Catalytic hydrogenolysis of polymers

Abstract

A method for the hydrocracking of a polymer is provided, comprising the steps of feeding into a reactor a polymer, hydrogen gas, and a supported organometallic catalyst, the supported organometallic catalyst being formed from an organometallic complex pre-catalyst and an acidic metal oxide support, the polymer reacting with the supported organometallic catalyst in the presence of hydrogen gas at a predetermined temperature in the reactor to produce a reduced polymer product having a weight average molecular weight less than that of the polymer.

Description

[Technical field]

[0001] Priority claim This application claims priority to U.S. Provisional Application No. 63 / 223,583, filed July 20, 2021, the entire contents of which are incorporated herein by reference in their entirety.

[0002] Government Rights Reference This invention was made with United States Government support under DE-FG02-03ER15457 awarded by the United States Department of Energy. The United States Government has certain rights in this invention. [Background technology]

[0003] The accumulation of post-consumer polymer waste is a growing concern given the serious detrimental effects it poses on the environment. Despite society's heavy reliance on these materials, less than 10% of post-consumer polymers are recycled in the United States, with most accumulating in landfills. Polypropylene (PP)- and polyethylene (PE)-based materials account for the largest proportion of these waste polymers, and the small proportion of these materials that are currently recycled is mostly recycled by mechanical means. However, recycled polymers are always of lower value than virgin polymers (produced directly from pure monomers). Thus, there are increasing efforts to study ways to produce valuable polymeric materials from post-consumer polymer waste. Summary of the Invention

[0004] The present disclosure provides supported organometallic catalysts for depolymerizing polymers via hydrogenolysis, a chemical reaction involving the catalytic cleavage of carbon-carbon or carbon-heteroatom single bonds by hydrogen (H2). The method can be used to convert long carbon chains in polymers such as polyolefins (e.g., polypropylene or polyethylene) to products with lower molecular weight than the starting polymer.

[0005] The supported organometallic catalysts of the present disclosure are highly electrophilic, formally cationic, earth-abundant, single-site organometallic catalysts chemisorbed onto an acidic metal oxide support (e.g., a sulfated alumina support with strong Bronsted acidity). The supported organometallic catalysts of the present disclosure mediate rapid hydrogenolytic cleavage of molecular and polymeric saturated hydrocarbons under mild conditions with onset of catalysis as low as 0.02 mol % catalyst loading and 0.5 atm H2 / 90°C. For polyethylene, quantitative hydrocracking to light hydrocarbons (e.g., hydrocarbons below C9) proceeds within 48 minutes, with an activity of 4000 mol (CH2 units)·mol (Zr) at 200°C / 2 atm H2 pressure. -1 h -1 Under similar solvent-free conditions, polyethylene-co-1-octene, isotactic polypropylene, and used sandwich bags are rapidly hydrocracked into lower molecular weight hydrocarbons. Such surprising results could find meaningful applications to help reduce reliance on fossil fuels and address the large amounts of plastic waste recycling and reuse in today's society.

[0006] An embodiment of the present disclosure provides a method for the hydrocracking of a polymer as defined herein. The method comprises the steps of feeding a polymer, hydrogen gas (H2) and a supported organometallic catalyst of the present disclosure into a reactor. The supported organometallic catalyst is formed from an organometallic complex pre-catalyst of formula I and an acidic metal oxide support. The organometallic complex pre-catalyst of formula I is MR m L x Formula I wherein m is 0 to 6, x is 0 to 6, M is a transition metal selected from the group consisting of Group 3 to 8 transition metals, R is independently selected from the group consisting of H, C1 to C8 hydrocarbyls or halogens, and each L is independently selected from the group consisting of C1 to C12 substituted or unsubstituted hydrocarbyls. The values ​​of m and x depend on the oxidation state of M. The method further includes reacting the polymer with a supported organometallic catalyst in a reactor at a predetermined temperature in the presence of hydrogen gas while stirring the mixture to produce a reduced polymer product having a lower weight average molecular weight than the polymer.

[0007] For various embodiments, M is selected from the group consisting of Group 4, Group 5, Group 6, or Group 8 transition metals. For various embodiments, M is selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Ru, Co, or Ni. Preferably, M is selected from the group consisting of Group 4, Group 5, or Group 6 transition metals. Preferably, M is selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Mo, or W. Most preferably, M is derived from a Group 4 transition metal selected from the group consisting of Ti, Zr, or Hf. For various embodiments, M is also preferably selected from the group consisting of Zr or Hf, where m is 0 and each L is independently selected from C1-C12 alkyl.

[0008] For various embodiments, the hydrocarbyl of L in formula I is independently selected from the group consisting of C1-C10 alkyl, C2-C10 alkenyl, or C5-C10 aryl. As used herein, aryl can include multiple ring structures (e.g., fused rings). Preferably, L in formula I is neopentyl (e.g., 2,2-dimethylpropyl).

[0009] For various embodiments, the acidic metal oxide support is a sulfated metal oxide (e.g., an oxide with strong Bronsted acidity). For various embodiments, the sulfated metal oxide is selected from the group consisting of sulfated aluminum oxide, sulfated zirconium (IV) oxide, sulfated tin (IV) oxide, sulfated hafnium (IV) oxide, sulfated titanium (IV) oxide, sulfated iron (III) oxide, sulfated zinc (II) oxide, sulfated silica oxide, or combinations thereof.

[0010] For various embodiments, the predetermined temperature of the method is greater than or equal to 60° C. and less than or equal to 300° C. Preferably, the predetermined temperature of the method is greater than or equal to 90° C. and less than or equal to 200° C. More preferably, the predetermined temperature of the method is greater than or equal to 110° C. and less than or equal to 150° C.

[0011] For various embodiments, reacting the polymer can include stirring the polymer with the supported organometallic catalyst in the presence of hydrogen gas at a speed of 500 rpm or more and 3000 rpm or less. Such stirring of the supported organometallic catalyst and polymer can better ensure thorough mixing of the polymer and the supported organometallic catalyst.

[0012] For various embodiments, the weight average molecular weight of the reduced polymer product produced according to the method of the present disclosure is less than that of the starting polymer. For various embodiments, the reduced polymer product is at least one of a volatile product, an oily product, or a waxy product, each of which is defined herein. For various embodiments, the reduced polymer product comprises less than 5 wt% of a waxy product based on the total weight of the reduced polymer product.

[0013] For various embodiments, the polymer is selected from the group consisting of polyolefins, polymers formed by polymerization of aromatic alkenes, or polymers formed by polymerization of conjugated dienes. For various embodiments, the polyolefin is preferably selected from the group consisting of polyethylene, polypropylene, C4-C12 linear or branched monoolefins, copolymers thereof, or combinations thereof. More preferably, the polyolefin is selected from the group consisting of polyethylene, polypropylene, or copolymers thereof.

[0014] For various embodiments, providing hydrogen gas to the reactor includes providing hydrogen gas to the reactor at a pressure of 0.1 to 100 atmospheres. Preferably, providing hydrogen gas to the reactor includes providing hydrogen gas to the reactor at a pressure of 0.2 to 50 atmospheres. More preferably, providing hydrogen gas to the reactor includes providing hydrogen gas to the reactor at a pressure of 0.5 to 4 atmospheres. For various embodiments, reacting the polymer with the supported organometallic catalyst in the presence of hydrogen gas at the predetermined temperature is for a period of 0.25 to 24 hours. For various embodiments, providing the supported organometallic catalyst in the reactor includes providing 0.01 mole percent (mol%) to 0.9 mol% M based on the monomer units of the polymer (e.g., -C2H4- monomer units of polyethylene).

[0015] For various embodiments, the supported organometallic catalyst is represented by Formula II: L y-x R x-z M n+ ··· O - (Acidic Metal Oxide Support) Formula II where M is selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Ru, Co, or Ni; R is independently selected from hydrogen, halogen, or L, where each L is independently selected from C1-C12 saturated or unsaturated hydrocarbyl, or C1-C12 silyl hydrocarbyl; n is 1, y is 3, x is 2 or 1, and z is 1 or 0. In some embodiments, when M is not in the highest possible oxidation state, n can be 2 or 3. For example, when M is either Co or Fe, L2Co 2+ ··· O - (acidic metal oxide support) or L2Fe 2+ ··· O - (acidic metal oxide support), n can be 2, x can be 1, and z can be 1. In formula II, "..." represents the O of the support material. - and M. n+ represents an electrostatic non-covalent bond between ··· O - " represents a weakly Lewis basic support material after deprotonation. Preferably, in formula II, M is selected from the group consisting of Ti, Zr, or Hf, each L is a C3-C8 saturated or unsaturated hydrocarbyl, n is 1, y is 3, x=1, and z=1. More preferably, in formula II, M is selected from the group consisting of Ti, Zr, or Hf, each L is a C5 saturated hydrocarbyl, n is 1, y is 3, x=1, and z=1.

[0016] Other principal features and advantages of the present disclosure will become apparent to one of ordinary skill in the art upon review of the following drawings, detailed description, and appended claims.

[0017] Exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings. [Brief description of the drawings]

[0018] [Figure 1]An example of an existing catalyst composed of a metal alkyl covalently bonded to a strongly Lewis basic oxide support material is shown (FIG. 1A).An example of a supported organometallic catalyst of the present invention composed of a cationic metal alkyl on a very weakly Lewis basic support with loose ionic metal-support interactions (i.e., the metal is non-covalently bonded to the support material) is shown (FIG. 1B).

[0019] [Diagram 2] Table 6 shows the weight percent of volatile products, DCM extractables, and solid products for the reduced polymer products.

[0020] [Diagram 3] Table 7 shows the weight percent of volatile products, DCM extractables, and solid products for the reduced polymer products.

[0021] [Figure 4] Table 8 shows the weight percent of volatile products, DCM extractables, and solid products for the reduced polymer products.

[0022] [Diagram 5] Table 13 shows the weight percent of volatile, oily and waxy products of the reduced polymer products.

[0023] [Figure 6] Table 14 shows the weight percent of volatile, oily and waxy products of the reduced polymer products.

[0024] [Figure 7] FIG. 1 shows the distribution of hydrocracking products (volatile products, DCM extractables and solid products) of the polyolefins shown in Table 17 at various stirring speeds.

[0025] [Figure 8] Table 17 shows the weight percent of volatile products, DCM extractables, and solid products for the reduced polymer products.

[0026] [Figure 9] Table 18 shows the hydrocracking product (volatile products, DCM extractables and solid products) distribution of the indicated polyolefins at given reaction conditions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The present disclosure provides a process for depolymerizing polymers by hydrogenolysis using supported organometallic catalysts. Hydrogenolysis is a chemical reaction involving the catalytic cleavage of carbon-carbon or carbon-heteroatom single bonds by hydrogen (H2). In the process of the present invention, a polymer is combined with hydrogen and the supported organometallic catalyst of the present disclosure under relatively mild conditions selected to induce hydrogenolysis of the polymer, resulting in polymer fragments, i.e., low molecular weight products. Using the process of the present invention, the long carbon chains of polymers such as polyolefins (e.g., polypropylene or polyethylene) can be converted into products with lower molecular weight than the starting polymer.

[0028] Compared to existing methods for depolymerizing polymers, the present disclosure utilizes supported organometallic catalysts under generally mild conditions, e.g., lower temperatures, lower H2 pressures, and low catalyst loadings, while still achieving high reaction rates. Furthermore, no solvent is required in the disclosed method, although a solvent may be used. At the same time, embodiments of the present disclosure enable very high activity to be achieved, e.g., two orders of magnitude higher than existing catalysts using similar conditions.

[0029] The supported organometallic catalysts of the present disclosure are highly electrophilic, formally cationic, earth-abundant, single-site organometallic catalysts chemisorbed onto acidic metal oxide supports (e.g., sulfated alumina supports with strong Bronsted acidity). The supported organometallic catalysts of the present disclosure mediate rapid hydrogenolytic cleavage of molecular and polymeric hydrocarbons (e.g., saturated hydrocarbons) under mild conditions with onset of catalysis as low as 0.02 mol % catalyst loading and 0.5 atm H2 / 90°C. For polyethylene, quantitative hydrocracking to volatile hydrocarbons (e.g., light hydrocarbons below C9) proceeds within 48 minutes, with activities of 4000 mol (CH2 units)·mol (Zr) at 200°C / 2 atm H2 pressure. -1 h -1 Under similar solvent-free conditions, polyethylene-co-1-octene, isotactic polypropylene, and used sandwich bags (e.g., low-density polyethylene) are rapidly hydrocracked into products with lower molecular weights than the starting polymers. Such surprising results could find meaningful applications in addressing the recycling and reuse aspects of the large amount of plastic waste in today's society, as well as helping to reduce dependency on fossil fuels.

[0030] definition Before the present compounds, components, compositions, and / or methods are disclosed and described, it is to be understood that this disclosure is not limited to particular compounds, components, compositions, reactants, reaction conditions, moieties, ligands, structures, etc., unless otherwise specified, which as such can vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0031] It should also be noted that, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless otherwise indicated. Thus, for example, reference to "a reduced polymer product" can include more than one reduced polymer product, thereby allowing for "reduced polymer products." Similarly, reference to "a halogen atom" in a moiety "substituted with a halogen atom" includes more than one halogen atom, such that the moiety may be substituted with more than one halogen atom, reference to "a substituent" includes one or more substituents, reference to "a ligand" includes one or more ligands, and so forth.

[0032] As used herein, a "polymer" includes a linear or branched homopolymer or a linear or branched copolymer. A polymer (e.g., homopolymer, copolymer, terpolymer, etc.) has two or more of the same or different monomer (i.e., mer) units derived from one or more different monomers. A "homopolymer" is a polymer having all the same type of polymer units (e.g., 100 wt% of the polymer units are derived from ethylene or 100 wt% of the polymer units are derived from propylene). A "copolymer" is a polymer having two or more types of polymer units that are different from each other, such as a polymer made by copolymerization of ethylene with a C3-C10 alpha-olefin or a polymer made by copolymerization of propylene with ethylene and / or a C4-C10 alpha-olefin. A "terpolymer" is a polymer having three types of polymer units that are different from each other. "Different" with respect to polymer units means that the polymer units differ from each other by at least one atom or that the polymer units are isometrically different. Thus, the definition of copolymer as used herein includes terpolymers, and the like.

[0033] The embodiment enables that the polymer can be a polyolefin. Polyolefins include homopolymers and / or copolymers made from olefin monomers, such as polymers made from ethylene (i.e., polyethylene), polymers made from propylene (i.e., polypropylene), and homopolymers and / or copolymers made from linear or branched higher alpha olefin C4 to C12 monomers (e.g., linear or branched C4 to C12 monoolefins). Examples of higher alpha olefin monomers include, but are not limited to, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 3,5,5-trimethyl-1-hexene. Examples of polyolefins include ethylene-based polymers, particularly homopolymers of polyethylene (e.g., formed from 100 wt % ethylene), and those having 50 wt % or more ethylene (e.g., 100 wt % ethylene). for exampleExamples of polyolefins include propylene-based polymers, such as homopolymers of polypropylene (e.g., formed from 100 wt. % propylene), and those having 50 wt. % or more propylene (e.g., polyethylene copolymers), copolymers of ethylene and 1-butene, copolymers of ethylene and 1-hexene, and copolymers of ethylene and 1-octene. Examples of polyolefins include propylene-based polymers, such as homopolymers of polypropylene (e.g., formed from 100 wt. % propylene), and those having 50 wt. % or more propylene (e.g., propylene copolymers). for example , polypropylene copolymers), particularly copolymers of propylene·1-butene, copolymers of propylene·1-hexene, and copolymers of propylene·1-octene. Other olefins that may be utilized include, for example, ethylenically unsaturated monomers, diolefins having from 4 to 18 carbon atoms, conjugated or non-conjugated dienes, polyenes, vinyl monomers, aromatic alkenes, and cyclic olefins. Examples of monomers include, but are not limited to, norbornene, norbornadiene, isobutylene, isoprene, vinylbenzocyclobutane, styrene, alkyl-substituted styrenes, ethylidene norbornene, dicyclopentadiene, and cyclopentene. In some embodiments, copolymers of ethylene can be produced by polymerizing, for example, in a gas phase polymerization process, ethylene with a comonomer having at least one alpha olefin having from 4 to 15 carbon atoms, preferably from 4 to 12 carbon atoms, and most preferably from 4 to 8 carbon atoms. Similarly, in some embodiments, copolymers of propylene can be produced, for example by polymerizing propylene with a comonomer having at least one alpha-olefin having from 4 to 15 carbon atoms, preferably from 4 to 12 carbon atoms, and most preferably from 4 to 8 carbon atoms, in a gas phase polymerization process. In another embodiment, ethylene and / or propylene can be polymerized with at least two different comonomers, one of which may be a diene, to produce a terpolymer.

[0034] As used herein, the groups of transition metals discussed and claimed herein can be found in Groups 4-10 of the IUPAC Periodic Table of the Elements, May 4, 2022 Edition.

[0035] As used herein, the term "hydrocarbyl" refers to a univalent group formed by removing a hydrogen atom from a hydrocarbon, such as, among others, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl, cyclohexylmethyl, phenyl, benzyl, naphthyl. Exemplary hydrocarbyls include alkyl, alkenyl, and aryl. Hydrocarbyls can be linear, branched, or cyclic.

[0036] As used herein, the term "substituted", e.g., in "substituted hydrocarbyl", refers to the group following the term having, in place of one or more hydrogens at any position, at least one moiety selected from the group consisting of halogen radicals, hydroxyl groups, carbonyl groups, carboxyl groups, amine groups, phosphine groups, alkoxy groups, phenyl groups, naphthyl groups, (C1-C20) alkyl groups, (C2-C10) alkenyl groups, and combinations thereof, etc., unless another type of substitution is specifically stated, e.g., "alkyl substituted" or "aryl substituted". When the term "substituted" precedes a list of possible substituents, it is intended that the term applies to all members of that group. That is, the phrase "substituted alkyl, alkenyl, and aryl" is to be interpreted as "substituted alkyl, substituted alkenyl, and substituted aryl".

[0037] When the term "sulfated" precedes a list of possible sulfated metal oxides, it is intended that the term applies to all members of that group, i.e., "sulfated aluminum oxide, zirconium (IV) oxide, tin (IV) oxide, hafnium (IV) oxide, titanium (IV) oxide, iron (III) oxide, zinc (II) oxide, silica oxide, or combinations thereof" shall be interpreted as "sulfated aluminum oxide, sulfated zirconium (IV) oxide, sulfated tin (IV) oxide, sulfated hafnium (IV) oxide, sulfated titanium (IV) oxide, iron (III) sulfate, zinc (II) sulfate, sulfated silica oxide, or combinations thereof."

[0038] As used herein, the term "alkyl" refers to a branched or unbranched (e.g., straight chain), cyclic or noncyclic saturated hydrocarbyl radical that is typically, but not necessarily, deficient by one hydrogen and contains from 1 to 50 carbon atoms, more preferably from 1 to 20 carbon atoms, and most preferably from 1 to 10 carbon atoms, such as, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, octyl, decyl, and cycloalkyl groups (e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, and cyclohexylethyl).

[0039] The term "alkenyl," as used herein, refers to a branched or unbranched, cyclic or acyclic hydrocarbyl radical containing at least one double bond and typically, but not necessarily, containing from 2 to 50 carbon atoms, more preferably from 2 to 20 carbon atoms, and most preferably from 2 to 10 carbon atoms, such as ethenyl, n-propenyl, isopropenyl, n-butenyl, isobutenyl, 4-octenyl, 2-decenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, and cyclohexadienyl, among others.

[0040] The term "aromatic" is used in its normal sense and includes unsaturation that is essentially delocalized across multiple bonds on the ring. As used herein, the term "aromatic" typically, but not necessarily, refers to a group that includes an aromatic ring or ring system that includes at least 5 and at most 50 carbon atoms, preferably at least 5 and at most 25 carbon atoms, more preferably at least 5 and at most 16 carbon atoms. Typical neutral unsubstituted aromatic compounds include benzene, naphthalene, anthracene, phenanthrene, pyridine, pyrazine, imidazole, pyrazole, oxazole, thiophene, pyrrole, triazole, indole, and benzimidazole. Typical charged unsubstituted aromatic compounds include cyclopropenyl cations and cyclopentadienyl anions.

[0041] As used herein, the term "aryl" refers to a group containing an aromatic ring or ring system, typically, but not necessarily, containing from 5 to 50 carbon atoms, preferably from 5 to 20 carbon atoms, and more preferably from 5 to 10 carbon atoms. Aryl groups herein include groups containing a single aromatic ring and groups containing multiple aromatic rings that are fused, covalently bonded, or linked to a common group (e.g., a methylene or ethylene moiety). More specific aryl groups include one aromatic ring or two or three fused or linked aromatic rings, such as phenyl, naphthyl, biphenyl, terphenyl, anthracenyl, phenanthrenyl, pyridinyl, pyrazinyl, imidazolyl, pyrazolyl, oxazolyl, thienyl, pyrrolyl, triazolyl, indolyl, and benzimidazolyl. Aryl groups can be unsubstituted or substituted with a halogen (preferably fluorine, chlorine or bromine, more preferably fluorine or bromine, even more preferably fluorine), hydrocarbyl (e.g., alkyl, alkenyl or alkynyl), heterohydrocarbyl, or heteroatom group. In certain embodiments, aryl substituents (substituents on an aryl group) contain from 1 to 40 atoms other than hydrogen, preferably from 1 to 20 atoms other than hydrogen, and more preferably from 1 to 10 atoms other than hydrogen.Substituted aryl groups include tolyl (methylphenyl), xylyl (dimethylphenyl), mesityl (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, chloropyridinyl, methylimidazolyl, phenylpyrrolyl, and ethylthienyl.

[0042] As used herein, the term "halogen" refers to fluorine, chlorine, bromine and iodine.

[0043] As used herein, the term "silylhydrocarbyl" refers to -SiR 1 R 2 R 3 refers to the radical, where R 1 , R 2 and R 3 is independently selected from the group consisting of hydrido, and optionally substituted alkyl, alkenyl, alkynyl, heteroatom-containing alkyl, heteroatom-containing alkenyl, heteroatom-containing alkynyl, aryl, heteroaryl, alkoxy, aryloxy, amino, silyl, and combinations thereof. In the "silyl hydrocarbyl", the silicon atom may be directly bonded to the metal, or a carbon atom of the "silyl hydrocarbyl" may be directly bonded to the metal.

[0044] The term "saturated" means containing no carbon-carbon double bonds, no carbon-carbon triple bonds, and (in heteroatom-containing groups) no carbon-nitrogen, carbon-phosphorus, and carbon-silicon double or triple bonds.

[0045] As used herein, "weight average molecular weight" (M w The term Mw is the mass of an individual polymer chain that contributes to the overall molecular weight of a polymer, and as is known in the art, Mw is calculated from the weight fraction distribution of molecules of various sizes. Mw can be measured by gel permeation chromatography (GPC), osmometry, light scattering, viscometry, freezing point depression, boiling point elevation, ultracentrifugation, mass spectrometry, and end group analysis, as is known in the art.

[0046] As used herein, the term "volatile products" or "volatiles" refers to straight or branched chain (where possible) hydrocarbons having fewer than nine carbons (e.g., less than C9).

[0047] As used herein, the term "oily product" or "DCM extract" refers to straight or branched chain hydrocarbons having between 9 and 26 carbons (e.g., C9-C26).

[0048] As used herein, the term "waxy product" or "solid" refers to straight or branched chain hydrocarbons having 27 or more carbons, which carbon number is less than the carbon number of the polymer from which the waxy product is formed in accordance with the present disclosure.

[0049] As used herein, the symbol "~" represents the word "approximately."

[0050] The abbreviation "atm" stands for atmospheric pressure (1 atm = 101.325 kPa), the abbreviation "mol" stands for mole, the abbreviation "℃" stands for degree Celsius, the abbreviation "kg" stands for kilogram, the abbreviation "L" stands for liter, the abbreviation "h" stands for hour, the abbreviation "min" stands for minute, the abbreviation "wt%" stands for weight percent, the abbreviation "ppm" stands for parts per million, the abbreviation "mg" stands for milligram, the abbreviation "rpm" stands for revolutions per minute, and the abbreviation "μm" stands for micrometer, i.e. 10 -6 Represents meters.

[0051] Polymers that may be depolymerized by hydrogenolysis using the supported organometallic catalysts of the present disclosure may include polyolefins formed by polymerizing olefins (e.g., ethylene, propylene, hexene, octene, and combinations thereof). As discussed herein, the olefin may be an alpha-olefin, such that the polyolefin is a polyalphaolefin. In various embodiments, the polymer is preferably selected from the group consisting of polyolefins, polymers (formed by polymerization of aromatic alkenes, e.g., styrene), and polymers (formed by polymerization of conjugated dienes, e.g., butadiene, isoprene, and the like). In various embodiments, the polyolefin is more preferably selected from the group consisting of polyethylene, polypropylene, linear or branched C4-C12 monoolefins, copolymers thereof, or combinations thereof. Most preferably, the polyolefin is polyethylene and polypropylene, copolymers thereof, or combinations thereof. The polymer may be linear or branched. The polymer may be a homopolymer or a copolymer. The polymers may have any tacticity and degree of tacticity, for example, greater than 90% isotactic, atactic, or syndiotactic. The polymers may have various weight average molecular weights (Mw), for example, in the range of 3 to 300 kg / mol, as known in the art for various commercial products.

[0052] An embodiment of the present disclosure provides a method for the hydrocracking of polymers as defined herein using a supported organometallic catalyst. The supported organometallic catalyst is formed from a specific combination of an acidic metal oxide support and an organometallic complex pre-catalyst. The supported organometallic catalyst of the present disclosure as defined herein has unexpectedly high activity in the hydrocracking of the disclosed polymers.

[0053] The disclosed method of hydrocracking includes feeding a polymer, hydrogen gas (H2) and a supported organometallic catalyst into a reactor. The supported organometallic catalyst is formed from an organometallic complex pre-catalyst of formula I and an acidic metal oxide support. The organometallic complex pre-catalyst of formula I is MR m Lx Formula I

[0054] In formula I, m is 0 to 6, and x is 0 to 6. As one of ordinary skill in the art would understand, the values ​​of m and x depend on the formal oxidation state of M in formula I. For example, when M is a group 4 transition metal (e.g., Zr, Hf, or Ti), m can be zero (0) and x can be 4. In a further example, when M is a group 5 transition metal (e.g., Nb or Ta), m can be 1 or 2 and x can be 3. In a further example, when M is a group 6 transition metal (e.g., W or Mo), m can be 1 or 2 and x can be 4. Other values ​​of m and x are of course possible.

[0055] In various embodiments, M is a transition metal selected from the group consisting of Group 3 to Group 8 transition metals. In various embodiments, M is preferably selected from the group consisting of Group 4, Group 5, Group 6, or Group 8 transition metals. More preferably, M is selected from the group consisting of Group 4, Group 5, or Group 6 transition metals. Specific examples of M include those selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Ru, Co, or Ni. Preferably, M is selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Mo, or W. Most preferably, M is derived from a Group 4 transition metal selected from the group consisting of Ti, Zr, or Hf.

[0056] In various embodiments, R is independently selected from the group consisting of H, C1-C8 hydrocarbyl, or halogen. When R is halogen, it is preferably fluorine. When R is hydrocarbyl, it is preferably C4-C8 hydrocarbyl. When R is hydrocarbyl, it is more preferably C5-C6 hydrocarbyl. When R is hydrocarbyl, it is most preferably C5 hydrocarbyl, where if M is a Group 5 transition metal, the (=CHtBu) moiety is preferred, and when M is a Group 6 transition metal, the (≡CtBu) moiety is preferred.

[0057] In various embodiments, each L is independently selected from the group consisting of C1-C12 substituted or unsubstituted hydrocarbyl. For various embodiments, the hydrocarbyl of L in formula I is independently selected from the group consisting of C1-C10 alkyl, C2-C10 alkenyl, or C5-C10 aryl. As used herein, aryl can include multiple ring structures (e.g., fused rings). Preferably, in various embodiments, the hydrocarbyl of L in formula I is independently selected from the group consisting of C4-C7 alkyl, C3-C7 alkenyl, or C5-C8 aryl. Most preferably, L in formula I is neopentyl (abbreviated herein as "Np", e.g., 2,2-dimethylpropyl). For various embodiments, each L can be the same or different.

[0058] In more specific embodiments, M is preferably selected from the group consisting of Zr or Hf. m is 0 and each L is independently selected from C1-C12 alkyl, with L preferably being neopentyl (e.g., 2,2-dimethylpropyl). In further examples, organometallic complex precatalysts of formula I include ZrNp4 (M=Zr, m=0, x=4, and L=Np), HfNp4 (M=Hf, m=0, x=4, and L=Np), TiNp4 (M=Ti, m=0, x=4, and L=Np), NbF2Np3 (M=Nb, m=2, R=F, x=3, L=Np), Ta (=CH t Bu)Np3(M=Ta, m=1, R=(=CH t Bu), x=3, L=Np), Nb(CH t Bu)Np3(M=Nb, m=1, R=(=CH t Bu), x=3, L=Np), W(C t Bu)Np3(M=W, m=1, R=(≡CtBu), x=3, L=Np), and Mo(C t Other exemplary organometallic complex precatalysts of formula I include, but are not limited to, MBz4 (Bz=benzyl; M=Ti, Zr, Hf), MAlyl4 (M=Ti, Zr, Hf), CrNp4, FeNp4, and CoNp3.

[0059] In various embodiments, the metal oxide used in forming the acidic metal oxide support can be selected from the group consisting of aluminum oxide (Al2O3), silicon oxide (e.g., SiO2), nickel (II) oxide, zirconium (IV) oxide, tin (IV) oxide, hafnium (IV) oxide, titanium (IV) oxide, iron (III) oxide, zinc (II) oxide, or mixtures thereof. In various embodiments, the acid used in forming the acidic metal oxide support can be selected from sulfuric acid, trifluoromethanesulfonic acid, fluorosulfonic acid, or fluorosulfonic acid plus antimony pentafluoride ("Magic Acid"). For various embodiments, the acidic metal oxide support is a strong Bronsted acidic oxide. Such oxides are generally classified as those having a Hammett acidity function (i.e., H0) value that is more negative than -15. Preferably, sulfated metal oxides can be used as the acidic metal oxide support. Exemplary sulfated metal oxides include sulfated alumina, sulfated silica, or combinations thereof. Zeolite H-ZSM-5 may also be used as the support material. For some embodiments, the support material is sulfated alumina.

[0060] The formation of the acidic metal oxide support can be accomplished in several ways. For example, under atmospheric conditions, an acid (e.g., 2.0 M aqueous sulfuric acid) can be added to a metal oxide (e.g., aluminum oxide) and stirred for a reaction time of 15 to 90 minutes. The reaction mixture ratio (e.g., acid:oxide molar ratio) can vary from 5:1 to 1:5. After the reaction time, the sulfated metal oxide is separated from the acid (e.g., by centrifugation) and then rinsed repeatedly with deionized (DI) water until the pH of the rinsed DI water reaches about 6. The resulting acidic metal oxide is then dried under vacuum at a temperature of 90 to 140° C. for about 12 to 24 hours. The acidic metal oxide solid can be ground (e.g., with a mortar and pestle) and sieved to the desired mesh (e.g., 180 mesh, 80 μm). The acidic metal oxide can then be calcined (e.g., in a tubular furnace) at a temperature of 400-650 °C for 2-4 hours with flowing O (about 2 L / min), after which the acidic metal oxide can be calcined under vacuum (e.g., by connecting to a high vacuum line and pumping to a low vacuum (e.g., about 10 -6 The acidic metal oxide is then placed in a tube furnace evacuated to 300-450 °C for 1 hour at a temperature of 300-450 °C. The acidic metal oxide is then cooled under vacuum and placed in an inert (e.g., argon) environment where it can be removed or stored under inert gas (e.g., argon).

[0061] In various embodiments, the supported organometallic catalyst is formed from an organometallic complex pre-catalyst of formula I and an acidic metal oxide support. Formation of the supported organometallic catalyst can be achieved by a chemisorption process (e.g., adsorption, where the adsorbed material is held by electrostatic chemical bonds) as follows: A molar ratio (varies from 1:20 to 5:20) of the organometallic complex pre-catalyst of formula I and the acidic metal oxide support are combined with a C4-C8 organic solvent (e.g., n-pentane) at a temperature of 20-30° C. to form a slurry. The slurry is allowed to react for 30 minutes to 4 hours. The resulting supported organometallic catalyst is then filtered, washed with fresh organic solvent, and dried under vacuum for at least 1 hour. The supported organometallic catalyst is stored under an inert atmosphere (e.g., argon).

[0062] For various embodiments, the supported organometallic catalysts discussed herein are represented by Formula II: L y-x R x-z M n+ ··· O - (Acidic Metal Oxide Support) Formula II where M is selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Ru, Co, or Ni; R is independently selected from hydrogen, halogen, or L, where each L is independently selected from C1-C12 saturated or unsaturated hydrocarbyl, or C1-C12 silyl hydrocarbyl; n is 1, y is 3, x is 2 or 1, and z is 1 or 0. In some embodiments, when M is not in the highest possible oxidation state, n can be 2 or 3. For example, when M is either Co or Fe, L2Co 2+ ··· O - (acidic metal oxide support) or L2Fe 2+ ··· O - (acidic metal oxide support), n can be 2, x can be 1, and z can be 1. In formula II, "..." represents the O of the support material. - and M. n+ represents an electrostatic non-covalent bond between ··· O -" represents a weak Lewis basic support material after deprotonation. Preferably, for formula II, M is selected from the group consisting of Ti, Zr or Hf, each L is a C3-C8 saturated or unsaturated hydrocarbyl, n is 1, y is 3, x is 1 and z is 1. More preferably, for formula II, M is selected from the group consisting of Ti, Zr or Hf, each L is a C5 saturated hydrocarbyl, n is 1, y is 3, x is 1 and z is 1. The supported organometallic catalyst may be one in which the acidic metal oxide support is a sulfated metal oxide support material, M is Ti, Zr or Hf, L is neopentyl, n is 1, y is 3, x is 1 and z is 1. When R is a halogen, it is preferably fluorine. Further examples of supported organometallic catalysts represented by formula II include those where M=Zr, L=Np, n=1, y=3, x=1 and z=1, so that R is absent; those where M=Hf, L=Np, n=1, y=3, x=1 and z=1, so that R is absent; those where M=Ti, L=Np, n=1, y=3, x=1 and z=1, so that R is absent; and those where M=Ta, L=Np, R=CH. t Bu, n=1, y=3, x=2 and z=1; M=Nb, L=Np, R=F, n=1, y=3, x=2 and z=0; M=Nb, L=Np, R=CH t Bu, n=1, y=3, x=2 and z=1; M=W, L=Np, R=C t Bu, n=1, y=3, x=2 and z=1; and M=Ta, L=Np, R=C t Bu, n=1, y=3, x=2 and z=1.

[0063] Methods for preparing supported organometallic catalysts from the organometallic complex pre-catalyst of formula I and an acidic metal oxide support are also described in the Examples below. In particular, the use of sulfuric acid treatment, calcination temperature, and inert solvents (e.g., dry hydrocarbons) in preparing the supported organometallic catalyst as described in the Examples below help ensure that the desired supported organometallic catalyst is achieved. In one embodiment, the supported organometallic catalyst is represented by the formula L2M + R···O - ···(acidic metal oxide support), where L and M are as defined herein, "+" represents a formal cationic charge on M, R is hydrogen or L, and "···" represents the O - and M. + represents an electrostatic non-covalent bond between ··· O - " represents a weakly Lewis basic support material after deprotonation.

[0064] The supported organometallic catalysts of the present disclosure are different from existing catalysts represented by the formula shown in Figure 1A. In particular, in the supported organometallic catalysts of the present disclosure, M is formally cationic, whereas in conventional catalysts, M is formally neutral. Also, in the supported organometallic catalysts, M is non-covalently / electrostatically bonded to the support material, whereas in conventional catalysts, M is covalently bonded. These differences are illustrated in Figures 1A and 1B. Figure 1A depicts an existing catalyst, and Figure 1B depicts an example of a supported organometallic catalyst of the present disclosure.

[0065] The method of the present invention further comprises reacting a polymer as defined herein with a supported organometallic catalyst in a reactor at a temperature in the presence of hydrogen gas to produce a reduced polymer product having a weight average molecular weight lower than that of the polymer. In various embodiments, the surface area of ​​the polymer can be increased prior to or during the reaction by a size reduction operation. Such size reduction operations can include, but are not limited to, chopping, shearing, pulverizing, shave, and / or grating the polymer into smaller pieces than before the size reduction operation.

[0066] The conditions used in the present process include parameters such as a given temperature, H2 pressure, time, and metal loading provided by the supported organometallic catalyst. Generally, these parameters are selected in combination to induce the desired hydrocracking reaction. Furthermore, the parameters can be adjusted to achieve the desired product or product yield, product distribution, activity, polymer conversion, or a combination thereof.

[0067] An exemplary predetermined temperature is a temperature within a range of 60° C. to 300° C. Preferably, the predetermined temperature is 90° C. or higher and 200° C. or lower. More preferably, the predetermined temperature is 110° C. or higher and 150° C. or lower.

[0068] For various embodiments, supplying hydrogen gas to the reactor comprises supplying hydrogen gas to the reactor at a pressure of at least 0.1 atmosphere and not more than 100 atmospheres. Preferably, supplying hydrogen gas to the reactor comprises supplying hydrogen gas to the reactor at a pressure of at least 0.2 atmosphere and not more than 50 atmospheres. More preferably, supplying hydrogen gas to the reactor comprises supplying hydrogen gas to the reactor at a pressure of at least 0.5 atmosphere and not more than 4 atmospheres.

[0069] For various embodiments, reacting the polymer can include stirring the polymer with the supported organometallic catalyst in the presence of hydrogen gas at a speed of 500 rpm or more and 3000 rpm or less. Such stirring of the supported organometallic catalyst and polymer can better ensure thorough mixing of the polymer and the supported organometallic catalyst.

[0070] In various embodiments, providing the supported organometallic catalyst in the reactor includes providing 0.01 mole percent (mol%) to 0.9 mol% M based on the monomer units of the polymer (e.g., -C2H4- monomer units of polyethylene). For example, exemplary metal loadings include metal loadings in the range of 0.01 mol% to 0.6 mol% metal (based on monomer units, e.g., monomer units formed from ethylene). Preferably, providing the supported organometallic catalyst in the reactor includes providing 0.005 mol% to 2.0 mol% M based on the monomer units of the polymer.

[0071] The method can be carried out using various types of reactor systems, such as batch reactor systems, semi-batch reactor systems, plug flow reactor systems, and continuous flow reactor systems. The volume of the reactor can be sufficient to ensure that there is a sufficient amount of hydrogen (e.g., moles of hydrogen) in the reactor relative to the polymer so that the desired reduced polymer product is achieved. In various embodiments, the continuous flow reactor system includes tubular reactors, continuous stirred tank reactor systems, fluidized bed reactors, and fixed bed reactors. To add heat to the reaction of the present disclosure, the reactor can be equipped with a heating jacket and / or heating coils. Heat can be provided to the reaction by supplying steam to the heating jacket and / or heating coils. Alternatively, the heating jacket and / or heating coils can use a thermal fluid system (e.g., thermal oil or a water / glycol mixture) to provide the heat required for the reaction of the present disclosure. Other techniques for adding heat to the reaction of the present disclosure are also possible.

[0072] For various embodiments, the step of reacting the polymer with the supported organometallic catalyst in the presence of hydrogen gas at a given temperature is for a period of at least 0.25 hours and not more than 24 hours. Other exemplary reaction times include reaction times in the range of 0.25 hours to 8 hours and reaction times in the range of 0.25 hours to 1.5 hours. Depending on the reactivity of the catalyst, the given temperature, and the pressure of hydrogen in the reactor, the reaction time can be varied to achieve a desired product or product profile of a reduced polymer product having a lower weight average molecular weight than the polymer.

[0073] For various embodiments, the reduced polymer products (e.g., hydrocracked polymer products) produced according to the methods of the present disclosure have a lower weight average molecular weight than the original polymer from which they are produced. The reduced polymer products produced by the present methods include fragments of the depolymerized polymer (e.g., starting polymer). The weight average molecular weight of these fragments is lower than the weight average molecular weight of the polymer itself. The reduced polymer products can be characterized as volatile products (which have a relatively low weight average molecular weight and are generally in gaseous / volatile form), oily products (which have a more moderate weight average molecular weight and are generally liquid), and waxy products (which have a higher weight average molecular weight but still a lower weight average molecular weight than the original polymer).

[0074] Volatile products can be characterized as having less than 9 carbons, oily products can be characterized as having between 9 and 26 carbons, and waxy products can be characterized as having more than 26 carbons (but still less than the original polymer). The exact carbon number and molecular weight ranges of the products depend on the starting polymer and the specific conditions used. Similarly, the amount of each type of product depends on the starting polymer and the specific conditions. However, embodiments of the method can be characterized as producing primarily volatile and oily products. In embodiments, the amount of waxy products produced can be less than 5 wt%, less than 4 wt%, or less than 3 wt%, based on the total weight of the reduced polymer product. The method can also be characterized as producing essentially zero (i.e., less than 0.1 wt%) products with a molecular weight greater than the polymer (e.g., the starting polymer). These values ​​can be stated for a particular set of conditions, e.g., 150° C., 2 atm H2, 2 hours, 0.06 mol % metal. The reduced polymer product can be recovered and used as desired.

[0075] The process of the invention (and the supported organometallic catalysts used therein) can be characterized by high activity and high conversion. Activity can be quantified by turnover frequency. The turnover frequency, measured at a particular set of conditions, e.g., 150°C, 2 atm H2, 2 h, 0.06 mol % metal, is at least 10 mol metal mol substrate. -1 h -1 , at least 100 mole metal mole substrate -1 h -1 , at least 250 mole metal mole substrate -1 h -1 or at least 500 mole metal mole substrate -1 h -1 Conversion refers to the combined weight of dichloromethane soluble and gaseous fractions recovered after the reaction as a percentage of the weight of the starting polymer. Conversion measured at a particular set of conditions, e.g., 150° C., 2 atm H2, 2 hours, 0.06 mol % metal, can be 10% or more, 50% or more, 90% or more, 95% or more, 98% or more, or 100%.

[0076] It should be noted that the results obtained by using the present method are not only surprising but also unexpected. Although similar catalysts have been used to induce olefin polymerization and arene hydrogenation, these are mechanistically distinct from polymer hydrogenolysis / depolymerization. This fact, and the inherent unpredictability underlying organometallic chemistry, make the remarkable activity of the present supported organometallic catalysts in the present method truly surprising. For example, the activity of the supported organometallic catalyst used in the following examples to depolymerize polyethylene at 150° C., 2 atm H2, 2 hours, and 0.06 mol % Zr metal was measured to be about two orders of magnitude higher than existing catalysts (wherein Zr is formally neutral and covalently bound to a metal oxide support). More specifically, the supported organometallic catalyst used in the examples is capable of depolymerizing polyethylene about 100 times faster than another catalyst (without a sulfated oxide support, used under similar conditions in "Dufaud, VR, et al., Angew Chem Int Edit 1998, 37(6), 806-810"). As another example, the supported organometallic catalyst used in the examples is capable of depolymerizing isotactic polypropylene approximately 180 times faster than another catalyst used under similar conditions in Dufaud et al. EXAMPLES

[0077] Materials and Methods All procedures involving air- and moisture-sensitive compounds were performed under high vacuum (10 -5 ~10 -6 Reactions were performed with rigorous exclusion of oxygen (O2) and moisture (e.g., HO) in flame-dried or furnace-dried Schlenk glassware connected to a 300-milliliter (1.2 torr) line or in an argon-filled MBRAUN glove box equipped with a high-volume recirculator (O2 < 1 ppm). Argon used on the high vacuum line (Airgas ultra-high purity (UHP) grade) was purified by passage through MnO / vermiculite and activated Davidson 4A molecular sieve columns.

[0078] All solvents were dispensed from activated alumina / CuO columns prior to use. n-Pentane (Sigma-Aldrich) was further purified by drying over Na / K alloy and then passing through a glass fiber filter in an argon glove box. Aluminum oxide (gamma, nanopowder 20-30 nm) was purchased from Nanostructured and Amorphous Materials Inc. Sulfuric acid (98%) was purchased from Fisher. n-Hexadecane (C16) was purchased from Sigma-Aldrich and purified by heating over Na at 120 °C for 48 hours (h) followed by degassing at room temperature (23 °C) and further purified by passing through a 0.22 μm PTFE syringe filter three times immediately prior to use. n-Hexadecane-d 34 (98%+D) was purchased from Cambridge Isotope Laboratories Inc. and purified in the same manner as C16. All polymer-containing parts that come into direct contact with C16 prior to hydrogenolysis experiments (i.e., syringes, syringe filters, needles, Teflon reactor caps) were treated overnight in an argon-filled glove box before use. Oxygen (UHP grade) used for calcination was purchased from Airgas and used without further purification. Deuterium (Sigma-Aldrich) and hydrogen (H2, Airgas UHP grade) were purified by passing through an oxygen / moisture trap (Matheson, model MTRP-0042-XX). Zirconium(IV) chloride and neopentylmagnesium chloride (1.0 M in Et2O) were purchased from Sigma-Aldrich and used without further purification. Tetra(neopentyl)zirconium (ZrNp4) was synthesized according to literature procedures (Davidson, PJ; Lappert, MF; Pearce, RJ Organometal. Chem. 1973, 57, 269-277) and heated at 70 °C and ca. 10 -6 It was purified by sublimation in torr.

[0079] The polyolefin in this example is Engage™ 8402 polyolefin elastomer (0.902 g / cm 3ethylene-octene copolymer having a density of 0.902 g / cm 3 ethylene-octene copolymer having a density of 0.902 g / cm; Affinity™ 1850G polyolefin plastomer (0.902 g / cm 3 polyethylene plastomer having a density of 0.87 g / cm; Affinity™ GA 1900 polyolefin plastomer (0.87 g / cm 3 The polyolefins used in this example were obtained from high density polyethylene (HDPE) milk jugs and HDPE fruit pouch caps.

[0080] Laboratory synthesized polyolefins were dried in the melt (130-165 °C) under high vacuum for 48 hours (h) before use in the hydrocracking reactions. Shaved pieces of polyolefin were taken from the puck formed by the melt drying process immediately prior to use.

[0081] Physical and analytical measurements Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis was performed by Galbraith Laboratories (Knoxville, Tennessee). 1 H(500MHz) and 13 C (125 MHz) NMR spectra were obtained using a Bruker Avance III system equipped with a DCH cryoprobe. 1 H MAS (400MHz) and 13 C CP-MAS (100 MHz) solid-state NMR measurements were obtained using a Bruker Avance III system equipped with a 4 mm Bruker HX probe. The rotor speed was set at 14 kHz for all spectra.

[0082] Gas chromatography-mass spectrometry (GC-MS) analysis of the hydrogenolysis product mixtures was performed on an Agilent GCMSD equipped with a DB5 column (oven program: 1.) 50°C hold for 2 minutes (min) 2.) Ramp at 30°C / min 3.) 300°C hold for 2 min). Split mode injection with 2 μL / injection and a split ratio of 100:1 was used. For GC-MS quantification of n-hexadecane, a four-point calibration (0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL) was performed for each group of samples analyzed by GC-MS, with a target sample concentration of approximately 0.2 mg / mL. Calibration standards were stored in airtight Teflon-valved glassware.

[0083] Diffuse reflectance infrared spectroscopy (DRIFTS) measurements were obtained on a Thermo 6700 infrared spectrometer equipped with a Harrick Praying Mantis DRIFTS attachment. ZnS windows were used for the DRIFTS cell. Anhydrous KBr was used as the background. The DRIFTS cell contained dry argon (O2 < 1 ppm / H2O < 1 ppm) from a glove box during all measurements. Surface area measurements were performed using a Micromeritics 3Flex surface characterization instrument. Brunauer-Emmett-Teller (BET) surface areas were measured using nitrogen gas adsorption analysis according to S. Brunauer, PH Emmett, E. Teller, J. Am. Chem. Soc. 1938, 60, 309-319.

[0084] Near-edge X-ray absorption structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements at the Zr K-edge (17998 eV) were performed at the 5BM-D beamline of the DND-CAT, a US advanced synchrotron radiation facility. ΔE / E = 1.4 × 10 -4A dual Si(111) monochromator with an energy resolution of 1000 Hz was used for energy selection. X-ray energy was calibrated using metallic Zr foil. Incident X-ray intensity was measured by a spectroscopic grade ionization chamber (FMB Oxford) filled with He 600 (Torr) / N2 100 (Torr) and detuned to 60% of its maximum for harmonic rejection. EXAFS spectra were collected in fluorescence mode using a passivation implanted planar silicon (PIPS) detector (Canberra). The sample and detector were positioned at 45 degrees (deg) and 90 deg, respectively, to the X-ray beam direction. Energy scans were performed from 250 eV below to 550 eV above the K-edge of Zr, which gave rise to EXAFS spectra.

[0085] Gel permeation chromatography (GPC) analysis was performed at 150 °C using 1,2,4-trichlorobenzene stabilized with 0.0125% butylated hydroxytoluene using a Polymer Laboratories PL-GPC220 equipped with three PLgel 10 μm MIXED-B LS300 × 7.5 mm columns. Calibration was performed using polystyrene standards (860–3,752,000 g / mol). Samples were prepared by dissolving the polymer in stabilized trichlorobenzene at 150 °C and shaking gently overnight to obtain a solution concentration of approximately 1.0 mg / mL. Samples were filtered through a 0.5 μm porous stainless steel filter before measurement.

[0086] AlS synthesis Sulfuric acid (2.0 M aqueous solution prepared from deionized (DI) water, 288 mL) was added to 7.0 g of aluminum oxide with stirring under atmospheric conditions. The suspension was stirred for 30 minutes and then centrifuged (4000 revolutions per minute (rpm), 5 minutes). The supernatant was discarded and the alumina was resuspended in DI water and centrifuged. This process was repeated until the pH reached about 6 (typically 7 washes in total). The resulting solid was then cooled to 120° C. and cooled to about 10° C. -6The powder was dried at 550 °C for 18 h at 250 rpm. The solid was then crushed in a mortar and pestle and sieved to 180 mesh (80 μm). The powder was loaded into a quartz boat and placed in a tube furnace and pre-fired at 550 °C for 3 h under O2 (approximately 2 L / min). A high vacuum line was then connected to the tube furnace and the powder was heated at 550 °C for approximately 10 -6 The furnace was pumped down to 450°C for 1 h at 450 torr. The furnace was cooled under vacuum and placed in an argon glove box. The AlS (white powder, 4.83 g) was collected and stored in a sealed container under argon.

[0087] Chemisorption of ZrNp4 on AlS to form supported organometallic catalysts (SOC) In a dry reaction vessel with frits on both sides, 25 mL of pentane was condensed onto a well mixed amount of ZrNp4 (66.67 mg, 0.177 mmol) and AlS (1.000 g). The resulting slurry was stirred at 25°C for 1 h and then filtered. After chemisorption, the solid turned pale yellow. The impregnated support was collected on a frit and washed five times with approximately 10 mL amounts of n-pentane, followed by drying in vacuum for 1 h. 1 H-NMR was used to confirm the presence of physisorbed (weakly bound) residual ZrNp4 by adding approximately 10 mg of the solid directly to the NMR tube using benzene-d6 or toluene-d8 as the solvent. If residual organometallics are present, ZrNp4 1 The catalyst was further washed with pentane as above until it was invisible on H-NMR. The catalyst was then stored in a sealed container at -40°C in an argon glove box until required for use. Alternatively, ZrNp4 and AlS were combined in a Teflon sealed valve, and pentane was then vacuum transferred into the valve. The mixture was stirred at 25°C for 1 hour. The pentane was removed in vacuum and the solids were separated by approximately 10 -6 Torr for 1 h and then stored as above. No difference in catalytic activity was observed for this alternative catalyst preparation. The SOC (AlS / ZrNp2) loading was determined by ICP-AES to be 1.40 wt% Zr (average of two batches with 1.38 and 1.42 wt% Zr). The BET surface area of ​​the catalyst by N2 physisorption was 184 m 2 / g, so the Zr coverage was 0.50Zr / nm 2 It is.

[0088] Synthesis of AlS / ZrH2, AlS / ZrD2 and pAlS / ZrH2 (pentane-treated AlS / ZrH2) Synthesis of AlS / ZrH2. In a glove box, AlS / ZrNp2 (200 mg) was placed in a 75 mL glass pressure reactor. The reactor was sealed, connected to a high pressure / high vacuum line, evacuated, and then charged with 1 atmosphere (atm, 101.325 kPa) of H2. The reactor was heated to 150 °C for 5 min and then evacuated. The color of the catalyst changed from light yellow to colorless. This cycle was repeated once more. The AlS / ZrH2 was then used for further reactions or measurements as needed. AlS / ZrD2 was synthesized in a similar manner to AlS / ZrH2, using D2 instead of H2. To synthesize pAlS / ZrH2, pentane (approximately 0.5 mL) was vacuum transferred via a high pressure / high vacuum line into a 75 mL pressure reactor containing AlS / ZrNp2 (200 mg). The reactor was heated at 150 °C for 5 min. A color change from colorless to pale yellow was observed during the first 30 seconds of heating. The catalyst was stored at -40°C in an argon glove box until needed.

[0089] General procedure for hexadecane hydrocracking using AlS / ZrNp2: In a glove box, C16 was passed through a 0.22 μm PTFE syringe filter directly into a heavy-walled glass pressure reactor containing a 10 mm egg-shaped stir bar. AlS / ZrNp2 was added to the reactor and sealed with a threaded Teflon cap fitted with a National Pipe Tapered Thread (NPT) valve. The vessel was carefully removed from the glove box and connected to a high pressure / high vacuum line. The reactor was degassed at room temperature for 90 seconds (s) and then filled with H2 at the required pressure. The reactor was placed in an oil bath set at the desired temperature and stirring was started starting at approximately 500 rpm. Once the oil bath thermocouple reached the reaction temperature, a time interval was started. At the end of the time interval, the reactor was removed from the oil bath and then cooled to room temperature in a water bath. At this point, headspace samples were taken as required. The reactor was vented through the NPT valve and opened to air. Approximately 5 mL of dichloromethane (DCM) was used to rinse the inside of the Teflon cap and NPT valve. These rinses were added to the reactor. The rinses were transferred to a syringe equipped with a 0.22 μm PTFE filter. The reactor was washed four times (x) with approximately 10 mL of clean DCM, with each rinse added to the syringe. The rinses were passed through the filter directly into a 100 mL volumetric flask. The filter was washed four times with approximately 5 mL of clean DCM, with the rinses added to the volumetric flask. The pipette used to transfer the DCM solution was also rinsed with clean DCM and added to the volumetric flask. The solution was diluted to the calibration mark and then further diluted to approximately 0.2 mg / mL using standard analytical techniques.

[0090] Typical Polyolefin Hydrocracking Procedure: In a glove box, AlS / ZrNp2 and the desired amount of polyolefin sample were loaded into a heavy-walled glass pressure reactor containing a 10 mm egg-shaped stir bar along with a loading of SOC, typically about 15 wt%. Lab-prepared polyolefin samples were prepared by shearing from larger pucks of pre-melted stock. Dow® polyolefin samples were used as is. Used polyolefin samples were comminuted using either a cheese grater or scissors. The reactor was sealed with a threaded Teflon cap fitted with an NPT valve. The vessel was carefully removed from the glove box and connected to a high pressure / high vacuum line. The reactor was degassed at room temperature for 90 seconds and then filled with 2 atm H2. The reactor was placed in an oil bath set at the desired temperature (90-200°C).

[0091] Once the polyolefin had melted and was in contact with the catalyst in the melt, a time interval was started. Agitation was typically initially set at 300 rpm and then increased to about 800 rpm after the polyolefin viscosity had sufficiently decreased. At the end of the time interval, the reactor was removed from the oil bath and then air-cooled to room temperature. If desired, a headspace sample was taken at this point. Headspace samples were taken by diffusing the reactor contents into an evacuated 500 mL Teflon-valved glass bulb. Individual analytical samples were collected through a septum and a gas-tight headspace syringe (50 μL). The reactor was vented through the NPT valve and opened to air. Approximately 5 mL of DCM was used to wash the inside of the Teflon cap and NPT valve. These washes were added to the reactor. The solids were isolated by suspending them in the DCM washes and then filtering them. The reactor was thoroughly washed to remove all residual material. The solid was washed with 3×5 mL portions of DCM and then dried overnight at about 1 Torr (133 Pascals) (solid fraction). The DCM was removed from the filtrate (DCM extract fraction) and the resulting liquid was dried overnight at about 1 Torr (133 Pascals).

[0092] AlS / ZrNp2 results The results seen in Table 1 show complete conversion of C16 using the general hexadecane hydrogenolysis procedure described above with AlS / ZrNp2. For the following data, run "a" in Table 1 was conducted at 2 atm H2 in a 500 mL reactor containing 3.0 g C16 and 200 mg AlS / ZrNp2 (Zr is 1.40 wt%). Run "b" in Table 1 was conducted at 2.5 atm H2 in a 350 mL reactor containing 1.483 g C16 and 178 mg AlS / ZrNp2 (Zr is 0.17 wt%). The average carbon chain length is calculated assuming only linear chains are present. 1 The conversion of C16 was estimated by H-NMR. As shown in Table 1, the conversion of C16 was 100%.

[0093] [Table 1]

[0094] Table 2 presents C16 hydrocracking reaction data at varying pressures. The results seen in Table 2 show the absence of H2 pressure dependence (and by extension H2 concentration dependence), which is consistent with zero-order reaction kinetics of H2. For the experiments in Table 2, there was 2.5 wt% AlS / ZrNp2 (1.40 wt% Zr) in the reactor. For experiment "a" in Table 2, there were 7 equivalents of H2 relative to C16.

[0095] [Table 2]

[0096] Table 3 presents the C16 hydrocracking reaction data for AlS / ZrNp2 (1.40 wt% Zr in the reactor, 0.6–5.44 wt% catalyst) with varying catalyst loading. The data shows a linear relationship (R 2 = 0.98451), which suggests first order reaction kinetics with respect to catalyst concentration.

[0097] [Table 3]

[0098] Table 4 presents data on C16 hydrocracking conversion as a function of time for AlS / ZrNp2 (1.40 wt% Zr in reactor, 2.5 wt% SOC). The data shows a linear relationship between time and C16 conversion (R 2 = 0.9346), suggesting that the conditions used in the kinetic experiments were pseudo-zero order.

[0099] [Table 4]

[0100] Table 5 presents data on the temperature dependence of C16 hydrocracking using AlS / ZrNp2 (1.40 wt% Zr in the reactor, 2.5 wt% catalyst). The data shows a linear relationship (R 2 =0.99924), which suggests a first order reaction with respect to reaction temperature.

[0101] [Table 5]

[0102] Table 6 shows the results of the synthesis of virgin laboratory-synthesized polyethylene homopolymer (M n is about 9 kg mol -1 2 presents data on the conversion of 1,2-dichloropropanediol (1,2-dichloropropanediol) to gaseous and DCM soluble hydrocarbons as a function of time. FIG. 2 shows the weight percent of volatiles, DCM extractables, and solids of the reduced polymer products of Table 6.

[0103] [Table 6]

[0104] Table 7 shows the results of the synthesis of new laboratory-synthesized isotactic polypropylene homopolymer (M n is about 36 kg mol -1 3 presents data on the conversion of 1,2-dichloropropanediol (1,2-dichloropropanediol) to gaseous and DCM soluble hydrocarbons as a function of time. FIG. 3 shows the weight percent of volatiles, DCM extractables, and solids of the reduced polymer products of Table 7.

[0105] [Table 7]

[0106] Table 8 shows the results of a fresh laboratory synthesis of polyethylene-co-1-octene (1-octene incorporation rate of 2.5%, M) using AlS / ZrNp2 (Zr in reactor was 1.40 wt%, catalyst was 13 wt%). n is about 7 kg mol -1 4 presents data on the conversion of volatiles, DCM extractables, and solids as a function of time for the reduced polymer products of Table 8.

[0107] [Table 8]

[0108] Discussion of the AlS / ZrNp2 results supported on an acidic metal oxide support, d 0 Formally cationic Zr(IV) hydrocarbyls are observed to catalyze the hydrocracking of polyolefins and alkanes currently known under the reported reaction conditions. Compared to formally neutrally charged Zr catalysts supported on weakly acidic surfaces, this system shows at least two orders of magnitude improvement in activity. Kinetic experiments show that the reaction is zero order for both hexadecane and H2, and first order for the catalyst. Both DRIFTS and SSNMR provide evidence for the presence of Zr hydride as the active species.

[0109] The AlS / ZrNp2 SOC used in the above alkane (C16) and polyolefin hydrocracking experiments is a formally cationic (i.e., charged) Zr alkyl complex adsorbed on / activated by an acidic metal oxide support (e.g., sulfated alumina support with very high Bronsted acidity, FIG. 1B). In contrast, conventional Zr alkane and polyolefin hydrocracking catalysts are formally neutrally charged (i.e., uncharged) Zr complexes covalently bound to weakly Bronsted acidic supports (FIG. 1A). Despite their similar bulk stoichiometry, the present cationic non-covalently bound Zr alkyl complexes significantly outperformed the conventional catalysts, successfully converting polyethylene and other polyolefins into volatile products (<C9), oily products (C9-C16), and volatile products (C9-C2H4-) at only 0.06 mol % Zr loading (based on -C2H4- monomer units) on the acidic metal oxide support after only 2 hours at 150 °C under 2 atm H2 pressure. 26 ), and a trace amount of waxy product (C 26 ~C 60 The organometallic complex precatalyst used in the above experiments, tetrakis(neopentyl)zirconium, is one of a series of electron-deficient Group 4 metal hydrocarbyls and hydrides that can be immobilized on acidic metal oxide supports, such as sulfated metal oxides (e.g., sulfated alumina). Although similar catalysts have been shown to be active for olefin polymerization and arene hydrogenation, it was entirely unexpected that they would activate saturated hydrocarbons and polyolefins to achieve high yields of depolymerized / hydrogenolysis products under relatively mild conditions. Indeed, as demonstrated above, the exemplary catalyst shown in FIG. 1B is highly active for alkane hydrocracking, mediating the complete conversion of polyethylene, isotactic polypropylene, and polyethylene-co-1-octene to light hydrocarbons and waxes in less than 2 hours using low catalyst loadings (0.06-0.13 mol % Zr) and mild conditions (150-190° C., 2 atm H2).

[0110] Formation of SOC by chemisorption of HfNp4 on AlS Tetra(neopentyl)hafnium (HfNp4) was synthesized according to literature procedures (Davidson, PJ; Lappert, MF; Pearce, RJ Organometal. Chem. 1973, 57, 269-277) and heated at 80°C and ca. 10 -6 The catalyst was purified by sublimation at 2000 torr. 25 mL of pentane was condensed onto a well mixed amount of HfNp4 (84.0 mg, 0.181 mmol) and AlS (1.000 g) in a dry reaction vessel with frits on both sides. The resulting suspension was stirred at 25 °C for 1 h and then filtered. After chemisorption, the solid remained white. The impregnated support was collected on a frit and washed five times with about 10 mL amounts of n-pentane and then dried in vacuum for 1 h. The catalyst was then stored in a sealed container at 25 °C in an argon glove box until required for use. The loading of SOC (AlS / HfNp2) was determined by ICP-AES to be 3.28 wt% Hf.

[0111] General procedure for C16 hydrogenolysis using AlS / HfNp2 In a glove box, C16 was passed through a 0.22 μm PTFE syringe filter directly into a heavy-walled glass pressure reactor containing the desired amount of SOC. The reactor was sealed with a threaded Teflon cap fitted with an NPT valve. The vessel was then degassed for 90 seconds at room temperature and backfilled with 2 atm H2. The reactor was placed in an oil bath set at 150°C and stirring was started starting at approximately 200 rpm. Once the oil bath thermocouple reached 147°C, a time interval was started. The time at which all of the C16 had disappeared was visually recorded. Headspace and condensation samples were taken and characterized by GC-Fid and GC-MS, respectively.

[0112] Table 9 presents C16 hydrocracking reaction data at varying pressures. The results seen in Table 9 show that there is no H2 pressure (and therefore H2 concentration) dependence, which is consistent with zero-order reaction kinetics of H2. For the experiments in Table 9, there was 4.2 wt% SOC in the reactor, which was AlS / HfNp2 (0.14 wt% Hf).

[0113] [Table 9]

[0114] Table 10 presents data for varying catalyst loadings for C16 hydrocracking reaction on AlS / HfNp2 (Hf is 3.28 wt%). The data show a linear relationship (R 2 = 0.9889), suggesting first-order reaction kinetics with respect to SOC concentration.

[0115] [Table 10]

[0116] Table 11 presents data on temperature variation during C16 hydrocracking using AlS / HfNp2 (Hf is 3.28 wt%). The data shows a linear relationship (R 2 = 0.8404), which suggests a first order reaction rate with respect to reaction temperature.

[0117] [Table 11]

[0118] Table 12 presents selected data from the hydrocracking reaction of polyethylene (Engage™ 8402) in a Parr 25 mL autoclave using AlS / HfNp2 (Hf at 3.28 wt %) with stirring starting at about 1500 rpm.

[0119] [Table 12]

[0120] Discussion of the AlS / HfNp2 results AlS / HfNp2 SOC is a structural analogue of AlS / ZrNp2 SOC, where the metal is replaced by Hf. As seen from the data above, AlS / HfNp2 SOC can rapidly catalyze the hydrocracking of polyolefins and alkanes. Although the rate of hydrocracking is slower than that of the Zr catalyst under the same conditions, it has been observed that the Hf system has higher thermal stability.

[0121] Ta(CH) on AlS t Formation of SOC by chemisorption of Bu)Np3 Ta(CH t Bu)Np3 was synthesized according to literature procedures (Schrock, RR; Fellmann, JDJAm. Chem. Soc., 1978, 100, 3359). Ta(CH t 20 mL of pentane was vacuum transferred to a mixture of AlS / Ta(CH)Np3 (100 mg, 0.215 mmol) and AlS (1.20 g). The resulting suspension was stirred at 25 °C for 2 h and then filtered. After chemisorption, the solid appears pale yellow in color. The impregnated support was collected on a frit and washed five times with approximately 10 mL amounts of pentane, then dried in vacuum for 1 h. The catalyst was stored at -40 °C in an argon glove box until needed. The solubility of AlS / Ta(CH)Np3 was 100 mg, 0.215 mmol) and AlS (1.20 g) was 100 g, as determined by ICP-AES. t The amount of SOC supported, which is Ta, was 2.75 wt%.

[0122] Formation of SOC by chemisorption of TiNp4 on AlS TiNp4 was synthesized according to literature procedure Cheon, J.; Rogers, DM; Girolami GSJAm. Chem. Soc., 1997, 119, 6804. 20 mL of pentane was vacuum transferred to a mixture of TiNp4 (53 mg, 0.159 mmol) and AlS (0.90 g) in a dry reaction vessel with dry frits on both sides. The resulting suspension was stirred at 25 °C for 1 h and then filtered. After chemisorption, the solid appears pale yellow in color. The impregnated support was collected on a frit and washed five times with approximately 10 mL amounts of pentane, then dried in vacuum for 1 h. The catalyst was stored at -40 °C in an argon glove box until required. The SOC loading of AlS / TiNp2 was approximately 0.7 wt% Ti.

[0123] Formation of SOC by chemisorption of NbF2Np3 on AlS NbF2Np3 was synthesized according to literature procedures (Schrock, RR; Fellmann, JDJAm. Chem. Soc., 1978, 100, 3359). 20 mL of pentane was vacuum transferred to a mixture of NbF2Np3 (100 mg, 0.215 mmol) and AlS (1.20 g) in a dry reaction vessel with dry frits on both sides. The resulting suspension was stirred at 25 °C for 2 h and then filtered. The impregnated support was collected on the frit and washed five times with approximately 10 mL amounts of pentane, then dried in vacuum for 1 h. The catalyst was stored at -40 °C in an argon glove box until required. The SOC loading of AlS / NbF2Np was approximately 1.4 wt% Nb.

[0124] Nb(CH) on AlS t Formation of SOC by chemisorption of Bu)Np3 NbCl2Np3 was synthesized according to literature procedures (Schrock, RR; Fellmann, JDJAm. Chem. Soc., 1978, 100, 3359). A 50 mL Schlenk flask was charged with 99 mg of NbCl2Np3 (0.26 mmol) along with 10 mL of pentane and a stir bar. After the NbCl2Np3 solution was cooled in a dry ice-acetone bath for 10 min, a pentane solution of LiNp (46 mg, 0.58 mmol) was added slowly via cannula transfer. The resulting suspension was stirred for an additional 10 min and then warmed to 0 °C in an ice bath. The color of the suspension changed from orange-yellow to wine red. A dry reaction vessel with dry frits on both sides was charged with AlS (1.20 g) and then cooled in an ice-water bath. The above wine red suspension was added to the AlS support via cannula filtration. The resulting suspension was stirred at 0 °C for 1 h and then filtered. After chemisorption, the solid appears pale yellow in color. The impregnated support was collected on a frit, washed five times with approximately 10 mL of pentane, and then dried in vacuum for 1 h. The catalyst was stored at -40 °C in an argon glove box until needed. SOC(AlS / Nb(CH t The amount of Nb supported was about 1.4 wt%.

[0125] W(C t Formation of SOC by chemisorption of Bu)Np3 W(C t W(C)Np was synthesized according to literature procedures (Dewan, JC; Schrock, R.R.J. Am. Chem. Soc., 1978, 100, 6774). t A mixture of Bu)Np3 (105 mg, 0.225 mmol) and AlS (1.23 g) was heated in a 66 °C oil bath for 5 h. 20 mL of pentane was vacuum transferred to the resulting mixture and then filtered. After chemisorption, the solid appears light brown in color. The impregnated support was collected on a frit and washed five times with approximately 10 mL amounts of pentane and then dried in vacuum for 1 h. The SOC was stored at -40 °C in an argon glove box until required. SOC(AlS / W(C tThe amount of supported Bu)Np) was about 2.8 wt% of W.

[0126] Mo(C) on AlS t Formation of SOC by chemisorption of Bu)Np3 Mo(C t Mo(C)Np was synthesized according to literature procedures (McCullough, LG; Schrock, RR; Dewan, JC; Murdzek. JCJAm. Chem. Soc., 1985, 107, 5987). t A mixture of SOC(AlS / Mo(C) was heated in an oil bath at 50 °C for 2 h. 10 mL of pentane was vacuum transferred to the resulting mixture and then filtered. After chemisorption, the solids appear light brown in color. The impregnated support was collected on a frit and washed five times with approximately 10 mL of pentane, then dried in vacuum for 1 h. The catalyst was stored at -40 °C in an argon glove box until required. t The amount of supported W was about 1.4 wt%.

[0127] A general C16 hydrogenolysis procedure for initial SOC screening In a glove box, C16 (typically about 1.5 g) was passed through a 0.22 μm PTFE syringe filter directly into a heavy-walled glass pressure reactor (350 mL volume) containing the desired amount of catalyst (typically about 170 mg). The reactor was sealed with a threaded Teflon cap fitted with an NPT valve. The vessel was then evacuated for 90 seconds at room temperature and refilled with 2 atm H2. The reactor was placed in an oil bath set at 150°C. A time interval was started when the oil bath thermocouple reached 147°C. The time at which all of the C16 had evaporated was recorded. Headspace and condensation samples were taken and characterized by GC-Fid and GC-MS, respectively.

[0128] AlS / Ta(CH t A general polyolefin hydrocracking procedure for Bu)Np. In the glove box, AlS / Ta(CH t Bu)Np and the desired amount of polyolefin sample were charged to a heavy-walled glass pressure reactor (350 mL volume) containing approximately 15 wt. % SOC loading. The reactor was sealed with a threaded Teflon cap fitted with an NPT valve. The reactor was evacuated and backfilled with 2 atm H2. The reactor was placed in an oil bath set at the desired temperature. Once the polyolefin had melted and was in contact with the catalyst, a time interval was started. Agitation was typically initially set at 300 rpm and then increased to 600 rpm once the polyolefin viscosity had sufficiently decreased. At the end of the time interval, the vessel was removed from the oil bath and then air-cooled to room temperature. Headspace samples were taken at this point, if desired. The reactor was vented through the NPT valve and opened to air. Approximately 5 mL of DCM was used to wash the inside of the Teflon cap and NPT valve. These washes were added to the reactor. The solids were suspended in the DCM washes and then filtered for recovery. The reactor was washed sufficiently many times to remove any residual material. The solid collected on the frit was washed approximately three times with 5 mL portions of DCM and then dried overnight at approximately 100 mTorr (waxy product). The DCM was removed from the filtrate (DCM extract fraction) and the resulting liquid was dried overnight at approximately 100 mTorr.

[0129] [Table 13]

[0130] FIG. 5 shows the weight percent of volatile, oily, and waxy products of the reduced polymer products of Table 13.

[0131] [Table 14]

[0132] FIG. 6 shows the weight percent of volatile, oily, and waxy products of the reduced polymer products of Table 14.

[0133] C16 Hydrogenolysis In a glove box, 300 mg of AlS / Ta(CH t Bu)Np was charged into a heavy-walled glass pressure reactor (volume 350 mL). The reactor was sealed with a threaded Teflon cap fitted with an NPT valve. The reactor was evacuated and refilled with 2 atm H2, then placed in an oil bath at 200° C. for 5 min. The reactor was evacuated and refilled with 1 atm C16 / H2 (1:1 ratio), then placed in an oil bath at 200° C. for 4 h. Headspace samples were measured by GC-Fid. The results are shown in Table 15. Table 15 presents the recorded time intervals for total evaporation of C16 by hydrogenolysis according to the method described above.

[0134] [Table 15]

[0135] conclusion Chemisorption of hydrocarbyl precursors of group V and group VI metals on acidic sulfated alumina (AlS) produces single-site cationic group V and group VI organometallic centers that are superactive in polyolefin hydrogenolysis. Ethane hydrogenolysis experiments reveal a new C-C bond activation mechanism for group V metals. The heavy metal catalysts show higher thermal stability than the corresponding single-site Zr catalysts.

[0136] Polyolefin Hydrocracking A general high pressure hydrocracking procedure using AlS / ZrNp2 In a glove box, catalyst (typically 10-3 wt%) and polyolefin were added to a 25-100 mL Parr reactor equipped with a magnetically coupled overhead stirrer and a PTFE reactor liner. The reactor was sealed, removed from the glove box, and connected to a high vacuum / high pressure line. The reactor was heated for approximately 10 min. -3After evacuating to torr, the reactor was charged with the desired pressure of H2 (typically 18 atm) at room temperature. The reactor was heated to the desired temperature and reaction temperature, stirring (200-1900 rpm) was started, and the reaction was initiated. If the reaction was carried out at a temperature higher than 150°C, slow stirring (approximately 200 rpm) was followed until the desired temperature was reached (typically 5-10 min). The reaction was allowed to proceed for the desired time interval, which was scheduled to start when the stirring was started. After the time interval had elapsed, the stirring was stopped and the reactor was removed from the furnace and cooled using forced air cooling. The reactor was depressurized and headspace samples were taken as required. The reaction mixture was worked up as described in the general polymer hydrocracking procedure.

[0137] A general procedure for polyolefin hydrocracking with toluene swelling. The reactor was charged with polyolefin and SOC as described in the general polyolefin hydrocracking procedure using AlS / ZrNp2. Dry toluene (0.5-2.0 mL) was also added to the reactor. The reactor was sealed and removed from the glove box. The reactor was heated to the desired temperature with slow stirring for about 30 minutes. The toluene was removed under reduced pressure (about 10 -6 Torr) and then the reactor was charged with H2 to the desired pressure. The reaction was carried out and worked up as described in the general polymer hydrogenolysis procedure.

[0138] Gas-phase NMR experiments 41.50 mg of catalyst was placed in a PTFE sealed NMR tube. The tube was connected to a high pressure / high vacuum line and heated for approximately 10 min. -6 The tube was evacuated to Torr. The tube was filled with 1 atm of H2 and then sealed (internal volume approximately 2.9 mL). NMR spectra were acquired at 10 min intervals. Between these 10 min intervals, the NMR tube was removed from the magnet and then shaken for approximately 2 min. After 90 min, the NMR tube was heated to 150° C. for 30 min to drive the reaction to completion. After this time, a final spectrum was acquired which confirmed that the only hydrocarbons present were methane and ethane. 1H-NMR measurements were obtained using a Bruker Avance III (600 MHz) equipped with a BBFO smart probe. The following acquisition parameters were used to obtain gas phase NMR spectra: acquisition time: 0.5 s, delay time: 20 s.

[0139] Activity calculations for polyolefin hydrocracking experiments The polyolefin hydrocracking activity is calculated as follows: 1.) The reaction product is 14.026 g mol -1 (-CH2- units) and take the fraction containing only the "volatiles" and "DCM extracts" fractions. 2.) Divide the molar amount of product by the number of moles of Zr added to the reaction. 3.) Divide the resulting number by the time (h) the reaction was allowed to proceed. The resulting number is the activity of the polymer hydrogenolysis reaction in units of: (moles CH2 of volatiles and DCM extracts)·(moles Zr). -1 h -1 .

[0140] Using 0.1 g of SOC (1.4 wt% Zr present in SOC), the reaction was allowed to proceed for 45 minutes to produce 0.5 g of combined DCM extractables and volatiles, and the activity was calculated as follows: 0.5g / 14.026(g mole -1 ) = 0.0356 moles (-CH2- units). 0.1 g of SOC contains 0.0014 g of Zr, and the Zr content is 0.0014 g / 91.22 (g mol -1 Zr) = 1.535 10 -5 (mol Zr) was added to the reaction. (0.0356 moles of -CH2- units) / (1.535 10 -5 (mol Zr) (0.75h) = 3097 (mol CH2-units) (mol Zr) -1 h -1 .

[0141] Table 16 presents the hydrogenolysis activity data for Dow® polyethylene resins carried out in a glass reactor as described above. The reaction conditions were 200° C., 0.3 g SOC, 1.0 g polyethylene, and 2 atm H2. The reaction was carried out until a significant amount of the starting polymer was consumed, as determined by visual inspection.

[0142] [Table 16]

[0143] Table 17 presents the hydrogenolysis activity data for Dow® polyethylene resins performed in a Parr reactor (25 mL) as described above. The reaction conditions were 200° C., 0.03 g catalyst, 1.0 g polyethylene, 18 atm H2 (reactor charged at 30° C.). The reaction was run until a significant amount of starting polymer was consumed, as determined by visual inspection.

[0144] [Table 17]

[0145] The product distributions for the hydrocracking of the polymer products (volatiles, DCM extractables and solid products) in Table 17 versus agitation speed are shown in Figure 7. For the reaction conditions presented in Table 17, the product distributions for the hydrocracking of Engage™ 8402, Engage™ 8450 and Affinity™ 1850-G (volatiles, DCM extractables and solid products) versus reaction time are shown in Figure 8.

[0146] Table 18 presents the hydrogenolysis activity data for commercial polyethylene resin with toluene swelling, carried out in a 350 mL glass reactor equipped with a magnetic stir bar as described above. The reaction conditions were 200°C, 0.1 g catalyst (0.0014 g Zr) per reaction, 1.0 g commercial polyethylene resin, and 2 atm H2. The reaction was carried out until a significant amount of starting polymer was consumed, as determined by visual inspection.

[0147] [Table 18]

[0148] For the reaction conditions presented in Table 18, the distribution of hydrocracking products (volatiles, DCM extractables and solid products) of Engage™ 8402, milk jug and HDPE fruit pouch caps are shown in FIG.

[0149] The term "exemplary" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure, "a" or "an" means "one or more" unless otherwise specified.

[0150] Unless otherwise noted, all numerical values ​​of parameters in this disclosure are preceded by the term "about," which means approximately. This encompasses the variations inherent in the measurement of the relevant parameter as understood by one of ordinary skill in the art. This also encompasses the exact value of the disclosed numerical value and values ​​close to the disclosed numerical value.

[0151] The foregoing description of exemplary embodiments of the present disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed, as modifications and variations are possible in light of the above teachings or may be acquired from practice of the present disclosure. The embodiments have been chosen and described for the purpose of explaining the principles of the present disclosure and as practical applications of the present disclosure to enable those skilled in the art to utilize the present invention in various embodiments and with various modifications suited to the particular applications contemplated. It is intended that the scope of the present disclosure be defined by the following claims.

Claims

1. 1. A process for the hydrocracking of polymers, comprising: providing the polymer, hydrogen gas, and a supported organometallic catalyst into a reactor, the supported organometallic catalyst comprising an organometallic complex pre-catalyst of Formula I; MR ｍ L ｘ Formula I wherein m is equal to or greater than 0 and equal to or less than 6, x is equal to or greater than 1 and equal to or less than 6, M is a transition metal selected from Group 3 to Group 8 transition metals, R is independently selected from H, C1 to C8 hydrocarbyl, or halogen, and each L is independently selected from C1 to C12 substituted hydrocarbyl, C1 to C12 unsubstituted hydrocarbyl, or C1 to C12 silyl hydrocarbyl, wherein the values ​​of m and x depend on the oxidation state of M. an acidic metal oxide support; and reacting the polymer with the supported organometallic catalyst in the reactor in the presence of the hydrogen gas at a predetermined temperature to produce a reduced polymer product having a weight average molecular weight lower than that of the polymer. Including, The method wherein the supported organometallic catalyst is represented by Formula II. L y-u R u-z M n+ . . . O − (acidic metal oxide support) Formula II In the formula, n is 1, y is 3, u is 2 or 1, and z is 1 or 0.

2. 10. The method of claim 1, wherein M is selected from a Group 4, 5, 6, or 8 transition metal.

3. 2. The method of claim 1, wherein M is selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, or Ru.

4. The method of claim 1, wherein L is independently selected from C1-C10 substituted or unsubstituted alkyl, C2-C10 substituted or unsubstituted alkenyl, or C5-C10 substituted or unsubstituted aryl.

5. The method of claim 1 , wherein the predetermined temperature is equal to or greater than 60° C. and equal to or less than 300° C.

6. 10. The method of claim 1, wherein the reduced polymer product is at least one of a volatile product, an oily product, or a waxy product.

7. 7. The method of claim 6, wherein the reduced polymer product comprises less than 5 weight percent of the waxy product, based on the total weight of the reduced polymer product.

8. 10. The method of claim 1, wherein the polymer is selected from a polyolefin, a polymer formed by polymerization of an aromatic alkene, or a polymer formed by polymerization of a conjugated diene.

9. 9. The method of claim 8, wherein the polyolefin is selected from polyethylene, polypropylene, linear or branched C4 to C12 monoolefins, copolymers thereof, or combinations thereof.

10. 2. The method of claim 1, wherein M is selected from Zr or Hf, m is 0, and each L is independently selected from C1 to C12 alkyl.

11. The method of claim 1, wherein M is selected from Ti, Zr, or Hf, each L is a C3 to C8 saturated or unsaturated hydrocarbyl, u is 1, and z is 1.

12. 2. The method of claim 1, wherein L is neopentyl.

13. The method of claim 1 wherein the acidic metal oxide support is a sulfated metal oxide.

14. 14. The method of claim 13, wherein the sulfated metal oxide is selected from sulfated aluminum oxide, sulfated zirconium (IV) oxide, sulfated tin (IV) oxide, sulfated hafnium (IV) oxide, sulfated titanium (IV) oxide, sulfated iron (III) oxide, sulfated zinc (II) oxide, sulfated silica oxide, or a combination thereof.

15. 2. The method of claim 1, wherein supplying hydrogen gas to the reactor comprises supplying the hydrogen gas to the reactor at a pressure of at least 0.1 atmospheres and not more than 100 atmospheres.

16. 10. The method of claim 1, wherein reacting the polymer comprises stirring the polymer with the supported organometallic catalyst in the presence of the hydrogen gas at a speed of at least 500 rpm and at most 3000 rpm.

17. 10. The method of claim 1, wherein reacting the polymer with the supported organometallic catalyst in the presence of hydrogen gas at the predetermined temperature is for a period of at least 0.25 hours and up to 24 hours.

18. 10. The method of claim 1, wherein providing the supported organometallic catalyst in the reactor comprises providing 0.01 mole percent (mol %) or greater and 0.9 mol % or less of M based on the monomer units of the polymer.

19. A supported organometallic catalyst of formula II. L ｙ－ｕ R ｕ－ｚ M ｎ＋ ...O － (Acidic Metal Oxide Support) Formula II wherein M is selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, or Ru; R is independently selected from hydrogen, halogen, or C1-C8 hydrocarbyl; each L is independently selected from C1-C12 saturated hydrocarbyl, C1-C12 unsaturated hydrocarbyl, or C1-C12 silyl hydrocarbyl; n is 1, y is 3, u is 2 or 1, and z is 1 or 0.

20. 20. The supported organometallic catalyst of claim 19, wherein M is selected from Ti, Zr, or Hf, each L is a C3 to C8 saturated or unsaturated hydrocarbyl, u is 1, and z is 1.

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