System and method for processing mixed plastic waste

Abstract

Systems and methods for processing mixed plastic waste can include one or more reactive extruders for initially dechlorinating and depolymerizing the mixed plastic waste and a catalytic reactive distillation column for further processing the dechlorinated, depolymerized mixed plastic waste. Depolymerization of the mixed plastic waste by one or more of the disclosed systems and methods produces at least a naphtha mixed feedstock and increases its yield.

Description

Systems and methods for treating mixed plastic waste

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Application No. 63 / 202,884, filed June 29, 2021, which is incorporated herein by reference in its entirety. Technical Field

[0003] This document discloses systems and methods for treating mixed plastic waste, and more particularly for converting mixed plastic waste into high-quality naphtha. This naphtha is suitable as a feedstock for chemical processing operations (such as steam cracking) or refining operations (such as fluid catalytic cracking). Background Technology

[0004] Fluid catalytic cracking (FCC) is a well-known and widely used process in the oil and gas industry to convert high-boiling, high-molecular-weight hydrocarbon fractions of crude oil into more valuable gasoline, olefin gases, and other products. Historically, the cracking of petroleum hydrocarbons has been carried out using thermal cracking technology; however, catalytic cracking processes have recently been implemented to produce byproduct gases with more carbon-carbon double bonds (i.e., olefins), resulting in products with higher octane numbers and increased economic value.

[0005] Typically, the feedstock for the FCC process comprises a portion of crude oil having a boiling point of 340°C or higher at atmospheric pressure and an average molecular weight ranging from about 200 to about 600 or higher. This feedstock portion of crude oil is commonly referred to as heavy gas oil or vacuum gas oil (HVGO). In the FCC process, this feedstock is heated to high temperatures and medium pressures before being contacted with the FCC catalyst. Upon contact with the feedstock, the FCC catalyst promotes the breaking down of long-chain molecules of the high-boiling-point hydrocarbon liquid into much shorter molecules, which can then be captured as vapor exiting the FCC unit.

[0006] Common FCC catalysts can be provided in the form of fine powders with a bulk density of approximately 0.8 g / cm³. 3 Approximately 0.96 g / cm³ 3 Furthermore, the particle size varies. For example, the average specific size of an FCC catalyst can range from about 10 μm to about 150 μm or from about 60 μm to about 100 μm. Desired FCC catalyst properties can include one or more of the following: high activity level, large pore size, good abrasion resistance, low coke yield, and / or good stability when exposed to high temperatures and / or steam. FCC catalysts can also be in the form of crystalline zeolite structures with various compositions and structures.

[0007] Fluid catalytic cracking processes can produce a slurry oil (often referred to as slurry oil or heavy catalytic cycle oil) as the heaviest fraction separating FCC products from the fractionation unit. The slurry oil is a refractory (i.e., essentially chemically inert) stream that passes through the reactor multiple times, rendering it unusable for further catalytic cracking. This slurry oil stream is highly aromatic and primarily consists of forced-condensation polycyclic aromatic structures, such as methyl-substituted phenanthrene, anthracene, pyrene, benzene, and larger aromatic structures. These structures typically include stable methyl groups generated by side-chain cleavage during catalytic cracking in the FCC unit and subsequent thermal treatment. The slurry oil stream typically leaves the FCC unit containing residual, spent FCC catalyst (e.g., in small particulate form). While spent FCC catalyst is less active than fresh FCC catalyst, it does possess some residual acidity and activity.

[0008] In industry, it is increasingly important to develop methods for utilizing certain waste and / or recyclable materials, such as mixed plastic waste (MPW). For example, industrial thermal anaerobic conversion (TAC) can convert MPW into pyrolysis oil, which, after appropriate purification steps, can be used as feedstock for more conventional naphtha cracking systems. However, currently implemented conversion processes of this type are inefficient semi-batch processes, producing pyrolysis oil with a wide boiling point range and a large number of contaminants (e.g., O, N, S, Cl, Si, etc.). Due to the presence of these contaminants, the resulting pyrolysis oil must be distilled and hydrogenated before being fed into a naphtha cracker to produce ethylene and propylene. Such additional processing steps can result in lower-than-desired yields of naphtha-range products. Furthermore, batch pyrolysis units are typically small in scale; for example, many units (e.g., about 10 to 15 units) are required to achieve the desired output. Therefore, it is desirable to provide a process for converting MPW in continuous flow mode in the presence of an acidic catalyst, which can further crack the initial decomposition products of the thermal conversion to increase the yield of naphtha-range products.

[0009] Furthermore, the batch processes commonly used in industry to convert MPW into useful products such as pyrolysis oil require specialized equipment and processes that are not easily scalable and / or cannot be integrated into existing refineries' existing processes. For example, incorporating such processes into existing refineries typically requires the construction of expensive, stand-alone pyrolysis reactors and hydrotreating facilities capable of handling mixed plastic waste. Summary of the Invention

[0010] The applicant has recognized the need for MPW conversion processes that utilize equipment and processes commonly found in refineries. Such MPW treatments can be integrated into existing refineries and would reduce the need for substantial construction costs, increased footprint, or additional equipment requirements. This disclosure provides one or more embodiments of systems and methods for treating mixed plastic waste to produce at least naphtha products. In one embodiment, this disclosure provides a two-stage catalytic reactive distillation method for treating input mixed plastic waste, the method involving introducing the mixed plastic waste into a reactive extrusion vessel maintained at a temperature sufficient to decompose the high molecular weight polymers therein. Subsequently, the partially depolymerized products are mixed with a high-boiling solvent and a reactive catalyst, and the combined mixture is fed into a multi-plate reactive distillation column, where the partially depolymerized products undergo further depolymerization in the presence of the reactive catalyst. One or more distillates can then be removed from the multi-plate reactive distillation column via one or more side streams. In one or more embodiments, at least one of the side streams contains naphtha products.

[0011] In one or more aspects, this disclosure provides a method for processing mixed plastic waste. In particular, such a method includes introducing a mixed plastic waste comprising multiple plastic polymers into a first reactive extrusion vessel. Optionally, certain other embodiments of the method may include feeding the mixed plastic waste into a shredder before introducing it into the first reactive extrusion vessel. In such embodiments, the shredder may be positioned to shred the mixed plastic waste to provide shredded mixed plastic waste. The average size (i.e., length and / or diameter) of such shredded mixed plastic waste may be about 4 mm or less.

[0012] In some embodiments, the first reactive extrusion vessel can be operated at a temperature sufficient to initially dechlorinate any of the chlorinated polymers in the plurality of plastic polymers. In some embodiments, the temperature sufficient to initially dechlorinate any of the chlorinated polymers in the plurality of plastic polymers is between about 300°C and about 350°C. In one or more embodiments, the mixed plastic waste containing the plurality of plastic polymers is fed into a second reactive extrusion vessel. In some embodiments, the second reactive extrusion vessel is operated at a temperature sufficient to initially depolymerize a portion of the plurality of plastic polymers in the mixed plastic waste. In some embodiments, the temperature sufficient to initially depolymerize the plurality of plastic polymers in the mixed plastic waste is between about 400°C and about 450°C. In some embodiments, the pressure in the second reactive extrusion vessel ranges from about 1 bar to about 100 bar. After initial depolymerization, the extruded product exiting the second reactive extrusion vessel can be mixed with a process solvent and a reactive catalyst to define a process feed stream. In some embodiments, the process solvent may include one or more of the following: carbon black oil, heavy catalytic cycle oil, vacuum gas oil, or any hydrocarbon with a boiling point range of about 300°C to about 565°C. In one embodiment, the final boiling point of the carbon black oil is about 565°C.

[0013] Subsequently, in some embodiments, the process feed stream can be fed into a multi-plate reactive distillation column, and more specifically, onto the plates of the multi-plate reactive distillation column. In such embodiments, the multi-plate reactive distillation column can be designed to further depolymerize at least another portion of the various plastic polymers in the process feed stream in the presence of the reactive catalyst. In some embodiments, the multi-plate reactive distillation column can provide countercurrent downward passage of the process feed stream through the multi-plate reactive distillation column, and upward passage of at least partially depolymerized plastic polymer vapors through the multi-plate reactive distillation column, thereby increasing naphtha yield. In some embodiments, the reactive catalyst is a core-shell catalyst having an active catalyst shell disposed on a non-porous core support, and the active catalyst shell has a density of about 5 to about 50 m² / g (m³). 2 The surface area is approximately 1 / g. In some embodiments, the reaction catalyst may include a silica support on which a silica-alumina active catalyst layer with a thickness of less than 10 nanometers is disposed. In other embodiments, the reaction catalyst may include a zirconium oxide sulfate catalyst and / or a calcium sulfate-supported trimetaphosphoric acid catalyst and / or a microporous cracking catalyst (such as ZSM-5).

[0014] The method according to this disclosure may include removing distillate via one or more distillate side streams connected to the multi-plate reactive distillation column. In some embodiments, for example, at least one of the distillate side streams may include naphtha. Additionally, the multi-plate reactive distillation column may include a bottom stream connected to the bottom portion of the column, the bottom stream being designed to remove the process solvent, unreacted plastic polymer, reactive catalyst, and coke stream therefrom. In one or more embodiments, at least a portion of the reactive catalyst and coke may be separated from the bottom stream, for example, using one or more filters configured to receive the stream from the bottom stream. In some embodiments, a portion of the process solvent and unreacted plastic polymer in the bottom stream may be recovered and returned to the process for mixing with the extruded product exiting the reactive extrusion vessel. Thus, with the addition of supplemental process solvent (and additional catalyst), the process solvent can be effectively recycled through the multi-plate reactive distillation column.

[0015] In one or more embodiments, a method for treating mixed plastic waste may include feeding the process feed stream into a plug flow reactor positioned upstream of the multi-plate reactive distillation column, thereby providing an intermediate depolymerization step. In such embodiments, the plug flow reactor is operated, in the presence of the reactive catalyst, at a time and temperature sufficient to depolymerize at least a second portion of the various plastic polymers in the process feed stream to produce a reactor outlet stream. Subsequently, in some embodiments, the reactor outlet stream is fed into the multi-plate reactive distillation column as described herein. For example, the reactor outlet stream is fed onto the trays of the multi-plate reactive distillation column. In one or more embodiments, the time and temperature sufficient to depolymerize at least a second portion of the various polymers in the process feed stream is from about 30 minutes to about 60 minutes and from about 400°C to about 450°C.

[0016] In one or more embodiments, the hydrogen chloride gas from the initial dechlorination of any of the chlorinated polymers in the plurality of plastic polymers can be fed into a gas-liquid contactor containing an aqueous alkali. In such embodiments, the hydrogen chloride gas can react with the aqueous alkali in the gas-liquid contactor to produce a non-volatile product. In one or more embodiments, at least a portion of the aqueous alkali can be added directly to the first reactive extrusion vessel to react with the hydrogen chloride gas generated during the initial dechlorination of any of the chlorinated polymers in the plurality of plastic polymers. In some embodiments, in addition to the mixed plastic waste, one or more compounds can be introduced into the second reactive extrusion vessel to promote the depolymerization of the mixed plastic waste and increase naphtha yield during the process. In some embodiments, for example, a hydrogen donor solvent can be added to the second reactive extrusion vessel (e.g., including the mixed plastic waste therein) to transfer hydrogen from the hydrogen donor solvent to radical compounds generated during the initial depolymerization of the plurality of plastic polymers in the mixed plastic waste, thereby reducing the formation of heavier hydrocarbon products and increasing naphtha yield. In other embodiments, gaseous hydrogen, a transition metal catalyst, and a sulfur-containing compound may be added to the reactive extrusion vessel to transfer hydrogen from the gaseous hydrogen to radical compounds generated during the initial depolymerization of the various plastic polymers in the mixed plastic waste, thereby reducing the formation of heavier hydrocarbon products and increasing naphtha yield. The specific transition metal catalyst and / or sulfur-containing compound can vary. In some embodiments, for example, the transition metal catalyst may include molybdenum octanoate or molybdenum naphthenate, and the sulfur-containing compound may include butyl sulfide. In embodiments where the process solvent is vacuum gas oil, about 0.5% to about 1.5% by weight of sulfur found in the vacuum gas oil can be used as the sulfur-containing compound described above. Furthermore, if the vacuum gas oil has been hydrotreated to reduce its sulfur content, such vacuum gas oil will have a hydrogen moiety as described above to provide radicals.

[0017] Other aspects of this disclosure provide systems for processing mixed plastic waste. Such systems are effective for depolymerizing the mixed plastic waste and recovering naphtha from it. In one or more embodiments, such systems may include a first reactive screw extruder having an inlet and an outlet into which the mixed plastic waste comprising multiple plastic polymers is supplied. Typically, the first reactive screw extruder is a single-screw extruder or a twin-screw extruder; however, other configurations are also possible. In some embodiments, the first reactive screw extruder may be configured to heat the mixed plastic waste to a temperature sufficient to initially dechlorinate any of the chlorinated polymers in the multiple plastic polymers. For example, the temperature sufficient to initially dechlorinate any of the chlorinated polymers in the multiple plastic polymers may be between about 300°C and about 350°C or between about 300°C and about 325°C. Optionally, in some embodiments, the system as described herein may include a shredder positioned upstream of the first reactive screw extruder. The shredder has an inlet and an outlet for receiving raw mixed plastic waste bales. The shredder is operable to shred the original mixed plastic waste bale and provide shredded mixed plastic waste through the outlet, which is then fed into the first reactive screw extruder. In some embodiments, the average size (i.e., length / diameter) of the shredded mixed plastic waste can be about 4 mm or less.

[0018] In some embodiments of the system, the first extruded product stream may be connected to and in fluid communication with the outlet of the first reactive screw extruder to receive a first extruded product comprising the mixed plastic waste from the outlet. In one or more embodiments, the system includes a second reactive screw extruder having an inlet and an outlet for receiving the first extruded product stream. In such embodiments, the second reactive screw extruder is configured to heat the mixed plastic waste of the first extruded product stream to a temperature sufficient to initially depolymerize a portion of the multiple plastic polymers. For example, the temperature sufficient to initially depolymerize the multiple plastic polymers may be between about 400°C and about 450°C. In some embodiments, the system includes a second extruded product stream connected to and in fluid communication with the outlet of the second reactive screw extruder to receive a second extruded product from the outlet. The system may also include a first separation unit having an inlet and an outlet connected to and in fluid communication with the second extruded product stream. The first separation unit may be configured to separate the second extruded product stream into solid material and separated extruded product. The solid material can be purged from the first separation unit by a purge stream.

[0019] In one or more embodiments, the separated extruded product stream is connected to the outlet of the first separation unit and a first inlet of the junction, and is in fluid communication between the outlet and the first inlet, allowing the separated extruded product to flow from the first separation unit to the junction. The junction also has a second inlet for receiving process solvent and reaction catalyst passing through it. In one embodiment, the junction is configured to mix the separated extruded product, the process solvent, and the reaction catalyst to define a process feed stream. The type of process solvent used in the system described herein can vary. For example, in some embodiments, the process solvent may include one or more of the following: carbon black oil or a mid-boiling range (300°C to 565°C) fraction of carbon black oil, heavy catalytic cycle oil, vacuum gas oil, or any hydrocarbon with a boiling range of about 300°C to about 565°C. In some embodiments, the reaction catalyst may be one or more of the following: a microporous cracking catalyst, a silica-alumina silica-supported catalyst having an active catalyst layer of less than 10 nanometers, a zirconium oxide sulfate catalyst, and a calcium sulfate-supported trimetaphosphoric acid catalyst.

[0020] In some embodiments, the system may include a multi-plate reactive distillation column having a feed inlet that receives the process feed stream from the junction. In some embodiments, the multi-plate reactive distillation column may provide the process feed stream (i.e., including extruded products, process solvents, and reaction catalysts) countercurrent downwards through the multi-plate reactive distillation column, and at least partially depolymerized plastic polymer vapor upwards through the multi-plate reactive distillation column. Typically, the multi-plate reactive distillation column includes multiple side streams connected to and in fluid communication with the multi-plate reactive distillation column. In some embodiments, for example, at least one of the multiple side streams is arranged to extract naphtha from the multi-plate reactive distillation column. In addition to the multiple side streams, the multi-plate reactive distillation column may also include a bottom stream connected to and in fluid communication with a portion of the multi-plate reactive distillation column near its bottom. In some embodiments, the bottom stream may be configured to receive a stream comprising the process solvent, unreacted plastic polymer, reaction catalyst, and coke.

[0021] In some embodiments, the system may include a plug flow reactor positioned between the first separation unit and the multi-plate reactive distillation column. In such embodiments, the plug flow reactor includes a reactor inlet in fluid communication with the junction to receive the process feed stream therefrom. The plug flow reactor may also have a reactor outlet in fluid communication with the feed stream inlet of the multi-plate reactive distillation column.

[0022] In some embodiments, the system may further include a second separation unit. In some embodiments, the second separation unit is connected to and in fluid communication with the bottom stream, such that the second separation unit separates at least a portion of the coke and the reaction catalyst from the bottom stream. The type of separation unit may vary based on the desired degree of separation and / or based on certain process parameters. In some embodiments, for example, the separation unit may include at least one of the following: a ceramic filter, a metal filter, a centrifuge, or a settling tank. In some embodiments, the system may further include a recirculation stream connected to and in fluid communication with the second separation unit and the junction to return at least a portion of the process solvent and unreacted plastic polymer in the bottom stream to the junction. In some embodiments, the system may further include a supplementary stream connected to and in fluid communication with the recirculation stream to introduce supplementary process solvent and supplementary reaction catalyst therein. In such embodiments, the supplementary stream may be in fluid communication with the separated extrusion product stream.

[0023] In some embodiments, the system may include a gas-liquid contactor connected to and in fluid communication with the first reactive screw extruder. For example, the gas-liquid contactor may be designed to convert gaseous hydrogen chloride received from the first reactive screw extruder into a recyclable non-volatile product, which escapes from the depolymerization of chlorinated polymers in the mixed plastic waste within the first reactive screw extruder. In some embodiments, the system described herein may include a reboiler connected to and in fluid communication with at least a portion of the bottoms stream. In such embodiments, the reboiler may be configured to evaporate at least some of the bottoms stream to generate vapor that is reinjected onto the lower tray of the multi-tray reactive distillation column.

[0024] These and other features, aspects, and advantages of this disclosure will become apparent from the following detailed description together with the accompanying drawings, which are briefly described below. Embodiments include any combination of two, three, four, or more features or elements as set forth in this disclosure or referenced in any one or more claims, regardless of whether such features or elements are expressly combined or otherwise referenced in the specific embodiment described herein or in the claims. This disclosure is intended to be read holistically such that, unless the context of this disclosure explicitly indicates otherwise, any separable feature or element in any aspect and embodiment of this disclosure should be considered as intended to be composable. Attached Figure Description

[0025] Brief description of the attached figures

[0026] This concludes the general description of the disclosure. Reference will now be made to the accompanying drawings, which do not need to be drawn to scale.

[0027] Figure 1 is a schematic diagram of a system for treating mixed plastic waste according to an embodiment of the present disclosure, the system comprising two reactive extrusion vessels and a multi-plate reactive distillation column; and

[0028] Figure 2 is a schematic diagram of a system for treating mixed plastic waste according to an embodiment of the present disclosure, the system including two reactive extrusion vessels, a plug flow reactor and a multi-plate reactive distillation column. Detailed Implementation

[0029] The methods and systems will be described more fully below with reference to specific embodiments, and in particular the various accompanying drawings provided herein. This disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Unless the context clearly indicates otherwise, as used in the specification and the appended claims, the singular forms “a” and “the” include the plural indicators.

[0030] The disclosure herein provides embodiments of systems and methods for treating mixed plastic waste (MPW) to produce naphtha products from it. Specifically, and as will be further discussed herein, this disclosure provides a two-stage catalytic reactive distillation process for treating mixed plastic waste. Certain embodiments of the systems and methods described herein offer advantages when compared to typical thermal anaerobic conversion (TAC) processes commonly used in industry and understood by those skilled in the art for converting MPW. For example, certain embodiments of the systems and methods of this disclosure can operate in a continuous flow mode in the presence of an acidic catalyst capable of further cracking the initial decomposition products of the thermal conversion to increase the yield of naphtha-range mixed feedstocks or products. Furthermore, the systems and methods disclosed herein can utilize equipment and processes commonly found in existing refineries. Therefore, the disclosed systems and methods can be more easily integrated into existing refineries without requiring the construction of expensive stand-alone pyrolysis reactors as described above and / or the hydrotreating units that might be necessary with conventional batch processes.

[0031] Typically, the methods and systems disclosed herein efficiently provide dechlorination and depolymerization of input mixed plastic waste (e.g., using one or more reactive screw extruders) and subsequently recover a series of mixed feedstocks, including naphtha mixtures, from a multi-plate reactive distillation column. In some embodiments, the systems and methods provided herein utilize a heavy fraction (referred to as slurry supernatant) from a fluid catalytic cracking (FCC) unit as the reactive process solvent for MPW. As mentioned above, the slurry supernatant is the refractory stream leaving the FCC unit and, due to the amount recycled through the FCC unit, cannot be further converted by the catalytic cracking process. However, the slurry supernatant typically contains residual, spent FCC catalyst (e.g., in small particulate form). While spent FCC catalyst is less active than fresh FCC catalyst, it does possess some residual acidity / activity, particularly capable of promoting the catalytic cracking of MPW. In other embodiments, the reactive process solvent for the catalytic cracking of MPW can be some other high-boiling-point process solvent readily available from existing refining processes.

[0032] Figure 1 is a non-limiting schematic diagram of a system for processing mixed plastic waste 100 according to one or more embodiments of the present disclosure. As shown in Figure 1, the system includes a first reactive screw extruder 102, a second reactive screw extruder 104, and a multi-plate reactive distillation column 106. Typically, a mixed plastic waste feed comprising a variety of different plastics (each plastic consisting of one or more plastic polymers) is supplied to the first reactive screw extruder 102 through inlet 108. As used herein, “mixed plastic waste” or “MPW” refers to any waste or waste plastic or polymer material and combinations thereof. Non-limiting examples of mixed plastic waste materials include one or more combinations of the following: polypropylene (PP), polyethylene (PE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), polylactic acid (PA), acrylonitrile butadiene styrene (ABS), and / or other known plastics. In one or more embodiments, the mixed plastic waste fed into the first reactive screw extruder 102 has been classified as comprising most polyolefins, namely polyethylene and polypropylene.

[0033] In one or more other embodiments, the system as described herein may include a shredder 110 positioned upstream of the first reactive screw extruder 102. In such embodiments, the system may be designed to receive larger bales of raw mixed plastic waste broken down by the shredder to provide a more manageable feed of shredded mixed plastic waste, which may then be fed into the first reactive screw extruder 102. For example, as depicted in FIG1, the shredder 110 may include an inlet 112 positioned to receive bales 114 (or loose raw mixed plastic waste) of raw mixed plastic waste and an outlet 116 feeding shredded mixed plastic waste 118 into the first reactive screw extruder 102 via a conveyor belt 120. The general type or configuration of the shredder may vary. For example, any industrial plastic shredder or recycling machine capable of crushing or otherwise breaking down raw mixed plastic waste is suitable. Examples of suitable types of shredders include plastic shredders, plastic pelletizers, plastic grinders, blow-down grinders, waste shredders, single-rotor or multi-rotor shredders, plastic refining mills, waste treatment systems, etc. However, it should be noted that other configurations are possible, as those skilled in the art will understand. For example, given a wide range of shredder designs, dimensions, and process parameters, various shredder shapes and process functions can be implemented to achieve desired process requirements and / or desired degrees of decomposition of the original mixed plastic waste. The original mixed plastic waste comes in various sizes and shapes. Shredding produces mixtures with smaller-sized products. Typically, a shredder is capable of breaking down the original mixed plastic waste into shredded mixed plastic waste with lengths / diameters of about 100 mm or less, about 50 mm or less, about 10 mm or less, about 5 mm or less, about 4 mm or less, or about 2 mm or less.

[0034] In some embodiments, for example, the outlet 116 of the shredder may be connected to one or more additional components capable of conveying the shredded mixed plastic waste feed 118 from the outlet 116 of the shredder to the inlet 108 of the first reactive screw extruder 102. As depicted in FIG1, for example, the system may include a conveyor belt 120 positioned to receive the shredded mixed plastic waste feed 118 and convey it to the inlet 108 of the first reactive screw extruder 102. While a conveyor belt is shown in the embodiment depicted in FIG1, this is not intended to be limiting, and the specific equipment used to convey the shredded mixed plastic waste from the outlet of the shredder to the first reactive screw extruder may vary. For example, any suitable conveying technology may be used instead of the conveyor belt depicted in FIG1, including but not limited to rotary conveyors, vibrating conveyors, one or more vibrating screens, chutes, funnels, and / or any other loading or conveying system commonly used in the art.

[0035] As described above, the system includes a first reactive screw extruder 102 having an inlet 108 positioned to receive a mixed plastic waste feed (e.g., shredded mixed plastic waste feed 118) comprising a variety of different plastics, each composed of plastic polymers, and an outlet 122. The first reactive screw extruder 102 can be configured to heat the mixed plastic waste feed to a temperature sufficient to initially dechlorinate any of the chlorinated polymers in the mixed plastic waste feed. "Dechlorination" generally refers to the process of removing chlorine atoms from the chlorinated plastic polymers (e.g., polyvinyl chloride) in the mixed waste plastics as hydrogen chloride gas. Chlorine removal is necessary to reduce the formation of chlorine free radicals, which can attack organic materials and form organochlorides that can be highly corrosive to downstream equipment. Gaseous hydrogen chloride is generated during the thermal decomposition of the chlorinated polymers within the first reactive extruder, where such thermal decomposition is entropy-driven. The temperature sufficient to initiate dechlorination can vary, for example, based on the type of plastic / polymer in the mixed plastic waste feed. In some embodiments, for example, the temperature within the first reactive screw extruder can be sufficient to substantially remove all chlorine from chlorine-based compounds in the mixed plastic waste. In some embodiments, the temperature sufficient to initiate dechlorination of any chlorine-containing polymer among the various plastic polymers can be between about 300°C and about 350°C, between about 300°C and about 325°C, between about 310°C and about 340°C, or between about 320°C and about 330°C. In some embodiments, the temperature sufficient to initiate dechlorination of any chlorine-containing polymer among the various plastic polymers can be about 350°C or lower, about 340°C or lower, about 330°C or lower, about 320°C or lower, or about 310°C or lower. After dechlorination, the chlorine content or concentration of the mixed plastic waste exiting the first reactive screw extruder can be less than 50 ppm, less than 40 ppm, less than 30 ppm, less than 25 ppm, less than 29 ppm, less than 10 ppm, or even less. Therefore, dechlorinated mixed plastic waste can contain less than about 25 ppm of chlorine, less than about 10 ppm of chlorine, or even less than about 5 ppm of chlorine.

[0036] The overall configuration of the first reactive screw extruder may vary. For example, in some embodiments, the first reactive screw extruder may be in the form of a single-screw extruder, or in other embodiments, it may be in the form of a twin-screw extruder. However, it should be noted that, as those skilled in the art will understand, other configurations are also possible. For example, given a wide range of screw and barrel designs, dimensions, and process parameters, various screw profiles and process functions can be implemented to achieve desired process requirements and / or desired initial depolymerization levels.

[0037] In one or more embodiments, the system of this disclosure may optionally include a gas-liquid contactor 124 (e.g., as depicted in FIG. 1) connected to and in fluid communication with the first reactive screw extruder 102 via a gas outlet 126 to mitigate gaseous hydrogen chloride that may be generated from the depolymerization of any chlorinated polymers (such as any polyvinyl chloride plastic) in the mixed plastic waste. A vacuum may be applied to the first reactive screw extruder 102 to vent released gaseous hydrogen chloride to the gas-liquid contactor 124. In another embodiment, nitrogen or other inert gas may be passed through the first reactive screw extruder 102 to sweep gaseous hydrogen chloride to the gas-liquid contactor 124. As known to those skilled in the art, polyvinyl chloride depolymerizes into gaseous hydrogen chloride and hydrocarbon polymers between about 285°C and 300°C. In some embodiments, the gas-liquid contactor 124 may be designed to convert gaseous hydrogen chloride received from the gas outlet 126 of the first reactive screw extruder 102 into a non-volatile product, which can be recovered from the gas-liquid contactor 124 via the gas-liquid contactor outlet 128. For example, the gas-liquid contactor may include an aqueous alkali capable of reacting with hydrogen chloride gas escaping from the first reactive screw extruder, thereby producing a recoverable non-volatile product, such as sodium chloride. The aqueous alkali can be added to the gas-liquid contactor 124 via a spray inlet 130. However, in one or more embodiments, in addition to adding the aqueous alkali via the spray inlet 130 of the gas-liquid contactor 124, or alternatively, at least a portion of the aqueous alkali can be added directly to the first reactive screw extruder 102 via an alkali inlet 132. As described above, gaseous hydrogen chloride escapes in the first reactive screw extruder from the depolymerization of chlorinated polymers in the mixed plastic waste (e.g., the depolymerization of PVC and other chlorinated polymers releases unwanted hydrogen chloride gas). In one or more embodiments, a solid alkali (e.g., potassium hydroxide, sodium hydroxide, or a combination of both), instead of the aqueous alkali described above, may be added to the first reactive screw extruder 102. In some embodiments, the solid alkali becomes a molten salt at temperatures below 200°C. The solid alkali reacts with chlorine released through the thermal decomposition of the chlorinated polymers to form potassium chloride or sodium chloride.

[0038] In one or more embodiments, the system of this disclosure may include a first extrusion product stream 134 connected to and in fluid communication with the outlet 122 of the first reactive screw extruder 102 to receive extruded products therefrom. As shown in FIG1, the system includes a second reactive screw extruder 104 having an inlet 136 into which dechlorinated mixed plastic waste (e.g., via the first extrusion product stream 134) is supplied, and an outlet 138 therefrom. The second reactive screw extruder 104 may be configured to heat the dechlorinated mixed plastic waste to a temperature sufficient to initially depolymerize a portion of the various plastic polymers in the mixed plastic waste. “Depolymerization” generally refers to the process of converting one or more polymers into a single monomer or a mixture of monomers, wherein this process is entropy-driven. For example, the tendency of a single polymer to depolymerize is indicated by its upper limit temperature; and above the respective upper limit temperature of each polymer, the depolymerization rate is greater than the polymerization rate, which inhibits the formation of a given polymer. Therefore, the temperature sufficient to cause initial thermal depolymerization can vary, for example, based on the type of plastic / polymer in the mixed plastic waste feed. In some embodiments, for example, the temperature within the second reactive screw extruder may be sufficient to convert multiple polymers in the mixed plastic waste into oligomers with a nominal molecular weight range of about 1,000 Daltons to about 20,000 Daltons, or about 5,000 Daltons to about 10,000 Daltons. In some embodiments, the temperature sufficient to initially depolymerize a portion of the plastic polymer may be between about 300°C and about 450°C, between about 325°C and about 425°C, or between about 350°C and about 400°C. In some embodiments, the temperature sufficient to initially depolymerize a portion of the plastic polymer may be at least about 300°C, at least about 350°C, at least about 400°C, or higher.

[0039] In addition to operating at elevated temperatures, the second reactive screw extruder 104 can also operate at non-atmospheric pressures. For example, the second reactive screw extruder can operate at elevated pressures generated within the second reactive screw extruder itself. In some embodiments, the pressure within the second reactive screw extruder can be between about 1 bar and about 100 bar, between about 20 bar and about 80 bar, or between about 40 bar and about 60 bar. In some embodiments, the pressure within the second reactive screw extruder can be at least about 1 bar, at least about 20 bar, at least about 40 bar, at least about 60 bar, at least about 80 bar, or higher. Conversely, the second reactive screw extruder can operate under a vacuum (e.g., pressures below atmospheric pressure). Under a vacuum, the second reactive screw extruder can operate at temperatures lower than those described above because, in a reduced-pressure environment, at least a portion of the initial depolymerization of the plastic polymer occurs at lower temperatures.

[0040] The overall configuration of the second reactive screw extruder may vary. In some embodiments, the second reactive screw extruder 104 may be in the form of a single-screw extruder, or in other embodiments, it may be in the form of a twin-screw extruder. However, it should be noted that, as those skilled in the art will understand, other configurations are also possible. For example, given a wide range of screw and barrel designs, dimensions, and process parameters, various screw profiles and process functions can be implemented to achieve desired process requirements and / or desired initial depolymerization levels.

[0041] In some embodiments, one or more compounds may be introduced into the second reactive screw extruder 104 along with the dechlorinated mixed plastic waste through reactor inlet 140 to promote depolymerization and / or minimize free radical formation during the initial depolymerization of the various plastic polymers in the mixed plastic waste feed, thereby reducing the formation of heavier hydrocarbon products and increasing downstream naphtha yield. In some embodiments, for example, a hydrogen donor solvent may be added to the second reactive screw extruder through said reactor inlet 140. "Hydrogen donor solvent" refers to any hydrocarbon solvent capable of transferring hydrogen to a hydrogen-poor matrix. The use of hydrogen donor solvents is particularly beneficial in stabilizing free radicals formed during depolymerization and producing higher product conversion yields. For example, adding a hydrogen donor solvent to the second reactive screw extruder can transfer hydrogen from the hydrogen donor solvent to free radical compounds generated during the initial depolymerization of the various plastic polymers in the mixed plastic waste.

[0042] Non-limiting examples of hydrogen donor solvents include subcritical and supercritical water, alcohols, decahydronaphthalene, glycerol, and tetrahydronaphthalene (e.g., 1,2,3,4-tetrahydronaphthalene). In some embodiments, the hydrogen donor solvent may include tetrahydronaphthalene. The amount of hydrogen donor solvent introduced into the second reactive screw extruder can vary. In some embodiments, the amount of hydrogen donor solvent can range from about 1% to about 10% by weight, or from about 2.5% to about 7.5% by weight, based on the total weight of the mixed plastic waste. In some embodiments, the amount of hydrogen donor solvent can be at least about 1%, at least about 2.5%, at least about 5%, or at least about 7.5% by weight, based on the total weight of the mixed plastic waste. Adding tetrahydronaphthalene to the second reactive screw extruder will generate an increase in pressure therein, which can be up to 550 psi. Therefore, the amount of tetrahydronaphthalene added must be selected to ensure that the pressure within the second reactive screw extruder does not exceed the design parameters.

[0043] In some embodiments, hydrogen can be used instead of a hydrogen donor solvent to stabilize free radical fragments of the polymer that may arise during initial depolymerization. Similar to the hydrogen donor solvent, using hydrogen to stabilize the free radical components reduces free radical recombination and thereby produces higher quality products, such as reduced olefins. In such embodiments, hydrogen can be added to the second reactive screw extruder through the reactor inlet 140 or separately through another inlet located within the second reactive screw extruder. In one or more embodiments, hydrogen is fed into the second reactive screw extruder at elevated pressures, such as above atmospheric pressure. In some embodiments, hydrogen is fed into the second reactive screw extruder at pressures of about 500 psig to about 1000 psig.

[0044] In some embodiments, a transition metal catalyst may be added to the reactive screw extruder in addition to or as an alternative to a hydrogen donor solvent and / or hydrogen. The type of transition metal catalyst may vary. For example, in some embodiments, the transition metal catalyst may include molybdenum octanoate or molybdenum naphthenate. The transition metal catalyst may be added directly to the second reactive screw extruder through reactor inlet 140. However, in some embodiments, the transition metal catalyst may be added separately to the second reactive screw extruder, for example, by positioning another inlet in the second reactive screw extruder. In some embodiments, the amount of transition metal catalyst added to the MPW feed ranges from about 100 to about 2,000 ppm of metal in the mixed plastic waste, from about 500 ppm to about 1,500 ppm, or from about 750 ppm to about 1,250 ppm. In some embodiments, the transition metal catalyst may be added to the MPW feed in amounts of at least about 100 ppm, at least about 500 ppm, at least about 1,000 ppm, at least about 1,500 ppm, or more than the amount in the mixed plastic waste. The role of the catalyst is to lower the temperature at which the mixed plastic waste undergoes initial depolymerization in the second reactive screw extruder.

[0045] In one or more embodiments, the sulfur-containing compound may be added together with the transition metal catalyst. In such embodiments, the sulfur-containing compound will sulfide the transition metal catalyst to obtain the desired form of the transition metal catalyst. For example, in some embodiments where the catalyst is molybdenum-based, the sulfur-containing compound will react with the molybdenum-based catalyst at a relatively low temperature to form MoS2. The type of sulfur-containing compound is not intended to be limiting and may include any sulfur-containing compound that will enhance catalyst activity, as will be understood by those skilled in the art. In some embodiments, for example, the sulfur-containing compound is a butyl sulfide. In such embodiments, the sulfur-containing compound may be added to the second reactive screw extruder through said reactor inlet 138 or separately through another inlet located in the second reactive screw extruder.

[0046] In one or more embodiments, the system of this disclosure may include a second extrusion product stream 142 connected to and in fluid communication with the outlet 138 of the second reactive screw extruder 104 to receive a second extrusion product therefrom.

[0047] In some embodiments, the system may include a first separation unit 144 connected to and in fluid communication with the second extruded product stream 142. In such embodiments, the first separation unit 144 may be configured to separate solid material from the second extruded product, which is recovered via a solids outlet stream 146. The second extruded product stream 142 has a viscosity similar to or slightly higher than that of water at the temperature of the stream. In one or more embodiments, a solvent may be added to the second extruded product to reduce its viscosity before it is introduced into the first separation unit 144. The mixed plastic waste bales 114 shredded in the shredder 110 may contain up to 10 percent non-plastic solid waste material. Therefore, the first separation unit 144 is required to separate the non-plastic solid material from the extracted product.

[0048] In one or more embodiments, the system may include a separated extruded product stream 148 connected to an outlet of a first separation unit 144 and a first inlet of a junction 150 and in fluid communication between the outlet and the first inlet, allowing the separated extruded product to flow from the first separation unit 144 to the junction 150. In some embodiments, the junction 150 may also have a second inlet receiving a recirculated stream 152 of process solvent and reaction catalyst (e.g., recycled process solvent, reaction catalyst, and fresh / replenished solvent and / or catalyst). The junction 150 is configured to combine and / or mix the separated extruded product stream entering therethrough the first inlet with the recirculated stream 152 of process solvent and reaction catalyst entering through the second inlet to form or define a process feed stream 154.

[0049] The type of process solvent used may vary depending on the system utilized. In some embodiments, the process solvent may include slurry supernatant / slurry or some other recycled / waste stream from one or more FCC processes within the refinery. In some embodiments, the process solvent may include one or more of the following: carbon black oil, heavy catalytic cycle oil, vacuum gas oil (which may be hydrotreated or unhydrotreated), or any hydrocarbon with a boiling range of about 300°C to about 565°C. For example, in some embodiments, the process solvent may be a mixture of carbon black oil, heavy catalytic cycle oil (slurry), and / or vacuum gas oil. In one embodiment, the process solvent is a medium-cut heavy catalytic cycle oil having a boiling range of about 300°C to about 565°C. In some embodiments, the process solvent is medium-cut carbon black oil having a boiling range of about 300°C to about 565°C. In other embodiments, the process solvent is vacuum gas oil having a boiling range of about 300°C to about 565°C. The mid-cut of the catalytic cycle oil, carbon black oil, and / or vacuum gas oil ensures that the process solvent is heavy enough to prevent distillation and separation from the desired naphtha blend feedstock, but also light enough to have a reduced asphaltenes content and mitigate coke formation. In one or more embodiments, the heavy catalytic cycle oil used in the systems and methods disclosed herein is prepared by filtering solids (primarily catalyst) from carbon black oil leaving the FCC unit, taking a mid-cut of the heavy catalytic cycle oil (i.e., the portion having a boiling point range of about 300°C to about 565°C), and then adding the filtered solids (i.e., catalyst) back into the mid-cut heavy catalytic cycle oil. It should be noted that the process solvent added to the mixed plastic waste typically contains a sulfur content ranging from about 0.5 wt% to about 1.5 wt%, such that the process solvent can also provide a hydrogen component when combined with the mixed plastic waste.

[0050] As described herein, the reaction catalyst can be mixed with the separated extrusion product stream and the process solvent. In some embodiments, the reaction catalyst may already be present in the process solvent (e.g., in the form of spent FCC catalyst in the process solvent), and / or additional / fresh reaction catalyst may be added to the process solvent and the separated extrusion product stream 148. In some embodiments, the reaction catalyst may be a core-shell catalyst having an active catalyst shell disposed on a non-porous core support. In some embodiments, for example, the active catalyst shell may have a diameter of about 5 to about 50 μm. 2 / g surface area. In some embodiments, the reaction catalyst may include a solid acid catalyst, such as a silica-alumina cracking catalyst. In some embodiments, the reaction catalyst may include a silica support on which a silica-alumina active catalyst layer with a thickness of less than 10 nanometers is disposed. In some embodiments, the reaction catalyst may be a zirconium oxide sulfate catalyst or a calcium sulfate-supported trimetaphosphoric acid catalyst. In other embodiments, the reaction catalyst may be a microporous cracking catalyst, such as ZSM-5, or other microporous catalysts with a higher surface area. In one or more embodiments, ZSM-5 may be a balanced catalyst comprising nickel and vanadium (ECAT). ECAT is available from FCC units or third-party suppliers at a lower cost than fresh ZSM-5 catalyst. It should be noted that the listed reaction catalysts are not intended to be limiting, and any reaction catalyst commonly used in catalytic cracking processes is suitable for the methods and systems provided herein.

[0051] The amount of reactive catalyst present in the process feed stream can vary based on the amount of spent catalyst present in the process solvent and / or based on the amount of fresh catalyst or replenishment process solvent added thereto. In some embodiments, for example, based on the total weight of the process feed stream, the reactive catalyst may be present in an amount of about 1% to about 10% by weight, about 2% to about 8% by weight, or about 4% to about 6% by weight. In some embodiments, based on the total weight of the mixed extrusion products, the reactive catalyst may be present in an amount of at least about 2% by weight, at least about 4% by weight, at least about 6% by weight, at least about 8% by weight, or higher.

[0052] As described above, the system includes a multi-plate reactive distillation column 106 having a feed inlet 156 connected to and in fluid communication with the process feed stream 154 containing separated mixed plastic waste, process solvents, and reaction catalysts. Although only one feed inlet is shown in the embodiment depicted in Figure 1, it should be noted that more than one feed inlet may be present. Therefore, in some embodiments, the feed inlet 156 may be positioned near the top portion of the multi-plate reactive distillation column, and a second feed inlet (e.g., also connected to and in fluid communication with the process feed stream) may be positioned at a height below the feed inlet 156.

[0053] Distillation columns are commonly used in commercial refining applications and catalytic cracking processes. In such applications, a feed stream can be fed into the distillation column, and the separated fractions of the feed stream can be continuously removed from the distillation column via one or more outlet streams. In some applications, the liquid feed stream can be separated into individual fractions by selective evaporation and / or condensation to remove the output fractions from the column. While the arrangement and / or configuration of multi-plate reactive distillation columns can vary, the multi-plate reactive distillation columns of one or more embodiments described herein can include a column (or tower) in the form of an external metal shell containing two or more trays at different pressures and temperatures, and therefore each tray has a different vapor-liquid equilibrium. For example, the temperature and pressure within a multi-plate reactive distillation column are typically highest near the bottom of the column and lowest near the top. The presence of two or more trays in a multi-tray reactive distillation column allows for the separation of different fractions of hydrocarbons based on their boiling points (e.g., heavier to lighter fractions from the bottom to the top of the column), enabling the separated fractions to be individually (or within a boiling point range) cracked and removed from the column by side-dip / flow. Lighter hydrocarbon fractions (e.g., naphtha) can be removed in the upper section of the column, while heavier hydrocarbon fractions travel downwards in the column, where further cracking occurs to break down those heavier hydrocarbons into lighter molecular weight hydrocarbons. The number of trays in a multi-tray reactive distillation column can vary and can include at least 2 trays, at least 3 trays, at least 4 trays, at least 5 trays, at least 6 trays, at least 7 trays, at least 8 trays, or more trays. In some embodiments, the number of trays in a multi-tray reactive distillation column may include at least 20 trays, at least 40 trays, at least 60 trays, at least 80 trays, at least 100 trays or more.

[0054] In some embodiments, the multi-plate reactive distillation column 106 can be configured to provide countercurrent and at least partially depolymerized plastic polymer vapors of the process feed stream 154 (i.e., comprising extruded products, process solvents, and reactive catalysts) within the multi-plate reactive distillation column. For example, the hot vapors generated by the catalytic cracking and depolymerization of various plastic polymers in the process feed stream 154 travel upward in the multi-plate reactive distillation column, while the process solvent, the heavier uncracked plastic polymers, and the reactive catalyst move downward through the column, countercurrent to the upward hot vapor stream. When lighter hydrocarbon fractions are formed, they volatilize and pass upward through the multi-plate reactive distillation column as hot vapors. In some embodiments, the lighter vapors rise through the multi-plate reactive distillation column and can be drawn off as a liquid stream boiling in the naphtha hydrocarbon range (e.g., C5–225°C) on the upper or middle plates, thereby eliminating the heavy tailing characteristics of most pyrolysis oil streams. Advantageously, the use of countercurrent allows heavier, uncracked plastic polymers and hydrocarbon fractions boiling above the naphtha hydrocarbon range to move downwards in the multi-plate reactive distillation column and react further with the reactive catalyst until they can be cracked, with a portion recovered as naphtha as described above. As disclosed above, process solvents are selected to reduce their quantity, which are carried upwards through the column and into various product / mixed feedstock side streams. However, depending on the process solvent used (e.g., vacuum gas oil), the process solvent itself can be at least partially distilled, producing naphtha and other mixed feedstocks / products, which are then separated through various side streams. Unreacted oligomers, process solvents, reactive catalysts, and char / coke are allowed to exit from the bottom of the multi-plate reactive distillation column, where these materials can be separated, recovered, and reintroduced into the process and / or sent to other processes. By providing countercurrent within a multi-plate reactive distillation column, significant depolymerization and improved naphtha yield can be achieved (e.g., providing approximately 99.6% product yield compared to approximately 0.4% coke produced).

[0055] In some embodiments, multi-plate reactive distillation columns can be operated under vacuum to increase naphtha volatilization during the depolymerization of mixed extrusion products. Therefore, multi-plate reactive distillation columns can be operated at pressures significantly lower than atmospheric pressure (i.e., vacuum pressure). Operating multi-plate reactive distillation columns under vacuum pressure can be particularly advantageous because it allows for the distillation / separation of compounds at lower temperatures than are necessary to distill / separate the same compounds at higher pressures. Lower operating temperatures also facilitate greater separation of uncracked compounds. Typically, heavier hydrocarbons are retained in multi-plate reactive distillation columns (i.e., not extracted from them by side pumping) because they have extremely high boiling points (e.g., 750°C or higher) and cannot be cracked under typical atmospheric distillation units. Therefore, operating multi-plate reactive distillation columns under vacuum lowers the temperatures required to boil these heavier fractions, thereby increasing the overall process yield.

[0056] In one or more embodiments, stripping steam or stripping hydrogen may also be injected into the near-bottom portion of a multi-plate reactive distillation column. In such embodiments, the multi-plate reactive distillation column may include one or more stripping gas injection ports located near its bottom portion. In some embodiments, injecting a stripping stream (e.g., composed of steam or hydrogen) near the bottom portion of a multi-plate reactive distillation column can improve process yield because it reduces the partial pressure of hydrocarbons within the various plastic polymers, allowing for additional evaporation of the heavier hydrocarbons. For example, introducing a stripping stream near the bottom of a multi-plate reactive distillation column can further heat the flow of various plastic polymers in the process feed stream, thereby allowing the recovery of lighter hydrocarbons when they are converted to the gas phase.

[0057] Typically, a multi-plate reactive distillation column includes multiple side streams or side draws connected thereto. As shown in Figure 1, for example, a first side stream 158 may be arranged to draw naphtha from the multi-plate reactive distillation column 106. In other embodiments, a multi-plate reactive distillation column may include one or more additional side streams arranged to draw naphtha and / or other distillates from the multi-plate reactive distillation column. For example, the multi-plate reactive distillation column 106 may include a second side stream 160 arranged to draw naphtha or another distillate product stream from the multi-plate reactive distillation column. It should be noted that the precise arrangement of the multiple side streams and / or their orientation relative to the multiple plates within the reactive distillation column can vary based on the desired product stream (e.g., based on boiling range), the composition of the mixed extruded product feed stream, and / or the operating conditions of the reactive distillation column. Furthermore, the throughput or capacity of the systems and methods disclosed herein can be scaled as desired by changing the dimensions of the multi-plate reactive distillation column 106.

[0058] As described above, at least a portion of the various plastic polymers in the mixed extrusion product may initially not react completely with the reactive catalyst (e.g., to achieve complete depolymerization and recovery as naphtha or some other desired distillate), and such unreacted polymers can be recovered via the bottom stream and circulated within the system. As shown in FIG1, the system 100 may include a bottom stream 162 connected to and in fluid communication with the bottom portion of the multi-plate reactive distillation column 106. In some embodiments, the bottom stream 162 may be configured to receive a stream from the multi-plate reactive distillation column comprising process solvents and / or unreacted plastic polymers and / or reactive catalysts and / or coke / coke formed on the catalyst. In some embodiments, the bottom stream 162 may optionally include a second junction 164 that directs at least a portion of the stream of the bottom stream 162 to one or more additional components (e.g., reboilers and / or separation units).

[0059] As shown in Figure 1, the system 100 may optionally include a reboiler 166 connected to and in fluid communication with the second junction 164 via a first stream of bottoms stream 168. In such embodiments, the reboiler 166 may be configured to evaporate at least a portion of the first stream of the bottoms stream 168 to generate vapor, which is then reinjected into the lower tray of the multi-tray reactive distillation column 106 via an inlet side stream 170 positioned near the bottom of the column. It should be noted that reinjecting heated vapor from the reboiler can benefit from providing additional heat near the bottom of the multi-tray reactive distillation column, which can facilitate further depolymerization of unreacted plastic polymers and lead to a more efficient process. Generally, as those skilled in the art will understand, the type of reboiler used in the systems described herein can vary. In one or more embodiments, the type of reboiler may vary based on the characteristics of the first stream of bottoms stream flowing into the reboiler (e.g., density, boiling point, etc.). In some embodiments, for example, the reboiler may be a combustion reboiler / heater that functions as a heat exchanger. In such embodiments, the combustion reboiler may include a pump that circulates a first stream of bottoms through heat transfer tubes in the reboiler to evaporate the first stream of bottoms before reinjecting it into a multi-plate reactive distillation column. Other non-limiting examples of reboilers that may be used in the systems described herein include, but are not limited to, kettle reboilers, forced circulation reboilers, thermosiphon reboilers, etc.

[0060] In some embodiments, the system 100 may further include a condenser 172 connected to and in fluid communication with the multi-plate reactive distillation column 106 via a condenser inlet 174 positioned near the top portion of the column. Typically, the condenser 174 may be configured to remove heat from the multi-plate reactive distillation column 106 by condensation, and specifically, may be used to remove additional heat introduced into the system via the reboiler 166. For example, heated vapors entering the condenser are converted to liquid in the condenser, thereby removing latent heat from the multi-plate reactive distillation column. In addition to removing excess heat from the multi-plate reactive distillation column, the condenser may also recover light fractions (e.g., lighter hydrocarbon vapors with boiling points below the naphtha hydrocarbon range) via a first condenser outlet stream 176, allowing these lighter hydrocarbon vapors to exit the condenser as a condensed liquid stream. In some embodiments, the system may include a second condenser outlet stream 178 connected to a condenser configured to recover even lighter fractions (e.g., light distillate hydrocarbon vapors with boiling points even lower than those recovered in the first condenser outlet stream 176). Similarly, unrecovered cooled liquid may be reintroduced into a multi-plate reactive distillation column to regulate heat within the column by a condenser inlet side stream 180 positioned near the top portion of the multi-plate reactive distillation column 106. Generally, as those skilled in the art will understand, the type of condenser used in the systems described herein can vary. For example, non-limiting examples of condensers suitable for use with the systems disclosed herein may include, but are not limited to, air-cooled condensers, water-cooled condensers, evaporative condensers, indirect contact condensers, direct contact condensers, two-tube condensers, shell and coil condensers, tubular condensers, etc.

[0061] In one or more embodiments, the system may optionally include a second separation unit 182. As shown in FIG1, the system includes a second separation unit 182 connected to and in fluid communication with the second junction 164 via a second stream of bottoms stream 184, such that the separation unit separates at least a portion of the reaction catalyst and the coke produced in the distillation column from the bottoms stream. The coke and reaction catalyst recovered from the second stream of the bottoms stream 184 can be removed from the second separation unit 182 via an outlet 188. The remaining portion of the reaction in the second stream of the bottoms stream (i.e., the portion not separated by the second separation unit 182) becomes a recirculation stream 152, which is connected to the second separation unit 182 and the junction 150 and is in fluid communication between the second separation unit and the junction. At least a portion of the reaction catalyst separated by the second separation unit 282 can be further separated from the coke and reintroduced into the recirculation stream 252 for reuse. As those skilled in the art will understand, the type of separation unit can vary based on the desired degree of separation and / or based on certain process parameters. In one or more embodiments, the separation unit may include, but is not limited to, at least one of the following: ceramic filter, metal filter, centrifuge, and settling tank.

[0062] In some embodiments, the system may further include a third stream of the bottom stream 152, which is connected to and in fluid communication with the second junction 164, which is connected to the bottom stream 162. As shown in FIG1, the system 100 includes a third stream 190 of the bottom stream, which is connected to and in fluid communication with the second junction 164, which is combined with the recirculation stream 152 to return at least a portion of the process solvent and unreacted plastic polymer in the bottom stream to the separated extrusion product stream 148 through the first junction 150.

[0063] In one or more embodiments, the system may further include a makeup stream that provides additional process solvent and / or reaction catalyst to a third stream of the recirculation stream and the bottoms stream. As shown in FIG1, the system includes a makeup stream 192 connected to and in fluid communication with the recirculation stream 152 and the third stream 190 of the bottoms stream to introduce additional process solvent and additional reaction catalyst therein as desired. In such embodiments, the makeup stream 192, the recirculation stream 152, and the third stream 190 of the bottoms stream may all be in fluid communication with the first junction 150 to deliver process solvent, reaction catalyst, and unreacted plastic polymer to the separated extrusion product stream 148. It should be noted that the makeup stream may be designed to provide fresh process solvent and catalyst, and / or may be designed to provide used process solvent or catalyst that may have been recovered from one or more processes within the refinery (e.g., slurry containing spent FCC catalyst from an FCC unit). In one or more embodiments, the additional process solvent and / or reaction catalyst may include any process solvent or reaction catalyst discussed herein. In at least some embodiments, one or more of the supplemental stream 192, the recirculated stream 152, and / or the third stream 190 of the bottoms stream can be hydrogenated with hydrocarbons in these streams by a hydrogenation processor (not shown) positioned upstream of the first junction 150. Such hydrogenation can enhance the stabilizing effect of the process solvent with respect to any free radicals that may be present in the separated extrusion product stream 148 when mixed at the first junction 150.

[0064] This document also discloses further embodiments of systems and methods for treating mixed plastic waste, which can be incorporated into one or more devices described above and one or more additional devices. Figure 2 depicts another embodiment of a system for treating mixed plastic waste, the system comprising a first reactive screw extruder 202, a second reactive screw extruder 204, and a multi-plate reactive distillation column 206. A mixed plastic waste feed is supplied to the first reactive screw extruder 202 through inlet 208. The mixed plastic waste feed comprises a variety of different plastics, each composed of a plastic polymer, as described above with respect to the embodiment shown in Figure 1.

[0065] Turning now to Figure 2, in one or more embodiments, the system may include a shredder 220 positioned upstream of the first reactive screw extruder 202. For example, as depicted in Figure 2, the shredder 210 may include an inlet 212 positioned to receive raw mixed plastic waste bales 214 (or loose raw mixed plastic waste) and an outlet 216 that feeds shredded mixed plastic waste 218 to the inlet 208 of the first reactive screw extruder 202 via a conveyor belt 220. The general type or configuration of the shredder may vary as described above with respect to the embodiments depicted in Figure 1. Referring back to Figure 2, in some embodiments, the outlet 216 of the shredder may be connected to one or more additional components capable of conveying the shredded mixed plastic waste feed 218 from the outlet 216 of the shredder to the inlet 208 of the first reactive screw extruder 202. As depicted in Figure 2, for example, the system may include a conveyor belt 220 positioned to receive the shredded mixed plastic waste feed 218 and convey it to the inlet 208 of the first reactive screw extruder 202. While a conveyor belt is shown in the embodiment depicted in Figure 2, this is not intended to be limiting, and the specific equipment used to convey the shredded mixed plastic waste from the shredder outlet to the first reactive screw extruder can vary. For example, any suitable conveying technology can be used in place of the conveyor belt depicted in Figure 2, including but not limited to rotary conveyors, vibrating conveyors, one or more vibrating screens, chutes, funnels, and / or any other loading or conveying system commonly used in the art.

[0066] As shown in Figure 2, some embodiments include a first reactive screw extruder 202 having an inlet 208 positioned to receive a mixed plastic waste feed (e.g., the shredded mixed plastic waste feed 218 described above), the mixed plastic waste feed comprising a variety of different plastics, each composed of plastic polymers, and an outlet 222. The first reactive screw extruder 202 can be configured to heat the mixed plastic waste feed to a temperature sufficient to initially dechlorinate any chlorinated polymers among the various plastic polymers in the mixed plastic waste feed. Chlorine removal is necessary to reduce the formation of chlorine free radicals, which can attack organic materials and form organochlorides, which can be highly corrosive to downstream equipment. The overall configuration of the first reactive screw extruder and the process conditions used therein (e.g., temperature, pressure, etc.) are similar to those described above with respect to the first reactive screw extruder in Figure 1.

[0067] In one or more embodiments, the system may optionally include a gas-liquid contactor 224 (e.g., as depicted in FIG. 2) connected to and in fluid communication with the first reactive screw extruder 202 via a gas outlet 226 to mitigate gaseous hydrogen chloride that may arise from the depolymerization of any polyvinyl chloride or other chlorinated plastics in the mixed plastic waste. In some embodiments, the gas-liquid contactor 224 may be designed to convert gaseous hydrogen chloride received from the gas outlet 226 of the first reactive screw extruder 202 into a non-volatile product that can be recovered from the gas-liquid contactor 224 via the gas-liquid contactor outlet 228. For example, the gas-liquid contactor may include an aqueous alkali capable of reacting with hydrogen chloride gas escaping from the first reactive screw extruder, thereby producing a recyclable non-volatile product, such as sodium chloride. Typically, the aqueous alkali is added to the gas-liquid contactor 224 via a spray inlet 230. However, in one or more embodiments, in addition to or as an alternative to adding aqueous alkali through the spray inlet 230 in the gas-liquid contactor 224, at least a portion of the aqueous alkali can be directly added to the first reactive screw extruder 202 through the alkali inlet 232. As described above, gaseous hydrogen chloride escapes from the depolymerization of chlorinated polymers in the mixed plastic waste in the first reactive screw extruder. (For example, the depolymerization of PVC and other chlorinated polymers releases hydrogen chloride gas, which is undesirable). In one or more embodiments, a solid alkali (e.g., potassium hydroxide, sodium hydroxide, or a combination of both) can be added to the first reactive screw extruder 202 instead of the aqueous alkali described above. The solid alkali becomes a molten salt below 200°C but reacts with chlorine released through the thermal decomposition of the chlorinated polymers to form potassium chloride or sodium chloride.

[0068] In one or more embodiments, the system may include a first extrusion product stream 234 connected to and in fluid communication with the outlet 222 of the first reactive screw extruder 202 to receive extruded products therefrom. As shown in FIG2, the system includes a second reactive screw extruder 204 having an inlet 236 into which dechlorinated mixed plastic waste (e.g., via the first extrusion product stream 234) is supplied, and an outlet 238 therefrom. The second reactive screw extruder 204 may be configured to heat the dechlorinated mixed plastic waste to a temperature sufficient to initially depolymerize a portion of the various plastic polymers in the mixed plastic waste. The overall configuration of the second reactive screw extruder and the process conditions used therein (e.g., temperature, pressure, etc.) are similar to those described above with respect to the second reactive screw extruder of FIG1.

[0069] In some embodiments, one or more compounds may be introduced together with the dechlorinated mixed plastic waste through reactor inlet 240 into the second reactive screw extruder 204 to promote depolymerization and / or minimize free radical formation during the initial depolymerization of multiple plastic polymers in the mixed plastic waste feed, thereby reducing the formation of heavier hydrocarbon products and increasing downstream naphtha yield. For example, any compound used in the initial depolymerization step involving the second reactive screw extruder of Figure 1 is suitable for the second reactive screw extruder of Figure 2. Such compounds include, but are not limited to, hydrogen donor solvents, hydrogen, transition metal catalysts, sulfur-containing compounds, and combinations thereof.

[0070] As depicted in Figure 2, the system may include a second extruded product stream 242 connected to and in fluid communication with the outlet 238 of the second reactive screw extruder 204 to receive a second extruded product therefrom. The second extruded product stream 242 may have a viscosity similar to or slightly higher than that of water. In one or more embodiments, a solvent may be added to the second extruded product to reduce its viscosity before it is introduced into the first separation unit 244.

[0071] As described, the system may include a first separation unit 244 connected to and in fluid communication with the second extruded product stream 242. In such embodiments, the first separation unit 244 may be configured to separate solid material from the second extruded product, which is recovered through a solids outlet stream 246. As previously described, the mixed plastic waste bale 214 shredded in the shredder 210 may contain up to 10 percent non-plastic solid waste material. Therefore, the first separation unit 244 is required to separate non-plastic solid material from the extracted product.

[0072] In one or more embodiments, the system of this disclosure may include a separated extrusion product stream 248 connected to an outlet of a first separation unit 244 and a first inlet of a junction 250 and in fluid communication between the outlet and the first inlet, allowing the separated extrusion product to flow from the first separation unit 244 to the junction 250. In some embodiments, the junction 250 may also have a second inlet receiving a recirculated stream 252 of process solvent and reaction catalyst (e.g., recycled process solvent, reaction catalyst, and fresh / replenished solvent and / or catalyst). The junction 250 is configured to combine and / or mix the separated extrusion product streams entering therethrough through the second inlet to form or define a process feed stream 254. The process solvent and reaction catalyst used are similar to those described above with respect to the embodiments shown in FIG1.

[0073] As shown in Figure 2, in one or more embodiments, the system may include a plug flow reactor 255 positioned between the first separation unit 244 and the multi-plate reactive distillation column 206. The plug flow reactor 255 has a reactor inlet 257 connected to and in fluid communication with the process feed stream 254, and also has a reactor outlet 259. Although only one feed stream is shown in the embodiment depicted in Figure 2, it should be noted that more than one feed stream may exist. The plug flow reactor 255 may be configured to heat the process feed stream to a temperature sufficient to further depolymerize another portion of the various plastic polymers in the mixed plastic waste. The temperature sufficient to cause further thermal depolymerization can vary, for example, based on the type of plastic / polymer in the process feed stream. In some embodiments, for example, the temperature within the plug flow reactor may be sufficient to convert the various polymers in the mixed plastic waste into oligomers with a nominal molecular weight range of about 1,000 Daltons to about 20,000 Daltons, or about 5,000 Daltons to about 10,000 Daltons. In some embodiments, the slug reactor can operate at elevated temperatures and / or at non-atmospheric pressures. The amount of depolymerization achieved within the slug reactor is directly related to the residence time of the process feed stream within the reactor. In some embodiments, the residence time can be from about 10 minutes to about 2 hours, or from about 30 minutes to about 1 hour. In some embodiments, the residence time within the slug reactor is at least about 10 minutes, at least about 20 minutes, at least about 30 minutes, at least about 40 minutes, or at least about 1 hour. In one embodiment, the residence time of the process feed stream within the slug reactor is about 30 minutes at a temperature ranging from 425°C to 450°C.

[0074] The overall configuration of a slug flow reactor can vary. For example, in some embodiments, the slug flow reactor may be in the form of a tubular slug flow reactor. In other embodiments, the reactor designated as a slug flow reactor may not be an actual slug flow reactor, but another reactor type, such as a continuous tubular reactor (CTR), a continuous stirred tank reactor (CSTR), etc. However, it should be noted that, as those skilled in the art will understand, other configurations are also possible. For example, given a wide range of slug flow and other reactor designs, sizes, and process parameters, various reactor shapes and process functions can be implemented to achieve desired process requirements and / or desired degrees of depolymerization.

[0075] As described above, the system includes a multi-plate reactive distillation column 206 having a feed inlet 256 connected to and in fluid communication with the reactor outlet 259 to receive the reactor product outlet stream 263. In embodiments where the plug flow reactor 255 is absent, bypassed, or otherwise not implemented, the process feed stream 254 is connected to and in fluid communication with the feed inlet 256. Although only one feed inlet is shown in the embodiment depicted in Figure 1, it should be noted that more than one feed inlet may be present. Thus, in some embodiments, the feed inlet 256 may be positioned near the top portion of the multi-plate reactive distillation column, and another feed inlet (e.g., also connected to and in fluid communication with the reactor product outlet stream) may be positioned at a height below the feed inlet 256. Typically, the arrangement and / or configuration of the multi-plate reactive distillation column can vary. Typically, a multi-plate reactive distillation column of one or more embodiments described herein may comprise a column (or tower) in the form of an external metal shell containing two or more trays at different pressures and temperatures, and thus each tray having a different vapor-liquid equilibrium. For example, the temperature and pressure within a multi-plate reactive distillation column are typically highest near the bottom and lowest near the top. The presence of two or more trays within a multi-plate reactive distillation column allows for the separation of different fractions of hydrocarbons (e.g., heavier to lighter fractions from the bottom to the top of the column) based on their boiling points, such that the separated fractions can be individually (or within a boiling point range) cracked and removed from the column by side-dip / flow. Lighter hydrocarbon fractions (e.g., naphtha) can be removed in the upper portion of the column, while heavier hydrocarbon fractions travel downwards within the column, where further cracking occurs to break down those heavier hydrocarbons into lighter molecular weight hydrocarbons. The number of trays in a multi-tray reactive distillation column can vary and may include at least 2 trays, at least 3 trays, at least 4 trays, at least 5 trays, at least 6 trays, at least 7 trays, at least 8 trays, or more trays. In some embodiments, the number of trays in a multi-tray reactive distillation column may include at least 20 trays, at least 40 trays, at least 60 trays, at least 80 trays, at least 100 trays, or more trays. Without being bound by theory, it should be noted that using a slug flow reactor in the embodiment depicted in Figure 2 can advantageously reduce the required size of the multi-tray distillation column and / or the amount of time required to operate the multi-tray reactive distillation column. For example, because the slug flow reactor provides a certain amount of further depolymerization of the various plastic polymers in the mixed plastic waste, less depolymerization is required in a multi-tray reactive distillation column to recover the desired product (e.g., naphtha).

[0076] As described above, the multi-plate reactive distillation column 206 is typically configured to provide countercurrent flow of the reactor product outlet stream 263 (i.e., comprising separated extruded products, process solvents, and reaction catalysts) and at least partially depolymerized plastic polymer vapors within the multi-plate reactive distillation column. In embodiments where the plug flow reactor 255 is absent, the multi-plate reactive distillation column 206 is configured to provide countercurrent flow of the process feed stream 254. Hot vapors generated from the catalytic cracking and depolymerization of the various plastic polymers in the reactor product outlet stream 263 (or process feed stream 254) travel upwards within the multi-plate reactive distillation column, while the process solvent, heavier uncracked plastic polymers, and reaction catalysts move downwards through the column, countercurrent to the upward hot vapor stream. When lighter hydrocarbon fractions are formed, they volatilize and pass upwards as hot vapors through the multi-plate reactive distillation column. In some embodiments, lighter vapors rise through a multi-plate reactive distillation column and can be drawn off as a liquid stream boiling in the naphtha hydrocarbon range (e.g., C5–225°C) on the upper or middle plates, thereby eliminating the heavy tailing characteristic of most pyrolysis oil streams. Advantageously, the use of countercurrent allows heavier, uncracked plastic polymers and hydrocarbon fractions boiling above the naphtha hydrocarbon range to move downwards in the multi-plate reactive distillation column and react further with the reactive catalyst until they can be cracked, with a portion recovered as naphtha as described above. As disclosed above, process solvents are selected to reduce the amount of process solvent, which is carried upwards through the column and into various product / mixed feedstock side streams. However, depending on the process solvent used (e.g., vacuum gas oil), the process solvent itself can be at least partially distilled, producing naphtha and other mixed feedstocks / products, and separated through various side streams. Unreacted oligomers, process solvents, reactive catalysts, and coke / coke are allowed to exit the bottom of the multi-plate reactive distillation column, where these materials can be separated, recovered, and reintroduced into the process and / or sent to other processes. By providing countercurrent within the multi-plate reactive distillation column, significant depolymerization and improved naphtha yields can be achieved (e.g., providing approximately 99.6% product yield compared to approximately 0.4% coke produced).

[0077] Typically, a multi-plate reactive distillation column includes multiple side streams or side draws connected thereto. As shown in Figure 2, for example, a first side stream 258 may be arranged to draw naphtha from the multi-plate reactive distillation column 206. In other embodiments, a multi-plate reactive distillation column may include one or more additional side streams arranged to draw naphtha and / or other distillates from the multi-plate reactive distillation column. For example, the multi-plate reactive distillation column 206 may include a second side stream 260 arranged to draw naphtha or another distillate product stream from the multi-plate reactive distillation column. It should be noted that the precise arrangement of the multiple side streams and / or their orientation relative to the multiple trays within the reactive distillation column can vary based on the desired product stream (e.g., based on boiling range), the composition of the mixed extruded product feed stream, and / or the operating conditions of the reactive distillation column. Furthermore, the throughput or capacity of the systems and methods disclosed herein can be scaled as desired by changing the diameter of the multi-plate reactive distillation column 206.

[0078] As described above, a portion of the various plastic polymers entering the feed inlet 256 of the multi-plate reactive distillation column 206 (i.e., through the reactor product outlet stream 263 if the slug reactor 255 is present, or through the process feed stream 254 if the slug reactor is absent) may not react completely with the reactive catalyst in the column 206 (e.g., to achieve complete depolymerization and recovery as naphtha or some other desired distillate) at least in the first pass. Unreacted polymers can be recovered via the bottom stream 262 and recycled within the system. As shown in FIG2, the system 200 includes a bottom stream 262 connected to and in fluid communication with the multi-plate reactive distillation column 206 near its bottom portion. In some embodiments, the bottom stream 262 may be configured to receive streams from the multi-plate reactive distillation column comprising process solvents and / or unreacted plastic polymers and / or reactive catalysts and / or coke / coke formed on the catalyst. In some embodiments, the bottom stream 262 may optionally include a second junction 264 that directs at least a portion of the stream of the bottom stream 262 to one or more additional components (e.g., the plug flow reactor 255 and / or the second separation unit 282).

[0079] As shown in Figure 2, in some embodiments, the system 200 may include a pump 275 and a heat exchanger 277 positioned between a multi-plate reactive distillation column and the second junction 264 and in fluid communication with the bottom stream 262. In such embodiments, the pump 275 may be configured to pump the bottom stream 262 to the heat exchanger 277. The type and capacity of the pump may vary based on the desired operating capacity of the multi-plate reactive distillation column. It should be noted that the use of a heat exchanger may be used to heat the bottom stream 262, which is then combined with the process feed stream 254 at the second junction 264 before being fed into the plug flow reactor 255. Such a configuration may be beneficial in providing additional heat to the process feed stream fed into the plug flow reactor, which may facilitate further depolymerization of unreacted plastic polymers and result in a more efficient process. Generally, as those skilled in the art will understand, the type of heat exchanger used in the systems described herein may vary. In one or more embodiments, the type of heat exchanger may vary based on the characteristics of the bottom stream flowing into the heat exchanger (e.g., density, boiling point, etc.). As shown in Figure 2, for example, the heat exchanger 277 is connected to the pump 275, which circulates the bottom stream through heat transfer tubes in the heat exchanger to heat the bottom stream, and then combines the bottom stream with the process feed stream and feeds it into the plug flow reactor 255.

[0080] In some embodiments, the system 200 may further include a condenser 272 connected to and in fluid communication with the multi-plate reactive distillation column 206 via a condenser inlet 274 located near the top portion of the multi-plate reactive distillation column 206. Typically, the condenser 272 may be configured to remove heat from the multi-plate reactive distillation column 274 by condensation. For example, heated vapors entering the condenser are converted to liquid in the condenser, thereby removing latent heat from the multi-plate reactive distillation column. In addition to removing excess heat from the multi-plate distillation column, the condenser may also recover light fractions (e.g., lighter hydrocarbon vapors with boiling points below the naphtha hydrocarbon range) through a first condenser outlet stream 276, allowing these lighter hydrocarbon vapors to be recovered as a condensed liquid stream leaving the condenser. In some embodiments, the system may include a second condenser outlet stream 278 connected to the condenser 272, the condenser being configured to recover even lighter fractions (e.g., light distillate hydrocarbon vapors with boiling points even lower than those recovered in the first condenser outlet stream 276). Similarly, unrecovered cooled liquid may be reintroduced into a multi-plate reactive distillation column to regulate heat within the column via a condenser inlet side stream 280 positioned near the top portion of the multi-plate reactive distillation column 206. Generally, as those skilled in the art will understand, and as described above with respect to Figure 1, the type of condenser used in the systems described herein can vary.

[0081] In one or more embodiments, the system may optionally include a second separation unit 282. As shown in FIG2, the system includes a second separation unit 282 connected to and in fluid communication with the second junction 264 via a second stream 284 of the bottoms stream, such that the second separation unit separates at least a portion of the reaction catalyst and the coke produced in the multi-plate reactive distillation column from the second stream of the bottoms stream. The coke and reaction catalyst recovered from the second stream 284 of the bottoms stream can be removed from the second separation unit 282 via an outlet 288. The remaining portion of the second stream of the bottoms stream (i.e., the portion not separated by the second separation unit 282) becomes a recirculation stream 252, which is connected to the second separation unit 282 and the first junction 250 and is in fluid communication between the second separation unit and the junction. At least a portion of the reaction catalyst separated by the second separation unit 282 can be further separated from the coke and reintroduced into the recirculation stream 252 for reuse. As will be understood by those skilled in the art and incorporated herein by reference, the type of separation unit may vary based on the desired degree of separation and / or on certain process parameters.

[0082] In one or more embodiments, the system may further include a replenishment stream that provides additional process solvent and / or reaction catalyst to the recycling stream. As shown in FIG2, the system includes a replenishment stream 292 connected to and in fluid communication with the recycling stream 252 to introduce supplementary process solvent and supplementary reaction catalyst therein as desired. In such embodiments, the replenishment stream 292 and the recycling stream 252 are combined to deliver process solvent, reaction catalyst, and unreacted plastic polymer through the first junction 250 to the separated extrusion product stream 248. It should be noted that the replenishment stream may be designed to provide fresh process solvent and catalyst, and / or may be designed to provide used process solvent or catalyst that may have been recovered from one or more processes within the refinery (e.g., slurry containing spent FCC catalyst from an FCC unit). In one or more embodiments, the supplementary process solvent and / or reaction catalyst may include any process solvent or reaction catalyst discussed herein.

[0083] As described above, some embodiments provide methods for treating mixed plastic waste, the methods comprising converting the mixed plastic waste into pyrolysis oil and catalytically cracking the pyrolysis oil to recover naphtha mixed feedstocks and / or other products therefrom. In one or more embodiments, such methods include introducing mixed plastic waste (e.g., mixed plastic waste comprising multiple plastic polymers) into a first reactive extrusion vessel, the first reactive extrusion vessel being maintained at an elevated temperature sufficient to initially dechlorinate the chlorinated plastic polymers contained therein. As described herein, the first reactive extrusion vessel may be in the form of a reactive screw extruder (e.g., a single-screw extruder or a twin-screw extruder). However, other types of extrusion vessels are also possible, as will be understood by those skilled in the art or as described above. In some embodiments, the first reactive extrusion vessel may be operated at a temperature sufficient to initially dechlorinate multiple plastic polymers in the mixed plastic waste. For example, in some embodiments, the temperature range sufficient to initially dechlorinate a portion of the plastic polymers may be about 300°C to about 350°C, about 310°C to about 340°C, or about 320°C to about 330°C. In some embodiments, the temperature sufficient to initially depolymerize a portion of the plastic polymer may be about 350°C or lower, about 340°C or lower, about 330°C or lower, about 320°C or lower, or about 310°C or lower.

[0084] In some embodiments, the methods disclosed herein may provide additional steps for breaking down the undisturbed mixed plastic waste package (or a single quantity of the undisturbed mixed plastic waste) into smaller, more manageable sizes. For example, in one or more embodiments, such a method may optionally include feeding the undisturbed mixed plastic waste package (or a quantity of the undisturbed mixed plastic waste) into a shredder before introducing the mixed plastic waste into a first reactive extrusion vessel. In such embodiments, the shredder may be positioned to shred the undisturbed mixed plastic waste to provide shredded mixed plastic waste. As described herein, the average length / diameter of the shredded mixed plastic waste may be about 100 mm or less, about 50 mm or less, about 10 mm or less, about 5 mm or less, about 4 mm or less, or about 2 mm or less.

[0085] In one or more embodiments, hydrogen chloride gas escaping from the initial dechlorination of any chlorinated polymers in the mixed plastic waste can be fed into a gas-liquid contactor containing an aqueous alkali before the dechlorinated mixed plastic waste is delivered to a second reactive extrusion vessel. In such embodiments, the hydrogen chloride gas can react with the aqueous alkali in the gas-liquid contactor to produce a non-volatile product (e.g., NaCl). The specific configuration of the gas-liquid contactor and / or the type of alkali contained therein can vary as described above and as will be understood by those skilled in the art. As described herein, in some embodiments of the method, at least a portion of the aqueous alkali can be added directly to the first reactive extrusion vessel to react with the hydrogen chloride gas generated during the initial dechlorination of the various plastic polymers in the mixed plastic waste.

[0086] In one or more embodiments, the disclosed method includes introducing a dechlorinated mixed plastic waste from a first reactive screw extrusion vessel (e.g., comprising multiple plastic polymers) into a second reactive extrusion vessel, the second reactive extrusion vessel being maintained at an elevated temperature sufficient to decompose the higher molecular weight polymers therein. As described herein, the second reactive extrusion vessel may be in the form of a reactive screw extruder (e.g., a single-screw extruder or a twin-screw extruder). However, other types of extrusion vessels are also possible, as will be understood by those skilled in the art or as described above. In some embodiments, the second reactive extrusion vessel may be operated at a temperature sufficient to initially depolymerize a portion of the multiple plastic polymers in the mixed plastic waste. For example, as described above, the temperature within the second reactive screw extruder may be sufficient to convert at least a portion of the polymers in the mixed plastic waste into oligomers with a nominal molecular weight range of about 1,000 Daltons to about 20,000 Daltons, or about 5,000 Daltons to about 10,000 Daltons. In some embodiments, the temperature sufficient to initially depolymerize a portion of the plastic polymer can be between about 400°C and about 450°C, about 410°C to about 440°C, or about 420°C to about 430°C. In some embodiments, the temperature sufficient to initially depolymerize a portion of the plastic polymer can be at least about 400°C, at least about 420°C, at least about 440°C, or higher.

[0087] In some embodiments, in addition to the dechlorinated mixed plastic waste, the method may further include introducing one or more compounds into a second reactive extrusion vessel to promote the depolymerization of the dechlorinated mixed plastic waste and increase naphtha yield during the process. In some embodiments, a hydrogen donor solvent may be added to the second reactive extrusion vessel (e.g., including the mixed plastic waste therein) to transfer hydrogen from the hydrogen donor solvent to radical compounds generated during the initial depolymerization of the various plastic polymers in the mixed plastic waste. The addition of hydrogen to the radical compounds reduces the formation of heavier hydrocarbon products and increases naphtha yield. It should be understood that specific hydrogen donor solvents are not intended to be limiting, and any hydrogen donor solvent discussed above is applicable to the disclosed methods. In other embodiments, gaseous hydrogen, a transition metal catalyst, and a sulfur-containing compound may be added to the second reactive extrusion vessel to transfer hydrogen from the gaseous hydrogen to radical compounds generated during the initial depolymerization of the various plastic polymers in the mixed plastic waste. The addition of hydrogen reduces the formation of heavier hydrocarbon products and increases naphtha yield. The specific transition metal catalyst and / or sulfur-containing compound can vary. In some embodiments, for example, the transition metal catalyst may comprise molybdenum octanoate or molybdenum naphthenate, and the sulfur-containing compound may comprise butyl sulfide. However, it should be understood that the specific transition metal catalyst and / or sulfur-containing compound is not intended to be limiting, and any transition metal catalyst and / or sulfur-containing compound discussed herein is intended to be suitable for the disclosed methods.

[0088] Following initial depolymerization, the extruded product (e.g., partially depolymerized plastic polymer) exiting the second reactive extrusion vessel is mixed with a high-boiling solvent and a reaction catalyst, and the combined mixture is fed into a multi-plate reactive distillation column, where the partially depolymerized product undergoes further depolymerization in the presence of the reaction catalyst. Specific process solvents and / or reaction catalysts may vary, and it should be understood that any process solvent and / or reaction catalyst described above with respect to the system of this disclosure is applicable to these methods. In some embodiments, the process solvent may include one or more of the following: carbon black oil, heavy catalytic cycle oil, vacuum gas oil, or any hydrocarbon stream boiling in the range of about 300°C to about 565°C. In some embodiments, the reaction catalyst may be a silica-alumina cracking catalyst and / or any other reaction catalyst described herein. Furthermore, based on the total weight of the process feed stream, the reaction catalyst may be present in an amount of about 1% to about 10% by weight, about 2% to about 8% by weight, or about 4% to about 6% by weight. In some embodiments, the reaction catalyst may be present in an amount of at least about 2%, at least about 4%, at least about 6%, at least about 8%, or higher by weight, based on the total weight of the mixed extrusion products.

[0089] After the extruded product is mixed with the process solvent and the reaction catalyst, the process feed stream can be fed into a multi-plate reactive distillation column. The specific configuration of the multi-plate reactive distillation column can vary, and it should be understood that any multi-plate reactive distillation column as described above is suitable for these methods. In one or more embodiments, the process feed stream is fed through the feed stream inlet onto the trays of the multi-plate reactive distillation column. In such embodiments, the multi-plate reactive distillation column can be designed to promote further depolymerization of at least another portion of the various plastic polymers in the process feed stream in the presence of the reaction catalyst. In some embodiments, for example, the multi-plate reactive distillation column can provide the process feed stream countercurrent downwards through the column and provide at least partially depolymerized plastic polymer vapor upwards through the column, thereby increasing naphtha yield.

[0090] In one or more embodiments, the method includes removing distillate via one or more distillate sidestreams connected to the multi-plate reactive distillation column. As described herein, the location and / or configuration of one or more distillate sidestreams can vary as desired based on the product to be recovered and the arrangement of the multi-plate reactive distillation column. In some embodiments, at least one of the distillate sidestreams can be configured to recover naphtha stream from the multi-plate reactive distillation column. In some embodiments, the multi-plate reactive distillation column may include one or more additional distillate sidestreams configured to recover naphtha or other mixed feedstocks or products therefrom. In addition to one or more distillate sidestreams, the multi-plate reactive distillation column may include a bottom stream connected to the bottom portion of the multi-plate reactive distillation column, the bottom stream being designed to remove the process solvent, unreacted plastic polymers, reactive catalysts, and / or coke / coke stream therefrom.

[0091] As described above, in some embodiments, the bottom stream can be separated into one or more separate streams, for example, which can be individually connected to and in fluid communication with one or more other components (e.g., reboilers and / or separation units and / or recirculation streams). Typically, at least a portion of the reactive catalyst and coke can be separated from the bottom stream, for example, using one or more filters configured to receive streams from the bottom stream (e.g., using separation units). In some embodiments, at least a portion of the process solvent and the unreacted plastic polymer in the bottom stream can be recovered and returned to the process for mixing with the extruded product exiting the reactive extrusion vessel. In other embodiments, the disclosed method may include passing at least a portion of the bottom stream into a reboiler to evaporate at least some of the bottom stream for reinjection into the multi-plate reactive distillation column.

[0092] As described herein and illustrated in Figure 2, some embodiments of the methods disclosed herein may include feeding the extruded product into a plug flow reactor positioned upstream of a multi-plate reactive distillation column. In such embodiments, the plug flow reactor may be operated to produce a reactor product outlet stream at a time and temperature sufficient to further depolymerize at least a second portion of the various plastic polymers in the extruded product, in the presence of a reactive catalyst. The reactor product outlet stream may then be fed into a multi-plate reactive distillation column, such that the reactor product outlet stream is fed onto the plates of the multi-plate reactive distillation column. In one or more embodiments, the time and temperature sufficient to depolymerize at least a second portion of the various polymers in the extruded product is from about 30 minutes to about 60 minutes and from about 400°C to about 450°C. In some embodiments, thermogravimetric analysis (TGA) data show that, for polyolefins, initial decomposition begins at about 400°C, while for polystyrene, initial decomposition begins at about 325°C. Except for PVC, most polymers begin to decompose below about 325°C. Furthermore, it should be noted that the use of a plug flow reactor can advantageously reduce the required size of a multi-plate distillation column and / or the amount of time required to operate a multi-plate reactive distillation column. For example, because the plug flow reactor provides a certain amount of further depolymerization of the various plastic polymers in the mixed plastic waste, less depolymerization is required in a multi-plate reactive distillation column to recover the desired product (e.g., naphtha).

[0093] When ranges are disclosed herein, a range beginning with any lower bound can be combined with any upper bound to enumerate ranges not explicitly listed, and a range beginning with any lower bound can be combined with any other lower bound to enumerate ranges not explicitly listed, and in the same way, a range beginning with any upper bound can be combined with any other upper bound to enumerate ranges not explicitly listed. Furthermore, references to values ​​within a range include every value within that range, even if not explicitly listed. Thus, each point or individual value can serve as its own lower or upper bound, or any other lower or upper bound, combined with any other point or individual value, to enumerate ranges not explicitly listed.

[0094] Benefiting from the teachings presented in the foregoing description, those skilled in the art will conceive of numerous modifications and other embodiments set forth herein. Therefore, it should be understood that this disclosure is not intended to be limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terminology is used herein, it is for general and descriptive purposes only and not for limiting purposes.

Claims

1. A method for treating mixed plastic waste, the method comprising: A mixture of plastic waste, comprising multiple plastic polymers, is introduced into a first reactive extrusion container; The first reactive extrusion vessel is operated at a temperature sufficient to initially dechlorinate any of the chlorine-containing polymers in the plurality of plastic polymers; The mixed plastic waste is fed from the first reactive extrusion vessel into a second reactive extrusion vessel; the second reactive extrusion vessel is operated at a temperature sufficient to initially depolymerize a portion of the various plastic polymers in the mixed plastic waste to produce an extruded product; the extruded product from the second reactive extrusion vessel is mixed with a process solvent and a reaction catalyst to define a process feed stream, the process solvent being one or more of the following: carbon black oil, heavy catalytic cycle oil, vacuum gas oil, or any hydrocarbon with a boiling point range of 300°C to 565°C; the process feed stream is then fed into multiple... A tray reactive distillation column, wherein the process feed stream is fed onto the trays of the multi-tray reactive distillation column; the multi-tray reactive distillation column is operated to promote the depolymerization of at least another portion of the various plastic polymers in the process feed stream in the presence of the reactive catalyst; distillate, which includes at least naphtha, is removed by one or more distillate side streams connected to the multi-tray reactive distillation column; and the process solvent, unreacted plastic polymers, reactive catalyst, and a portion of coke are removed by a bottom stream connected to the bottom portion of the multi-tray reactive distillation column. Separate at least a portion of the reaction catalyst and the coke from the bottom stream; and return at least a portion of the process solvent and the unreacted plastic polymer in the bottom stream to mix with the extruded product leaving the reactive extrusion vessel.

2. The method of claim 1, wherein operating the multi-plate reactive distillation column includes promoting the countercurrent downward flow of the process feed stream through the multi-plate reactive distillation column, and at least partially depolymerized plastic polymer vapors flowing upward through the multi-plate reactive distillation column.

3. The method according to claim 1, further comprising: Hydrogen chloride gas released from the initial dechlorination of the chlorine-containing polymer among the various plastic polymers is passed into a gas-liquid contactor containing an aqueous alkali. And to react the hydrogen chloride gas with the aqueous alkali from the gas-liquid contactor to produce a non-volatile product.

4. The method of claim 3, further comprising: At least a portion of the aqueous alkali is added to the first reactive extrusion vessel to react with the hydrogen chloride gas generated during the initial dechlorination of the chlorine-containing polymer in the plurality of plastic polymers.

5. The method of claim 1, wherein separating at least a portion of the coke from the bottom stream is performed by filtering at least a portion of the bottom stream using a filter.

6. The method of claim 1, wherein the process solvent in the process feed stream is a combination of the process solvent returned from the bottom stream and the replenished process solvent.

7. The method of claim 6, wherein the supplemental process solvent contains a supplemental reaction catalyst that enhances the depolymerization of the plurality of plastic polymers in the mixed plastic waste.

8. The method of claim 1, further comprising: At least one of stripping steam or stripping hydrogen is injected into the portion of the multi-plate reactive distillation column near the bottom.

9. The method of claim 1, further comprising: Add a hydrogen donor solvent to the second reactive extrusion vessel containing the mixed plastic waste; And free radical compounds generated during the initial depolymerization of the various plastic polymers in the mixed plastic waste, which transfer hydrogen from the hydrogen donor solvent to the mixed plastic waste.

10. The method of claim 1, further comprising: Gaseous hydrogen, along with a transition metal catalyst and a sulfur-containing compound, is added to the second reactive extrusion vessel containing the mixed plastic waste. And free radical compounds generated during the initial depolymerization of the various plastic polymers in the mixed plastic waste, which transfer hydrogen from the gaseous hydrogen to the mixed plastic waste.

11. The method according to claim 10, wherein the transition metal catalyst is molybdenum octanoate or molybdenum naphthenate.

12. The method of claim 10, wherein the sulfur-containing compound is a butyl sulfide.

13. The method of claim 1, wherein operating the multi-plate reactive distillation column comprises operating the multi-plate reactive distillation column under vacuum to increase naphtha volatilization during the depolymerization of at least another portion of the plurality of plastic polymers.

14. The method according to claim 1, wherein the reaction catalyst is a core-shell catalyst having an active catalyst shell disposed on a non-porous core support, the active catalyst shell having a diameter of 5 to 50 μm. 2 / g of surface area.

15. The method according to claim 1, wherein the reaction catalyst comprises a silica support, and a silica-alumina active catalyst layer with a thickness of less than 10 nanometers is disposed on the silica support.

16. The method according to claim 1, wherein the reaction catalyst comprises a zirconium oxide sulfate catalyst or a calcium sulfate-supported tripyrphosphate catalyst.

17. The method according to claim 1, wherein the reaction catalyst is a microporous cracking catalyst.

18. The method according to claim 1, wherein the process solvent is a medium-cut of the heavy catalytic cycle oil having a normal boiling point range of 300°C to 565°C.

19. The method according to claim 1, wherein the process solvent is a medium-cut carbon black oil having a normal boiling point range of 300°C to 565°C.

20. The method of claim 1, further comprising: At least a portion of the bottom stream is fed into a reboiler to evaporate at least some of the bottom stream; And the evaporated bottom stream is injected into the lower plate of the reactive distillation column.

21. The method of claim 1, wherein the temperature range sufficient to initially dechlorinate any of the chlorinated polymers in the plurality of plastic polymers is 300°C to 350°C.

22. The method of claim 1, wherein the temperature range sufficient to initially depolymerize a portion of the plurality of plastic polymers in the mixed plastic waste is 400°C to 450°C.

23. The method of claim 1, wherein the pressure in the second reactive extrusion vessel ranges from 1 bar to 100 bar.

24. The method of claim 1, further comprising: The mixed plastic waste is fed into a shredder before being introduced into the first reactive extrusion vessel; And to shred the mixed plastic waste in the shredder to provide shredded mixed plastic waste.

25. The method of claim 24, wherein the average size of the shredded mixed plastic waste is 4 mm or less.

26. The method of claim 1, further comprising: The process feed stream is fed into a plug flow reactor positioned upstream of the multi-plate reactive distillation column; the plug flow reactor is operated, in the presence of the reaction catalyst, at a time and temperature sufficient to depolymerize at least a second portion of the various plastic polymers in the process feed stream to produce a reactor product outlet stream; The reactor product outlet stream is fed into the multi-plate reactive distillation column, and the reactor product outlet stream is fed onto the plates of the multi-plate reactive distillation column.

27. The method of claim 26, wherein the time and temperature range sufficient to depolymerize the at least second portion of the plurality of polymers in the process feed stream is 30 to 60 minutes and 400°C to 450°C.

28. The method of claim 1, wherein the mixed plastic waste introduced from the first reactive extrusion container has a chlorine content of less than 50 ppm.

29. The method of claim 1, wherein the mixed plastic waste exiting the first reactive extrusion container has a chlorine concentration of less than 10 ppm.

30. A system for treating mixed plastic waste, the system comprising: A first reactive screw extruder has an inlet and an outlet for receiving a mixed plastic waste having a variety of plastic polymers, and the first reactive screw extruder is configured to heat the mixed plastic waste to a temperature sufficient to initially dechlorinate any of the chlorine-containing polymers in the variety of plastic polymers; A first extrusion product stream, the first extrusion product stream being connected to and in fluid communication with the outlet of the first reactive screw extruder to receive a first extrusion product from the outlet, the first extrusion product stream comprising the mixed plastic waste; A second reactive screw extruder has an inlet and an outlet for receiving the first extruded product stream, and is configured to heat the mixed plastic waste of the first extruded product stream to a temperature sufficient to cause a portion of the various plastic polymers to initially depolymerize. A second extruded product stream, the second extruded product stream being connected to and in fluid communication with the outlet of the second reactive screw extruder, for receiving a second extruded product from the outlet; A first separation unit having an inlet and an outlet connected to and in fluid communication with the second extruded product stream, the first separation unit being configured to separate the second extruded product stream into solid material and separated extruded product, the solid material being purged from the first separation unit by a purge stream; A separated extruded product stream, the separated extruded product stream being connected to the outlet of the first separation unit and a first inlet of the junction and in fluid communication between the outlet and the first inlet, so that the separated extruded product can flow from the first separation unit to the junction, the junction having a second inlet for receiving process solvent and reaction catalyst passing through it, the junction being configured to mix the separated extruded product, the process solvent and the reaction catalyst to define a process feed stream, the process solvent being one or more of the following: carbon black oil, heavy catalytic cycle oil, vacuum gas oil or any hydrocarbon with a boiling point range of 300°C to 565°C; a multi-plate reactive distillation column having a feed stream inlet for receiving the process feed stream from the junction; Multiple side streams are connected to and in fluid communication with the multi-plate reactive distillation column, and at least one of the multiple side streams is arranged to extract naphtha from the multi-plate reactive distillation column. The bottom stream is connected to and in fluid communication with the multi-plate reactive distillation column near its bottom portion, and the bottom stream contains the process solvent, unreacted plastic polymer, the reaction catalyst, and coke. A second separation unit is connected to and in fluid communication with the bottom stream of the column, and the second separation unit is configured to separate at least a portion of the coke and the reaction catalyst from the bottom stream of the column; And a recirculation stream, which is connected between the second separation unit and the second inlet of the junction and is in fluid communication between the second separation unit and the second inlet, to return at least a portion of the process solvent and unreacted plastic polymer in the bottom stream to the junction.

31. The system of claim 30, wherein the first reactive screw extruder is a single-screw extruder or a twin-screw extruder.

32. The system of claim 30, wherein the second reactive screw extruder is a single-screw extruder or a twin-screw extruder.

33. The system of claim 30, wherein the reaction catalyst is selected from the group consisting of: microporous cracking catalysts, silica-alumina silica-supported catalysts having an active catalyst layer of less than 10 nanometers, zirconium oxide sulfate catalysts, and calcium sulfate-supported trimetaphosphoric acid catalysts.

34. The system of claim 30, further comprising: A supplementary flow, which is connected to and in fluid communication with the recirculation flow to introduce supplementary process solvents and supplementary reaction catalysts therein, is in fluid communication with the junction.

35. The system of claim 30, wherein the process solvent is a medium-cut of the heavy catalytic cycle oil having a normal boiling point range of 300°C to 565°C.

36. The system of claim 30, wherein the process solvent is a medium-cut carbon black oil having a normal boiling point range of 300°C to 565°C.

37. The system of claim 30, wherein the multi-plate reactive distillation column has one or more stripping gas injection ports disposed near its bottom portion.

38. The system of claim 30, wherein the first separation unit is at least one of the following: a ceramic filter, a metal filter, a centrifuge, or a settling tank.

39. The system of claim 30, wherein the second separation unit is at least one of the following: a ceramic filter, a metal filter, a centrifuge, or a settling tank.

40. The system of claim 30, further comprising: A gas-liquid contactor is connected to and in fluid communication with the first reactive screw extruder, the gas-liquid contactor being configured to convert gaseous hydrogen chloride received from the first reactive screw extruder into a recyclable non-volatile product, the gaseous hydrogen chloride escaping from the dechlorination of chlorinated polymers in the mixed plastic waste within the first reactive screw extruder.

41. The system of claim 30, further comprising: A reboiler connected to and in fluid communication with at least a portion of the bottom stream, the reboiler being configured to evaporate at least some of the bottom stream and generate vapor for re-injection onto the lower tray of the multi-tray reactive distillation column.

42. The system of claim 30, wherein the feed inlet is located near the top portion of the multi-plate reactive distillation column.

43. The system of claim 42, wherein the multi-plate reactive distillation column has a second feed inlet in fluid communication with the junction, the second feed inlet being positioned at a certain height below the feed inlet.

44. The system of claim 30, further comprising: A shredder is positioned upstream of the first reactive screw extruder, the shredder having an inlet and an outlet for receiving raw mixed plastic waste bales, the shredder being operable to shred the raw mixed plastic waste bales and provide shredded mixed plastic waste through the outlet.

45. The system of claim 44, wherein the average size of the shredded mixed plastic waste is 4 mm or less.

46. ​​The system of claim 30, further comprising: A slug reactor, positioned between the junction and the multi-plate reactive distillation column, the slug reactor having a reactor inlet in fluid communication with the junction to receive the process feed stream therefrom, and a reactor product outlet in fluid communication with the feed stream inlet of the multi-plate reactive distillation column.

47. A method for treating mixed plastic waste, the method comprising: Mixed plastic waste containing multiple plastic polymers is introduced into a first reactive screw extruder; The first reactive screw extruder is operated at a temperature sufficient to initially dechlorinate any of the chlorinated polymers in the plurality of plastic polymers, the temperature range being 300°C to 350°C; the mixed plastic waste is fed into a second reactive screw extruder; a hydrogen donor solvent or gaseous hydrogen and a transition metal catalyst are added to the second reactive screw extruder containing the mixed plastic waste; the second reactive screw extruder is operated at a temperature sufficient to initially depolymerize a portion of the plurality of plastic polymers in the mixed plastic waste, the temperature range being 400°C to 450°C; a residence time is provided for the mixed plastic waste within the second reactive screw extruder to allow hydrogen to transfer from the gaseous hydrogen or hydrogen donor solvent to free radical compounds generated during the initial depolymerization of the portion of the plurality of plastic polymers in the mixed plastic waste, to produce an extruded product; solid material is separated from the extruded product exiting the second reactive screw extruder to provide a purified extruded product; The purified extrusion product is mixed with a process solvent and a reactive catalyst to define a process feed stream, the process solvent being one or more of the following: carbon black oil, heavy catalytic cycle oil, vacuum gas oil, or any hydrocarbon boiling in the range of 300°C to 565°C; the process feed stream is fed into a reactive distillation column, the process feed stream being fed onto the trays of the reactive distillation column; the reactive distillation column is operated to promote the depolymerization of at least another portion of the plurality of plastic polymers in the presence of the reactive catalyst; the distillate, at least naphtha, is removed from the reactive distillation column by one or more distillate side streams connected to the reactive distillation column; the process solvent, unreacted plastic polymers, reactive catalyst, and coke are removed from the bottom stream by a stream connected to the bottom portion of the reactive distillation column; at least a portion of the reactive catalyst and the coke are separated from the bottom stream. At least a portion of the process solvent and the unreacted plastic polymer in the bottom stream of the column is returned to mix with the extruded product in the process feed stream, thereby circulating the process solvent through the reactive distillation column and between its outlet and inlet; and supplementary process solvent is added to the circulated process solvent.

48. The method according to claim 47, wherein the reaction catalyst comprises a silica support, and a silica-alumina active catalyst layer with a thickness of less than 10 nanometers is disposed on the silica support.

49. The method of claim 47, wherein the reaction catalyst comprises a zirconium oxide sulfate catalyst or a calcium sulfate-supported tripyrphosphate catalyst.

50. The method of claim 47, wherein the reaction catalyst is a microporous cracking catalyst.

51. The method of claim 47, wherein the process solvent is a medium-cut carbon black oil having a normal boiling point range of 300°C to 565°C.

52. The method of claim 47, wherein the process solvent is a medium-cut of the heavy catalytic cycle oil having a normal boiling point range of 300°C to 565°C.

53. The method of claim 47, further comprising: At least one of stripping steam or stripping hydrogen is injected into a portion of the reactive distillation column near the bottom.

54. The method of claim 47, wherein the hydrogen donor solvent contains tetrahydronaphthalene.

55. The method of claim 47, wherein operating the reactive distillation column comprises operating the reactive distillation column under vacuum to increase naphtha volatilization during the depolymerization of at least another portion of the plurality of plastic polymers.

56. The method of claim 47, further comprising: At least a portion of the bottom stream is passed into a reboiler to evaporate at least some of the bottom stream for re-injection into the reactive distillation column.

57. The method of claim 47, wherein the initial depolymerization of said portion of said plurality of plastic polymers in said mixed plastic waste converts higher molecular weight polymers into oligomers having a nominal molecular weight between 5,000 Daltons and 10,000 Daltons.

58. The method of claim 47, further comprising: Hydrogen chloride gas released from the initial dechlorination of any of the chlorine-containing polymers in the plurality of plastic polymers is passed into a gas-liquid contactor containing an aqueous alkali. And to react the hydrogen chloride gas with the aqueous alkali from the gas-liquid contactor to produce a non-volatile product.

59. The method of claim 58, further comprising: At least a portion of the aqueous alkali is added to the first reactive screw extruder to react with the hydrogen chloride gas generated during the initial dechlorination of any of the chlorine-containing polymers in the plurality of plastic polymers.

60. The method of claim 47, wherein the pressure in the second reactive screw extruder ranges from 1 bar to 100 bar.

61. The method of claim 47, further comprising: The mixed plastic waste is fed into a shredder before being introduced into the first reactive extrusion vessel; And operate the shredder to shred the mixed plastic waste into shredded mixed plastic waste.

62. The method of claim 61, wherein the average size of the shredded mixed plastic waste is 4 mm or less.

63. The method of claim 47, further comprising: The process feed stream is fed into a plug flow reactor positioned upstream of the reactive distillation column; the plug flow reactor is operated, in the presence of the reaction catalyst, at a time and temperature sufficient to depolymerize at least a second portion of the various plastic polymers in the process feed stream and to produce a reactor product outlet stream; The reactor product outlet stream is fed into the reactive distillation column, and the reactor product outlet stream is fed onto the trays of the reactive distillation column.

64. The method of claim 63, wherein the time and temperature range sufficient to depolymerize the at least second portion of the plurality of polymers in the process feed stream is 30 to 60 minutes and 400°C to 450°C.

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