herein as “blank”) and larger zeolite Beta crystals (Sample 2) as shown in FIG. 1A and FIG. IB respectively. As compared with the blank, LDPE decomposition onset over USC zeolite Beta decreases by about 100°C to 250°C to 300°C, showing multiple decomposition events. (FIG. 1A) While the polyolefin decomposition is effectively activated over USC zeolite Beta at temperatures lower than 300°C, the dm / dt peaks occurred at higher temperatures for larger Beta crystals. FIG. 1A provides agraph of the TGA data in “high-resolution” mode of the pyrolytic decomposition of LDPE over USC zeolite Beta and uncatalyzed thermal pyrolysis (“blank”) of LDPE. FIG. IB provides the graph of the thermogravimetric analysis having a constant temperature ramp rate of the pyrolytic decomposition of low-density polyethylene over about 20 wt.% of USC zeolite Beta and zeolite Beta (larger crystals).

[0099] A micro-pyrolyzer was integrated with on-line gas chromatography to evaluate the pyrolysis product composition. Thermal pyrolysis without a catalyst is not significant at 300°C and thus, was also performed at 550°C. FIG. 2A provides a GC chromatogram of the different effluents taken from the pyrolyzer at about 20 wt.% of USC zeolite Beta at 300°C and without catalyst at 550°C in the pyrolyzer. FIG. 2B is a graph that compares the composition of the effluent of pyrolysis at 300°C using USC zeolite Beta and at 550°C without a catalyst (the USC zeolite Beta), respectively. FIG. 2B shows a percentage of various aliphatic compounds in the C4 to C9 range. Less than 1 wt.% aromatics was detected at 300°C over USC zeolite Beta.

[0100] Formation of molecules with more than 10 carbon numbers is significantly suppressed over USC zeolite Beta. C4 to C9 olefin content is similar for catalytic and thermal pyrolysis. (FIG. 2B) More branched aliphatic compounds are formed when the zeolite is present and due to acid catalysis and modification of the primary' pyrolysis products.

[0101] Larger batch experiments used 1 liter (“L”) round-bottom flask equipped with an overhead condenser. 1 .0 wt.% USC zeolite Beta was pre-mixed with LDPE and reaction was carried out under N2 flow' in absence of stirring. Condensates were collected from the reactor overhead and analyzed offline by GC analysis. Like the TGA and micro-pyrolyzer testing, we confirmed that USC zeolite Beta effectively allows for decomposition of LDPE in the temperature of about 280°C to 300°C and at larger scales.

[0102] FIG. 3 is a graph of condensates collected from the overhead of the pyrolyzer operated at about 280°C to 300°C and analyzed offline by GC. LPDE was pre-mixed with 1 wt.% UCS Beta powder. The mixture was not stirred during the reaction. FIG. 3 shows the percentage of various aliphatic compounds in C4 to C5 (C4-C5) range: olefin, paraffin, linear and branched. Compared to thermal pyrolysis, the formation of molecules with more than 10 carbon atoms was significantly suppressed over USC zeolite Beta. Although the proportion of C4 to C9 olefinic and paraffinic compounds were similar for catalytic and thermal pyrolysis, thermal pyrolysis produced more linear aliphatic compounds. More branched compounds were formed over USC zeolite Beta due to acid catalysis and modification of the primary' pyrolysis products. Furthermore, less than 1 wt.% aromatics were detected at 300°C when the zeolitewas present. This data indicates that the performance of USC zeolite Beta observed with TGA and micro-pyrolyzer translates to a larger scale.Example 2EMM-20 Zeolite (USC MFI) vs. ZSM-5 Crystals

[0103] Similar to the analysis of the UCS Beta zeolite of Example 1 and as compared with a blank experiment. EMM-20 (USC MFI, Sample 3) is effective in decreasing pyrolysis onset to a lower temperature. In this example, the TGA analysis was performed under N2 flow in “high-resolution” mode and at a constant temperature ramp rate. LDPE (ExxonMobil LD117. NM. 1.6 g / 10 min Melt Index (190°C / 2.16 kg and 0.929 g / cm3 density)) was mixed with about 20 wt.% -30 wt.% of catalyst powder. The blank test was performed in absence of catalyst. EMM-20 is an ultra-small cry stal form of ZSM-5 (Framework Type MFI) and described in WO2014 / 099261, WO2014 / 099262, and US 10,662,068, Col. 4, 1. 8 through Col. 5, 1. 55, incorporated herein by reference.

[0104] FIG. 4A is a graph of the TGA in “high-resolution” mode of the pyrolytic decomposition of LDPE over EMM-20 and uncatalyzed thermal pyrolysis (“blank”) of LDPE. Compared to the blank, LDPE decomposition onset over USC zeolite Beta decreased by about 100°C from 350°C to 380°C to 240°C to 300°C. In FIG. 4B, the dashed frame highlights the 200°C to 300°C temperature range where EMM-20 activates the LDPE decomposition.

[0105] FIG. 4B provides a comparison of the performance of EMM-20 (MFI framework) zeolite (Sample 3) with two progressively larger ZSM-5 (MFI framework) cry stals (Sample 4 and 5). ZSM-5 (MFI) is described in US Pat. No. 3,702,886 (non-ultrasmall crystal) and US Patent No. 5,240,892 (small crystal). EMM-20 is described in WO2014 / 099261 and WO2014 / 099262.

[0106] Extemal-to-total surface ratio of large cry stal size ZSM-5, small crystal size ZSM-5, and EMM-20 are 13%, 25%, and 65% respectively. FIG. 4B is a graph of the TGA with a constant temperature ramp rate of the pyrolytic decomposition of LDPE over EMM-20 zeolite, large crystal size ZSM-5 and small crystal size ZSM-5. FIG. 4B shows that as the extemal-to-total surface ratio increases, dm / dt (change in mass over time) maxima shifts to lower temperatures. At the same time, the area under the shoulder at 250°C increases significantly for EMM-20.

[0107] Both FIG. IB and FIG. 4B demonstrate that for pyrolysis over zeolitic catalysts, extemal-to-total surface ratio is a parameter to be optimized. The hydroxyls and other defects on the zeolite’s external surface effectively catalyze the polyolefin decomposition.Concentration of these surface hydroxyls and defects increases as the zeolite particle gets smaller. Having a high specific external surface area will limit (internal) mass transport (diffusion) limitations of the polymer to the active site (acid site) of the solid acid materials. As a result, we discovered that high specific external surface area provides higher activity (better reaction kinetics) at lower temperature and higher conversion to smaller hydrocarbons. It is surprising that even at very high ratio of external to total specific surface area, where there is a limited internal specific surface area inside the zeolite pores, the type of zeolite framework (pore structure) can impact product distribution significantly.

[0108] Higher specific external surface area (> 40% external vs. total) in zeolites is beneficial when processing (highly viscous) polymer melts, agnostic to which type of zeolite is applied, and that this is different in terms of product distribution and activity from using other high specific surface area (amorphous) solid acids. Example 3, below. Micropore volume, as described in Table 1 herein, is interesting in this respect as well, as having micropore volume (z.e., structured micropores) distinguishes zeolites from other amorphous solid acid materials with high external to total specific surface area.

[0109] The extemal-to-total surface ratio on the onset temperature of the pyrolytic decomposition of LDPE was evaluated by a comparison of EMM-20 zeolite and other zeolites. The zeolites described herein as well as the ultra-small zeolitic materials with a high extemal- to-total surface ratio (greater than 40 percent) due to the size of the primary particles (zeolite). More generally these are smallest distinguishable condensed particles formed during crystallization / precipitation synthetic preparation of inorganic materials. Primary particles in their turn form larger agglomerates (secondary particles) which will have interparticle voids and spaces and specific surface area. See e.g., Studies in Surface Science and Catalysis, v.123, (1999), Chapter 9. FIG. 9.3 incorporated herein by reference. The use of the ultra small crystals (“USC”) with high specific external surface area are crucial for several reasons: 1) the polymers will not be able to diffuse into the zeolite hence the chemistry will occur on the surface of the zeolite, 2) locations of the acid sites have to be located internally and externally to achieve the acid cracking, 3) surfaces of zeolites can have partially formed pores whihc can help with confinement without causing diffusional limitations. These USC can be small crystals with the defined surrface areas but can also be hierchical in nature, i.e. limited to several crystallographic unit cells thickness.

[0110] Table 1 immediately below provides the physical properties of various zeolites and crystals.Table 1

[0111] As provided in Table 1, external -to-total specific surface area ratio was calculated from the ratio of Brunauer-Emmett-Teller (BET) specific surface area, obtained from N2 physisorption, and the specific external surface area is obtained from the t-plot applied to the N2 isotherm. Micropore volume was also obtained using the t-plot method.

[0112] FIG. 5 shows the results of the TGA analysis of various zeolites under N flow in high resolution mode and with a constant temperature ramp rate. LDPE was mixed with 20 wt.% of catalyst powder. The blank test was performed without catalyst. Dashed frame highlights 200°C to 300°C temperature range where most zeolitic materials are not as effective as USCs to active LDPE decomposition. USC zeolite Beta and EMM-20 were shown as most effective for LDPE decomposition at temperatures below 300°C.

[0113] Additional USC zeolites having external to total specific surface area ratio greater than 40% and less than 70% include: (a) synthesized zeolites having micropores with large alkali cations and / or an organic structure directing agent C OSDA") and (b) zeolite crystals where mesopores are generated by either a bottom-up or top-down approach. See Xi cheng, J., et al. (2019) “Modem Synthesis Strategies for Hierarchical Zeolites: Bottom-Up Versus Top- Down Strategies, ’ Advanced Powder Technology, v.30(3), pp. 467-484.Example 3Larger Scale Catalytic Pyrolysis Over Ultra-Small Crystal Zeolite Catalysts Beta and EMM-20

[0114] FTGs. 6A, 6B, 6C and 6D show the decomposition of a typical low density polyethylene (LDPE, ExxonMobil LD150BW, 0.75 Melt Index (190°C / 2.16 kg), 0.923 g / cm3 density ) over 20 wt.% of various zeolite and amorphous solid acid catalysts as determined by thermal gravimetric analysis. The decomposition curve for the same LDPE in the absence of catalyst is included in the figure for reference. The ultra-small crystal zeolite and high external specific surface area amorphous silica-alumina catalysts show high weight loss between 200°C to 400°C, and more characteristically between 200°C and 300°C (shown in the inset of the figures) compared to the other zeolite frameworks (ZSM-11. Sample 14) and larger crystals of the same framework type (z.e. Beta. Sample 2) and ZSM-5 (Sample 4 and 5) and thermal pyrolysis.

[0115] In order to demonstrate the beneficial product distribution of ultra-small crystal zeolites vs. other types of catalysts, 250 gram of the same LDPE pellets were physically mixed with 2.5 gram of various solid acid catalyst powders and added to a 2 L round-bottom flask equipped with a vigreux column, and subsequently a hot (80°C) condenser, a cold condenser (5°C), a cold trap cooled with a dry ice / isopropylalcohol mixture and finally a Tadler™ gas sampling bag for light gas collection and analysis. For the pyrolysis experiments, the roundbottom flask was initially purged with a high flow of nitrogen for 5 minutes and after that the nitrogen flow was stopped and the flask w as gradually heated (10 to 20°C / min) to 300°C. After the melt phase reached 300°C, the temperature of the melt was increased stepwise with 10°C increments to a point where the first liquid products started to be collected and temperature w as then held steady until no more liquid was collected. At that point, the temperature was increased further in a stepwise manner, and so on, until either the LDPE was completely converted or the maximum temperature of the setup (450°C) was reached and no more liquid or gas phase sample was collected. For reference, the same experiment was also run in the absence of any catalyst (z.e., “thermal pyrolysis”).

[0116] Total liquid yield was weighed and measured, and gas yield was calculated byweighing the remaining pyrolysis bottoms (without catalyst) and subtracting pyrolysis bottoms and liquid yield from the total loaded LDPE feed. Ultimate conversion was 100% (grams remaining in the bottom - grams of catalyst) I grams of LDPE loaded and after keeping the sample at 450°C until no further liquid or gas phase products evolved from the flask. The cold trap contents were brought to room temperature after the experiment and any evolving gasphase products were collected using Tadler™ gas sampling bags. Any remaining liquid yield from the cold trap was analyzed and added to total liquid yield.

[0117] Gas chromatography coupled with flame ionization detection ( 'FID ') and mass spectrometry (“MS”) were applied to characterize the carbon number and individual < C5 isomers (where possible) of the pyrolysis products and Ifl NMR analysis was performed on a Fourier 80 benchtop 80 MHz NMR instrument (Bruker) to obtain a relative comparison of aromatic and olefinic content in the liquid fractions collected.

[0118] Table 2 below shows the conversion, liquid and gas yields and compositional information of the products formed from catalytic pyrolysis over ultrasmall crystal zeolites, with a high external to total specific surface area ratio, in comparison to thermal pyrolysis and an amorphous silica-alumina (Siral 40 HPV, Sasol) with high external to total specific surface area. The ultra-small crystal zeolites show higher overall conversion, in the case of EMM-20 even at significantly lower final pyrolysis temperature. Remarkably, near-complete conversion is obtained in the case of the ultra-small crystal zeolite catalysts with higher gas yields, liquid products have an average lower carbon number and the overall gas phase light olefin yields and are much improved over thermal pyrolysis and / or pyrolysis over the amorphous silica alumina with high external to total specific surface area ratio.

[0119] Acid site density and strength is another parameter known to influence ultimate catalytic pyrolysis yield. Si / A12 molar ratios are a common proxy for zeolite acid site density and strength. For USC Beta (Sample 1) and larger crystal Beta (Sample 2), Si / A12 ratios were in a very similar range. For the EMM-20 catalyst (Sample 3) and small crystal ZSM-5 (Sample 4) there was a significant difference in Si / AE ratios. However, the gas phase product distribution (in terms of olefin content and propylene content) for the high Si / A12 ratio EMM-20 showed very close resemblance to the USC Beta catalyst. Both observations underline the importance of high specific external surface area to total specific surface area ratio in order to obtain high catalytic pyrolysis yield.

[0120] FIG. 7 illustrates the carbon number distribution of liquid products obtained from thermal pyrolysis, and catalytic pyrolysis over USC zeolite Beta, EMM-20 and Siral HPV (amorphous silica-alumina). Together with Table 2, the data illustrates an exceptional performance of the ultra-small crystal zeolite catalysts over thermal pyrolysis without catalysts as well as conventional lower specific external surface area zeolites (Sample 2 and 4) and amorphous silica-alumina material (Siral HPV). Further, with respect to the experiments summarized in Table 2 below, data trends show that the liquid yield for the high specificexternal surface area zeolite samples is high than conventional zeolites and thermal pyrolysis and between about 50.0 wt.% and about 75.0 wt.%. Gas yields are lower for the high specific external surface area zeolites vs. their conventional references and the gas phase olefin content for sample 1 and 3 is characteristically high and above 60 mol% with propylene content above 30 mol%. Ultimate conversion is close to 100% for both samples and this conversion is achieve at lower temperature compared to conventional zeolite and amorphousTable 2Example 4Decomposition of Polypropylene over USC Zeolite Beta and EMM-20

[0121] Polypropylene (PP, ExxonMobil PP5341E1, 0.83 g / 10 min Melt Index (230°C / 2.16 kg) and 0.900 g / cm3 density) was mixed with 20 wt.% of various zeolite and amorphous catalysts powder and weight loss was measured as a function of temperature using TGA methodology. Figures 8A-C show the decomposition curves as determined by thermalgravimetric analysis. PP was also thermally cracked (thermal pyrolysis, for example, without the use of catalyst) for comparison with pyrolysis over the various catalytic materials. As shown in FIG. 8A and FIG. 8B. the USC zeolites Beta and EMM-20 show relatively high weight loss in the 250°C to 350°C region compared to the other catalysts and compared to thermal pyrolysis. The results also indicate that even though amorphous silica-alumina catalyst has similar external to total specific surface area, the USC zeolite Beta and EMM-20 zeolite materials provide superior process performance at low temperature decomposition of PP similar to that observed for LDPE in Examples 1, 2 and 3 described above.Additional Embodiments

[0122] Additionally, or alternately, the invention relates to:

[0123] Embodiment 1. A process for decomposing polyolefins comprising the steps of: contacting a polyolefin with a zeolite having an external to total specific surface area ratio of at least 40 percent to provide a mixture; and pyrolyzing the mixture to a temperature of 400°C or less, wherein the polyolefin is thermally decomposed in the absence of oxygen to produce a yield of chemical-value product comprising C2 to C4 olefin and C5 to C20+olefin.

[0124] Embodiment 2. The process for decomposing polyolefins of embodiment 1, wherein the chemical-value product is produced in a gas phase and a liquid phase.

[0125] Embodiment 3. The process of embodiment 2, wherein the gas phase comprises C2 to C4 olefin and the liquid phase comprises C5 to C20+ olefin.

[0126] Embodiment 4. The process for decomposing polyolefins of embodiment 1, wherein the process produces a liquid yield of 50 percent or greater at 95 percent conversion or greater at pyrolysis temperature of 400°C or less.

[0127] Embodiment 5. The process for decomposing polyolefins of embodiment 1, wherein the process produces a gas phase olefin yield of 60 mol percent or greater.

[0128] Embodiment 6. The process for decomposing polyolefins of embodiment 1, wherein the process produces a gas phase propylene yield of 30 mol percent or greater.

[0129] Embodiment 7. The process for decomposing polyolefins of embodiment 1, wherein the pyrolysis product comprises less than 1 wt.% aromatic compounds.

[0130] Embodiment 8. The process for decomposing polyolefins of embodiment 1, wherein the pyrolysis product comprises more branched aliphatic compounds than linear aliphatic compounds.

[0131] Embodiment 9. The process for decomposing polyolefins of embodiment 1, wherein the pyrolysis mixture comprises less than or equal to 1 wt% of the zeolite.

[0132] Embodiment 10. The process for decomposing polyolefins of any of the preceding embodiments, wherein the polyolefins are a mixture of one or more polymers.

[0133] Embodiment 11. The process for decomposing polyolefins of any of the preceding embodiments, wherein the zeolite is an ultra-small crystal of the BEA or MFI framework.

[0134] Embodiment 12. The process for decomposing polyolefins of embodiment 10, wherein the zeolite is USC zeolite Beta or EMM-20.

[0135] Embodiment 13. The process for decomposing polyolefins of any of the preceding embodiments, wherein the polyolefin is low-density polyethylene.

[0136] Embodiment 14. The process for decomposing polyolefins of any of the preceding embodiments, wherein the polyolefin comprises a mixture of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE).

[0137] Embodiment 15. The process for decomposing polyolefins of any of the preceding embodiments, wherein the polyolefin is polypropylene.

[0138] Embodiment 16. The process for decomposing polyolefins of any of the preceding embodiments, where the formation of compounds with more than 10 carbon atoms is less than formation of compounds with more than 10 carbon atoms or greater.

[0139] Embodiment 17. A process for decomposing polyolefin in a plastic waste comprising the steps of: providing a plastic waste comprising one or more polyolefins; pyrolyzing the plastic waste to produce an effluent; separating the polyolefins from the effluent; contacting the polyolefins with a zeolite having an external to total specific surface area ratio of between 40 percent and 70 percent to provide a mixture; and pyrolyzing the mixture to a temperature 400°C or less, wherein the polyolefins are thermally decomposed in the absence of oxygen to yield a chemical-value product comprising C4 to C20+olefin in an amount of 95 percent or greater.

[0140] Embodiment 18. A process for decomposing polyolefin in a plastic waste of embodiment 17, comprising the steps of separating the polyethylene plastic waste from a mixed plastic waste.

[0141] Embodiment 19. A process for decomposing polyolefin in a plastic waste of any of the preceding embodiments, wherein the pyrolysis product comprises fuel components.

[0142] Embodiment 20. The process for decomposing polyolefin in a plastic waste of embodiment 19 wherein the fuel component is used as a transportation-quality fuel.

[0143] Embodiment 21. The process for decomposing polyolefin in a plastic waste of any of the preceding embodiments, wherein the zeolite is a USC zeolite Beta and / or EMM-20 zeolite.

[0144] Embodiment 22. The process for decomposing polyolefin in a plastic waste, wherein the polyolefin is polyethylene or polypropylene.

[0145] Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

Claims

CLAIMS1. A process for decomposing polyolefins comprising the steps of: contacting a polyolefin with a zeolite having an external to total specific surface area ratio of at least 40 percent to provide a mixture; and pyrolyzing the mixture to a temperature of 400°C or less, wherein the polyolefin is thermally decomposed in the absence of oxygen to produce a yield of chemical-value product comprising C2 to C4 olefin and C5 to C20+olefin.

2. The process for decomposing polyolefins of claim 1, wherein the chemical-value product is produced in a gas phase and a liquid phase.

3. The process of claim 2, wherein the gas phase comprises C2 to C4 olefin and the liquid phase comprises C5 to C20+ olefin.

4. The process for decomposing polyolefins of claim 1, wherein the process produces chemical-value products comprising an amount of gas phase olefin greater than 60 mole percent (“mol.%”); an amount of propylene greater than 30 mol.% and a liquid yield greater than 50 wt.%.

5. The process for decomposing polyolefins of claim 1, wherein the pyrolysis product comprises less than 1 wt.% aromatic compounds.

6. The process for decomposing polyolefins of claim 1, wherein the pyrolysis product comprises more branched aliphatic compounds than linear aliphatic compounds.

7. The process for decomposing polyolefins of claim 1, wherein the mixture comprises less than or equal to 1 wt.% of the zeolite.

8. The process for decomposing polyolefins of claim 1, wherein the polyolefins are one or more polymers.

9. The process for decomposing polyolefins of claim 1, wherein the zeolite is an ultrasmall or hierarchical crystal of the BEA or MFI framework.

10. The process for decomposing polyolefins of claim 9, wherein the zeolite is USC zeolite Beta or EMM-20.

11. The process for decomposing polyolefins of claim 1, wherein the polyolefin is low- density polyethylene.

12. The process for decomposing polyolefins of claim 1 wherein formation of molecules having more than 10 carbon atoms is less than formation of compounds having 10 carbon atoms or less.

13. A process for decomposing polyolefin in a plastic waste comprising the steps of: providing a plastic waste comprising one or more polyolefins; pyrolyzing the plastic waste to produce an effluent; separating the polyolefins from the effluent; contacting the polyolefins with a zeolite having an external to total specific surface area ratio of between 40 percent and 70 percent to provide a mixture; and pyrolyzing the mixture to a temperature 400°C or less, wherein the polyolefins are thermally decomposed to produce chemical-value products comprising an amount of gas phase olefin greater than 60 mole percent (“mol.%”); an amount of propylene greater than 30 mol.% and a liquid yield greater than 50 wt.%.

14. A process for decomposing polyolefin in a plastic waste of claim 13, wherein the pyrolysis product comprises fuel components.

15. The process for decomposing polyolefin in a plastic waste of claim 14 wherein the fuel component is used as a transportation-quality fuel.

16. The process for decomposing polyolefin in a plastic waste of claim 13, wherein the zeolite is a USC zeolite Beta and / or EMM-20 zeolite.

17. The process for decomposing polyolefin in a plastic waste of claim 13, wherein the polyolefin is polyethylene or polypropylene.

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