Catalyst For Decomposing A Plastic

A catalyst for decomposing a plastic includes a porous support having an exterior surface and defines at least one pore therein. The catalyst also includes a depolymerization catalyst component disposed on the exterior surface of the porous support for depolymerizing the plastic. The depolymerization catalyst component includes a Ziegler-Natta catalyst, a Group IIA oxide catalyst, or a combination thereof. The catalyst further includes a reducing catalyst component disposed in the at least one pore. The catalyst is formed by a method that includes the step of disposing the depolymerization catalyst component on the exterior surface. The method further includes the step of disposing the reducing catalyst component in the at least one pore.

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Description
RELATED APPLICATIONS

This application claims priority to and all the advantages of U.S. Provisional Patent Application Ser. No. 61/630,894, filed Dec. 21, 2011, which is expressly incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to a catalyst for decomposing a plastic and a method of forming the catalyst. More specifically, the present disclosure relates to a catalyst including a depolymerization catalyst component and a reducing catalyst component.

BACKGROUND

Plastics are typically made from non-renewable petroleum resources and are often non-biodegradable. In the United States, plastics are produced in amounts exceeding 115,000 million pounds annually. Plastics are used in many industries to form products for sale in both industrial and residential markets. In industrial markets, plastics are used to form packaging, insulation, construction products, etc. In residential markets, plastics are used to form bottles, containers, and the like.

Plastics such as polyethylene terephthalate (PET), high density polyethylene (HDPE), and polyvinyl chloride (PVC), have commonly accepted Recycling Codes of from 1 to 3, respectively, as developed by the American Plastics Council. These aforementioned plastics are more widely recycled and re-used than many other types of plastics. However, plastics such as polyethylenes having Recycling Codes of 2, 4, and 7, polypropylene having a Recycling Code of 5, and polystyrene having a Recycling Code of 6, can also be recycled. Yet, recycling efforts for polyethylenes, polypropylene, and polystyrene have not been maximized.

Only a small fraction of the plastics produced each year are recycled and re-used. To ease in recycling, the plastics are usually crushed, melted, and/or broken down. Plastics that are not recycled and re-used present potential environmental pollution risks when discarded, are not utilized for energy or raw materials, and contribute to an increased reliance on non-renewable petroleum resources. Traditionally, plastics are recycled according to one of two methods including open- and closed-loop recycling. Closed-loop recycling involves using the plastic as an input to make the same product again. Open-loop recycling involves using the plastic as an input to make other products. For example, open-loop recycling may be used to form diesel fuel using the plastic as an input. However, neither of these methods are particularly efficient because of the complexities involved in processing plastics of different colors, textures, and consistencies and producing other products.

One particular type of open loop recycling includes decomposition of a plastic by heating, in the absence of a catalyst, to reverse polymerize the plastic and form monomers. After the plastic is decomposed, the monomers can then be used in a variety of manufacturing or commercial processes. Traditionally, this decomposition through heating forms monomers having an inconsistent and/or unpredictable number of carbon atoms, while leaving much of the plastic unusable. Formation of monomers having unpredictable numbers of carbon atoms inhibits the monomers from being effectively recycled into other products.

Another particular type of open-loop recycling includes catalytic cracking, which improves on the decomposition of plastic by heating alone. As is known in the art, catalytic cracking involves reverse polymerizing a plastic, in the presence of a catalyst, to form monomers. Traditionally, the catalysts used in catalytic cracking procedures include classic Lewis acids such as AlCl3, metal tetrachloroaluminates, zeolites, superacids, gallosilicates, metals on carbon, and basic oxides. However, many of these catalysts are ineffective in selectively cracking the plastics to form specific monomers. Although traditional catalytic cracking is more efficient in forming monomers than simple decomposition of plastics through heating alone, many of these traditional catalysts still form monomers having an inconsistent and/or unpredictable number of carbon atoms and still leave much of the plastic unusable and un-cracked.

Diesel fuel traditionally includes hydrocarbons having 11 to 25 carbons. However, the various types of open-loop recycling described above traditionally result in diesel fuel having an insufficient amount of hydrocarbons having 11 to 25 carbons for the diesel fuel to be commercially used. Accordingly, there remains an opportunity to provide an improved catalyst.

SUMMARY OF THE DISCLOSURE AND ADVANTAGES

The present disclosure provides a catalyst for decomposing a plastic. The catalyst includes a porous support having an exterior surface and defining at least one pore therein. The catalyst also includes a depolymerization catalyst component disposed on the exterior surface of the porous support for depolymerizing the plastic. The depolymerization catalyst component includes a Ziegler-Natta catalyst, a Group IIA oxide catalyst, or a combination thereof. The catalyst further includes a reducing catalyst component disposed in the at least one pore. The present disclosure also provides a method of forming the catalyst. The method includes the step of disposing the depolymerization catalyst component on the exterior surface. The method further includes the step of disposing the reducing catalyst component in the at least one pore.

The catalyst of the instant disclosure tends to allow for controlled and efficient formation of specific hydrocarbons e.g. having from 4 to 40 carbons, which can be used as fuel. The catalyst also tends to allow for increased decomposition of plastic thereby reducing reliance on, and slowing depletion of, non-renewable energy sources. The catalyst further tends to reduce a need for new mining and drilling operations on unused land and also reduces energy expenditure associated with refining petroleum to form fuels. Still further, the catalyst tends to reduce potential environmental pollution by allowing for the decomposition of the plastics that are discarded in landfills and by reducing runoff and soil erosion from the mining and drilling operations. The catalyst tends to contribute to decomposition of the plastic and direct formation of these hydrocarbons, typically without a need for additional processing or purification. Also, the catalyst tends to be inexpensive to dispose of or recycle. The method the instant disclosure allows for controlled disposition of catalyst components on the catalyst. This controlled disposition permits formation of the catalyst such that the catalyst can be used to decompose the plastic for efficiently producing the hydrocarbons.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the subject disclosure will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of one embodiment of the catalyst including the porous support, the depolymerization catalyst component, and the reducing catalyst component;

FIG. 2 is a cross-sectional view of one embodiment of the catalyst;

FIG. 3 is a perspective view of another embodiment of the catalyst;

FIG. 4 is a perspective view of yet another embodiment of the catalyst.

 DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure provides a catalyst 10 for decomposing a plastic, as shown in FIGS. 1-4. The plastic of the present disclosure may be any plastic known in the art. The plastic may be a polymerization product of monomers including, but not limited to, aliphatic monomers, aromatic monomers, and combinations thereof. The plastic may be a polymerization product of monomers including unsaturated monomers such as alkenes and dienes having carbon-carbon double bonds, alkynes having carbon-carbon triple bonds, and styrene monomers. The plastic may be recyclable according to the Recycling Codes developed by the American Plastics Council. Prior to recycling, the plastic may be found in commercial products including, but not limited to, containers, packaging, insulation, construction products, and combinations thereof. However, it is contemplated that the plastic may be in any form.

In one embodiment, the plastic is selected from the group of polyethylene, polypropylene, polystyrene, and combinations thereof. Polypropylene corresponds to Recycling Code 5 and can traditionally be found in food containers, medicine bottles, etc. Polystyrene (PS) corresponds to Recycling Code 6 and can typically be found in compact disc jackets, food service applications, food trays, egg cartons, pharmaceutical containers, cups, plates, cutlery, and the like.

In another embodiment, the polyethylene is selected from the group of low density polyethylene (LDPE), which corresponds to Recycling Code 4, linear low density polyethylene (LLDPE), which may be classified under Recycling Code 7, high density polyethylene (HDPE), which corresponds to Recycling Code 2, and combinations thereof. Low density polyethylene may be found in dry cleaning products, in food storage bags and bottles, and the like. Linear low density polyethylene is typically found in liquid containers, food containers, etc. High density polyethylene is traditionally found in food, cosmetic, and detergent bottles, in storage containers, in cereal box liners, in grocery, trash and retail bags, etc. It is contemplated that the plastic may be atactic, isotactic, hemi-isotactic, or syndiotactic, as is known in the art. For descriptive purposes only, the chemical structures of polyethylene, polypropylene, and polystyrene are shown below:

wherein n may be any integer.
Also for descriptive purposes only, generic chemical structures of atactic, isotactic, and syndiotactic polypropylene are shown below:

wherein n may be any integer.

Referring back to FIGS. 1-4, the catalyst 10 for decomposing the plastic includes a porous support 12, a depolymerization catalyst component A, and a reducing catalyst component B. The plastic is typically decomposed in the presence of the catalyst 10 to form one or more hydrocarbons. The one or more hydrocarbons typically each independently have 4 to 40, 5 to 39, 6 to 38, 7 to 37, 8 to 36, 9 to 35, 10 to 34, 11 to 33, 12 to 32, 13 to 31, 14 to 30, 15 to 29, 16 to 28, 17 to 27, 18 to 26, 19 to 25, 20 to 24, 21 to 23, or 22 to 23, carbon atoms (carbons), or any combination thereof. In one embodiment, the one or more hydrocarbons each have 5 to 25 carbons. It is to be appreciated the terminology set forth above describe a number of carbon atoms typically describes a molecular distribution of the hydrocarbons formed or the total number of carbon atoms in each of the one or more hydrocarbons. In various embodiments, the plastic is decomposed to form hydrocarbons having 5 to 25 carbons. More specifically, in certain embodiments, the plastic is depolymerized in the presence of the depolymerization catalyst component A to form unsaturated hydrocarbons having, e.g. 5 to 25 carbons. In other embodiments, the unsaturated hydrocarbons having, e.g. 5 to 25 carbons, are reduced in the presence of the reducing catalyst component B to form saturated hydrocarbons having 5 to 25 hydrocarbons. Without reducing the unsaturated hydrocarbons in the presence of the reducing catalyst component B, the unsaturated hydrocarbons may undesirably continue to depolymerize in the presence of the depolymerization catalyst component A. Typically, hydrocarbons having 5 to 25 carbons are suitable for use as/in diesel fuel. In contrast, hydrocarbons having 5 to 10 carbons are typically suitable for use as/in gasoline. Typically, the depolymerization catalyst component A and the reducing catalyst component B cooperate to decompose the plastic. In various embodiments, if gasoline fuel is a desired output or result, the molecular distribution for the hydrocarbons formed may be from 4 to 16, from 5 to 11, or from 5 to 10 carbons. In other embodiments, if diesel fuel is a desired output or result, the molecular distribution for the hydrocarbons formed may be from 5 to 35, from 10 to 30, or from 11 to 24 carbons. In one embodiment, the diesel fuel is further defined as light diesel fuel and has a cetane value of from 42 to 55.

Referring back to the porous support 12, the porous support has an exterior surface 14 and defines at least one pore 16 therein, as shown in FIGS. 1-4. The porous support 12 may have or be any structure known in the art including a crystalline or an irregular structure. In addition, the at least one pore 16 may be defined uniformly or randomly throughout the porous support 12. In various embodiments, the porous support 12 includes two or a plurality of pores 16 wherein each pore 16 independently has a uniform or irregular structure. Any one pore may have a structure that is the same or different from the structure of any other pore. The at least one pore 16 typically extends into the porous support 12, and may extend through the porous support 12, or a combination thereof. Typically, the porous support 12 has a crystalline structure wherein the plurality of pores 16 may be defined and/or disposed uniformly or heterogeneously or randomly through or on or in the porous support 12. The porous support 12 may be further defined as a molecular sieve, clay, glass, ceramic, charcoal, silica gel, or sol-gel. In various embodiments, the porous support 12 is further defined as a molecular sieve.

Typically, the at least one pore 16 has a pore size of from 3 to 20, from 3 to 12, from 3 to 6 angstroms (A). Alternatively, the at least one pore 16 has a pore size of from 3 to 19, from 4 to 18, from 5 to 17, from 6 to 16, from 7 to 15, from 8 to 14, from 8 to 13, from 9 to 12, from 9 to 11 Å. The pore size may be alternatively described as any value, or range of values, both whole and fractional, within or between any one or more values described above. In various embodiments, the aforementioned pore size may vary by ±1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, etc. %. Without intending to be bound by any particular theory, it is believed that the pore size contributes to the decomposition of the hydrocarbons because the at least one pore 16 permits hydrocarbons of particular molecular weight and/or sizes into the at least one pore 16 thereby preventing or minimizing further depolymerization, as described in detail below. A non-limiting example of a suitable molecular sieve is a 13X molecular sieve. The 13X molecular sieve has a pore size of about 10 Å.

In other embodiments, the molecular sieve is further defined as a zeolite. Zeolites are hydrated silicates of aluminum and may include sodium and/or calcium. One common chemical formula of zeolites is Na2.Al2O3.xSiO2.xH2O. Suitable non-limiting examples of zeolites include AFG, IFR, OFF, ABW, ACO, SAO, ASV, ISV, OSO, AET, AEI, SAS, BEA, ITE, PAR, AFI, AEL, SAT, BIK, JBW, PAU, AFX, AEN, SAV, BOG, KFI, RON, ANA, AFN, SBE, BRE, LIO, RSN, AST, AFO, SBS, CAS, LOV, RTE, BPH, APR, SBT, CFI, LTN, RTH, CAN, AFS, VFI, CHI, MAZ, RUT, CGS, AFT, WEI, CON, MEI, SFE, CHA, AFY, ZON, DAC, MEL, SFF, DFT, AHT, DDR, MEP, SGT, EDI, APC, DOH, MFI, STF, ERI, APD, DON, MFS, STI, FAU, ATN, EAB, MON, STT, GIS, ATO, EMT, MOR, TER, LAU, ATS, EPI, MSO, TON, LEV, ATT, ESV, MTF, TSC, LOS, ATV, EUO, MTN, VET, LTA, AWO, FER, MTT, VNI, LTL, AWW, FRA, MTW, VSV, MER, CGF, GME, MWW, WEN, PHI, CLO, GON, NAT, YUG, RHO, CZP, GOO, NES, SOD, DFO, HEU, NON, THO, OSI, ZSM, and combinations thereof. A non-limiting example of a suitable zeolite is a ZSM 34 zeolite. The ZSM 34 zeolite has a pore size of about 5 Å.

Referring back, the depolymerization catalyst component A is disposed on the exterior surface 14 of the porous support 12 for depolymerizing the plastic to form the hydrocarbons. More specifically, the depolymerization catalyst component A may be disposed on and in direct contact with, or on and spaced apart from, the exterior surface 14 of the porous support 12. In certain embodiments, the depolymerization catalyst component A may be disposed on and in direct contact with, or on and spaced apart from, the exterior surface 14 and the depolymerization catalyst component A may be disposed in and in direct contact with, or in and spaced apart from, an interior of the at least one pore 16 of the porous support 12. Said differently, the depolymerization catalyst component A may be disposed both on the exterior surface 14 of the porous support and simultaneously in the at least one pore 16 of the porous support 12.

The depolymerization catalyst component A includes or is a Ziegler-Natta catalyst, a Group IIA oxide catalyst, or a combination thereof. As described above, the plastic is typically depolymerized in the presence of the depolymerization catalyst component A to form the hydrocarbons. In some embodiments, the depolymerization catalyst component A is further defined as a Ziegler-Natta catalyst. For example, the Ziegler-Natta catalyst may be or include one or more heterogeneous supported catalysts such as TiCl3 supported on MgCl2 and homogenous catalysts such as metallocene catalysts and non-metallocene catalysts. Typically, a metallocene catalyst is or includes a metal atom such as Ti, Zr, or Hf complexed with two organic ligands. Typically, a non-metallocene catalyst includes various metal atoms complexed with a variety of ligands with the ligands including oxygen, nitrogen, phosphorus, and/or sulfur.

In various other embodiments, the Ziegler-Natta catalyst is further defined as a metallocene catalyst. Although the exact mechanism of depolymerizing the plastic in the presence of the metallocene catalyst is not known, the mechanism is likely influenced by kinetic, thermodynamic, electronic, and/or steric interactions of the plastic and the metallocene catalyst and may utilize a type of reverse-Arlman-Cossee mechanism to depolymerize the plastic. Without intending to be limited by any particular theory, it is believed that the mechanism involves coordination of carbon atoms in the plastic with the metal atom of the metallocene catalyst involving pi bonding- and anti-bonding-orbitals of the carbon atoms and d-orbitals of the metal atom.

The metallocene catalyst may be chiral or achiral, may be symmetric or asymmetric, and may be homogeneous or heterogeneous. The metallocene catalyst may include any organic or inorganic moieties known in the art. The terminology “metallocene catalyst” includes both metallocene and post-metallocene catalysts. As is known in the art, metallocenes are organometallic coordination compounds that include cyclopentadienyl derivatives of a transition metal or metal halide, i.e., a constrained metal site is sterically hindered due to orientation between two pi-carbocyclic ligands. Three non-limiting examples of suitable metallocenes include dicyclopentadienyl-metals having the general formula (C5H5)2M, dicyclopentadienyl-metal halides having the general formula (C5H5)2MR1-3, and monocylopentadienyl-metal compounds with the general formula (C5H5)2MR1-3, wherein X is a halogen and R is an organic moiety. When the two pi-carbocyclic ligands are unbridged, the metallocene is non-stereorigid and typically has C2v symmetry, i.e., the metallocene has a plane of symmetry. When the two pi-carbocyclic ligands are bridged, a stereorigid metallocene, also known as an ansa metallocene, is formed and typically has C1, C2, or Cs symmetry, wherein a Cs symmetric molecule has a plane of symmetry and is not chiral. In one embodiment, the plastic is atactic and the metallocene catalyst is an achiral C2v symmetric metallocene. In another embodiment, the plastic is hemi-isotactic and the metallocene catalyst is a C1 symmetric metallocene. In yet another embodiment, the plastic is isotactic and the metallocene catalyst is a chiral C2 symmetric metallocene. In a further embodiment, the plastic is syndiotactic and the metallocene catalyst is a Cs symmetric metallocene.

In other embodiments, the metallocene catalyst is selected from the group of Kaminsky catalysts, Brintzinger catalysts, Ewen/Razavi catalysts, and combinations thereof. In these other embodiments, the metallocene catalyst is or includes a Kaminsky catalyst.

As is known in the art, Kaminsky and Brintzinger catalysts are based on metallocenes of Group IV transition metals and include halogens. These metallocene catalysts are typically homogeneous. For descriptive purposes only, generic chemical structures of Kaminsky and Brintzinger catalysts are shown below:

wherein M is typically a Group IV transition metal including, but not limited to, titanium, zirconium, hafnium, and X is typically a halogen.

In certain embodiments, the metallocene catalyst includes zirconium. In various embodiments, the metallocene catalyst including zirconium is further defined as bis(cyclopentadienyl)zirconium(IV). In other embodiments, the metallocene catalyst is or includes dichlorobis(2-methylindenyl)zirconium (IV). In yet other embodiments, the metallocene catalyst is dichlorobis(2-methylindenyl)zirconium (IV), which has a chemical formula of C20H18Cl2Zr, a molecular weight of 420.49 grams/mole, and a CAS number of 165688-64-2, and is commercially available from Sigma Aldrich Corporation of St. Louis, Mo. For descriptive purposes only, a chemical structure of dichlorobis(2-methylindenyl)zirconium (IV) is shown below:

As is also known in the art, Ewen/Razavi catalysts are similar to Kaminsky and Brintzinger catalysts. These catalysts are also typically homogeneous. For descriptive purposes only, a common chemical structure of a Ewen/Razavi catalyst are shown below:

wherein M is typically a Group IV transition metal, E is typically selected from the group of carbon and silicon, and R′ and R″ may each independently include any organic moiety and may be the same or may be different.

The post-metallocene catalysts are typically homogeneous single-site systems, such that catalytic properties can be controlled by modification of the structure of the post-metallocene catalyst. Many post-metallocene catalysts include early transition metals. However, late transition metals may also be included such as nickel, palladium, iron, or combinations thereof. Non-limiting examples of post-metallocene catalysts that are suitable for use as the depolymerization catalyst component A are Brookhart, Grubbs, and Fujita catalysts. For descriptive purposes only, common chemical structures of the Brookhart, Grubbs, and Fujita catalysts are shown below:

wherein R may be any organic or inorganic moiety known in the art.

For descriptive purposes only, the depolymerization of polyethylene, polypropylene, and polystyrene, in the presence of the metallocene catalyst and heat, is shown below in three separate reaction schemes:

wherein n may be any integer and typically is from 1 to 40.

In other embodiments, the depolymerization catalyst component A is or includes a Group IIA oxide catalyst. The Group IIA oxide catalyst may be or include one or more oxides of beryllium, magnesium, calcium, strontium, barium, radium, or combinations thereof. In certain embodiments, the Group IIA oxide catalyst is further defined as magnesium oxide, calcium oxide, barium oxide, and/or combinations thereof. Typically, the Group IIA oxide is further defined as barium oxide.

In various embodiments, the depolymerization catalyst component A includes molecules with customizable alkaline and acidic sites. If the depolymerization catalyst component A includes alkaline and acidic sites in the same molecule, the alkaline and acidic sites may be in the form of aluminum titanates, mixture of aluminum hydroxides or oxides, titanium oxides, titania, alkali or alkaline metal titanate, or combinations thereof. Specifically, the depolymerization catalyst component A may include the aluminum and titanium oxides with varying ratios of acidity and alkalinity.

Referring back, the reducing catalyst component B is disposed in the at least one pore 16 for reducing the hydrocarbons. More specifically, the reducing catalyst component B may be disposed in and in direct contact with, or in and spaced apart from, an interior of the at least one pore 16 of the porous support 12. The reducing catalyst component B may be any reducing catalyst known in the art. As described above, the hydrocarbons are typically reduced in the presence of the reducing catalyst component B in the at least one pore 16 of the porous support 12. It is believed that the hydrocarbons which can enter the at least one pore 16 of the porous support 12 are reduced. Once the hydrocarbons enter the at least one pore 16, the hydrocarbons may be reduced which may result in the termination of the depolymerization of the hydrocarbons within the at least one pore 16. By controlling the pore size of the at least one pore 16, the molecular distribution of the hydrocarbons may be controlled. For example, the catalyst 10 for decomposing the plastic having a pore size of 10 Å may form hydrocarbons having 5 to 25 carbon which are suitable for use as diesel fuel while the catalyst 10 for decomposing the plastic having a pore size of 5 Å may form hydrocarbons having a lower molecular distribution which are suitable for use as gasoline fuel.

The reducing catalyst component B may be or include mono- and/or di-hydride catalysts, and/or metallic catalysts including, but not limited to, platinum, palladium, nickel, rhodium, ruthenium, iridium, titanium, and combinations thereof. In certain embodiments, the reducing catalyst component B is or includes a transition metal catalyst. The transition metal catalyst may be or include a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof.

In various embodiments, the reducing catalyst component B is or includes a Group IA hydride catalyst, a Group IIA hydride catalyst, or a combination thereof. The Group IA hydride catalyst may be or include lithium aluminum hydride (LAH), sodium hydride, or a combination thereof. The Group IIA hydride catalyst may be or include magnesium hydride, calcium hydride, or a combination thereof.

In other embodiments, the reducing catalyst component B is selected from the group of Wilkinson's catalyst, Crabtree's catalyst, and combinations thereof. For descriptive purposes only, the chemical structures of Wilkinson's and Crabtree's catalysts are shown below:

For descriptive purposes only, the reaction of the reducing catalyst component B with the hydrocarbons is shown below in three separate reaction schemes:

wherein n may be any integer.

In certain embodiments, the exterior surface 14 is substantially free of the reducing catalyst component B and/or the at least one pore 16 is substantially free of the depolymerization catalyst component A. The terminology “substantially free of the reducing catalyst” describes an amount of the reducing catalyst component B on the exterior surface 14 of less than 10, less than 5, or less than 1 part(s) by weight based on 100 parts by weight of the depolymerization catalyst component A on the exterior surface 14. The terminology “substantially free of the depolymerization catalyst” describes an amount of the depolymerization catalyst component A in the at least one pore 16 of less than 10, less than 5, or less than 1 part(s) by weight based on 100 parts by weight of the reducing catalyst component B in the at least one pore 16. In other embodiments, the reducing catalyst component B is different from the depolymerization catalyst component A.

The catalyst 10 for decomposing the plastic may also include, and/or be utilized with, a reducing agent. The reducing agent may react with the hydrocarbons and acts in concert with the reducing catalyst component B to reduce any hydrocarbons having carbon-carbon double and triple bonds to hydrocarbons having carbon-carbon single bonds, i.e., saturated monomers or hydrocarbons. The reducing agent may be any reducing agent known in the art and typically includes hydrogen gas (H2), metal hydrides catalyzed by transition metals, and combinations thereof. Typically, the reducing agent includes H2 modified with nitrogen gas (N2) added as a gas stream to aid in eventual removal of the monomers. The reducing agent may react in a symmetrical or asymmetrical manner and in a directed or non-directed manner.

The catalyst 10 for decomposing the plastic may also include and/or be utilized with one or a plurality of co-catalysts. The co-catalyst is typically utilized to increase catalyst functionality and efficiency. If the co-catalyst is included, the co-catalyst is selected from the group of methylaluminoxane, alumoxane, alkylaluminums such as trimethylaluminum and triethylaluminum, and halo-alkyls such as diethylaluminum chloride, diethylaluminum bromide, diethylaluminum iodide, and combinations thereof. Additionally, if the co-catalyst is included, the co-catalyst may be present in any amount. In various embodiments, the co-catalyst is present in an amount of less than or equal to 100, less than or equal to 50, or less than or equal to 10, parts by weight based on 100 parts by weight of the depolymerization catalyst component A.

The catalyst 10 for decomposing the plastic may further include and/or be utilize one or more of a plurality of modifiers. It is contemplated that the modifier may be added to the depolymerization catalyst and/or the co-catalyst. Although any modifier known in the art may be used, typically, the modifier is selected from the group of carboxylic acid esters, amines, cycloalkyltrienes, fluoride ions, ethers, ketones, phosphines, organophosphates, and combinations thereof. The modifier is typically added to the catalyst 10 and/or co-catalyst to increase catalyst functionality and efficiency. If the modifier is included, the modifier is typically present in an amount of less than or equal to 100, more typically of less than or equal to 50, and most typically of less than or equal to 10, parts by weight per 100 parts by weight of the depolymerization catalyst component A.

The present disclosure further provides a method of forming the catalyst 10 for decomposing the plastic. The method includes the step of disposing the depolymerization catalyst component A on the exterior surface 14. It is to be appreciated that the terminology “disposed” may be used interchangeably with the terminology “deposited” throughout the present disclosure. The depolymerization catalyst component A may be disposed on the exterior surface 14 by any method.

However, in various non-limiting embodiments, the depolymerization catalyst component A does not participate in an ion exchange reaction with the porous support 12 such that the depolymerization catalyst component A is not incorporated into the structure of the porous support 12. It is to be appreciated that, in one embodiment, the at least one pore 16 of the porous support 12 is different than the structure of the porous support 12. In certain embodiments, the step of disposing the depolymerization catalyst component A on the exterior surface 14 is further defined as including the step of providing a water immiscible solvent and combining the depolymerization catalyst component A and the water immiscible solvent to form a mixture. The depolymerization catalyst component A and the water immiscible solvent may be combined by any method known in the art. The water immiscible solvent may be any solvent known in the art that is substantially immiscible in water. The terminology “substantially” describes an amount of the water immiscible solvent which is miscible in water of less than 10, less than 5, or less than 1 part(s) by weight based on 100 parts by weight of water. Typically, the water immiscible solvent is or includes toluene, xylene, aliphatic and aromatic hydrocarbons, or combinations thereof. In some embodiments, the step of disposing also includes the steps of providing water and impregnating the at least one pore 16 of the porous support 12 with the water. The at least one pore 16 of the porous support 12 may be impregnated with water by any method known in the art. Typically, the at least one pore 16 is impregnated with the water through capillary action between the water and the at least one pore 16 of the porous support 12. In other embodiments, the step of disposing further includes the step of combining the mixture and the porous support 12 after the at least one pore 16 is impregnated with the water to dispose the depolymerization catalyst component A on the exterior surface 14 of the porous support 12. The mixture and the porous support 12 may be combined by any method known in the art. Moreover in some embodiments, the step of disposing includes further includes the step of removing the water immiscible solvent and the water from the porous support 12. The water immiscible solvent and the water may be removed from the porous support 12 by any method known in the art. In certain embodiments, the porous support 12 is air dried and/or dried for from 1 minute to 168 hours, from 1 hour to 96 hours, from 24 hours to 72 hours, from 36 hours to 60 hours, or from 42 hours to 54 hours at a temperature of from 0 to 220, from 10 to 210, from 20 to 200, from 30 to 190, from 40 to 180, from 50 to 170, from 60 to 160, from 70 to 150, from 80 to 140, from 90 to 130, or from 100 to 120° C. Typically, the porous support 12 is dried for 48 hours at temperatures from 20° C. to 110° C.

The method further includes the step of disposing the reducing catalyst component B in the at least one pore 16. The reducing catalyst component B may be disposed in the at least one pore 16 by any method.

However, in various non-limiting embodiments, the reducing catalyst component B does not participate in an ion exchange reaction with the porous support 12 such that the reducing catalyst component B is not incorporated into the structure of the porous support 12. In some embodiments, the step of disposing also includes the steps of providing a transition metal salt and a solvent, and combining the transition metal salt and the solvent to form a solution. The transition metal salt may be or include any salt of a transition metal known in the art. The transition metal salt may be or include salts of iron, nickel, palladium, platinum, and combinations thereof with the anions of the salts including fluorine, chlorine, bromine, or iodine. Typically, the transition metal salt is or includes FeCl3, NiCl2, PdCl2, PtCl2, or combinations thereof. The solvent may be or include any solvent capable of solvating the transition metal salt in the solution. The transition metal salts and the solvent may be combined by any method known in the art to form the solution. In some embodiments, the step of disposing further includes the step of impregnating the at least one pore 16 of the porous support 12 with the solution. The at least one pore 16 of the porous support 12 may be impregnated with the solution by any method known in the art. Typically, the at least one pore 16 may be impregnated with the solution through capillary action between the solution and the at least one pore 16 of the porous support 12. Typically, the amount of solution utilized to impregnate the at least one pore 16 is about equivalent to an internal volume of the porous support 12. This equivalency typically minimizes contamination of the exterior surface 14 of the porous support 12 with the solution. Further in some embodiments, the step of disposing includes the step of drying the porous support 12 impregnated with the solution. The porous support 12 impregnated with the solution may be air dried and/or dried e.g. for from 1 minute to 168 hours, from 1 hour to 48 hours, from 6 hours to 42 hours, from 12 hours to 36 hours, or from 18 hours to 30 hours at a temperature, e.g. of from 0 to 220, from 10 to 210, from 20 to 200, from 30 to 190, from 40 to 180, from 50 to 170, from 60 to 160, from 70 to 150, from 80 to 140, from 90 to 130, or from 100 to 120, ° C. Typically, the porous support 12 is dried for 12 hours at 20° C. and for 24 hours 110° C. Moreover, in some embodiments, the step of disposing includes the step of reducing the transition metal salt to the transition metal catalyst in the solution thereby forming the reducing catalyst component B and disposing the reducing catalyst component B in the at least one pore 16 of the porous support 12. The transition metal salt may be reduced to the transition metal by any method known in the art, such as hydrogenation and/or adjustment to pH. In certain embodiments, the step of reducing the transition metal salt to the transition metal catalyst may be further defined as adjusting the pH of the solution.

The pH of the solution may be adjusted to a pH of from 1 to 14, from 3 to 14, from 5 to 14, from 6 to 14, from 7 to 13, from 8 to 12, or from 9 to 11 to reduce the transition metal salt to the transition metal. Alternatively, the pH of the solution may be adjusted to a pH of >1, >2, >3, >4, >5, >6, >7, >8, >9, or >10. In other embodiments, the step of reducing the transition metal salt to the transition metal catalyst may be further defined has hydrogenating the transition metal salt. The transition metal may be hydrogenated with hydrogen gas to reduce the transition metal salt to the transition metal. In one embodiment, sodium borohydride is utilized to adjust the pH of the solution to >10 and concurrently hydrogenate thereby reducing the transition metal salt to the transition metal. However, it is to be appreciated that any substance capable of adjusting pH and/or hydrogenating may be utilized to adjust the pH of the solution and/or hydrogenate.

Still further in some embodiments, the step of disposing may include removing the solvent from the solution. The solvent may be removed from the solution by any method known in the art. In various embodiments, the porous support 12 is dried for a time from 1 minute to 168 hours, from 1 hour to 48 hours, from 6 hours to 42 hours, from 12 hours to 36 hours, or from 18 hours to 30 hours at a temperature of from 0 to 220, from 10 to 210, from 20 to 200, from 30 to 190, from 40 to 180, from 50 to 170, from 60 to 160, from 70 to 150, from 80 to 140, from 90 to 130, or from 100 to 120,° C. Typically, the porous support 12 is dried for 24 hours at 110° C.

In certain embodiments, the step of disposing the depolymerization catalyst component A on the exterior surface 14 occurs before the step of disposing the reducing catalyst component B in the at least one pore 16. In other embodiments, the step of disposing the reducing catalyst component B in the at least one pore 16 occurs before the step of disposing the depolymerization catalyst component A on the exterior surface 14.

In other embodiments, the method yet further includes the step of disposing the depolymerization catalyst component A on the exterior surface 14 and in the at least one pore 16 of the porous support 12 simultaneously or sequentially. In some embodiments, the step of disposing is further defined as providing a solvent and combining the depolymerization catalyst component A and the solvent to form a mixture. The depolymerization catalyst component A and the solvent may be combined by any method known in the art. The solvent may be any solvent. Typically, the solvent includes toluene, methyl ethyl ketone, aliphatic and aromatic hydrocarbons, or combinations thereof. Further in some embodiments, the step of disposing further includes combining the mixture and the porous support 12 to dispose the depolymerization catalyst component A on the exterior surface 14 of the porous support 12 and in the at least one pore 16 of the porous support 12. The mixture and the porous support 12 may be combined by any method known in the art. Moreover in some embodiments, the step of disposing includes removing the solvent from the porous support 12. The solvent may be removed from the porous support 12 by any method known in the art. In certain embodiments, the porous support 12 is air dried and/or dried for from 1 minute to 168 hours, from 1 hour to 96 hours, from 24 hours to 72 hours, from 36 hours to 60 hours, or from 42 hours to 54 hours at a temperature of from 0 to 220, from 10 to 210, from 20 to 200, from 30 to 190, from 40 to 180, from 50 to 170, from 60 to 160, from 70 to 150, from 80 to 140, from 90 to 130, or from 100 to 120° C. Typically, the porous support 12 is dried for 12 hours at 20° C. and for 24 hours at 110° C.

In various embodiments, the step of disposing the depolymerization catalyst component A on the exterior surface 14 and in the at least one pore 16 occurs before the step of disposing the reducing catalyst component B in the at least one pore 16. In other embodiments, the step of disposing the reducing catalyst component B in the at least one pore 16 occurs before the step of disposing the depolymerization catalyst component A on the exterior surface 14 and in the at least one pore 16.

EXAMPLES Inventive Example 1

A 0.4% solution of PdCl2 is prepared by the dilution of 0.4 g of PdCl2 in 100 g of solvent wherein the solvent includes water acidified with HCl such that the solvent is visibly clear. 50 ml of the 0.4% solution of PdCl2 is combined with a 13X molecular sieve which includes an exterior surface and at least one pore. The 13X molecular sieve is present in an amount such that total pore volume of the 13X molecular sieve is more than 50 ml. This typically ensures that the 50 ml 0.4% solution of PdCl2 impregnates the at least one pore through capillary action. The 13X molecular sieve combined with PdCl2 is then dried for 24 hours at a temperature of 110° C. 0.5 g of sodium borohydride is then combined with 60 ml of water to form a sodium borohydride solution. The sodium borohydride solution is then combined with the dried 13X molecular sieve to reduce the PdCl2 to Pd and then dispose the Pd in the at least one pore wherein the Pd is the reducing catalyst component thereby forming a 13X molecular sieve including the Pd. The 13X molecular sieve including Pd is then dried for 24 hours at a temperature of 110° C.

The at least one pore of the 13X molecular sieve including the Pd is then impregnated with 50 ml of water. 0.2 g of bis(cyclopentadienyl)zirconium(IV) (Zr) is combined with 150 ml of toluene to form a mixture. The mixture and the 13X molecular sieve including the Pd are combined, air dried for 12 hours, and then dried for 48 hours at 110° C. to dispose Zr, as the depolymerization catalyst component A, on the exterior surface thereby forming a 13X molecular sieve including the Zr disposed on the exterior surface and the Pd disposed in the at least on pore.

Inventive Example 2

A 0.4% solution of PdCl2 is prepared by the dilution of 0.4 g of PdCl2 in 100 g of solvent wherein the solvent includes water acidified with HCl such that the solvent is visibly clear. 50 ml of the 0.4% solution of PdCl2 is combined with a 13X molecular sieve which includes an exterior surface and at least one pore. The 13X molecular sieve is present in an amount such that total pore volume of the 13X molecular sieve is more than 50 ml. This typically ensures that the 50 ml 0.4% solution of PdCl2 impregnates the at least one pore through capillary action. The 13X molecular sieve combined with PdCl2 is then dried for 24 hours at a temperature of 110° C. 0.5 g of sodium borohydride is then combined with 60 ml of water to form a sodium borohydride solution. The sodium borohydride solution is then combined with the dried 13X molecular sieve to reduce the PdCl2 to Pd and then dispose the Pd in the at least one pore wherein the Pd is the reducing catalyst component thereby forming a 13X molecular sieve including the Pd. The 13X molecular sieve including Pd is then dried for 24 hours at a temperature of 110° C.

0.2 g of bis(cyclopentadienyl)zirconium(IV) (Zr) is combined with 100 ml of toluene and 150 ml of methyl ethyl ketone to form a mixture. The mixture and the 13X molecular sieve including the Pd are combined, air dried for 12 hours, and then dried for 24 hours at 110° C. to dispose Zr, as the depolymerization catalyst component on the exterior surface and in the at least one pore thereby forming a 13X molecular sieve including the Zr disposed on the exterior surface and in the at least one pore, and the Pd disposed in the at least one pore.

Comparative Example 1

The catalyst of Comparative Example 1 includes the same porous support as above but does not include the depolymerization catalyst component disposed on the exterior surface and the reducing catalyst component disposed in the at least one pore. Instead, bis(cyclopentadienyl)zirconium(IV), as the depolymerization catalyst component, is disposed on an exterior surface and in an at least one pore of a 13X molecular sieve. No reducing catalyst component is utilized to form Comparative Example 1.

More specifically, 0.2 g of bis(cyclopentadienyl)zirconium(IV) (Zr) is combined with 100 ml of toluene and 150 ml of methyl ethyl ketone to form a mixture. The mixture and a 13X molecular sieve are combined, air dried for 12 hours, and then dried for 24 hours at 110° C. to dispose Zr, as the depolymerization catalyst component on the exterior surface and in the at least one pore.

Decomposition of Plastics

After each of the catalysts of Example 1, Example 2, and Comparative Example 1 are formed, each is used to independently decompose a mixture of polyethylene and polypropylene (Recycling Codes 4 and 5). More specifically, the plastics for each example are cut into pieces and loaded into a heated vessel in the presence of the aforementioned catalysts. The plastics are exposed to a constant stream of nitrogen (N2) and hydrogen (H2) and heated to 450° C. At approximately 380° C., products from the decomposition of the plastics start to distill over. At the end of the trial, the hydrocarbons collected from each of the examples are analyzed via GC/MS (gas chromatography/mass spectroscopy) to determine percent yield of the hydrocarbons recovered for hydrocarbons having 11-25 carbon atoms, and percent yield of the hydrocarbons recovered for hydrocarbons having 5-10 carbon atoms. These yields are set forth in Table 1 below.

As shown in Table 1 below, Inventive Example 1 with the Zr disposed on the external surface and the Pd disposed in the at least one pore generally provides a higher percentage of diesel fuel (C11-C25) than Comparative Example with the Zr disposed on the external surface and in the at least one pore. Inventive Example 2 with the Zr disposed on the external surface and in the at least one pore, and the Pd disposed in the at least one pore, also generally provides for a higher percentage of diesel fuel (C11-C25) than both Comparative Example and Example 1. Without intending to be bound by any particular theory, it is believed that the Zr and the Pd in the at least one pore of Example 2 cooperate synergistically thereby increasing yield of hydrocarbons having 11 to 25 carbon atoms during decomposition of the plastic.

TABLE 1 Comparative Example 1 Example 2 Example 1 Porous Support 13X 13X 13X Molecular Molecular Molecular Sieve Sieve Sieve Catalyst in Pore Zr Zr Zr Catalyst on Surface Pd Zr and Pd Zr Reducing Agent H2 H2 H2 Percent Gasoline 52  5 59 (C5-C10) Percent Diesel 48 95 41 (C11-C25)

It is contemplated that, in one or more non-limiting embodiments, one or more compounds, chemistries, method steps, components, etc., as described in the concurrently filed PCT Application (Attorney Docket No. 065632.00003 Entitled: “Method for Recycling a Plastic” to S. Ramesh), the entirety of which is expressly incorporated herein by reference, may be utilized.

One or more of the values described above may vary by ±5%, ±10%, ±15%, ±20%, ±25%, etc. so long as the variance remains within the scope of the disclosure. Unexpected results may be obtained from each member of a Markush group independent from all other members. Each member may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims. The subject matter of all combinations of independent and dependent claims, both singly and multiply dependent, is herein expressly contemplated. The disclosure is illustrative including words of description rather than of limitation. Many modifications and variations of the present disclosure are possible in light of the above teachings, and the disclosure may be practiced otherwise than as specifically described herein.

Claims

1. A catalyst for decomposing a plastic, said catalyst comprising:

a porous support having an exterior surface and defining at least one pore therein;
a depolymerization catalyst component disposed on said exterior surface of said porous support for depolymerizing the plastic, said depolymerization catalyst component comprising a Ziegler-Natta catalyst, a Group IIA oxide catalyst, or a combination thereof; and
a reducing catalyst component disposed in said at least one pore.

2. The catalyst of claim 1 wherein said depolymerization catalyst component is a Ziegler-Natta catalyst.

3. The catalyst of claim 2 wherein said Ziegler-Natta catalyst is further defined as a metallocene catalyst.

4. The catalyst of claim 3 wherein said metallocene catalyst comprises zirconium.

5. The catalyst of claim 4 wherein said metallocene catalyst comprising zirconium is further defined as bis(cyclopentadienyl)zirconium(IV).

6. The catalyst of claim 1 wherein said depolymerization catalyst component is a Group IIA oxide catalyst.

7. The catalyst of claim 6 wherein said Group IIA oxide catalyst is further defined as barium oxide.

8. The catalyst of claim 1 wherein said reducing catalyst component comprises a transition metal catalyst.

9. The catalyst of claim 8 wherein said transition metal catalyst comprises a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof.

10. The catalyst of claim 1 wherein said reducing catalyst component comprises a Group IA hydride catalyst, a Group IIA hydride catalyst, or a combination thereof.

11. The catalyst of claim 1 wherein the plastic is selected from the group of polyethylene, polypropylene, polystyrene, and combinations thereof.

12. The catalyst of claim 1 wherein said exterior surface is substantially free of said reducing catalyst component and said at least one pore is substantially free of said depolymerization catalyst component.

13. The catalyst of claim 1 wherein said reducing catalyst component is different from said depolymerization catalyst component.

14. The catalyst of claim 1 wherein said porous support is further defined as a molecular sieve and said at least one pore has a pore size of from 3 angstroms to 20 angstroms.

15. The catalyst of claim 1 wherein said plastic is decomposed to form a hydrocarbon having 5 to 25 carbons.

16. A method of forming a catalyst comprising a porous support having an exterior surface and defining at least one pore therein, a depolymerization catalyst component disposed on the exterior surface of said porous support for depolymerizing the plastic, the depolymerization catalyst component comprising a Ziegler-Natta catalyst, a Group IIA oxide catalyst, or a combination thereof, and a reducing catalyst component disposed in the at least one pore, said method comprising the steps of:

disposing the depolymerization catalyst component on the exterior surface; and
disposing the reducing catalyst component in the at least one pore.

17. The method of claim 16 wherein the depolymerization catalyst component is a Ziegler-Natta catalyst.

18. The method of claim 17 wherein the Ziegler-Natta catalyst is further defined as a metallocene catalyst.

19. The method of claim 18 wherein the metallocene catalyst comprises zirconium.

20. The method of claim 19 wherein the metallocene catalyst comprising zirconium is further defined as bis(cyclopentadienyl)zirconium(IV).

21. A method of claim 16 wherein the depolymerization catalyst component is a Group IIA oxide catalyst.

22. The method of claim 21 wherein the Group IIA oxide catalyst is further defined as barium oxide.

23. The method of claim 16 wherein the reducing catalyst component comprises a transition metal catalyst.

24. The method of claim 23 wherein the transition metal catalyst comprises a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof.

25. The method of claim 16 wherein the reducing catalyst component comprises a Group IA hydride catalyst, a Group IIA hydride catalyst, or a combination thereof.

26. The method of claim 16 wherein the exterior surface is substantially free of the reducing catalyst component and the at least one pore is substantially free of the depolymerization catalyst component.

27. The method of claim 16 wherein the reducing catalyst component is different from the depolymerization catalyst component.

28. The method of claim 16 wherein the porous support is further defined as a molecular sieve and the at least one pore has a pore size of from 3 angstroms to 20 angstroms.

29. The method of claim 16 wherein the step of disposing the reducing catalyst component in the at least one pore is further defined as:

providing a transition metal salt and a solvent;
combining the transition metal salt and the solvent to form a solution;
impregnating the at least one pore of the porous support with the solution;
reducing the transition metal salt to the transition metal catalyst in the solution thereby forming the reducing catalyst component and disposing the reducing catalyst component in the at least one pore of the porous support; and
removing the solvent from the solution.

30. The method of claim 29 wherein the step of reducing the transition metal salt to the transition metal catalyst is further defined as adjusting the pH of the solution.

31. The method of claim 30 wherein the step of reducing the transition metal salt to the transition metal catalyst is further defined as hydrogenating the transition metal salt.

32. The method of claim 16 wherein the step of disposing the depolymerization catalyst component on the exterior surface is further defined as:

providing a water immiscible solvent;
combining the depolymerization catalyst component and the water immiscible solvent to form a mixture;
providing water;
impregnating the at least one pore of the porous support with the water;
combining the mixture and the porous support after the at least one pore is impregnated with the water to dispose the depolymerization catalyst component on the exterior surface of the porous support; and
removing the water immiscible solvent and the water from the porous support.

33. The method of claim 32 wherein the step of disposing the depolymerization catalyst component occurs before the step of disposing the reducing catalyst component.

Patent History
Publication number: 20140371055
Type: Application
Filed: Dec 21, 2012
Publication Date: Dec 18, 2014
Inventor: Swaminathan Ramesh (Canton, MI)
Application Number: 14/366,851