Supported transition‑metal catalysts for polyolefin hydrogenolysis and methods for hydrogenolysis of a polyolefin feed

Abstract

Surface‑bound procatalysts for hydrogenolysis of a polyolefin feed include an acidic sulfated support and cationic transition metal complexes M+Ly surface‑bound to at least one surface sulfate site QS − of the acidic sulfated support. The transition metal M is selected from the group consisting of Fe, Ni, Co, Cu, and Zn. The y number of ligands is 1, 2, or 3. Each ligand is a monodentate or multi‑dentate ligand coordinated to the transition metal with a hapticity greater than 1. Methods for hydrogenolysis of a polyolefin feed include contacting the surface‑bound procatalyst with a hydrogen feed to form active catalyst sites comprising hydride complexes M+H each surface‑bound to at least one anionic site of the sulfated support; contacting the active catalyst sites with the polyolefin feed in the presence of hydrogen; and allowing the polyolefin feed to react in the reactor to obtain a hydrogenolyzed product.

Description

85992-WO-PCT / DOW 85992 WO1SUPPORTED TRANSITION-METAL CATALYSTS FOR POLYOLEFIN HYDROGENOLYSIS AND METHODS FOR HYDROGENOLYSIS OF A POLYOLEFIN FEEDCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 686,545 filed August 23, 2024, the contents of which are incorporated in their entirety herein.TECHNICAL FIELD

[0002] The present disclosure is directed to catalysts for polyolefin hydrogenolysis and methods including the same and, more particularly, to polyolefin hydrogenolysis catalyzed by an organometallic procatalyst supported on a very strongly acidic support and to methods for hydrogenolysis of a polyolefin feed.BACKGROUND

[0003] Plastic waste typically comprises polypropylene (PP), polyethylene (PE), polystyrene (PS)-based materials, or their mixtures. Plastic waste is typically recycled by thermomechanical processes or chemical recycling processes. However, the recycled materials — particularly those processed mechanically — often remain a mixture of different plastics. Consequently, the quality of recycled materials tends to be inferior to that of virgin plastics, which are made directly from pure monomers. Improving the quality of recycled materials is thus important for the production of high-quality recycled plastic products.

[0004] Chemical recycling processes have been explored as alternatives to produce high-quality recycled plastic materials. Among various chemical recycling processes, pyrolysis has been adopted as a current industrial technology for recycling plastic waste. However, pyrolysis is an unselective and energy-intensive process. On the other hand, polyolefin hydrogenolysis is a chemical process that catalytically breaks down polyolefin compounds into smaller hydrocarbon molecules by adding H>, resulting in valuable saturated hydrocarbons. These valuable saturated hydrocarbons find application in various sectors, including serving as feedstock for gasoline and lubricant production.85992-WO-PCT / DOW 85992 WO2SUMMARY

[0005] Though limited methods of polyolefin hydrogenolysis seem to have been found to produce high-quality recycled plastic materials, the current application of polyolefin hydrogenolysis has a need for further development of economical, efficient, and versatile catalysts that can hydrogenolyze wide ranges of polyolefins, especially polyolefins typically involved in recycling streams. Catalysts that include precious metals such as Pd, Pt, Ru, or Re exhibit low activity, leading to a slow polyolefin hydrogenolysis reaction rate with significant coke formation. However, few of those catalysts can readily hydrogenolyze branched polypropylene and polystyrene.

[0006] Hydrogenolysis catalysts disclosed herein address the foregoing needs by providing surface-bound procatalysts that are capable of hydrogenolyzing wide ranges of polyolefins, including polyethylene, polypropylene, polystyrene, and their copolymers, for example. Particularly disclosed herein are surface-bound procatalysts for the hydrogenolysis of a polyolefin feed. The surface-bound procatalysts include an acidic sulfated support and cationic transition metal complexes M+Tysurface-bound to at least one surface sulfate site Qs~ of the acidic sulfated support, where M is a transition metal selected from the group consisting of Fe, Ni, Co, Cu, and Zn; each L is a monodentate or multi-dentate ligand -coordinated to M with a hapticity greater than 1 and independently selected from the group consisting of C2-C40 unsaturated hydrocarbons, C2-C40 unsaturated hydrocarbyls, and C1-C40 heterohydrocarbons; y denotes a number of the ligands in the cationic transition metal complex; y is 1, 2, or 3; and the cationic transition metal complex contains from 2 to 6 metal-ligand bonds.

[0007] Also disclosed herein are methods for hydrogenolysis of a polyolefin feed. The methods include contacting a surface-bound procatalyst with a hydrogen feed, whereby the ligands L of at least a portion of the cationic transition metal complexes M+Fysurface-bound to the acidic sulfated support disassociate from the transition metal complexes M+Fyto form active catalyst sites comprising hydride complexes M+H each surface-bound to at least one anionic site of the acidic sulfated support, where the at least one anionic site is chosen from surface sulfate sites or surface oxide sites; contacting the active catalyst sites with a polyolefin feed in a reactor in the presence of hydrogen; and allowing the polyolefin feed to react in the reactor to obtain a hydrogenolyzed product.85992-WO-PCT / DOW 85992 WO3

[0008] Also disclosed herein are methods of regenerating spent catalyst sites. The methods include contacting the spent catalyst sites with an alkylaluminum to form regenerated catalyst sites. The molar ratio of the alkylaluminum to the spent catalyst sites is greater than or equal to 3 and less than or equal to 20.

[0009] These and other features, aspects, and advantages will become better understood with reference to the following description and the appended claims.

[0010] Additional features and advantages of embodiments described herein will be set forth in the detailed description that follows and, in part, will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description that follows, the claims, as well as the appended drawings.

[0011] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the disclosure. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0013] FIG. 1 is a schematic of an example preparation of an active catalyst (4) by activating a surface-bound procatalyst (3) prepared by contacting a procatalyst (1) with a surface group of an acidic sulfated support (2);

[0014] FIG. 2A is a graph of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) vibrational spectra of the specific example surface-bound proctalyst and the activated catalyst of FIG. 1 ;85992-WO-PCT / DOW 85992 WO4

[0015] FIG. 2B is an X-ray Photoelectron Spectroscopy (XPS) analysis of the example surface-bound procatalyst of FIG. 1;

[0016] FIG. 2C is an Electron Paramagnetic Resonance (EPR) analysis of the example surface-bound procatalyst of FIG. 1;

[0017] FIG. 2D is a XPS analysis of the example active catalyst of FIG. 1;

[0018] FIG. 3A is a gas chromatography-mass spectrometry (GC-MS) chromatogram of dichloromethane (DCM)-soluble hydrocarbon produced by the hydrogenolysis of branched polyethylene catalyzed by the example surface-bound procatalyst of FIG. 1 ;

[0019] FIG. 3B is a schematic diagram of carbon-carbon bond cleavage in the hydrogenolysis of a branched polyethylene, with selectivity toward cleavage at branch sites;

[0020] FIG. 4A is a gel permeation chromatography (GPC) analysis of DCM-soluble hydrocarbon produced by the hydrogenolysis of post-consumer isotactic polypropylene;

[0021] FIG. 4B is a GPC analysis of solids produced by the hydrogenolysis of post-consumer linear polyethylene;

[0022] FIG. 5 is a GPC analysis of DCM-soluble hydrocarbon produced by the hydrogenolysis of post-consumer isotactic polypropylene in the presence of polyvinyl chloride; and

[0023] FIG. 6 is a GPC analysis of DCM-soluble hydrocarbon produced by the hydrogenolysis of isotactic polypropylene using a regenerated catalyst.DETAILED DESCRIPTION

[0024] Reference will now be made in detail to surface-bound procatalysts for hydrogenolysis of a polyolefin feed. Methods involving the surface-bound procatalysts for hydrogenolysis of a polyolefin feed will be discussed subsequently.

[0025] Without being bound by any particular theory, d° catalysts including precious early transition metals such as Mo, W, or Re, with sufficient electrophilicity could rapidly cleave polyolefin C-C bonds. However, identification of comparably electrophilic catalysts containing more abundant late transition metals such as Fe, Ni, Co, Cu, or Zn remains a significant challenge.

[0026] With the surface-bound procatalysts disclosed herein, an electrophilic catalyst containing late transition metals unexpectedly results by chemically adsorbing (z.e., by85992-WO-PCT / DOW 85992 WO5 chemisorption) charge -neutral late transition metal complex procatalysts onto a surface of a very strongly acidic support to form cationic transition metal complexes bound to the surface of the very strongly acidic support, resulting in a surface-bound procatalyst. The acidic support can be a strongly Bronsted acidic support. The surface-bound procatalyst is capable of being activated or converted to form active catalyst sites. The active catalyst sites include metal hydride complexes each surface-bound to the very strongly acidic support. The formation of electrophilic catalysts containing late transition metals described herein is versatile. The electrophilic catalysts may be prepared from wide ranges of charge-neutral late transition metal complex procatalysts coordinated by different ligands.

[0027] FIG. 1 is a non-limiting schematic example of a process for preparing a surface-bound procatalyst and an active catalyst from one exemplary charge-neutral late transition metal complex illustrated as Ni(COD)2, though it should be readily understood that other surface-bound procatalysts and active catalysts exemplified in this disclosure are possible. According to the process of FIG. 1, charge -neutral transition metal complex procatalysts MLy(for example, bis(cycloctadiene)nickel, Ni(COD)2, 1) may be bound to an acidic sulfated support (e.g. sulfated alumina, AIS, 2). The charge-neutral transition metal complex procatalysts become cationic M+Fyupon binding to at least one surface sulfate site Qs~ of the acidic sulfated support to form surface-bound procatalysts (e.g. AlS / Ni(COD)2, 3). When the surface-bound procatalysts are contacted with a hydrogen feed, the ligands L of at least a portion of the cationic transition metal complexes M+Fysurface-bound to the acidic sulfated support disassociate from the transition metal complexes M+Fyto form active catalyst sites. The active catalyst sites include hydride complexes M+H each bound to at least one anionic site of the acidic sulfated support, where the at least one anionic site is chosen from surface sulfate sites or surface oxide sites (e.g. AlS / NiH, 4). Details of the formation will be described below and in Examples.

[0028] The term “procatalyst” herein refers to a precursor compound capable of being activated or converted to an active catalyst having catalytic activity as a result of a chemical treatment or a series of chemical treatments on the procatalysts. Non-limiting examples of chemical treatments include adsorption of the procatalyst onto a support, hydrogen treatment of the procatalyst, removal of an atom or chemical group from the procatalyst, or combinations thereof. In some examples, adsorption or hydrogen treatment of the procatalyst may result in the removal of an atom or chemical group from the procatalyst. In some examples, adsorption or85992-WO-PCT / DOW 85992 WO6 hydrogen treatment of the procatalyst may result in the formation of a charged species having catalytic activity.

[0029] The term “hapticity” refers to the topological coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. A ligand capable of coordinating to a metal center via an uninterrupted and contiguous series of atoms may be described with the eta-notation (r|H) known and understood by those skilled in the art as indicating bonding topology between a ligand and a metal center. In the eta-notation pH, the superscript H is a numerical index referring to a number of contiguous atoms in the ligand that are involved in coordination to the metal center of the metal-ligand complex. For example, a ligand coordinated to a transition metal with a hapticity greater than 1 (for example, p2, p3, p4, p5, or p6) means that at least two contiguous atoms in the ligand are involved in coordination to the metal center.

[0030] Some ligands can coordinate with metals in more than one possible orientation, where the different orientations result in different hapticities. For example, cyclopentadienyl ligands are known to coordinate with metal centers in various orientations depending on various chemical aspects, including the identity of the metal, to result in possible ligand hapticities of 1, 3, or 5. When a ligand coordinates with a hapticity of 1 (p1) to a metal, the ligand is considered for purposes of this disclosure to be a univalent ligand. When a ligand coordinates with a hapticity of greater than 1 to a metal (for example, p2, p3, p4, p5, or p6), the ligand is considered for purposes of this disclosure not to be a univalent ligand. No hydrocarbyl ligand or hydrocarbon ligand lacking a double bond is capable of coordinating with a metal with a hapticity greater than 1. Examples of strictly univalent ligands include saturated hydrocarbyls and saturated heterohydrocarbyls, such as neopentyl (Np). Other types of ligands may include double bonds or triple bonds yet still coordinate only with a hapticity of 1 (p1). Examples of such ligands include, without limitation, =CHtBu and =C‘Bu.

[0031] Examples of ligands capable of having a hapticity greater than 1 include unsaturated hydrocarbyls, saturated or unsaturated heterohydrocarbyls, unsaturated hydrocarbons, and saturated or unsaturated heterohydrocarbons, any of which may be substituted or unsubstituted. It should be understood that many ligands capable of coordinating with a hapticity greater than 1 also may be capable of coordinating with a hapticity of exactly one, depending on the identity of the metal center and the orientation of the ligand with respect to the metal center that results from the number of electrons participating in the bonding. An p1complex of a transition metal M with85992-WO-PCT / DOW 85992 WO7 a ligand L shall be regarded herein as being discrete and different from an r|6complex of the same transition metal M with the same ligand L.

[0032] Examples of substituted or unsubstituted, unsaturated hydrocarbyls capable of coordinating with metal centers with a hapticity of greater than 1 include substituted or unsubstituted, unsaturated (C2-C4o)hydrocarbyl.

[0033] When used to describe certain carbon atom-containing chemical groups, an expression having the form “Cx-Cy” or a parenthetical expression having the form “(Cx-Cy)” means that the unsubstituted form of the chemical group has from x carbon atoms to y carbon atoms, inclusive of x and y. For example, a C1-C40 hydrocarbon or a (C1-C40) hydrocarbon is a hydrocarbon having from 1 to 40 carbon atoms in its unsubstituted form, and a C1-C40 alkyl or a (Ci-C4o)alkyl is an alkyl group having from 1 to 40 carbon atoms in its unsubstituted form. In some embodiments and general structures, certain chemical groups may be substituted by one or more substituents such as R or Rs, where superscript S may be represented using various symbols or letters. An Rssubstituted version of a chemical group defined using the “(Cx-Cy)” parenthetical may contain more than y carbon atoms depending on the identity of any groups Rs. For example, a “(Ci- C4o)alkyl substituted with exactly one group Rs, where Rsis phenyl (—Cel ls)’" may contain from 7 to 46 carbon atoms. Thus, in general, when a chemical group defined using the “(Cx-Cy)” parenthetical is substituted by one or more carbon atom-containing substituents Rs, the minimum and maximum total number of carbon atoms of the chemical group is determined by adding to both x and y the combined sum of the number of carbon atoms from all of the carbon atom-containing substituents Rs.

[0034] The term “substitution” or “substituted” means that at least one hydrogen atom (-H) bonded to a carbon atom or heteroatom of a corresponding unsubstituted compound or function group is replaced by a substituent (e.g. Rs).

[0035] The term “-H” means a hydrogen or hydrogen radical that is covalently bonded to another atom. “Hydrogen” and “-H” are interchangeable, and unless clearly specified mean the same.

[0036] The term “saturated” means lacking carbon-carbon double bonds, carbon-carbon triple bonds, and (in heteroatom-containing groups) carbon-nitrogen, carbon-phosphorous, and carbonsilicon double bonds. Where a saturated chemical group is substituted by one or more substituents Rs, one or more double and / or triple bonds optionally may or may not be present in substituents85992-WO-PCT / DOW 85992 WO8Rs. The term “unsaturated” means containing one or more carbon-carbon double bonds, carbon-carbon triple bonds, and (in heteroatom-containing groups) carbon-nitrogen, carbon-phosphorous, and carbon-silicon double bonds, not including any such double bonds that may be present in substituents Rs, if any, or in (hetero) aromatic rings, if any.

[0037] The term “(C2-C40) unsaturated hydrocarbon” means a hydrocarbon contains one or more double bonds and / or triple bonds of from 2 to 40 carbon atoms. Examples of (C2-C40) unsaturated hydrocarbon capable of coordinating to a metal via more than one atoms include (C2- Cis)alkene, (C5-Ci4)cycloalkene, (Ce-C2o)arene, ethylene, cyclooctadiene, norbornene, cyclododecatriene, bis(4- rt-butylphenyl)ethene, benzene, cycloheptatriene, cyclooctatetraene, naphthalene, anthracene, and diene.

[0038] The term “(C2-Cis)alkene” means an unsubstituted or substituted (by one or more Rs), straight chain or branched chain, unsaturated hydrocarbon of from 2 to 18 carbon atoms, of which at least 2 from 2 to 18 of the carbon atoms form a double bond. Examples of (C2-Cis)alkene include ethylene, allyl, bis(4-tert-butylphenyl)ethane, butylene, and diene.

[0039] The term “(C5-Ci4)cycloalkene” means an unsubstituted or substituted (by one or more Rs), cyclic, unsaturated hydrocarbon of from 5 to 14 carbon atoms, of which at least 2 from 5 to 14 of the carbon atoms form a double bond. Examples of (C5-Ci4)cycloalkane include cyclopentadiene, cyclooctadiene, norbornene, cyclododecatriene, cycloheptatriene, and cyclooctatetraene.

[0040] The term “(C6-C2o)arene” means an unsubstituted or substituted (by one or more Rs) mono-, bi- or tricyclic aromatic hydrocarbon of from 6 to 20 carbon atoms, of which at least from 6 to 14 of the carbon atoms are aromatic ring carbon atoms, and the mono-, bi- or tricyclic hydrocarbon comprises 1, 2, or 3 rings, respectively; wherein the 1 ring is aromatic and the 2 or 3 rings independently are fused or non-fused and at least one of the 2 or 3 rings is aromatic. Examples of unsubstituted (Ce-C2o)arene include 2-(Ci-C5)alkyl-benzene, 2,4-bis(Ci- Cs)alkyl-benzene, benzene, fluorenene, tetrahydrofluorenene, indacene, hexahydroindacene, indene, naphthene, tetrahydronaphthene, anthracene, and phenanthrene. Examples of substituted (Ce-C2o)arene are 2,4-bis[(C2o)alkyl]-benzene, polyfluorobenzene, pentafluorobenzene, and fluoren-9-one.

[0041] The term “(C1-C40) heterohydrocarbon” refers to a saturated or unsaturated, substituted or unsubstituted (C1-C40) hydrocarbon in which one or more carbon atoms are replaced with a85992-WO-PCT / DOW 85992 WO9 heteroatom. The term “heteroatom” refers to an atom other than hydrogen or carbon or a group of atoms containing at least one atom that is neither hydrogen nor carbon. Examples of heteroatom include O, S, S(O), S(O)2, Si(Rc)2, P(Rp), N(RN), -N=C(RC)2, -Ge(Rc)2- or -Si(Rc)-, where each Rc, each RN, and each Rpis unsubstituted (Ci-Cis)hydrocarbyl or -H. Examples of heterohydrocarbons capable of coordinating to a metal via more than one atoms include substituted or unsubstituted (Ci-C4o)heteroalkane, (C2-C4o)heteroalkene, (C5- Ci4)heterocycloalkene, or (C5-C2o)heteroarene, such as azobenzene, imine, pyridine, furane, thiophene, pyrrole, indole, and quinolone.

[0042] The term “(C5-C2o)heteroarene” means an unsubstituted or substituted (by one or more Rs) mono-, bi- or tricyclic aromatic heterohydrocarbon of from 5 to 20 carbon atoms, of which at least from 5 to 13 of the carbon atoms are aromatic ring carbon atoms, and the mono-, bi- or tricyclic hydrocarbon comprises 1, 2, or 3 rings, respectively; wherein the 1 ring is aromatic and the 2 or 3 rings independently are fused or non-fused and at least one of the 2 or 3 rings is aromatic. Examples of unsubstituted (C5-C2o)heteroarene include 2-(Ci-C5)alkyl-pyridine, 2-(Ci- Cs)alkyl-furane, 2-(Ci-C5)alkyl-thiophene, 2,4-bis(Ci-C5)alkyl-pyridine, 2,4-bis(Ci- Cs)alkyl-furane, 2,4-bis(Ci-C5)alkyl-thiophene, pyridine, furane, thiophene, pyrrole, indole, quinolone, isoquinoline, benzofuran, benzothiophene, phenanthroline, carbazole, acridine, and phenanthridine. Examples of substituted (C5-C2o)heteroarene are furfural, 2,2 ’-bipyridine, 2-thiophenecarboxaldehyde, and 5-bromo-2-furaldehyde.

[0043] The term “(Ci-C4o)hydrocarbyl” means a hydrocarbon radical of from 1 to 40 carbon atoms and the term “(Ci-C4o)hydrocarbylene” means a hydrocarbon diradical of from 1 to 40 carbon atoms, in which each hydrocarbon radical and each hydrocarbon diradical is aromatic or non-aromatic, saturated or unsaturated, straight chain or branched chain, cyclic (including mono- and poly-cyclic, fused and non-fused polycyclic, including bicyclic, having at least 3 carbon atoms) or acyclic and is unsubstituted or substituted by one or more Rs.

[0044] Examples of (Ci-C4o)hydrocarbyl include unsubstituted or substituted (Ci-C4o)alkyl, (Ce-C4o)aryl, (C3-C4o)cycloalkyl. The terms “(Ci-C4o)alkyl” and “(Ci-Cis)alkyl” mean a saturated straight or branched hydrocarbon radical of from 1 to 40 carbon atoms or from 1 to 18 carbon atoms, respectively, that is unsubstituted or substituted by one or more Rs. Examples of unsubstituted (Ci-C4o)alkyl include unsubstituted (Ci-C2o)alkyl, unsubstituted (Ci-Cio)alkyl, unsubstituted (Ci-Cs)alkyl, methyl, ethyl, 1 -propyl, 2-propyl, 1 -butyl, 2-butyl, 2-methylpropyl,85992-WO-PCT / DOW 85992 WO101,1 -dimethylethyl, 1 -pentyl, 1 -hexyl, 1 -heptyl, 1 -nonyl, 1 -decyl, allyl, and cyclopentadienyl. Examples of substituted (Ci-C4o)alkyl are substituted (Ci-C2o)alkyl, substituted (Ci-Cio)alkyl, and trifluoromethyl.

[0045] Examples of unsaturated hydrocarbyls include unsaturated (C2-C4o)hydrocarbyl, such as (C2-Ci2)alkenyl, (Ce-C2o)aryl, phenyl, naphthyl, cyclopentadienyl, cyclohexadienyl, biphenyl, terphenyl, anthracenyl, phenanthrenyl. Substituted aryl groups include methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, styryl, allylphenyl, propynylphenyl, chlorophenyl, fluorophenyl, difluorophenyl, trifluorophenyl, tetrafluorophenyl, pentafluorophenyl, pentafluorobiphenyl, methoxyphenyl, ethoxyphenyl, dimethoxyphenyl, trifluoromethylphenyl, bis(trifluoromethyl)phenyl, dimethylaminophenyl, dimethylaminoethylphenyl, phenoxyphenyl, methylcarboxyphenyl, ethylcarboxyphenyl, methoxynaphthyl, nitrophenyl, dinitrophenyl, cyanophenyl, dicyanophenyl. Examples of substituted or unsubstituted, unsaturated hydrocarbyls capable of coordinating with metal centers with a hapticity of greater than 1 include allyl and cyclopentadienyl.

[0046] The term “(C6-C4o)aryl” means an unsubstituted or substituted (by one or more Rs) mono-, bi- or tricyclic aromatic hydrocarbon radical of from 6 to 40 carbon atoms, of which at least from 6 to 14 of the carbon atoms are aromatic ring carbon atoms, and the mono-, bi- or tricyclic radical comprises 1, 2, or 3 rings, respectively; wherein the 1 ring is aromatic and the 2 or 3 rings independently are fused or non-fused and at least one of the 2 or 3 rings is aromatic. Examples of unsubstituted (Ce-C4o)aryl include unsubstituted (Ce-C2o)aryl, unsubstituted (Ce- Cis)aryl, 2-(Ci-C5)alkyl-phenyl, 2, 4-bis(Ci-C5)alkyl -phenyl, phenyl, 4-tertbutylphenyl, fluorenyl, tetrahydrofluorenyl, indacenyl, hexahydroindacenyl, indenyl, dihydroindenyl, naphthyl, tetrahydronaphthyl, and phenanthrene. Examples of substituted (Ce-C4o)aryl are substituted (Ci-C2o)aryl, substituted (C6-Cis)aryl, 2,4-bis[(C2o)alkyl] -phenyl, polyfluorophenyl, pentafluorophenyl, and fluoren-9-one-l-yl.

[0047] The term “(C3-C4o)cycloalkyl” means a saturated cyclic hydrocarbon radical of from 3 to 40 carbon atoms that is unsubstituted or substituted by one or more Rs. Other cycloalkyl groups (e.g., (Cx-Cy)cycloalkyl) are defined in an analogous manner as having from x to y carbon atoms and being either unsubstituted or substituted with one or more Rs. Examples of unsubstituted (C3- C4o)cycloalkyl include unsubstituted (C3-C2o)cycloalkyl, unsubstituted (C3-Cio)cycloalkyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and85992-WO-PCT / DOW 85992 WO11 cyclodecyl. Examples of substituted (C3-C4o)cycloalkyl are substituted (C3-C2o)cycloalkyl and substituted (C3-Cio)cycloalkyl.

[0048] Examples of (Ci-C4o)hydrocarbylene include unsubstituted or substituted (Ce- C4o)arylene, (C3-C4o)cycloalkylene, and (Ci-C4o)alkylene (e.g., (Ci-C2o)alkylene). In some embodiments, the diradicals are on the same carbon atom (e.g., -CH2-) or on adjacent carbon atoms (z.e., 1,2- diradicals), or are spaced apart by one, two, or more than two intervening carbon atoms (e.g., respective 1,3-diradicals, 1,4-diradicals, etc.).

[0049] The term “(Ci-C4o)alkylene” means a saturated straight chain or branched chain diradical (z. e. , the radicals are not on ring atoms) of from 1 to 40 carbon atoms that is unsubstituted or substituted by at least one Rs. Examples of unsubstituted (Ci-Csojalkylene include unsubstituted (Ci-C2o)alkylene, including unsubstituted -CH2CH2-, -(CH2)3-, -(CH2)4-,which “C*” denotes a carbon atom from which a hydrogen atom is removed to form a secondary or tertiary alkyl radical. Examples of substituted (Ci-Csojalkylene include substituted (Ci- C2o)alkylene, -CF2-, and -C(O)-.

[0050] The term “(Ci-C4o)heterohydrocarbyl” means a heterohydrocarbon radical of from 1 to 40 carbon atoms, and the term “(Ci-C4o)heterohydrocarbylene” means a heterohydrocarbon diradical including from 1 to 40 carbon atoms, where each heterohydrocarbon has one or more heteroatoms. The radical of the heterohydrocarbyl is on a carbon atom or a heteroatom, and diradicals of the heterohydro car by lene may be on: (1) one or two carbon atoms, (2) one or two heteroatoms, or (3) a carbon atom and a heteroatom. Each (Ci-Csojheterohydrocarbyl and (Ci- Csojheterohydrocarbylene may be unsubstituted or substituted (by one or more Rs), aromatic or non-aromatic, saturated or unsaturated, straight chain or branched chain, cyclic (including mono- and poly-cyclic, fused and non-fused polycyclic), or acyclic.

[0051] The (Ci-C4o)heterohydrocarbyl may be unsubstituted or substituted (Ci- C4o)heteroalkyl, (Ci-C4o)hydrocarbyl-0-, (Ci-C4o)hydrocarbyl-S-, (Ci-C4o)hydrocarbyl-S(0)-, (Ci-C4o)hydrocarbyl-S(0)2-, (Ci-C4o)hydrocarbyl-Si(Rc)2-, (Ci-C4o)hydrocarbyl-N(RN)-, (Ci- C4o)hydrocarbyl-P(Rp)-, (C2-C4o)heterocycloalkyl, (C2-Ci9)heterocycloalkyl-(Ci-C2o)alkylene, (C3-C2o)cycloalkyl-(Ci-Ci9)heteroalkylene, (C2-Ci9)heterocycloalkyl-(Ci-C2o)heteroalkylene, (C4-C4o)heteroaryl, (C4-Ci9)heteroaryl-(Ci-C2o)alkylene, (C6-C2o)aryl-(Ci-Ci9)heteroalkylene, or (C4-Ci9)heteroaryl-(Ci-C2o)heteroalkylene, pyridinyl, pyrazinyl, imidazolyl, pyrazolyl,85992-WO-PCT / DOW 85992 WO12 oxazolyl, thienyl, pyrrolyl, triazolyl, indolyl, benzimidazolyl, chloropyridinyl, methylimidazolyl, phenylpyrrolyl, and ethylthienyl.

[0052] The term “(C4-C4o)heteroaryl” means an unsubstituted or substituted (by one or more Rs) mono-, bi- or tricyclic heteroaromatic hydrocarbon radical of from 4 to 40 total carbon atoms and from 1 to 10 heteroatoms, and the mono-, bi- or tricyclic radical comprises 1, 2 or 3 rings, respectively; wherein the 2 or 3 rings independently are fused or non- fused and at least one of the 2 or 3 rings is heteroaromatic. Other heteroaryl groups (e.g., (Cx-Cy)heteroaryl generally, such as (C4-Ci2)heteroaryl) are defined in an analogous manner as having from x to y carbon atoms (such as 4 to 12 carbon atoms) and being unsubstituted or substituted by one or more than one Rs.

[0053] The aforementioned heteroalkyl may be saturated straight or branched chain radicals containing (C1-C50) carbon atoms, or fewer carbon atoms and one or more of the heteroatoms. Tikewise, the heteroalkylene may be saturated straight or branched chain diradicals containing from 1 to 50 carbon atoms and one or more than one heteroatoms. The heteroatoms, as defined above, may include Si(Rc)3, Ge(Rc)3, Si(Rc)2, Ge(Rc)2, P(Rp)2, P(Rp), N(RN)2, N(RN), N, O, ORC, S, SRC, S(O), and S(O)2, wherein each of the heteroalkyl and heteroalkylene groups are unsubstituted or substituted by one or more Rs.

[0054] The term “independently selected” is used herein to indicate that the each T ligand can be identical or different (e.g., all T ligands may be C2-C40 unsaturated hydrocarbons, or a portion of T ligands may be C2-C40 unsaturated hydrocarbons and a portion of T ligands may be C1-C40 saturated or unsaturated heterohydrocarbons, etc.) A named T ligand will generally have the structure that is recognized in the art as corresponding to T ligands having that name. These definitions are intended to supplement and illustrate, not preclude, the definitions known to those of skill in the art.

[0055] The surface-bound procatalysts for hydrogenolysis of a polyolefin feed include the cationic transition metal complexes M+Ty. In examples of the cationic transition metal complexes M+Ty, the transition metal M may be selected from the group consisting of Fe, Ni, Co, Cu, and Zn. In specific examples, the transition metal is Ni.

[0056] In examples of the cationic transition metal complexes M+Fy, at least one L is a monodentate or multi-dentate ligand coordinated to M with a hapticity greater than 1, such from 2 to 8, from 2 to 6, or from 4 to 6, such as 4, 5, or 6. In some limited examples of the cationic transition metal complexes M+Fy, each L is a monodentate or multi-dentate ligand coordinated to85992-WO-PCT / DOW 85992 WO13M with a hapticity greater than 1, such as from 2 to 8, from 2 to 6, or from 4 to 6. In such examples, every L is a multivalent ligand having a hapticity greater than 1 and no L is a univalent ligand having a hapticity of 1. In further examples, no ligand L is selected from C1-C12 saturated or unsaturated hydrocarbyl or C1-C12 silyl hydrocarbyl coordinating to the metal with a hapticity of 1.

[0057] In some cases, at least one L or each L is a monodentate ligand coordinated to M with a hapticity greater than 1. In other cases, at least one L or each L is a bidentate ligand coordinated to M with a hapticity of greater than 1. In another cases, at least one L or each L is a tridentate ligand coordinated to M with a hapticity of greater than 1. At least one L or each L is independently selected from the group consisting of C2-C40 unsaturated hydrocarbons, C2-C40 unsaturated hydrocarbyls, and C1-C40 saturated or unsaturated heterohydrocarbons. In some specific examples, the cationic transition metal complexes may have 2 or more monodentate ligands. The 2 or more monodentate ligands L may be joined through a bridging structure to form a multi-dentate ligand. Examples of the bridging structure include (Ci-C4o)alkylene or (Ci- C4o)heteroalkylene, such as -CR2-, -SiR2- -GeR2- where each R is H, (Ci-C4o)hydrocarbyl, or (Ci-C4o)heterohydrocarbyl. For example, the cationic transition metal complexes herein may comprise two identical or different cyclopentadienyl groups linked by -CR2- or -SiR2- where each R is H, substituted or unsubstituted (Ci-C4o)alkyl, or substituted or unsubstituted (Ci- C4o)heteroalkyl.

[0058] In examples of the cationic transition metal complexes M+Ly, each L may be selected from the group consisting of C2-C40 unsaturated hydrocarbons, including substituted or unsubstituted (C2-C4o)alkene, (C2-C4o)alkyne, (Cs-Cujcycloalkene, or (Ce-C2o)arene. In some examples, each L may be selected from the group consisting of ethylene, benzene, cycloheptatriene, cyclooctadiene, cyclooctatetraene, naphthalene, and anthracene. In additional examples, L may be selected from substituted or unsubstituted cyclooctadiene (COD), substituted or unsubstituted cyclododecatriene (cdt), substituted or unsubstituted norbornene (nor), ethylene, or ArCHCHAr, where each Ar is a substituted or unsubstituted aryl.

[0059] In examples of the cationic transition metal complexes M+Ly, each L may be selected from the group consisting of C2-C40 unsaturated hydrocarbyls, including substituted or unsubstituted (C2-C4o)alkyl or (C5-C4o)cycloalkyl. In some examples, each L may be allyl or85992-WO-PCT / DOW 85992 WO14 cyclopentadienyl. In additional examples, L may be substituted or unsubstituted cyclopentadienyl (Cp).

[0060] In the cationic transition metal complexes M+Ly, each L may be selected from the group consisting of C1-C40 heterohydrocarbons, including substituted or unsubstituted (Ci- C4o)heteroalkane, (C2-C4o)heteroalkene, (C2-C4o)heteroalkyne, (C5-Ci3)heterocycloalkene, or (C5-C4o)heteroarene.

[0061] In some specific examples of the cationic transition metal complexes, the cationic transition metal complex M+Lyis selected from the group consisting of Ni+(COD)2, Ni+(Cp)2, Ni+(ArCHCHAr)3, Ni+(cdt), and Ni+(nor)3. In one example of the cationic transition metal complex M+Ly, subscript y is 2, M is nickel, and L is unsubstituted cyclooctadiene coordinated to M with a hapticity greater than 1, whereby the cationic transition metal complex is Ni+(COD)2. In one example of the cationic transition metal complex M+Ly, subscript y is 2, M is nickel, and L is substituted or unsubstituted cyclopentadienyl coordinated to M with a hapticity greater than 1, whereby the cationic transition metal complex is Ni+(Cp)2. In one example of the cationic transition metal complex M+Ly, subscript y is 3, M is nickel, and L is ArCHCHAr coordinated to M with a hapticity greater than 1, whereby the cationic transition metal complex is Ni+(ArCHCHAr)3, where Ar is substituted or unsubstituted aryl. In one example of the cationic transition metal complex M+Ly, subscript y is 3, M is nickel, and L is norbornene coordinated to M with a hapticity greater than 1, whereby the cationic transition metal complex is Ni+(nor)3. In one example of the cationic transition metal complex M+Ly, subscript y is 1, M is nickel, and L is cyclododecatriene coordinated to M with a hapticity greater than 1, whereby the cationic transition metal complex is Ni+(cdt).

[0062] The surface-bound procatalysts for hydrogenolysis of a polyolefin feed include the acidic sulfate support. Examples of the acidic sulfate support include sulfated alumina (AIS), sulfated zirconia, or sulfated silica. The acidic sulfate support may have a Hammett acidity less than or equal to -12, such as less than or equal to -13, less than or equal to -14. In specific examples, the acidic sulfate support has a Hammett acidity less than or equal to -12.4 and greater than or equal to -14.5. For example, in embodiments, the acidic sulfate support may be sulfated alumina (AIS) having a Hammett acidity less than or equal to -12.4 and greater than or equal to85992-WO-PCT / DOW 85992 WO15

[0063] The acidic sulfated support may have at least one anionic site. Examples of anionic sites include surface sulfate sites or surface oxide sites. The cationic transition metal complexes M+Eymay be surface-bound to at least one anionic site of the acidic sulfated support and thereby form the surface-bound procatalyst disclosed and described herein. The cationic transition metal complexes M+Eymay be bound to at least one surface sulfate site or at least one surface oxide site. In some examples, each cationic transition metal complex M+Eyis bound to a surface sulfate site. In non-limiting examples, the charge-neutral transition metal complexes MEyare selected from Ni(COD)2 (as in the schematic of FIG. 1), Ni(ArCHCHAr)3, Ni(Cp)2, Ni(nor)s, or Ni(cdt).

[0064] The charge-neutral transition metal complexes may be bound to a surface sulfate site of a sulfated alumina (AIS) to form corresponding cationic transition metal complexes Ni+(COD)2, Ni+(ArCHCHAr)3, Ni+(Cp)2, Ni+(nor)3, or Ni+(cdt) each bound to a surface sulfate site of AIS as surface-bound procatalysts, AlS / Ni(COD)2, AlS / Ni(ArCHCHAr)3, Al / Ni(Cp)2, AlS / Ni+(nor) 3, or AlS / Ni+(cdt), respectively. In examples, the charge-neutral transition metal complexes MEymay be selected from Ni(COD)2, Ni(ArCHCHAr)3, or Ni(Cp)2. When adsorbed on an acidic sulfated support, the charge-neutral transition metal complexes MEyform a surface-bound procatalyst as the corresponding cationic transition metal complexes M+Ey(z. e. , Ni+(COD)2, Ni+(ArCHCHAr)3, or Ni+(Cp)2, respectively) bound to at least one surface sulfate site of a sulfated alumina (AIS) (z. e. , AlS / Ni+(COD)2, AlS / Ni+(ArCHCHAr)3, or Al / Ni+(Cp)2, respectively). In a specific example, the charge -neutral transition metal complexes MEyare Ni(COD)2. With adsorption on an acidic sulfated support, the charge -neutral transition metal complexes Ni(COD)2 form the corresponding cationic transition metal complexes M+Ey(z.e., Ni+(COD)2) bound to at least one surface sulfate site of a sulfated alumina (AIS) to result in a surface-bound procatalyst (z.e. , AlS / Ni+(COD)2).

[0065] The surface-bound procatalysts disclosed and described herein may be activated or converted to active catalysts having catalytic activity for hydrogenolysis of polyolefins by contacting the surface-bound procatalysts with a hydrogen feed to form active catalyst sites. Upon contacting the surface-bound procatalysts with a hydrogen feed, the ligands E of at least a portion of the cationic transition metal complexes M+Lybound to the acidic sulfated support may disassociate from the cationic transition metal complexes M+Lyto form active catalyst sites comprising hydride complexes M+H each bound to at least one anionic site of the acidic sulfated support, the at least one anionic site may be chosen from surface sulfate sites or surface oxide sites.85992-WO-PCT / DOW 85992 WO16

[0066] In specific examples, the cationic transition metal complexes are Ni+(COD)2, Ni+(ArCHCHAr)3, Ni+(Cp)2, Ni+(nor)3, or Ni+(cdt), and the corresponding surface-bound procatalysts are AlS / Ni(COD)2, AlS / Ni(ArCHCHAr)3, Al / Ni(Cp)2, AlS / Ni+(nor)3, or AlS / Ni+(cdt), respectively. It should be understood that a surface-bound procatalyst may include as few as one to as many as hundreds, thousands, or millions of individual cationic transition metal complexes bound to at least one surface sulfate site. Upon contacting of the surface-bound procatalysts with a hydrogen feed, the COD, ArCHCHAr, Cp, nor, or cdt ligands of at least a portion of the Ni+(COD)2, Ni+(ArCHCHAr)3, Ni+(Cp)2, Ni+(nor)3, or Ni+(cdt) complexes surface-bound to the acidic sulfated alumina support disassociate from the complexes to form active catalyst sites comprising surface-bound nickel hydride complexes Ni+H. Each individual nickel hydride complex is bound to at least one anionic site of the acidic sulfated alumina support.

[0067] The charge-neutral transition metal complexes MLyare loaded onto the acidic sulfated support to a loading ratio defined on a metal basis, namely, as the total weight of metal in the transition metal complexes on the acidic sulfated support divided by a total weight of the acidic sulfated support and the transition metal complexes surface-bound to the acidic sulfated support. In specific examples, the loading ratio may be less than 2% by weight metal, less than 1% by weight metal, less than 0.8% by weight metal, or less than 0.7% by weight metal, based on the total weight of the acidic sulfated support and the transition metal complexes surface-bound to the acidic sulfated support.

[0068] Reference will now be made in detail to embodiments of methods of hydrogenolysis of a polyolefin feed utilizing the surface-bound procatalysts.

[0069] Methods herein for hydrogenolysis of a polyolefin feed utilizing the surface-bound procatalysts include contacting the surface-bound procatalyst with a hydrogen feed, whereby the ligands L of at least a portion of the cationic transition metal complexes M+Lysurface-bound to the acidic sulfated support disassociate from the transition metal complexes M+Lyto form active catalyst sites comprising hydride complexes M+H each surface-bound to at least one anionic site of the acidic sulfated support, the at least one anionic site chosen from surface sulfate sites or surface oxide sites; contacting the active catalyst sites with a polyolefin feed in a reactor in the presence of hydrogen; and allowing the polyolefin feed to react in the reactor to obtain a hydrogenolyzed product.85992-WO-PCT / DOW 85992 WO17

[0070] Unexpectedly, the surface-bound procatalysts and catalysts disclosed and described herein exhibit significantly high catalytic activity toward not only polyethylene, but also toward polypropylene and polystyrene that are not as readily hydrogenolyzed. Therefore, the polyolefin feed may include a polyethylene, a polypropylene, a polystyrene, or combinations or copolymers thereof.

[0071] Further, compared to various late transition metal catalysts and d° early transition metal catalysts, the surface-bound procatalysts and catalysts described herein exhibit comparable or greater catalytic activity, even with selectivity toward hydrogenolytic cleavage of bonds (320) in branched polyolefins that are adjacent to branch points over bonds (310) adjacent to non-branch points of the branched polyolefins as illustrated in FIG. 3B.

[0072] In some examples, the polyolefin feed may include a copolymer of ethylene and an a-olefin. In some examples, the polyolefin feed may include a copolymer of ethylene and an a-olefin selected from (C3-C12) a-olefins, such as 1 -hexene or 1 -octene.

[0073] Moreover, existing late transition metal catalysts and d° early transition metal catalysts exhibit low catalytic activity toward propylene and polystyrene as a result of the high structural regularity and the stability of aromatic groups. The selectivity toward hydrogenolytic cleavage of bonds (320) in branched polyolefins make these surface-bound procatalysts and catalysts described herein suitable for hydrogenolyzing branched polymers having highly regular structures (z.e., isotactic propylene) and branched polymers having aromatic side groups (z.e., polystyrene). The polyolefin feed may also include a polypropylene having an isotacticity of greater than or equal to 74%, such as greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, or greater than or equal to 95%. In some embodiments, the polyolefin feed may include atactic polypropylene or polystyrene.

[0074] The methods for hydrogenolysis of a polyolefin feed may be applied to polyolefin feeds in which the polyolefins are linear or substantially linear or in which the polyolefins are branched or highly branched. In examples for which the polyolefins are branched, the polyolefins of the polyolefin feed may have a branching ratio defined as a number of branches per thousand carbon atoms (1000 C) in the polyolefin. A branch in this context is a single carbon atom that is bonded to at least three other carbon atoms that are part of a continuing chain of the polymer. In some examples of the methods herein, the branching ratio of each polyethylene in the polyolefin feed may be from 1 to 356 branches per 1000 C, such as from 1 to 5 branches per 1000 C, from 1 to85992-WO-PCT / DOW 85992 WO1824 branches per 1000 C, from 1 to 48 branches per 1000 C, from 1 to 150 branches per 1000 C, from 5 to 24 branches per 1000 C, from 5 to 48 branches per 1000 C, from 5 to 150 branches per 1000 C, from 5 to 356 branches per 1000 C, from 24 to 48 branches per 1000 C, from 24 to 150 branches per 1000 C, from 24 to 356 branches per 1000 C, from 48 to 150 branches per 1000 C, from 48 to 356 branches per 1000 C, or from 150 to 356 branches per 1000 C. In specific examples, a linear polyethylene may have a branching ratio of greater than or equal to 1 branch per 1000 C and less than or equal to 5 branch per 1000 C. A branched polyethylene may have a branching ratio of from 24 to 48 branches per 1000 C, from 24 to less than or equal to 64 branches per 1000 C, or from 48 to 64 branches per 1000 C. A highly branched polyolefin such as isotactic polypropylene or atactic polypropylene may have a branching ratio greater than 356.

[0075] As a result of the high catalytic activity and selectivity of the surface-bound procatalysts disclosed and described herein, the polyolefin feed may be embodied as a stream of recyclable materials. The recyclable materials may include at least one of a polyethylene-based material, a polypropylene-based material, or a polystyrene-based material. The stream of recyclable materials may further include any contaminant material commonly found in a stream of recyclable materials produced by consumer recycling efforts. Examples of such contaminant materials include polyvinyl chlorides, antioxidants, plasticizers, polyolefin additives, or combinations thereof.

[0076] Contacting the polyolefin feed with the active catalyst sites may allow a significant portion of the polyolefin feed to be converted to obtain a hydrogenolyzed product. The hydrogenolyzed product may include a volatile hydrocarbon fraction, a solvent-soluble hydrocarbon fraction, and a residual solid fraction. The volatile hydrocarbon fraction may include small molecule hydrocarbons such as methane, ethane, or propane. The solvent-soluble hydrocarbon fraction may include liquid hydrocarbons and wax hydrocarbons that can be dissolved and thus extracted by a selective solvent (for example, dichloromethane, DCM). The term “liquid hydrocarbon” refers to substituted or unsubstituted hydrocarbons or heterohydrocarbons having a boiling temperature less than or equal to 200 °C. The term “wax hydrocarbon” refers to substituted or unsubstituted hydrocarbons or heterohydrocarbons having a melting temperature less than or equal to 70 °C. The residual solid fraction may include unreacted plastics.

[0077] The high hydrogenolysis activity of the surface-bound procatalysts and catalysts described herein is evident in the contents of hydrogenolyzed product. Particularly, in some85992-WO-PCT / DOW 85992 WO19 examples, the hydrogenolyzed product obtained by hydrogenolysis of a polyolefin feed according to the methods herein may include from 15 wt.% to 91 wt.% liquid hydrocarbons, based on a total weight of the hydrogenolyzed product. As further illustrated in the Examples herein, the weight percentage of hydrogenolyzed product (liquid or wax) that can be extracted by solvents such as dichloromethane (DCM) — DCM-soluble hydrocarbon — may be of from 9 wt. % to 99 wt.%, such as from 50 wt.% to 99 wt.%, from 70 wt.% to 99 wt.%, from 80 wt.% to 99 wt.%, from 85 wt.% to 99 wt.%, from 90 wt.% to 99 wt.%, from 70 wt.% to 95 wt.%, from 70 wt.% to 90 wt.%, from 80 wt.% to 95 wt.%, or from 80 wt.% to 90 wt.%.

[0078] The high activity of the surface-bound procatalysts and catalysts described herein leads to a very low weight percentage of unreacted polymers or solids that cannot be extracted by solvent. For example, the weight percentage of solids remaining after the complete of hydrogenolysis of a polyolefin feed by the methods herein may be less than 45 wt.%, such as less than 25 wt.%, less than 10 wt.%, less than 5 wt.%, less than 3 wt.%, or less than 1.5 wt.%.

[0079] In some examples, the surface-bound procatalysts and catalysts described herein produce primarily liquid or wax hydrocarbons that can be used as valuable feedstocks. For example, the weight percentage of solvent-soluble hydrocarbons obtained by hydrogenolysis of a polyolefin feed according to the methods herein may be from 80 wt.% to 99 wt.%, the weight percentage of remaining solids may be from 0.1 wt.% to 8 wt.%, and the weight percentage of volatiles or gaseous product may be from 0.5 wt.% to 20 wt.%.

[0080] The conversion of the polyolefin feed, as used herein, is the ratio of total weight of solvent-soluble hydrocarbon and volatile hydrocarbon to the total weight of the polyolefin feed. The conversion of the polyolefin feed upon hydrogenolysis according to methods herein may be greater than or equal to 50 wt.%, such as greater than or equal to 75 wt.%, greater than or equal to 80 wt.%, greater than or equal to 90 wt.%, greater than or equal to 95 wt.%. In some examples, the conversion of the polyolefin feed upon hydrogenolysis according to methods herein may be from 50 wt.% to 99.9 wt.%, such as from 70 wt.% to 99.9 wt.%, from 80 wt.% to 99.9 wt.%, from 90 wt.% to 99.9 wt.%, from 70 wt.% to 95 wt.%, from 80 wt.% to 95 wt.%, from 90 wt.% to 95 wt.%, from 70 wt.% to 90 wt.%, from 80 wt.% to 90 wt.%, or from 70 wt.% to 80 wt.%.

[0081] Depending on the composition of the polyolefin feed, the hydrogenolyzed product may include linear, branched, or cyclic alkanes. Furthermore, when the polyolefin feed comprises polystyrene, the hydrogenolyzed product may comprise a saturated cyclic hydrocarbon polymer,85992-WO-PCT / DOW 85992 WO20 oligomer, or monomer. In specific embodiments, when the polyolefin feed comprises polystyrene, the hydrogenolyzed product may comprise cyclohexane, methylcyclohexane, ethylcyclohexane, 1,3-dicyclohexylpropane, or 1,3-dicyclohexylbutane.

[0082] The hydrogenolysis activity of different polyolefins may vary. For example, the hydrogenolysis activity of non-polyethylene polyolefins may be greater than that of polyethylene polyolefins. For example, after 120-minute of reaction time, the conversion of isotactic polypropylene feed may remain at least 20% greater than that of polyethylene. Therefore, utilizing the differences in the hydrogenolysis activity, the surface-bound procatalysts and catalysts disclosed herein may be utilized to carry out selective hydrogenolysis and thus separation of polyolefin mixtures (z.e., stepwise hydrogenolysis) by varying the reaction conditions or composition of the surface-bound procatalysts. The ability to selectively hydrogenolyze and thus separate polyolefin mixtures would enable the production of high-quality and high-purity recycled plastic materials close to virgin plastic materials.

[0083] In examples of methods for hydrogenolysis herein, the contacting of the polyolefin feed with the catalyst system in the reactor in the presence of the hydrogen gas may be performed at a temperature from 100 °C to 300 °C, such as from 100 °C to 250 °C, from 100 °C to 200 °C, from 100 °C to 150 °C, from 150 °C to 300 °C, from 150 °C to 250 °C, from 150 °C to 225 °C, from 150 °C to 200 °C, from 150 °C to 175 °C, from 175 °C to 300 °C, from 175 °C to 250 °C, from 175 °C to 225 °C, from 175 °C to 200 °C, from 200 °C to 300 °C, from 200 °C to 250 °C, or from 250 °C to 300 °C.

[0084] In examples of methods for hydrogenolysis herein, the contacting of the polyolefin feed with the catalyst system in the reactor in the presence of the hydrogen gas may be performed under a hydrogen pressure from 1 atm to 50 atm, such as from 1 atm to 40 atm, from 1 atm to 30 atm, from 1 atm to 20 atm, from 1 atm to 10 atm, from 1 atm to 5 atm, from 5 atm to 50 atm, from 5 atm to 40 atm, from 5 atm to 30 atm, from 5 atm to 20 atm, from 5 atm to 10 atm, from 10 atm to 50 atm, from 10 atm to 40 atm, from 10 atm to 30 atm, from 10 atm to 20 atm, from 20 atm to 50 atm, from 20 atm to 40 atm, from 20 atm to 30 atm, from 30 atm to 50 atm, from 30 atm to 40 atm, or from 40 atm to 50 atm. For other examples, the hydrogen pressure may be from 2 atm to 17 atm, from 5 atm to 17 atm, from 10 atm to 17 atm, from 15 atm to 17 atm, from 5 atm to 10 atm, from 5 atm to 15 atm, or from 10 atm to 15 atm.85992-WO-PCT / DOW 85992 WO21

[0085] In examples of methods for hydrogenolysis herein, the contacting of the polyolefin feed with the catalyst system in the reactor in the presence of the hydrogen gas may be performed for a reaction time from 5 minutes to 600 minutes, such as from 20 minutes to 360 minutes, from 20 minutes to 240 minutes, from 20 minutes to 180 minutes, from 20 minutes to 120 minutes, from 20 minutes to 60 minutes, from 20 minutes to 40 minutes, from 40 minutes to 600 minutes, from 40 minutes to 360 minutes, from 40 minutes to 240 minutes, from 40 minutes to 180 minutes, from 40 minutes to 120 minutes, from 40 minutes to 60 minutes, from 60 minutes to 600 minutes, from 60 minutes to 360 minutes, from 60 minutes to 240 minutes, from 60 minutes to 180 minutes, from 60 minutes to 120 minutes, from 120 minutes to 600 minutes, from 120 minutes to 360 minutes, or from 120 minutes to 240 minutes.

[0086] In specific examples, methods for hydrogenolysis herein, the contacting of the polyolefin feed with the catalyst system in the reactor in the presence of the hydrogen gas may be performed at temperature from 100 °C to 300 °C under a hydrogen pressure from 1 atm to 50 atm for a reaction time from 5 minutes to 600 minutes.

[0087] To carry out the stepwise hydrogenolysis, the methods disclosed and described hereinabove may include a first hydrogenolysis and a second hydrogenolysis. In some examples, the first hydrogenolysis may include contacting the polyolefin feed with first active catalyst sites in the reactor in the presence of the hydrogen gas at a first temperature from 100 °C to 300 °C; a first hydrogen pressure from 1 atm to 50 atm; and a first reaction time from 5 minutes to 600 minutes. In other examples, the first hydrogenolysis may include contacting the polyolefin feed with first active catalyst sites in the reactor in the presence of the hydrogen gas at a first temperature from 100 °C to 250 °C; a first hydrogen pressure from 2 atm to 17 atm; and a first reaction time from 5 minutes to 120 minutes.

[0088] The second hydrogenolysis may include separating the hydrogenolyzed product from an unhydrogenolyzed portion of the polyolefin feed and recycling the unhydrogenolyzed portion of the polyolefin feed in the reactor. The unhydrogenolyzed portion of the polyolefin feed may comprise a polyethylene, an oligomer of ethylene, a propylene, a styrene, or combinations thereof. The second step of hydrogenolysis may further include contacting the unhydrogenolyzed portion of the polyolefin feed with second active catalyst sites in the reactor in the presence of the hydrogen gas at a second temperature from 150 °C to 250 °C; a second hydrogen pressure from 2 atm to 17 atm; and a second reaction time from 10 minutes to 120 minutes. The first active85992-WO-PCT / DOW 85992 WO22 catalyst sites and the second active catalyst sites may be identical or different. The first temperature and the second temperature may be identical or different. The first hydrogen pressure and the second hydrogen pressure may be identical or different. The first reaction time and the second reaction time may be identical or different. Contacting the unhydrogenolyzed portion of the polyolefin feed with second active catalyst sites in the reactor in the presence of the hydrogen gas would allow the unhydrogenolyzed portion of the polyolefin feed to react in the reactor to obtain a second hydrogenolyzed product. The second hydrogenolyzed product may contain 95 wt.% to 100 wt.% of liquid hydrocarbon, based on the total weight of the second hydrogenolyzed product.

[0089] For the surface-bound procatalysts and catalysts described herein, that the presence of contaminant material has been shown to not reduce the activity of polyolefin hydrogenolysis activity. For example, Polyvinyl chloride (PVC) is a common impurity in the z-PP recycling stream. As illustrated in Examples, the presence of contaminant material such as polyvinyl chlorides may significantly increase the hydrogenolysis activity of the methods herein toward polyolefins in general, including propylene.

[0090] Regenerating hydrogenolysis catalysts, such as Group IV catalysts, have been challenging as recognized by those skilled in the art. Unexpectedly, spent catalyst sites resulted from the hydrogenolysis methods disclosed and described herein can be regenerated by low-cost alkylaluminum. As illustrated in Examples, the regenerated catalyst sites can be once again used to hydrogenolyze polyolefins, and the regenerated catalyst sites retain the high selectivity toward hydrogenolytic cleavage of bonds (320) in branched polyolefins as the original active catalyst sites disclosed and described herein.

[0091] Reference will now be made in detail to embodiments of methods of regenerating the spent catalyst sites and methods for hydrogenolysis of a polyolefin feed using the regenerated catalyst sites.

[0092] Methods of regenerating the spent catalyst sites include contacting the spent catalyst sites with an alkylaluminum. In examples of methods of regenerating the spent catalyst sites, the alkylaluminum has a formula of A1RA3, where each RAis independently (Ci-C4o)hydrocarbyl. For example, each RAmay be independently (Ci-C4o)alkyl, such as (Ci-C2o)alkyl, (Ci-Cio)alkyl, ethyl, or methyl. For example, the alkylaluminum may be triethylaluminum.85992-WO-PCT / DOW 85992 WO23

[0093] In examples of methods of regenerating the spent catalyst sites, a molar ratio of the alkylaluminum to the spent catalyst sites, determined by the moles of metal of the spent catalyst sites, is greater than or equal to 3 and less than or equal to 20. For example, the molar ratio of the alkylaluminum to the spent catalyst sites may be greater than or equal to 3 and less than or equal to 10, greater than or equal to 3 and less than or equal to 6, greater than or equal to 4 and less than or equal to 10, or greater than or equal to 4 and less than or equal to 6.

[0094] Methods for hydrogenolysis of a polyolefin feed using the regenerated catalyst sites include contacting the regenerated catalyst sites with a polyolefin feed in a reactor in the presence of hydrogen and allowing the polyolefin feed to react in the reactor to obtain a hydrogenolyzed product. In examples of methods for hydrogenolysis of a polyolefin feed using the regenerated catalyst sites, the polyolefin feed may comprise a polyethylene, a polypropylene, a polystyrene, or combinations or copolymers thereof. In some examples, the polyolefin feed may include a copolymer of ethylene and a a-olefin. In some examples, the polyolefin feed may include a copolymer of ethylene and a a-olefin selected from (C3-C12) a-olefins, such as 1 -hexene or 1 -octene. In further examples, the polyolefin feed may be a stream of recyclable materials, the recyclable materials comprising at least one of a polyethylene-based material, a polypropylene-based material, or a polystyrene-based material.

[0095] It is also contemplated that the methods for hydrogenolysis of a polyolefin feed using the regenerated catalyst sites may either integrate with or operate independently from the methods for hydrogenolysis using the surface-bound procatalyst disclosed and described herein. For example, the methods for hydrogenolysis using the surface-bound procatalyst disclosed and described herein may further include steps of regenerating the spent catalyst sites according to the methods of regeneration disclosed and described herein.EXAMPLES

[0096] The following Examples are offered by way of illustration and are presented in a manner such that one skilled in the art should recognize are not meant to be limiting to the present disclosure as a whole or to the appended claims.85992-WO-PCT / DOW 85992 WO24Example 1 Preparation of Surface-Bound Procatalyst 3 AlS / Ni(C0D)2

[0097] Surface-bound procatalyst 3 AlS / Ni(COD)2 (COD = 1,5 -cyclooctadiene) was prepared by chemisorption of a commercially available Ni(COD)2 (Sigma-Aldrich, >98%, Aspira Scientific, Inc., >98%) onto highly Bronsted acidic sulfated alumina (AIS) (prepared from alumina obtained from Nanoamor, 99.9%, Sigma Aldrich, Nano US Research). Specifically, surface-bound procatalyst 3 was obtained via stirring a pentane slurry mixture of AIS and Ni(COD)2 in a 26 : 1 ratio by weight (mg / mg) at room temperature followed by pentane washing (5 times) to remove physically absorbed Ni(COD)2. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (Thermo iCap7600) analysis and Elemental Analysis (EA) (Midwest Microlab, Inc. (Indianapolis, IN)) reveal a C-to-Ni ratio of 15.8 : 1. The Ni loadings on the AIS support is 0.73% by weight nickel, based on the total weight of the surface-bound procatalyst.Example 2 Preparation of Surface-Bound Procatalyst 5 AlS / Ni(Cp)2

[0098] Surface-bound procatalyst 5 AlS / Ni(Cp)2 (Cp = -cyclopentadienyl) was prepared by stirring a pentane slurry mixture of AIS andNi(Cp)2 (Sigma Aldrich, 98%, Fisher Scientific, 98%) in a 31 : 1 ratio by weight (mg / mg) at room temperature followed by pentane washing (5 times) to remove physically absorbed Ni(Cp)2. The Ni loadings on the AIS support is 0.87% by weight.Example 3Preparation of Surface-Bound Procatalyst 6 AlS / Ni(ArCHCHAr)3

[0099] Surface-bound procatalyst 6 AlS / Ni(ArCHCHAr)3 (Ar = 4-tertbutylphenyl) was prepared by stirring a pentane slurry mixture of AIS and Ni(ArCHCHAr)3 (Strem, >97%) in a 8 : 1 ratio by weight (mg / mg) at room temperature followed by pentane washing (5 times) to remove physically absorbed Ni(ArCHCHAr)3. The Ni loadings on the AIS support is 0.68% by weight.Example 4 Preparation of Catalyst 4 (AlS / NiH)

[0100] Catalyst 4 was obtained by subjecting surface-bound procatalysts example 3, 5, or 6 described herein to hydrogen treatments under flowing H2 (2 atm) at 200 °C.85992-WO-PCT / DOW 85992 WO25Characterization of Surface-Bound Procatalyst 3 (AlS / Ni(C0D)2) and Catalyst 4 (AlS / NiH)

[0101] The structures of surface-bound procatalyst 3 (AlS / Ni(COD)2) and catalyst 4 (AlS / NiH) illustrated in FIG. 1 are supported by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) (Thermo 6700) analysis, Electron Paramagnetic Resonance (EPR) analysis, X-ray Photoelectron Spectroscopy (XPS) analysis (Thermo Scientific ESCAEAB 250Xi), X-ray Absorption Spectroscopy (XAS) analysis, and Solid-State Nuclear Magnetic Resonance (SS-NMR) analysis (Bruker Avance III).

[0102] Referring to FIG. 2A, DRIFTS analysis reveals intense alkyl C-H stretching bands at 2900-3000 cm'1and weak vinyl C-H stretching bands at 3000 to 3100 cm'1. FIG. 2B shows that the measured binding energy of Ni2P3 / 2 (854.4 eV) is about 2 eV lower than the predicted binding energy of a Ni(II) species loaded on an acidic support, suggesting that the central Ni atom of the surface-bound procatalyst 3 is in an oxidation state less than +2. DRIFTS analysis reveals the presence of shake-up peaks, suggesting that the central Ni atom of the surface-bound procatalyst 3 is paramagnetic (has unpaired electrons) and thus the central Ni atom of surface-bound procatalyst 3 is not in an oxidation state of 0. Referring to FIG. 2C, EPR analysis shows an axially symmetric spin Vi Ni(I) sites with g values of 2.0339, 2.0308 and 2.509, suggesting that the unpaired electron is localized on a Ni dx2-y2orbital. Accordingly, the analysis discussed above supports that the surface-bound procatalyst 3 has a structure as shown in FIG. 1.

[0103] With respect to Catalyst 4, DRIFTS analysis reveals the complete disappearance of all C-H stretching bands, indicating that the complete removal of the COD ligands and the formation of nickel hydride NiH species. FIG. 2D shows that the measured binding energy of Ni2P3 / 2 (856.81 eV) agreed with the predicted binding energy of a Ni(II) species loaded on acidic support, suggesting that the central Ni atom of catalyst 4 is in an oxidation state of +2. XPS analysis of spent catalyst 4 and air-exposed surface-bound procatalyst 3 reveal high binding energy of Ni2P3 / 2 (856.89 eV and 856.98 eV, respectively), again suggesting that the central Ni atom of catalyst 4 is in an oxidation state of +2. XAS measurements on surface-bound procatalyst 3, catalyst 4, spent catalyst 4, and air-exposed surface-bound procatalyst 3 show the absence of Ni-Ni bonds, suggesting that no Ni nanoparticles are formed or present during hydrogenolysis catalysis. Accordingly, the analysis discussed above supports that catalyst 4 has a structure as shown in FIG. 1.85992-WO-PCT / DOW 85992 WO26Characterization of Surface-Bound Procatalyst 5 (AlS / Ni(Cp)2) and Surface-Bound Procatalyst 6 (AlS / Ni(ArCHCHAr)3)

[0104] DRIFTS analysis of the structures of surface-bound procatalyst 5 (AlS / Ni(Cp)2) and surface-bound procatalyst 6 (AlS / Ni(ArCHCHAr)3) before and after hydrogen treatments reveals the formation of nickel hydride NiH species of catalyst 4.General Procedures for the Hydrogenolysis of Polyolefins

[0105] The hydrogenolysis of additive-free, lab-synthesized linear polyethylene (linear PE), branched polyethylene (PECO, poly(ethylene-co-l -octene); Dow Affinity GA1900), isotactic polypropylene (z-PP), and atactic polystyrene (aPS) is carried out in a Parr reactor (Parr Series 5500 Compact Micro Reactor, Parr Instrument Company) with an internal volume of 25 mL. Table 1 lists selected properties of various polyolefin supports demonstrated in examples.TABEE 1 : Selected Properties of Polyolefin Supports

[0106] To carry out the polyolefin hydrogenolysis, a polyolefin sample and one of the surface-bound procatalysts 3, 5, and 6 are loaded into a PTFE liner in the Parr reactor inside a glovebox. Unless specified otherwise, the hydrogenolysis is carried out with 0.033 mole percentage (mol%) of Ni surface-bound procatalysts with respect to moles of CH2 units in the starting polyolefin. The Parr reactor is sealed inside the glovebox and then transferred into a heater outside of the glove box. After degassing, the Parr reactor is refilled and pressurized with hydrogen gas under a hydrogen pressure of 17 atm at room temperature. The reaction is carried out at a85992-WO-PCT / DOW 85992 WO 1 predetermined temperature (200 °C for PE and z-PP or 250 °C for PS) for a predetermined length (from 20 minutes to 24 hours). The reactants are stirred at 1000 rpm.General Procedures for the Characterization of the Hydrogenolyzed Product

[0107] The dichloromethane (DCM) soluble hydrocarbons are collected and separated from residual solids. The weights of DCM-soluble hydrocarbons and residual solids are determined after removing DCM and drying at about 100 mTorr overnight. The percentage of volatile hydrocarbons were calculated using mass balance. The product distribution of volatile product is measured with GC-FID.

[0108] The hydrogenolysis activity of polyolefin samples utilizing the surface-bound procatalysts disclosed and described herein are compared with previously reported hydrogenolysis studies. To enable a direct comparison, the hydrogenolysis activity is reported according to Equation (1):. . . > mole (CH2 in volatile hydrocarbons)+moZe (CH2 in DCM-soluable hydrocarbons) ... iCLll / lL — ( 1 ) mole(Ni)xreaction time in hourThe DCM-soluble hydrocarbons are analyzed by GC-MS chromatogram, GPC-IR, VT-NMR,11 l-NMR, and13C-NMR under conditions generally used and known to a person of ordinary skill in the art.Hydrogenolysis of Polyethylene

[0109] The hydrogenolysis of linear polyethylene (linear PE) and branched polyethylene (PECO) were carried out according to the general procedure described hereinabove at a reaction temperature of 200 °C. The hydrogenolyses of linear polyethylene (linear PE) (Example 1, El) and branched polyethylene (PECO) (Example 2, 3, and 4, E2-E4) are discussed herein. Table 2 below summarizes the activities and products of polyethylene hydrogenolysis catalyzed by surface-bound procatalysts 3, 5, and 6. Table 1 compares E2, E3, and E4 with the hydrogenolysis catalyzed by AIS support only (Comparative Example 1, CE1), Ni(COD)2 precursor only (CE2), and Ni(COD)2 adsorbed on less acidic alumina support (CE3 and CE4) and silica support (CE5). Furthermore, Table 2 below compares the hydrogenolysis activity catalyzed by the presently disclosed surface-bound procatalyst (E2) with the hydrogenolysis activity catalyzed by the previously reported Ni catalyst containing Ni nanoparticles on silica support (CE6 and CE7).85992-WO-PCT / DOW 85992 WO28TABLE 2: Hydrogenolysis of Polyethylene by the Indicated Catalytic Materials

[0110] Referring to Table 2, E2-E4 demonstrate that surface-bound procatalysts including cationic Ni complexes -with monodentate and multi-dentate ligands coordinated to a Ni center with a hapticity greater than 1 are promising candidates to be activated or converted to polyolefin hydrogenolysis catalysts having high activity. E2, E3, and E4 all demonstrate significant hydrogenolysis activity of polyethylene catalyzed by surface-bound procatalysts 3, 5, and 6, in the order of E2 (surface-bound procatalyst 3) > E3 (surface-bound procatalyst 5) > E4 (surface-bound procatalyst 6). Notably, the hydrogenolysis activity of polyethylene catalyzed by surface-bound procatalyst 5 (E3) is comparable to that catalyzed by surface-bound procatalyst 3 (E2).

[0111] As shown in Table 2, 29.2 wt.% of linear PE is converted into DCM-soluble hydrocarbons and volatile hydrocarbons within 4 hours (El), and GC-FID analysis of the volatile hydrocarbon products reveals that the content of undesired methane is negligible. The hydrogenolysis activity of branched PECO (E2) appears to be significantly enhanced compared to El . The starting PECO was determined to have a high degree of branching (51 and 48 branches per thousand carbon atoms respectively) by the GPC-IR and VT-NMR measurements, suggesting about 14 mol% of 1-octene incorporation. As shown in Table 2, the hydrogenolysis of PECO catalyzed by surface-bound procatalyst 3 converts 77.1 wt.% of branched PECO into DCM-soluble hydrocarbon (50.2 wt.%) and volatile hydrocarbon (26.9 wt.%) within 2 hours.85992-WO-PCT / DOW 85992 WO29

[0112] The capability of the presently disclosed surface-bound procatalysts to selectively hydrogenolyze branched polyolefins is supported by comparing the content of the DCM-soluble hydrocarbons produced by surface-bound procatalyst 3 (E2) and AIS-supported d°-early transition metal catalysts (AlS / HfNp2 and AIS / TaNps). As shown in FIGS. 3 A and 3B, GC-MS chromatogram of the DCM-soluble hydrocarbons shows that the hydrogenolysis catalyzed by surface-bound procatalyst 3 (E2) produces a significantly greater amount of 7-methyl alkane derivatives (22 wt.% to 36 wt.%) — products of the cleavage of C-C bonds (320) between two adjacent n-hexyl group as indicated in FIG. 3B. On the other hand, the hydrogenolysis catalyzed by AIS-supported d°-early transition metal catalysts (AlS / HfNp2 and AIS / TaNps) produces only 4 wt.% to 9 wt.% of 7-methyl alkane derivatives. This observation supports the finding of greater hydrogenolysis activity of branched PECO discussed above.

[0113] Comparing E2, CE1, and CE2, the effect of chemisorption ofNi(COD)2 onto the highly acidic sulfated alumina (AIS) is prominent. Neither the acidic AIS support (CE1) nor the precursor Ni(COD)2 (CE2) alone are capable of carrying out the hydrogenolysis. The result confirms that the chemisorption of Ni(COD)2 onto the highly acidic sulfated alumina (AIS) generates electrophilic Ni and thus enables hydrogenolysis.

[0114] Comparing E2 and CE3-CE5, the effect of the support acidity is apparent. Substituting the highly acidic sulfated alumina support (AIS) with less acidic alumina support (AI2O3) and silica support (SiO2) significantly reduces the hydrogenolysis activity toward polyethylene. As shown in Table 2, the activity of E2 is 77-fold greater than CE5 and 110-fold greater than CE5. Furthermore, comparing CE3 and CE4, no hydrogenolysis activity is observed after 8 hours with Ni(COD)2 adsorbed on the less acidic alumina support, suggesting the deactivation of the catalyst over time.

[0115] Furthermore, the presently disclosed surface-bound procatalysts demonstrate the capability to catalyze efficient hydrogenolysis at a reduced temperature under a reduced pressure. As shown in Table 3 below, surface-bound procatalyst 3 effects hydrogenolysis of polyethylene at 200 °C, significantly lower the reaction temperatures (280 °C and 300 °C) for the reported Ni catalysts (Ni nanoparticles on SiO2), under a reduced hydrogen pressure (17 atm vs. 30 atm). At the reduced temperature, E2 shows a 13-fold greater activity than that of the Ni catalysts.85992-WO-PCT / DOW 85992 WO30TABLE 3: Hydrogenolysis of Polyethylene - Comparison of Procatalyst 3 with SiCh / Ni NanoparticlesHydrogenolysis of Isotactic Polypropylene

[0116] The hydrogenolysis of isotactic polypropylene (z-PP) was carried out according to the general procedure described hereinabove at a reaction temperature of 200 °C. The hydrogenolysis activity of highly branched z-PP (Branching ratio: 356 branches per 1000 C) is discussed herein. Table 4 below summarizes the activities and products of z-PP hydrogenolysis catalyzed by surface-bound procatalyst 3 for various lengths of reaction time (Examples 5 to 8, E5 to E8).

[0117] As shown in Table 4, the hydrogenolysis of z-PP catalyzed by surface-bound procatalyst 3 demonstrates high activity. Comparing E8 of Table 4 and E2 of Table 2, the hydrogenolysis activity of branched z-PP is greater than that of the branched PECO even after 2 hours (120 minutes). As shown in E8, more than 89.7 wt.% of z-PP is converted into DCM-soluble hydrocarbon, and only 8.3 wt.% of z-PP is converted into volatile hydrocarbons. Furthermore, GPC analysis of DCM-soluble hydrocarbons produced within the first 20-minute of hydrogenolysis (E5) show that 534 mg of z-PP with average 621 carbon chain length (Number Average Molar Mass, Mn, about 8700 g / mol) is cleaved down to short chain alkanes with 64 carbons (Mn about 900 g / mol) while negligible amounts (1 wt.%) of volatile hydrocarbon are produced. These results suggest that the surface-bound procatalysts disclosed herein are efficient in catalyzing the hydrogenolysis of z-PP. The results further suggest that the surface-bound procatalysts are capable of converting highly branched z-PP into higher value-added oil and wax products than gaseous alkanes.85992-WO-PCT / DOW 85992 WO31

[0118] Notably, the acidic AIS demonstrates moderate cracking activity arising from the Bronsted acid sites. However, as shown in Table 4, in the absence of the adsorbed Ni(COD)2, only 7.9 wt.% of z-PP is converted into DCM-soluble hydrocarbons while 19.5 wt.% of z-PP is converted into gaseous alkanes. This difference in product distribution is significant as it indicates that the active Ni catalyst sites are responsible for the high hydrogenolysis activity discussed hereinabove.TABTE 4: Hydrogenolysis of Isotactic PolypropyleneHydrogenolysis of Atactic Polystyrene

[0119] The hydrogenolysis of atactic polystyrene (aPS) was carried out according to the general procedure described hereinabove at a reaction temperature of 250 °C. The hydrogenolysis activity of aPS is discussed herein. Table 5 below summarizes the activities and products of aPS hydrogenolysis catalyzed by surface-bound procatalyst 3 for various lengths of reaction time (E9 to E13).

[0120] GPC analysis of the DCM-soluble hydrocarbon produced within the first 20-minutes of hydrogenolysis (E9) shows that 516 mg of aPS with a Mn of 116,500 g / mol was converted into hydrocarbons with a Mn of 371 g / mol, which is in the range of vinylcyclohexane oligomers with three repeating units (333 g / mol). The average Mn continues to decrease as the reaction time is lengthened. See E10 to E13 of Table 5.

[0121] GC-MS analysis shows that the DCM-soluble hydrocarbon contains cyclohexyl alkanes, including ethylcyclohexane, 1,3 -dicyclohexylpropane, and 1,3-dicyclohexylbutane. Comparative hydrogenolysis of toluene and ethylbenzene were conducted under comparable85992-WO-PCT / DOW 85992 WO32 catalytic conditions, and conversion of toluene to methylcyclohexane as well as ethylbenzene to ethylcyclohexane was also observed. The results indicate that the surface-bound procatalysts disclosed herein are capable of hydrogenating unsaturated cyclic hydrocarbons, including aromatic hydrocarbons.TABLE 5: Hydrogenolysis of Atactic Polystyrene (Acros organic)Stepwise Hydrogenolysis

[0122] As discussed above, the surface-bound procatalysts disclosed herein are particularly capable of catalyzing hydrogenolysis of branched polyolefins. Taking advantage of the high hydrogenolysis activity and ability of the catalysts for cleaving bonds at branch points selectively over non-branch points of branched polyolefins, the surface-bound procatalysts herein are capable of chemically separating linear and branched polyolefins in post-consumer plastics by stepwise hydrogenolysis demonstrated herein.

[0123] Stepwise hydrogenolysis was conducted to separate post-consumer polyolefin mixtures comprising 20 wt.% linear PE and 80 wt.% z-PP, obtained from a water bottle cap and a water cup (Examples 14-17, E14 to El 7). The content of hydrogenolyzed product of the post-consumer polyolefin mixture was analyzed by GPC after 60 minutes of hydrogenolysis and is summarized in Table 6 below.TABLE 6: GPC Analysis of Stepwise Hydrogenolysis of Mixtures of z-PP and Linear PE85992-WO-PCT / DOW 85992 WO33

[0124] Referring to FIG. 4A, GPC analysis shows that the DCM-soluble hydrocarbon exhibits a high degree of branching, indicating that it was produced from the highly branched z-PP. Referring to FIG. 4B, GPC analysis indicates that the solids consist primarily linear PE. VT-NMR spectroscopy confirms that the microstructures of residual solids is generally consistent with that of a linear PE structure. TheNMR spectrum of the DCM soluble hydrocarbon (El 7) is identical to that of the DCM soluble hydrocarbon produced by the hydrogenolysis of isotactic polypropylene obtained from a water cup. Further demonstrations showed that stepwise hydrogenolysis is feasible with a high PE content, up to 50 wt.% of PE.Hydrogenolysis of Post-Consumer Isotactic Polypropylene in the Presence of Impurity

[0125] As noted hereinabove, polyvinyl chloride (PVC) is a common impurity in the z-PP recycling stream. As discussed herein, the presently disclosed surface-bound procatalysts are capable of catalyzing polyolefins in the presence of impurity such as polyvinylchloride.

[0126] The hydrogenolysis of z-PP was conducted in the presence of 0 wt.%, 10 wt.%, and 50 wt.% of PVC additive. Table 7 below summarizes the activities and products of z-PP hydrogenolysis catalyzed by surface-bound procatalyst 3 in the presence of PVC additive (Examples 18-22, El 8 to E22). As shown in FIG. 5, GPC analysis of DCM-soluble hydrocarbon products shows that the presence of PVC led to significantly enhanced conversion of z-PP, as evidenced by the reduced Mn of the DCM-soluble hydrocarbon and the increased fraction of the volatile hydrocarbon. Furthermore, PVC and z-PP alone under similar catalytic conditions (17 atm H2, 200 °C, 1000 rpm for 2 hours) yields no conversion into either DCM-soluble or volatile gaseous product. The results suggest a synergistic effect between PVC and the catalyst support.85992-WO-PCT / DOW 85992 WO34Table ?: Catalytic AlS / Ni(C0D)2 i-PP (Sigma Aldrich) Hydrogenolysis Data in thePresence of Varying Amounts of PVCRegeneration of Spent Catalyst Sites

[0127] The process of regenerating the spent catalyst sites begins with heating the white spent catalyst at 200 °C under a vacuum for 20 hours to remove physical or chemically adsorbed water. Subsequently, the spent catalyst sites are treated with triethylaluminum (AlEts) in pentane for 10 minutes, and the white spent catalyst turns gray.

[0128] Table 8 below summarizes the activities and products of PECO hydrogenolysis catalyzed by the spent catalyst sites treated with varying quantities of AlEts (Examples 23-30, E23 to E30). As shown in Table 8, the hydrogenolysis activity of the AlEts treated spent catalyst sites achieved ca. 50% of the original catalytic activity when the spent catalyst sites were treated with greater than 3 equivalents and less than 20 equivalents of AlEts. Comparing E27 and E32, treating the AIS support with 4 equivalents AlEts yielded negligible hydrogenolysis activity, confirming that the AlEts treatment process restores the Ni active sites.Table 8: Hydrogenolysis of Polyethylene by the Spent Catalyst Sites Treated with the Indicated Quantities of AlEts|a|85992-WO-PCT / DOW 85992 WO35Hydrogenolysis of Isotactic Polypropylene with the Regenerated Catalyst

[0129] The hydrogenolysis of z-PP was performed to evaluate the activity and selectivity of the AlEts treated Ni active sites and to assess the feasibility of repeated regeneration. Table 9 summarizes the activities and products of z-PP hydrogenolysis catalyzed by the same batch of the spent catalyst over four cycles of treatment with 4 equivalents of AlEts.

[0130] As shown in Table 9, the AlEts treated Ni sites exhibited significantly higher activity of -4300 for z-PP hydrogenolysis than for PECO hydrogenolysis (Example 27 of Table 8) indicating that this treatment method effectively preserves the catalytic features of the original catalyst. Specifically, the AlEts treated Ni sites retained a strong preference for cleaving branched C-C bonds over linear C-C bonds. Additionally, the AlEts treated catalyst maintained high activity and selectivity for oil formation throughout the four cycles of regeneration. As shown in FIG. 6, after the first AlEts treatment cycle, GPC analysis of the DCM soluble hydrocarbon reveals no significant decline in catalytic activity, underscoring the practical potential of this approach for polyolefin upcycling.85992-WO-PCT / DOW 85992 WO36TABLE 9: Hydrogenolysis of Isotactic Polypropylene with the AIEts Treated Spent Catalyst Sites over Four Cycles of Regeneration

[0131] As demonstrated at least through the Examples herein, surface-bound procatalysts comprising cationic transition metal complexes of late transition metals selected from the group consisting of Fe, Ni, Co, Cu, and Zn chemically adsorbed onto a highly acidic sulfated support can efficiently hydrogenolyze wide-ranges of polyolefins, including even highly branched polyolefins such as polypropylenes and polystyrenes. Spent catalyst sites can be regenerated by commercially available trialkyl aluminum, and the regenerated catalyst sites maintain as high selectivity as the original procatalysts.

[0132] It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[0133] All numerical ranges herein expressed in the format “from X to Y” are to be interpreted as including the endpoints X and Y and all numbers between the endpoints.

[0134] While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.

Claims

85992-WO-PCT / DOW 85992 WO37CLAIMS1. A surface-bound procatalyst for hydrogenolysis of a polyolefin feed, the surface-bound procatalyst comprising an acidic sulfated support and cationic transition metal complexes M+Lysurface-bound to at least one surface sulfate site Qs~ of the acidic sulfated support, where:M is a transition metal selected from the group consisting of Fe, Ni, Co, Cu, and Zn; at least one L is a monodentate or multi-dentate ligand coordinated to M with a hapticity greater than 1 and independently selected from the group consisting of C2-C40 unsaturated hydrocarbons, C2-C40 unsaturated hydrocarbyls, and C1-C40 heterohydrocarbons, ; y denotes a number of the ligands in the cationic transition metal complex; y is 1, 2, or 3; and the cationic transition metal complex contains from 2 to 6 metal-ligand bonds.

2. The surface-bound procatalyst according to claim 1, wherein each ligand L is selected from the group consisting of cyclooctadiene (COD), cyclopentadienyl (Cp), 1,2-diarylethylene (ArCHCHAr), cyclododecatriene (cdt), and norbornene (nor), where rings of the ligand are substituted or unsubstituted.

3. The surface-bound procatalyst according to claim 2, wherein the cationic transition metal complex M+Lyis selected from the group consisting of Ni+(C0D)2, Ni+(Cp)2, Ni+(ArCHCHAr)3, Ni+(cdt), and Ni+(nor)3.

4. The surface-bound procatalyst according to claim 2, wherein the cationic transition metal complex M+Lyis selected from the group consisting of Ni+(C0D)2, Ni+(Cp)2, and Ni+(ArCHCHAr)3.

5. The surface-bound procatalyst according to claim 2, wherein the cationic transition metal complex M+Lyis Ni+(C0D)2.

6. The surface-bound procatalyst according to any one of claims 1 to 5, wherein the acidic sulfated support has a Hammett acidity from -12.4 to -14.5.85992-WO-PCT / DOW 85992 WO387. A method for hydrogenolysis of a polyolefin feed, the method comprising: contacting a surface-bound procatalyst according to any one of claims 1 to 6 with a hydrogen feed, whereby the ligands L of at least a portion of the cationic transition metal complexes M+Lysurface-bound to the acidic sulfated support disassociate from the transition metal complexes M+Lyto form active catalyst sites comprising hydride complexes M+H each surface-bound to at least one anionic site of the acidic sulfated support, where the at least one anionic site is chosen from surface sulfate sites or surface oxide sites; contacting the active catalyst sites with a polyolefin feed in a reactor in the presence of hydrogen; and allowing the polyolefin feed to react in the reactor to obtain a hydrogenolyzed product.

8. The method according to claim 7, wherein the polyolefin feed comprises a polyethylene, a polypropylene, a polystyrene, or combinations or copolymers thereof.

9. The method according to any one of claims 7 to 8, wherein the polyolefin feed comprises a copolymer of ethylene and an a-olefin.

10. The method according to any one of claims 7 to 9, wherein: the polyolefin feed comprises polystyrene; and the hydrogenolyzed product comprises a saturated cyclic hydrocarbon polymer, oligomer, or monomer.

11. The method according to any one of claims 7 to 10, wherein the polyolefin feed comprises a polypropylene having an isotacticity of greater than or equal to 74%.

12. The method according to any one of claims 7 to 11, wherein the hydrogenolyzed product comprises from 15 wt.% to 91 wt.% liquid hydrocarbons, based on a total weight of the hydrogenolyzed product.

13. The method according to any one of claims 7 to 12, wherein contacting the polyolefin feed with the catalyst system in the reactor in the presence of the hydrogen gas is performed at a first temperature from 100 °C to 300 °C;85992-WO-PCT / DOW 85992 WO39 a first hydrogen pressure from 1 atm to 50 atm; and a first reaction time from 5 minutes to 600 minutes.

14. The method according to any one of claims 7 to 13, wherein the polyolefin feed is a stream of recyclable materials, the recyclable materials comprising at least one of a polyethylene-based material, a polypropylene-based material, or a polystyrene-based material.

15. The method according to claim 14, wherein the stream of recyclable materials further comprises a contaminant material selected from polyvinyl chlorides, antioxidants, plasticizers, polyolefin additives, or combinations thereof.

16. A method of regenerating spent catalyst sites, comprising: contacting the spent catalyst sites according to any one of claims 7 to 15 with an alkylaluminum to form regenerated catalyst sites, wherein a molar ratio of the alkylaluminum to the spent catalyst sites is greater than or equal to 3 and less than or equal to 20.

17. The method according to claim 16, wherein the alkylaluminum has a formula of A1RA3, where each RAis independently (Ci-C4o)hydrocarbyl.

18. The method according to claim 16 or claim 17, wherein the alkylaluminum is triethylaluminum.

19. The method according to any one of claims 16 to 18, wherein the molar ratio of the alkylaluminum to the spent catalyst sites is greater than or equal to 3 and less than or equal to 6.

20. A method for hydrogenolysis of a polyolefin feed, the method comprising: contacting the regenerated catalyst sites according to any one of claims 16 to 19 with a polyolefin feed in a reactor in the presence of hydrogen; and allowing the polyolefin feed to react in the reactor to obtain a hydrogenolyzed product.

21. The method according to claim 20, wherein:85992-WO-PCT / DOW 85992 WO40 the polyolefin feed comprises a polyethylene, a polypropylene, a polystyrene, or combinations or copolymers thereof; or the polyolefin feed comprises a copolymer of ethylene and an a-olefin; or the polyolefin feed is a stream of recyclable materials, the recyclable materials comprising at least one of a polyethylene-based material, a polypropylene-based material, or a polystyrene-based material.

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