Process for converting plastic waste into polypropylene

Abstract

A method for converting plastic waste into polypropylene includes (a) converting the plastic waste into a hydrocarbon liquid stream and a gaseous hydrocarbon stream in a catalytic pyrolysis unit, wherein the gaseous hydrocarbon stream is greater than about 60% by weight of the output and contains greater than about 40% by weight of light olefins; (b) introducing the gaseous hydrocarbon stream into one or more separation units to produce a first propylene stream, a first ethylene stream, a first butene stream, and a saturated gas stream, wherein the saturated gas stream contains C1 to C4 saturated hydrocarbons; (c) optionally, feeding the first propylene stream into a purification unit to produce a polymer-grade propylene stream; and (d) feeding the first propylene stream and, if present, the polymer-grade propylene stream into a polymerization unit to produce polypropylene.

Description

[0001] Cross-reference to related applications This application claims priority to U.S. Provisional Application No. 63 / 597,309, filed November 8, 2023, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] This technology generally relates to the conversion of plastic waste into polypropylene. Specifically, the technology involves using a unit configuration to directly convert plastic waste into polypropylene and maximize polypropylene yield. Background Technology

[0003] Catalytic pyrolysis represents an attractive method for recycling plastic waste, involving the degradation of polymeric materials by heating them in the absence of oxygen and in the presence of a catalyst. Although catalytic pyrolysis has been extensively studied, there remains a need to develop more efficient methods that maximize the yield of desired products such as light olefins. In particular, propylene is a high-demand light olefin due to its use in many of the world's largest and fastest-growing synthetic materials and thermoplastics.

[0004] This disclosure provides a method for directly converting plastic waste into polypropylene using a series of connected process units. The method described herein increases the net yield of propylene and reduces the size of the catalytic pyrolysis unit required to feed a given size polymerization unit, thereby reducing capital costs, operating costs, and separation and purification costs, and also reducing the need to find additional outlets for non-propylene products. Summary of the Invention

[0005] In one aspect, there is a method for converting plastic waste into polypropylene, the method comprising: (a) In a catalytic pyrolysis unit, plastic waste is converted into a liquid hydrocarbon stream and a gaseous hydrocarbon stream, wherein the gaseous hydrocarbon stream is greater than about 60% by weight of the output and the gaseous hydrocarbon stream contains greater than about 40% by weight of light olefins. (b) The gaseous hydrocarbon stream is introduced into one or more separation units to produce a first propylene stream, a first ethylene stream, a first butene stream and a saturated gas stream, wherein the saturated gas stream comprises C1 to C4 saturated hydrocarbons; (c) Optionally, the first propylene stream is fed into the purification unit to produce a polymer-grade propylene stream; and (d) The first propylene stream and, if present, the polymer-grade propylene stream are fed into the polymerization unit to produce polypropylene.

[0006] In some implementations, the method further includes: The first ethylene stream and the first butene stream are fed into a metathesis unit to produce a second propylene stream, wherein the metathesis unit contains a metathesis catalyst; The first propylene stream and the second propylene stream are combined to produce a combined propylene stream; Optionally, the combined propylene stream is fed into a purification unit to produce a polymer-grade propylene stream.

[0007] In some implementations, the method further includes: The first ethylene stream and the first butene stream are fed into one or more separation units before being fed into the metathesis unit.

[0008] In some implementations, converting plastic waste also includes generating a liquid product stream in a catalytic pyrolysis unit.

[0009] In some embodiments, the liquid product stream comprises one or more of alkanes, isoparaffins, olefins, cycloalkanes, aromatic compounds, organochlorides, or combinations thereof. In some embodiments, the liquid product stream is recycled by returning it to the catalytic pyrolysis unit. In some embodiments, the liquid product stream is fed into a secondary cracking unit to produce a third propylene stream.

[0010] In some implementations, the method further includes: The third propylene stream is combined with the first propylene stream, the second propylene stream, or any combination thereof to produce a combined propylene stream; Optionally, the combined propylene stream is fed into a purification unit to produce a polymer-grade propylene stream.

[0011] In some implementations, the polypropylene is a homopolymer polypropylene.

[0012] In some embodiments, the polymerization unit comprises one or more reactors. In some embodiments, additional ethylene or 1-butene is added to the polymer-grade propylene feed stream prior to step (c). In some embodiments, the polymer-grade propylene feed stream is fed into the polymerization unit together with additional ethylene or 1-butene to produce copolymer polypropylene. In some embodiments, the copolymer polypropylene is a random copolymer polypropylene. In some embodiments, the copolymer polypropylene is an impact copolymer polypropylene.

[0013] In some embodiments, the gaseous hydrocarbon feed stream in step (b) is separated by distillation. In some embodiments, isobutylene is removed from the first butene feed stream after step (b).

[0014] In some embodiments, one or more of the first ethylene stream and the first butene stream are purified to provide a chemical or polymer-grade ethylene stream, a chemical or polymer-grade butene stream, or any combination thereof.

[0015] In some implementations, the metathesis unit utilizes a catalyst containing ruthenium or molybdenum.

[0016] In some embodiments, the petroleum-based olefin stream is not added to the liquid hydrocarbon stream after step (a). In some embodiments, the petroleum-based olefin stream is not added to the gaseous hydrocarbon stream after step (a). In some embodiments, the petroleum-based olefin stream is not added to the liquid hydrocarbon stream after step (a), and the petroleum-based olefin stream is not added to the gaseous hydrocarbon stream after step (a). In some embodiments, the petroleum-based olefin stream is not added to the first propylene stream or the combined propylene stream after step (b). In some embodiments, the petroleum-based olefin stream is not added to the polymer-grade propylene stream before step (d).

[0017] In another aspect, polypropylene produced by any of the methods described herein is provided. Attached Figure Description

[0018] Figure 1 This is an illustrative depiction of an exemplary embodiment of a method for converting plastic waste into polypropylene as described herein.

[0019] Figure 2 This is an illustrative depiction of an exemplary embodiment of a method for converting plastic waste into polypropylene using a metathesis unit as described herein.

[0020] Figure 3 This is an illustrative depiction of an exemplary embodiment of a method for converting plastic waste into polypropylene using a secondary pyrolysis unit as described herein.

[0021] Figure 4 This is an illustrative depiction of an exemplary embodiment of a method for converting plastic waste into polypropylene using a recycling loop as described herein. Detailed Implementation

[0022] Various implementation schemes are described below. It should be noted that the specific implementation schemes are not intended as an exhaustive description or as a limitation on the broader aspects discussed herein. An aspect described in conjunction with a particular implementation scheme is not necessarily limited to that scheme and can be implemented with one or more other implementation schemes.

[0023] As used herein, “approximately” will be understood by those skilled in the art and will vary to some extent depending on the context in which it is used. If those skilled in the art are unaware of the use of this term, “approximately” means at most + or -10% of a particular term, taking into account the context in which it is used.

[0024] Unless otherwise stated herein or clearly contrary to the context, the use of the terms “a,” “an,” and “the,” and similar indicators, in the context of describing elements (especially in the context of the following claims), should be interpreted as covering both singular and plural. Unless otherwise stated herein, the enumeration of numerical ranges herein is intended only to serve as a shorthand for referring one by one to each individual numerical value falling within that range, and each individual numerical value is incorporated into this specification as if enumerated one by one herein. Unless otherwise stated herein or clearly contrary to the context, all methods described herein may be performed in any suitable order. Unless otherwise stated, the use of any and all instances or exemplary wording (e.g., “for example”) provided herein is intended only to better elucidate the embodiments and is not intended to limit the scope of the claims. None of the wording in the specification should be construed as indicating that any unclaimed element is essential.

[0025] This document discloses a method for directly converting plastic waste into polypropylene using a series of connected method units. Specifically, the methods described herein involve using unit configurations to maximize the polypropylene yield from the catalytic pyrolysis of plastic waste. Specifically, the methods described herein combine at least a catalytic pyrolysis unit and a polymerization unit. The catalytic pyrolysis unit receives plastic waste and converts it into ethylene, propylene, and butene, wherein propylene can be added to a propylene polymerization unit. As described herein, metathesis units, secondary cracking units, and / or recycling loops can be used to improve the net yield of propylene.

[0026] As demonstrated in the examples, the addition of metathesis and / or secondary pyrolysis units reduces the size of the catalytic pyrolysis unit required to feed a given size polymerization unit, thereby reducing capital and operating costs. Another advantage of the methods described herein is that the conversion of waste plastics into polypropylene occurs in one location, thus ensuring that the polypropylene is undoubtedly 100% recycled content. In contrast, almost all other methods require mathematical “mass balance” methods to estimate the recycled content.

[0027] Figure 1The illustration shows one embodiment of the method disclosed herein for directly converting plastic waste into polypropylene. Examples of suitable plastic waste include, but are not limited to, those comprising non-chlorinated plastics (e.g., polyolefins, polyethylene, polypropylene, polystyrene, copolymers, etc.), chlorinated plastics (e.g., polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), etc.), or mixtures thereof. Other examples of plastic waste include at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyamide, polycarbonate, polyurethane, polyester, natural and synthetic rubber, tires, filled polymers, composites, and plastic alloys.

[0028] like Figure 1 As shown, plastic waste is loaded or fed into a catalytic pyrolysis unit to produce liquid and gaseous hydrocarbon streams. The catalytic pyrolysis unit can be any suitable container configured to convert waste plastics into gaseous and liquid products (e.g., simultaneously). This container can be configured for gaseous, liquid, vapor-liquid, gas-solid, liquid-solid, or slurry phase operations. The container may contain one or more inert materials or pyrolysis catalyst beds comprising sand, zeolite, alumina, catalytic cracking catalysts, or combinations thereof. These beds can be fluidized beds, rotating beds, moving beds, or screw conveyor beds. In some embodiments, the movement of the beds can be used to assist in the regeneration of the catalyst over time.

[0029] The hydrocarbon liquid stream may contain C6+ hydrocarbons, including alkanes, isoalkanes, alkenes, cycloalkanes, aromatic compounds, organochlorides, or combinations thereof. Examples of alkanes that may be present in the hydrocarbon liquid stream include, but are not limited to, C1 to C6+ hydrocarbons. 22 N-chain alkanes and iso-chain alkanes. Examples of olefins that may be present in a hydrocarbon liquid stream include, but are not limited to, C2 to C4. 10 Olefins and combinations thereof. Examples of cycloalkanes that may be present in a liquid hydrocarbon stream include, but are not limited to, cyclopentane, cyclohexane, cycloheptane, and cyclooctane. Non-limiting examples of aromatics present in a liquid hydrocarbon stream include benzene, toluene, xylene, ethylbenzene, propylbenzene, trimethylbenzene, tetramethylbenzene, butyronylbenzene, dimethylnaphthalene, biphenyl, etc., or combinations thereof.

[0030] The gaseous hydrocarbon stream can contain C2-C5 hydrocarbons, including propylene, ethylene, butene, C1 to C4 saturated hydrocarbons, and any combination thereof. Figure 1 As shown, a gaseous hydrocarbon feed stream is introduced into a separation unit to produce a propylene feed stream, an ethylene feed stream, a butene feed stream, and a saturated gas feed stream, wherein the saturated gas feed stream contains C1 to C4 saturated hydrocarbons.

[0031] The gaseous hydrocarbon stream can be output at a rate greater than about 60 wt%, including outputs of greater than about 65 wt%, greater than about 70 wt%, greater than about 75 wt%, greater than about 80 wt%, greater than about 85 wt%, greater than about 90 wt%, greater than about 95 wt%, and greater than about 99 wt%. The gaseous hydrocarbon stream can be output at a rate from about 60 wt% to about 95 wt%, including outputs of about 60 wt% to about 99 wt%, outputs of about 60 wt% to about 99.9 wt%, and outputs of about 60 wt% to about 99.99 wt%. In some embodiments, the gaseous hydrocarbon stream can be output at a rate of about 60 wt%, about 65 wt%, about 70 wt%, about 75 wt%, about 80 wt%, about 85 wt%, about 90 wt%, about 95 wt%, about 99 wt%, about 99.9 wt%, or about 99.99 wt%.

[0032] The gaseous hydrocarbon feed stream may contain more than about 40% by weight of light olefins (such as ethylene, propylene, and butene), including more than about 45% by weight, more than about 50% by weight, more than about 55% by weight, more than about 60% by weight, more than about 65% by weight, and more than about 70% by weight.

[0033] The one or more separation units can be any suitable separation unit configured to separate a gaseous hydrocarbon stream into a propylene stream, an ethylene stream, a butene stream, and a saturated gas stream. For example, the one or more separation units can use a distillation column, a cryogenic distillation column, an extractive distillation column, a selective adsorption unit, a selective absorption unit, or a combination thereof.

[0034] like Figure 1 As shown, the propylene stream can then optionally be fed into a purification unit before being fed into one or more propylene polymerization units to produce a polymer-grade or chemical-grade propylene stream. The purification unit may contain any suitable purification unit suitable for converting plastic waste into polypropylene. The polymer-grade propylene stream can then be fed into a polymerization unit to produce polypropylene polymer. The polymerization unit may contain one or more suitable polymerization reactors suitable for converting plastic waste into polypropylene and producing many different types of polypropylene grades.

[0035] Before feeding the polypropylene steam into one or more polymerization units, additional ethylene or 1-butene may be added to the polypropylene steam, which may be further purified to provide a chemical or polymer-grade ethylene or 1-butene steam. Feeding the polypropylene steam together with additional ethylene or 1-butene into one or more polymerization units containing one or more polymerization reactors produces copolymer polypropylene (e.g., random copolymer polypropylene and impact copolymer polypropylene). For example, impact copolymer polypropylene can be produced by producing pure propylene in a first reactor and then producing propylene and ethylene in a second reactor.

[0036] Figure 2 This is another illustrative implementation using complex decomposition units. For example... Figure 2 As shown, ethylene and / or butene streams from a separation unit can be fed into a metathesis unit to produce a second propylene stream containing propylene. In some cases, ethylene and / or butene streams can be fed into a purification unit to provide chemical or polymer-grade ethylene and / or butene streams. Using metathesis reactions to convert ethylene and butene streams into propylene maximizes propylene yield. The metathesis unit contains a metathesis reactor (which contains a metathesis catalyst). Typically, olefin metathesis refers to a reaction that requires the redistribution of olefin fragments through the breaking and regeneration of carbon-carbon double bonds; this process is also known as transalkylidenation. Lummus Technology's Olefins Conversion Technology (OCT) provides an example of olefin metathesis for converting ethylene and butene into propylene.

[0037] The metathesis unit may comprise any suitable metathesis reactor, such as a continuous flow reactor, batch reactor, fixed-bed reactor, fluidized-bed reactor, catalytic distillation column reactor, or a combination thereof. The metathesis unit can operate under conditions suitable for the metathesis of ethylene and butene into propylene, such as temperatures equal to or greater than about 50°C, alternatively equal to or greater than about 100°C, alternatively equal to or greater than about 150°C, or alternatively equal to or greater than about 200°C; pressures from about 1 psi to about 1,500 psi, alternatively about 10 psi to about 1,000 psi, or alternatively about 25 psi to about 500 psi; and an operating time of about 0.1 hr. −1 Up to approximately 100 hours −1 Alternatively, approximately 1 hour −1 Up to approximately 50 hours −1 Or alternatively, approximately 5 hours −1 Up to approximately 25 hours −1 WHSV.

[0038] Non-limiting examples of metathesis catalysts suitable for use in this disclosure include organometallic compounds, Schrock catalysts, alkylmolybdenum-1, alkyltungsten-1, Grubbs catalysts, ruthenium carbenoid complexes, ruthenium carbenoid complexes modified with chelated isopropoxystyrene ligands, Hoveyda catalysts, diphenylalkylamino-based catalysts, and combinations thereof. Examples of suitable catalysts include those containing ruthenium or molybdenum.

[0039] like Figure 2 As shown, the propylene stream produced by the metathesis unit (e.g., the second propylene stream) can then be combined with the propylene stream produced by the separation unit (e.g., the first propylene stream) to provide a combined propylene stream. The combined propylene stream can then optionally be fed into a purification unit to produce a polymer-grade or chemical-grade combined propylene stream. The purification unit may contain any suitable purification unit suitable for converting plastic waste into polypropylene. The polymer-grade combined propylene stream can then be fed into a polymerization unit to produce polypropylene polymer. The polymerization unit may contain any suitable polymerization reactor suitable for converting plastic waste into polypropylene.

[0040] Before feeding the combined polypropylene stream into the polymerization unit, additional ethylene or 1-butene may be added to the combined polypropylene stream, which may be further purified to provide a chemical or polymer-grade ethylene or 1-butene stream. Feeding the polypropylene stream together with additional ethylene or 1-butene into a polymerization unit containing one or more reactors produces copolymer polypropylene (e.g., random copolymer polypropylene and impact copolymer polypropylene).

[0041] Figure 3 Another illustrative embodiment using a secondary pyrolysis unit is shown. For example... Figure 3 As shown, the conversion of plastic waste also includes generating a liquid product stream in a catalytic pyrolysis unit. In some embodiments, the liquid product stream comprises one or more of alkanes, isoalkanes, alkenes, cycloalkanes, aromatic compounds, organochlorides, or combinations thereof. In some embodiments, the liquid product stream can be purified by removing benzene, toluene, xylene, and / or any aromatic compounds before being fed into the secondary cracking unit. Such pre-separation of aromatic compounds is preferred but not necessary from a capital-scale and selectivity perspective. The secondary cracking unit is a chemical conversion process designed to introduce a light hydrocarbon liquid with a boiling range between 30°C and 250°C and produce a mixed stream of gas and liquid (including propylene) with significantly reduced molecular weights. This conversion is achieved by contacting the light hydrocarbon liquid with a catalyst at a temperature between 400°C and 600°C. Figure 3As shown, a liquid product stream is fed into a secondary cracking unit to produce a propylene stream, which can be combined with the first propylene stream. The propylene yield from this method can range from 5% to 30% by weight and can be adjusted based on unit operating variables and catalyst quality. Several commercial methods meet this requirement. One specific implementation of this method is the MAXOFIN™ catalytic olefins technology offered by KBR.

[0042] Figure 4 Another illustrative embodiment using a recirculation loop unit is shown. For example... Figure 4 As shown, converting plastic waste also includes generating a liquid product stream in a catalytic pyrolysis unit. In some embodiments, the liquid product stream comprises one or more of alkanes, isoalkanes, olefins, cycloalkanes, aromatic compounds, organochlorides, or combinations thereof. Figure 4 As shown, the liquid product stream can be sent back to the catalytic pyrolysis unit.

[0043] Although the above methods are discussed in the context of a single catalytic pyrolysis unit; a single separation unit; a single metathesis unit; a single purification unit; and a polymerization unit, etc., it should be understood that any suitable configuration for producing propylene from plastic waste can be used, wherein any given configuration may contain 1, 2 or more catalytic pyrolysis units; 1, 2 or more separation units; 1, 2 or more metathesis units; 1, 2 or more purification units; 1, 2 or more metathesis units; etc.

[0044] One aspect provides a method for converting plastic waste into polypropylene. The method includes (a) converting the plastic waste into a liquid hydrocarbon stream and a gaseous hydrocarbon stream in a catalytic pyrolysis unit, wherein the gaseous hydrocarbon stream is greater than about 60% by weight of the output and contains greater than about 40% by weight of light olefins; (b) introducing the gaseous hydrocarbon stream into one or more separation units to produce a first propylene stream, a first ethylene stream, a first butene stream, and a saturated gas stream, wherein the saturated gas stream contains C1 to C4 saturated hydrocarbons; (c) optionally, feeding the first propylene stream into a purification unit to produce a polymer-grade propylene stream; and (d) feeding the first propylene stream and, if present, the polymer-grade propylene stream into a polymerization unit to produce polypropylene.

[0045] In some embodiments, the method further includes feeding a first ethylene stream and a first butene stream into a metathesis unit to produce a second propylene stream, wherein the metathesis unit contains a metathesis catalyst; merging the first propylene stream and the second propylene stream to produce a merged propylene stream; and optionally, feeding the merged propylene stream into a purification unit to produce a polymer-grade propylene stream.

[0046] In some embodiments, the method further includes feeding the first ethylene stream and the first butene stream into one or more separation units before feeding them into the metathesis unit.

[0047] The conversion of plastic waste can also include generating a liquid product stream in a catalytic pyrolysis unit. In some embodiments, the liquid product stream includes one or more of alkanes, isoalkanes, olefins, cycloalkanes, aromatic compounds, organochlorides, or combinations thereof. In some embodiments, the liquid product stream is recycled by returning the stream to the catalytic pyrolysis unit.

[0048] The liquid product stream can be fed into a secondary pyrolysis unit to produce a third propylene stream. In some embodiments, the method includes combining the third propylene stream with a first propylene stream, a second propylene stream, or any combination thereof to produce a combined propylene stream; and optionally, feeding the combined propylene stream into a purification unit to produce a polymer-grade propylene stream.

[0049] The polypropylene can be a homopolymer of polypropylene.

[0050] In some embodiments, the polymerization unit includes one or more reactors. An optional step of feeding the first propylene stream into the purification unit involves adding additional ethylene or 1-butene to the polymer-grade propylene stream. Feeding the polymer-grade propylene stream together with additional ethylene or 1-butene into the polymerization unit can produce a copolymer of polypropylene and ethylene or 1-butene. In some embodiments, the copolymerized polypropylene is a random copolymer of polypropylene. In some embodiments, the copolymerized polypropylene is an impact copolymer of polypropylene.

[0051] In some implementations, the gaseous hydrocarbon stream is separated by distillation.

[0052] In some embodiments, isobutylene is removed from the first butene stream after the introduction step. One or more of the first ethylene stream and the first butene stream can be purified to provide a chemical or polymer-grade ethylene stream, a chemical or polymer-grade butene stream, or any combination of two or more of these.

[0053] In some implementations, the metathesis unit utilizes a catalyst containing ruthenium or molybdenum.

[0054] In some embodiments, the petroleum-based olefin stream is not added to the liquid hydrocarbon stream. In some embodiments, the petroleum-based olefin stream is not added to the gaseous hydrocarbon stream after step (a). In some embodiments, the petroleum-based olefin stream is not added to either the liquid hydrocarbon stream or the gaseous hydrocarbon stream after step (a). In some embodiments, the petroleum-based olefin stream is not added to the first propylene stream or the combined propylene stream after step (b). In some embodiments, the petroleum-based olefin stream is not added to the polymer-grade propylene stream before step (d).

[0055] In another aspect, a method for converting plastic waste into polypropylene is provided. The method may include (a) converting the plastic waste into a liquid hydrocarbon stream and a gaseous hydrocarbon stream in a catalytic pyrolysis unit, wherein the gaseous hydrocarbon stream is greater than about 60% by weight of the output and contains greater than about 40% by weight of light olefins; (b) introducing the gaseous hydrocarbon stream into a first separation unit to produce a first propylene stream, a first ethylene stream, a first butene stream, and a saturated gas stream, wherein the saturated gas stream contains C1 to C4 saturated hydrocarbons; (c) feeding the first ethylene stream and the first butene stream into a metathesis unit to produce a second propylene stream, wherein the metathesis unit contains a metathesis catalyst; (d) combining the first propylene stream and the second propylene stream to produce a combined propylene stream; (e) optionally, feeding the combined propylene stream into a purification unit to produce a polymer-grade propylene stream; and (f) feeding the polymer-grade propylene stream into a polymerization unit to produce polypropylene.

[0056] Converting plastic waste may include generating a liquid product stream in a catalytic pyrolysis unit. In such embodiments, the liquid product stream may include one or more of alkanes, isoalkanes, olefins, cycloalkanes, aromatic compounds, organochlorides, or combinations thereof. The liquid product stream is fed into a secondary pyrolysis unit to generate a third propylene stream. The method may further include combining the third propylene stream with a first propylene stream, a second propylene stream, or any combination thereof to generate a combined propylene stream; and optionally, feeding the combined propylene stream into a purification unit to generate a polymer-grade propylene stream.

[0057] This document also provides information on the production of polypropylene using any of the methods described herein.

[0058] The invention, which is generally described herein, will be more readily understood by referring to the following embodiments, which are provided by way of illustration and are not intended to limit the invention. Example

[0059] Example 1. Figure 2The illustration shows an embodiment of a method for converting plastic waste into polypropylene according to the present disclosure, which utilizes a catalytic pyrolysis unit, an olefin metathesis unit, and a polymerization unit to convert plastic waste into polypropylene.

[0060] The catalytic pyrolysis unit can directly convert mixed waste plastics into light olefins and other valuable products. For example, using a ZSM-5-based catalyst, polypropylene can be converted into the compounds shown in the table below.

[0061] These weight percentages are not added up to 100% because 5 to 10% of the plastic is used to generate heat for this endothermic reaction.

[0062] The propylene polymerization reactor is designed to receive propylene feed. For some products, copolymerization of propylene and ethylene, or copolymerization of propylene and 1-butene, can be performed.

[0063] A 20KTA propylene polymerization reactor requires an 80KTA catalytic pyrolysis unit to match the propylene output and input, and approximately 75% of the products from this catalytic pyrolysis unit will need to find another outlet. These products (ethylene, butene, benzene, toluene, xylene) are commercially available because they are made from recycled contents and can be used to form recycled polymers.

[0064] The metathesis unit can be used to react ethylene with cis / trans-2-butene to form propylene. Therefore, if cis / trans-2-butene is approximately 8% by weight from the “other butenes” in the table above, the net content of propylene formed as a percentage by weight of plastic waste input would be 16% + 25% = 40%.

[0065] At 40%, the catalytic pyrolysis unit would need to be 50 KTA to match the propylene input of a 20 KTA polymerization unit. In other words, the addition of the metathesis unit reduces the size of the catalytic pyrolysis unit required to feed a polymerization reactor of a given size. This smaller unit for the catalytic pyrolysis unit will save capital and operating costs, reduce separation and purification costs, and reduce the need to find additional outlets for non-propylene products.

[0066] Example 2. This example illustrates an embodiment of a method for converting plastic waste into polypropylene according to the present disclosure, which utilizes a catalytic pyrolysis unit, an olefin metathesis unit, a polymerization unit, and a secondary pyrolysis unit to convert plastic waste into polypropylene (see [link to documentation]). Figure 2 and 3 ).

[0067] To further increase propylene yield, a secondary cracking unit can be used, which converts light hydrocarbon liquids (preferably alkanes) into propylene. The secondary cracking unit is a chemical conversion process designed to introduce light hydrocarbon liquids with boiling ranges between 30°C and 250°C and produce a gas-liquid mixture with a significantly reduced molecular weight. This conversion is achieved by contacting the light hydrocarbon liquids with a catalyst at a temperature between 400°C and 600°C. The propylene yield from this method can range from 5% to 30% by weight and can be adjusted based on unit operating variables and catalyst quality. Several commercial methods meet this requirement. One specific embodiment of this method is the MAXOFIN™ catalytic olefins technology offered by KBR. Figure 3 In the reaction scheme shown, benzene, toluene, and xylene can be separated from the light hydrocarbon liquid stream before it enters the secondary cracking unit. Such pre-separation of aromatic compounds is preferred but not necessary from a capital scale and selectivity perspective.

[0068] This disclosure describes two methods for increasing propylene yield between a catalytic pyrolysis unit and an olefin polymerization unit. These methods can be applied together when they process different feed streams, or separately (i.e., only the metathesis unit or only the secondary cracking unit).

[0069] Using both metathesis and secondary pyrolysis units can increase propylene yield to 45% based on input plastics. At 45%, the catalytic pyrolysis unit needs to be 44 KTA in size to match the propylene input of a 20 KTA polymerization unit. In other words, the addition of the metathesis unit reduces the size of the catalytic pyrolysis unit required to feed a polymerization reactor of a given size. This smaller unit for catalytic pyrolysis will save capital and operating costs, reduce separation and purification costs, and reduce the need to find additional outlets for non-propylene products.

[0070] Although certain embodiments have been illustrated and described, it should be understood that variations and modifications may be made to them in accordance with common art without departing from the art as defined in its broader aspects as in the following claims.

[0071] The embodiments exemplified herein can be suitably implemented in the absence of any one or more elements or limitations not specifically disclosed herein. Therefore, terms such as “comprising,” “including,” and “containing” should be interpreted broadly and not restrictively. Furthermore, the terms and expressions used herein have been used as descriptive rather than restrictive terms, and it is not intended to exclude any equivalents of the features shown and described or portions thereof, but rather to recognize that various modifications may be made within the scope of the claimed technology. Additionally, the phrase “consistently of…” will be understood to include those specifically listed elements and those additional elements that do not materially affect the basic and novel features of the claimed technology. The phrase “consisting of…” excludes any unspecified elements.

[0072] This disclosure is not limited to the specific embodiments described herein. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and compositions within the scope of this disclosure, other than those listed herein, will be apparent to those skilled in the art from the foregoing description. Such modifications and variations are intended to fall within the scope of the appended claims. This disclosure is limited only by the terms of the appended claims and the full scope of their equivalents. It is to be understood that this disclosure is not limited to specific methods, reagents, compounds, or compositions, which are of course variable. It is also to be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to constitute limitation.

[0073] Furthermore, when features or aspects of this disclosure are described in terms of the Markush group, those skilled in the art will recognize that this disclosure is also described in terms of any single member or subgroup of members of that Markush group.

[0074] As those skilled in the art will understand, for any and all purposes, particularly in providing a written description, all scopes disclosed herein also encompass any and all possible subscopes and combinations thereof. Any enumerated scope can be readily considered sufficiently descriptive and permissible to be divided into at least two, three, four, five, ten, etc., equal parts. As a non-limiting example, each scope discussed herein can be readily divided into a lower third, a middle third, and an upper third, etc. As those skilled in the art will also understand, all language such as “at most,” “at least,” “greater than,” and “less than” includes the enumerated numerical value and refers to a scope that can subsequently be divided into subscopes as discussed above. Finally, as those skilled in the art will understand, a scope includes each individual member.

[0075] All publications, patent applications, granted patents, and other documents mentioned in this specification are incorporated herein by reference, just as each individual publication, patent application, granted patent, or other document is expressly and individually indicated to be incorporated herein by reference in its entirety. Definitions contained in the text incorporated by reference are excluded to the extent that they contradict the definitions in this disclosure.

[0076] Other embodiments are set forth in the following claims.

Claims

1. A method for converting plastic waste into polypropylene, the method comprising: (a) In a catalytic pyrolysis unit, plastic waste is converted into a liquid hydrocarbon stream and a gaseous hydrocarbon stream, wherein the gaseous hydrocarbon stream is greater than about 60% by weight of the output and the gaseous hydrocarbon stream contains greater than about 40% by weight of light olefins. (b) The gaseous hydrocarbon stream is introduced into one or more separation units to produce a first propylene stream, a first ethylene stream, a first butene stream and a saturated gas stream, wherein the saturated gas stream comprises C1 to C4 saturated hydrocarbons; (c) Optionally, the first propylene stream is fed into a purification unit to produce a polymer-grade propylene stream; and (d) The first propylene stream and, if present, the polymer-grade propylene stream are fed into the polymerization unit to produce polypropylene.

2. The method according to claim 1, further comprising: The first ethylene stream and the first butene stream are fed into a metathesis unit to generate a second propylene stream, wherein the metathesis unit contains a metathesis catalyst. The first propylene stream and the second propylene stream are combined to produce a combined propylene stream; Optionally, the combined propylene stream is fed into a purification unit to produce a polymer-grade propylene stream.

3. The method according to claim 2, further comprising: The first ethylene stream and the first butene stream are fed into one or more separation units before being fed into the metathesis unit.

4. The method according to any one of claims 1-3, wherein converting plastic waste further includes generating a liquid product stream in a catalytic pyrolysis unit.

5. The method according to claim 4, wherein the liquid product stream comprises one or more of alkanes, isoalkanes, alkenes, cycloalkanes, aromatic compounds, organochlorides, or combinations thereof.

6. The method according to claim 4 or 5, wherein the liquid product stream is recycled by returning the stream to the catalytic pyrolysis unit.

7. The method according to any one of claims 4-6, wherein the liquid product stream is fed into a secondary pyrolysis unit to produce a third propylene stream.

8. The method of claim 7, further comprising: The third propylene stream is combined with the first propylene stream, the second propylene stream, or any combination thereof to produce a combined propylene stream; and Optionally, the combined propylene stream is fed into a purification unit to produce a polymer-grade propylene stream.

9. The method according to any one of claims 1-8, wherein the polypropylene is a homopolymer of polypropylene.

10. The method according to any one of claims 1-9, wherein the polymerization unit comprises one or more reactors.

11. The method according to any one of claims 1-10, wherein additional ethylene or 1-butene is added to the polymer-grade propylene feed stream prior to step (c).

12. The method of claim 11, wherein the polymer-grade propylene stream is fed into a polymerization unit together with additional ethylene or 1-butene to produce copolymer polypropylene.

13. The method of claim 12, wherein the copolymer polypropylene is a random copolymer polypropylene.

14. The method of claim 12, wherein the copolymer polypropylene is an impact copolymer polypropylene.

15. The method according to any one of claims 1-14, wherein the gaseous hydrocarbon stream in step (b) is separated by distillation.

16. The method according to any one of claims 1-15, wherein isobutylene is removed from the first butene stream after step (b).

17. The method according to any one of claims 1-16, wherein one or more of the first ethylene stream and the first butene stream are purified to provide a chemical or polymer-grade ethylene stream, a chemical or polymer-grade butene stream, or any combination thereof.

18. The method according to any one of claims 1-17, wherein the metathesis unit utilizes a catalyst comprising ruthenium or molybdenum.

19. The method according to any one of claims 1-18, wherein after step (a), a petroleum-based olefin stream is not added to the hydrocarbon liquid stream.

20. The method according to any one of claims 1-19, wherein a petroleum-based olefin stream is not added to the gaseous hydrocarbon stream after step (a).

21. The method according to any one of claims 1-20, wherein after step (b), no petroleum-based olefin stream is added to the first propylene stream or the combined propylene stream.

22. The method according to any one of claims 1-21, wherein the petroleum-based olefin stream is not added to the polymer-grade propylene stream prior to step (d).

23. A polypropylene produced by any one of claims 1-22.

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