Catalytic pyrolysis of waste plastics using acid catalysts

Abstract

Provided herein are catalytic pyrolysis processes for conversion of a plastic waste to an olefin product where at least a portion of the plastic waste is pyrolyzed in the presence of an acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter to form the olefin product comprising a liquid olefin product of C9+ olefin and a gas olefin product of C2 olefin, C3 olefin, and C4 olefin.

Description

CATALYTIC PYROLYSIS OF WASTE PLASTICS USING ACID CATALYSTCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to US Provisional Application No. 63 / 733,773 filed December 13, 2024, the disclosure of which is incorporated herein by reference.FIELD

[0002] The present disclosure relates to a catalytic process to increase olefin yield in recycling of plastic waste.BACKGROUND

[0003] There is increasing demand from society and associated policy / regulatory drivers for more circular plastics. Converting difficult-to-recycle and highly heterogeneous waste plastics into building blocks from which virgin polymers can be made is an attractive approach. The state-of-the art advanced recycling technology is thermal pyrolysis, either in a stand-alone unit or via co-processing.SUMMARY

[0004] Provided herein are catalytic pyrolysis processes for conversion of a plastic waste to an olefin product comprising the steps of introducing the plastic waste into a pyrolysis unit; and pyrolyzing at least a portion of the plastic waste in the presence of an acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter to form the olefin product comprising a liquid olefin product and a gas olefin product. The gas olefin product comprises C2 olefin, C3 olefin, and C4 olefin and the liquid olefin product comprises C9+ olefin.

[0005] Also provided are catalytic pyrolysis processes for conversion of a plastic waste to an olefin product comprising the steps of heating the plastic waste to provide a liquid plastic waste; and pyrolyzing the liquid plastic waste with an acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter to produce the olefin product comprising greater than 35 weight percent (“wt.%”) of C2-C4 olefins, less than 30 wt.% of C9+ olefins, less than 10 wt.% aromatics, and less than 5 wt.% methane.

[0006] These and other features and attributes of the present disclosure and their advantageous applications and / or uses will be apparent from the detailed description which follows.DESCRIPTION OF THE DRAWINGS

[0007] To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, wherein:

[0008] FIG. 1 is a thermal gravimetric analysis (TGA) graph showing high-density polyethylene (“HDPE”) weight loss versus temperature. Onset and completion temperatures in the presence of acid catalysts were lower than onset and completion temperatures without a catalyst indicating acid catalysts shift the pyrolysis operating temperature to a lower temperature.

[0009] FIG. 2 is a chart showing acid catalysts reduce the liquid yield from HDPE compared with thermal pyrolysis in the absence of an acid catalyst. With CHA, the C2-C4 olefins yield increases, liquids yield decreases, with only slight increases in methane, aromatics (BTX - benzene, toluene, and xylenes), and coke yield.

[0010] FIG. 3 is a chart providing olefin product distributions in wt.% from catalytic pyrolysis of HDPE in the presence of acid catalysts according to the present processes and compared with thermal process where an acid catalyst is not used.

[0011] FIG. 4 is a TGA graph showing linear low-density polyethylene (“LLDPE”) weight loss versus temperature. Onset and completion temperatures in the presence of the acid catalyst CHA were lower than onset and completion temperatures without the catalyst, indicating acid catalysts shift the pyrolysis temperature lower.

[0012] FIG. 5 is a chart showing that CHA reduces the liquid yield from LLDPE compared with thermal pyrolysis. With CHA, the C2-C4 olefins yield increases, liquids yield decreases, and with only slight increases in methane and coke yield, and lower amounts of aromatics (BTX - benzene, toluene, and xylenes).

[0013] FIG. 6 is a chart showing olefin product distributions in wt.% from catalytic pyrolysis of LLDPE in the presence of the CHA acid catalyst according to the present processes and in comparison, with thermal processes where an acid catalyst is not used.

[0014] FIG. 7 is a TGA graph showing polypropylene (“PP”) weight loss versus temperature. The onset and completion temperatures in the presence of the acid catalyst CHA were lower than the onset and completion temperatures without a catalyst, indicating acid catalysts shift the pyrolysis temperature lower.

[0015] FIG. 8 is a graph showing CHA reduces the liquid yield from PP compared with thermal pyrolysis. With CHA, the C2-C4 olefins yield increases, liquids yield decreases, and with only slight increases in coke yield, comparable amount of methane and lower aromatics (BTX - benzene, toluene, and xylenes).

[0016] FIG. 9 is a chart showing a product distribution in wt.% from a catalytic pyrolysis of PP in the presence of CHA according to the present processes and in comparison, with thermal processes where an acid catalyst is not used.DETAILED DESCRIPTION

[0017] Before the present compounds, components, compositions, and / or methods are disclosed and described, it is to be understood that unless otherwise indicated this disclosure is not limited to specific compounds, components, compositions, reactants, reaction conditions, ligands, catalyst structures, or the like, as such may vary, unless otherwise specified. It is also to be understood that the terminology used herein is for the purpose of describing different embodiments and is not intended to be limiting.

[0018] All numerical values within this detailed description and claims should be considered modified by “about” or “approximately” the indicated value to account for experimental error and variations.

[0019] For the purposes of this disclosure, the following definitions will apply:

[0020] As used herein, the terms “a” and “the” as used herein are understood to encompass the plural as well as the singular.

[0021] As provided herein, a reference to a “Cx” fraction, stream, portion, feed, or other quantity is defined as a fraction (or other quantity) where 50 wt.% or more of the fraction corresponds to hydrocarbons having “x” number of carbons. When a range is specified, such as “Cx-Cy”, 50 wt.% or more of the fraction corresponds to hydrocarbons having a number of carbons between “x” and “y”. A specification of “Cx+” (or “Cx-”) corresponds to a fraction where 50 wt.% or more of the fraction corresponds to hydrocarbons having the specified number of carbons or more (or the specified number of carbons or less).

[0022] The term “plastic waste” refers to and means any classification of consumer waste plastics, post-consumer waste and / or post-industrial waste.

[0023] As described herein, the term “polyolefin” refers to and includes high-density polyethylene (“HDPE”), low-density polyethylene (“LDPE”), linear low-density polyethylene (“LLDPE”), polyethylene (“PE”), and polypropylene (“PP”), or mixtures thereof. Polyolefin further includes co-polymers of various olefins, such as butene, hexenes, and / or any other olefins suitable for polymerization. As used herein, the term “polyolefin” further includes polyethylene terephthalate (“PET”) and polystyrene (“PS”).

[0024] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as ranges from any lower limit may be combined with any otherlower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0025] As described herein, the present processes are catalytic pyrolysis processes for conversion of a plastic waste to an olefin product. The processes include introducing the plastic waste into a pyrolysis unit and pyrolyzing at least a portion of the plastic waste in the presence of an acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter. An olefin product of a liquid olefin product and a gas olefin product are produced. The gas olefin product comprises C2 olefin, C3 olefin, and C4 olefin and the liquid olefin product comprises C9+ olefin.

[0026] In an embodiment, the plastic waste is first heated to provide a liquid plastic waste. The liquid plastic waste is pyrolyzed with the acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter. In an embodiment, the olefin product has greater than 35 wt.% C2-C4 olefins, less than 30 wt.% of C9+ olefins, less than 10 wt.% aromatics, and less than 5 wt.% methane.

[0027] Consumer waste plastics or “plastic waste” are classified and include polyethylene terephthalate waste (plastics recycle classification type 1), high density polyethylene waste (plastics recycle classification type 2), polyvinyl chloride waste (plastics recycle classification type 3), low density polyethylene waste (plastics recycle classification type 4), polypropylene waste (plastics recycle classification type 5), polystyrene waste (plastics recycle classification type 6) and other polymer waste (plastics recycle classification type 7).

[0028] As used herein, the plastic waste can be a post-consumer waste and / or a postindustrial waste. For example, the post-consumer waste includes a waste plastic, a waste rubber, a textile, modified cellulose, wet-laid products, and / or combinations thereof. In an embodiment, the plastic waste comprises at least 30 wt.% of polyethylene and / or polypropylene.

[0029] To recycle a plastic waste, a feed stream of a plastic waste (or “plastic feedstock”) is heated to a temperature that pyrolyzes the plastic feedstock under thermal pyrolysis and produces a pyrolysis plastics effluent stream. The plastic feedstock is pyrolyzed (heating in the absence of oxygen) using one or more of various pyrolysis methods including fast pyrolysis and other pyrolysis methods such as vacuum pyrolysis, slow pyrolysis, and the like. Fastpyrolysis is an intense, short duration process that can be carried out in a variety of pyrolysis reactors such as fixed bed pyrolysis reactors, fluidized bed pyrolysis reactors, circulating fluidized bed reactors, or other pyrolysis reactors capable of fast pyrolysis. Fast pyrolysis includes rapidly imparting a relatively high temperature to feedstocks for a very short residence time, typically about 0.5 seconds to about 0.5 minutes, and then rapidly reducing the temperature of the pyrolysis effluent before chemical equilibrium can occur. By this approach, the structures of polymers are broken into reactive chemical fragments that are initially formed by depolymerization and volatilization reactions, but do not persist for any significant length of time.

[0030] The heating and cooling of products produced in a pyrolysis plastic waste reactor (a reactor sometimes referred as a “pyrolyzer” or a “pyrolysis unit”) can be performed in any convenient manner. For example, at least a portion of the heating of the plastic waste feedstock to the pyrolysis temperature can be performed at a heating rate of 100°C per second or more, or 200°C per second or more, such as up to l,000°C per second or possibly still faster. WO 2020 / 252228 Al

[0033] ,

[0034] ,

[0035] and

[0038] incorporated by reference; see also, US2021 / 0130700 at ffl]

[0171] to

[0177] ,

[0031] Both operating temperature of the pyrolysis plastic waste reactor and reaction time depend in part on the desired products. Higher temperatures increase selectivity for ethylene, while lower temperatures increase selectivity for propylene. Shorter reaction times (at or above 500°C) reduce or minimize formation of coke. In an embodiment, the reaction time can correspond to 0.1 seconds to 6.0 seconds, or 0.1 seconds to 5.0 seconds, or 0.1 seconds to 1.0 seconds, or 1.0 seconds to 6.0 seconds, or 1.0 seconds to 5.0 seconds.

[0032] To control olefin partial pressure and to improve ethylene and propylene yields, a diluent steam is fed into the reactor. Steam also serves as a fluidizing gas. The weight ratio of steam to plastic feedstock can be between 0.3 : 1 to 10: 1.

[0033] Pyrolyzed plastic (“pyoil”) is then cooled to below 500°C at the end of the reaction time. An effluent stream from the pyrolysis plastic waste reactor typically includes the heat carrier particles, the diluent gas stream, a pyrolyzed product, and other products such as olefin and oil. Most notably, simpler lighter hydrocarbon molecules, including ethylene and propylene, are often generated at significant fractions within the effluent stream.

[0034] In an embodiment, the plastic feedstock is fed into a thermal cracker and heated to a temperature between 500°C and 900°C for a given reaction time. The pyrolysis plastics waste reactor melts plastic waste in a fluidized flow, or in a transport or pneumatic conveyance flow, with a dilute phase of heat carrier particles. A quasi-dense bed of plastic and heat carrierparticles undergo pyrolysis at the bottom of the pyrolysis waste plastics reactor. Gaseous pyrolyzed plastic and heat carrier particles flow upwardly upon size reduction due to pyrolysis. Alternatively, the pyrolysis plastic waste reactor can be a continuous stirred tank reactor, a rotary kiln, or an auger reactor. In an embodiment, the pyrolysis plastic waste reactor employs an agitator.

[0035] In an embodiment, the pyrolysis waste plastics reactor is a fluidized bed where the plastic feedstock is mixed with heated fluidizing particles. Sand is an example of a suitable type of fluidizing particle for the fluidized bed. During operation, sand (or another type of heat transfer particle) can be passed into a regenerator to bum off coke and heat the particles. Often additional heat is supplied in the regenerator to compensate for the coke in the process. Typically, the heated particles are mixed with the plastic waste feedstock prior to entering the reactor. By heating the heat transfer particles to a temperature above the desired pyrolysis temperature, the heat transfer particles can provide at least a portion of the heat needed to achieve the pyrolysis temperature. For example, the heat transfer particles can be heated to a temperature that is greater than the desired pyrolysis temperature by 100°C or more. Optionally, if the plastic feedstock, sand, and fluidizing steam do not provide sufficient material to form a fluidized bed, additional fluidizing gas can be added, such as additional nitrogen. However, this might cause a corresponding increase in the volume of gas flow that needs to be handled during product recovery.

[0036] Upon exiting from the pyrolysis plastic wastes reactor, the heat transfer particles are separated from the vapor portions of the effluent using a cyclone or another solid / vapor separator. Such a separator can also remove any other solids present after pyrolysis. It is noted that separation using a cyclone separator can result in an increase in N2 in the steam cracker effluent, which can make product recovery more challenging. Optionally, in addition to a cyclone or other primary solid / vapor separator, one or more filters can be included at a location downstream from the cyclone to allow for removal of fine particles that become entrained. As provided herein, the production of polymer-grade olefin fractions is most desirable. US Pub. No. 2022 / 0195309.Production of Olefin Product

[0037] In the present processes, to begin the conversion of plastic waste to an olefin product, the plastic waste is first heated and begins to melt reducing the viscosity of the plastic waste and providing a fluidized flow or a transport or pneumatic conveyance flow, sometimes with a dilute phase of heat carrier particles. The heating of a plastic waste can be performed in any convenient manner. In an embodiment, at least a portion of a plastic waste feedstock isheated at a heating rate of 100°C per second or more, or 200°C per second or more, or possibly still faster. The plastic waste is introduced into a pyrolysis unit and at least a portion of the plastic waste is pyrolyzed in the presence of an acid catalyst to form the olefin product. The pyrolysis unit operates at a temperature of 550°C or less, and at a pressure of 15 psig to 75 psig. In an embodiment the plastic waste is co-fed with 30 wt.% steam or less.

[0038] In an embodiment, as described above, the pyrolysis unit is a fluidized bed reactor, a transported bed reactor, an ablative (vortex) reactor, an extruder reactor, a microwave reactor, a fixed bed reactor, a vacuum reactor, an autoclave reactor, a rotary kiln, or a tubular reactor. Generally, the plastic waste is catalytically pyrolyzed substantially without or in the absence of oxygen.

[0039] The olefin product of the present processes includes a liquid olefin product and a gas olefin product. The gas olefin product comprises C2 olefin, C3 olefin, and C4 olefin and the liquid olefin product comprises C9+ olefin. In an embodiment, at least 45 wt.% of the olefin product is the gas olefin. In an embodiment, less than 10 wt.% of the olefin product is the liquid olefin. In an embodiment, the olefin product comprises less than 10 wt.% aromatics such as benzene, toluene, and xylenes and less than 5 wt.% of methane.

[0040] As shown in the Examples, in the present processes, pyrolysis of the plastic waste begins, as is indicated by the loss of weight in the TGA, at a temperature of at least 25°C lower than the temperature in the same process operated under the same conditions without the acid catalyst. In addition, at least 20 wt.% less of liquid olefin product is produced in comparison with an amount of liquid olefin product made in a thermal pyrolysis of the plastic waste under the same conditions. Further, in the present process, more than 10 wt.% of the gas olefin product is produced in comparison with the gas olefin product produced in a thermal pyrolysis of the plastic waste under the same conditions. Also shown, the olefin product contains greater than 35 weight percent (“wt.%”) C2-C4 olefin, less than 30 wt.% of C9+ olefin; and less than 5 wt.% coke.

[0041] In an embodiment, polyolefins are the plastic waste feedstock. Here, a particle size of the polyolefins is reduced and mixing the polyolefins with a solvent or carrier. Where the polymer waste / polyolefins are introduced into the pyrolysis reactor at least partially as solids, having a small particle size can facilitate transport of the solids into the pyrolysis reactor. Smaller particle size can potentially also contribute to achieving a desired level of conversion of the polymers / polyolefms under the short residence time conditions of the pyrolysis.

[0042] In an embodiment, the plastic waste feedstock is polyethylene (“PE”), high-density polyethylene (“HDPE”), low-density polyethylene (“LDPE”), linear low-density polyethylene(“LLDPE”) polyethylene, polyethylene terephthalate (“PET”), polypropylene (“PP”), polystyrene (“PS”) or mixtures thereof. In an embodiment, the plastic waste feedstock is substantially HDPE, linear low-density polyethylene (“LLDPE”), LDPE, PE or a mixture thereof. In an embodiment, the plastic feedstock includes at least one of polyethylene and / or polypropylene of at least 30 wt.%.

[0043] Polyethylene can be any type of polyethylene of HDPE, LLDPE, or LDPE. In addition to polyethylene and / or polypropylene, the polyolefin feedstock can optionally include one or more of polystyrene, polyvinylchloride, polyamide (e.g., nylon), polyethylene terephthalate, and ethylene vinyl acetate. Still other polyolefins can correspond to polymers (including co-polymers) of butadiene, isoprene, and isobutylene. In an embodiment, the polyethylene and polypropylene are present in the mixture as a co-polymer of ethylene and propylene. More generally, polyolefins include co-polymers of various olefins, such as ethylene, propylene, butene, hexenes, and / or any other olefins suitable for polymerization.

[0044] Unless otherwise specified, weight of polyolefin polymer in the plastic waste feedstock corresponds to weights relative to the total polymer content in the polyolefin feedstock. Any additives, modifiers, or other components included in a formulated polymer are included in this weight. However, the weight percentages described herein exclude any solvents or carriers used so that the polyolefin feedstock corresponds to a solution or slurry of polymers. For compatibility with introducing the pyrolysis product in a steam cracking process train, the polyolefin feedstock can include limited amounts of polymers different from polyethylene and / or polypropylene. In various aspects, the polyolefin feedstock for pyrolysis can include 55 wt.% to 100 wt.% of polyethylene, polypropylene, copolymer of ethylene and propylene, other C4-C6 olefins and / or dienes, or a combination thereof. In embodiments where the polyolefin feedstock corresponds to 95 wt.% or more of polymers derived from ethylene and propylene, the polyolefin feedstock can include 10 wt.% of more of ethylene monomers and 10 wt.% or more of propylene monomers.

[0045] The plastic waste can include polyvinyl chloride (“PVC”) or polyvinylidenechloride (“PVDC”). PVDC is used, for example, in blister packaging. In a further embodiment, the polyolefin feedstock does not include more than five percent PVC or PVDC. In a further embodiment, the plastic waste feedstock does not include more than about three percent PVC or PVDC. In a further embodiment, the plastic waste feedstock is no more than about two percent PVC or PVDC. In another embodiment, the plastic waste feedstock can include no more than ten percent of a condensation polymer such as a polyester, a polyamide, polyethylene terephthalate, polyamide or polyurethane.

[0046] In an embodiment, the plastic waste can further comprise additives, modifiers, packaging dyes, and / or other components typically added to a polymer during and / or after formulation. The plastic waste feedstock further includes components typically found in plastic wastes. Finally, the feedstock can include one or more solvents or carriers so that the polyolefin feedstock corresponds to a solution or slurry of the polyolefin polymers.

[0047] In an embodiment, the plastic waste feedstock can optionally include 0.1 wt.% to 1.0 wt.%, of polyvinyl chloride, polyvinylidene chloride, or a combination thereof, and / or 0.1 wt.% to 1.0 wt.% polyamide. Polyvinyl chloride is roughly 65 wt.% chlorine. As a result, pyrolysis of polyvinyl chloride (and / or polyvinylidene chloride) can result in formation of substantial amounts of hydrochloric acid relative to the initial weight of the polyvinyl chloride.

[0048] In limited amounts, the hydrochloric acid that results from pyrolysis of polyvinyl chloride and / or polyvinylidene chloride can be removed using guard beds prior to allowing the pyrolysis product to enter the steam cracking process train.

[0049] With regards to polyamide, pyrolysis results in the formation of NON. Limited amounts of NON can be handled by the steam cracking process train. In other aspects, from 0.1 wt.% to 10 wt.% of polyvinyl chloride and / or polyvinylidene chloride can optionally be included in the feed by including additional chlorine removal stages prior to combining the polyolefin pyrolysis product with the steam cracking processing train.

[0050] Pyrolyzed plastic waste, the olefin product, is then cooled to below 500°C at the end of the reaction time. An effluent stream from the pyrolysis unit typically includes the heat carrier particles, the diluent gas stream, a pyrolyzed product (olefin product), and other products such as oil. Most notably, simpler lighter hydrocarbon molecules, including ethylene and propylene, are often generated at significant fractions within the effluent stream.

[0051] A quasi-dense bed of plastic and heat carrier particles undergo pyrolysis at the bottom of the pyrolysis waste plastics reactor. Gaseous pyrolyzed plastic and heat carrier particles flow upwardly upon size reduction due to pyrolysis.

[0052] In an embodiment of the present processes, the acid catalyst is used in an amount of less than or equal to 5 wt.% (relative to the amount of the plastic waste) or less than or equal to 10 wt.%, less than or equal to 15 wt.%, less than or equal to 25 wt.%, or less than or equal to 50 wt.%.Acid Catalysts

[0053] As described below, the pyrolysis process requires less than or equal to 50 wt.% acid catalyst where at least one catalyst is the acid catalyst having a pore opening between 0.3 nm and less than 0.45 nm in diameter.

[0054] The use of the acid catalyst reduces the pyrolysis temperature of the plastic wastes and impacts the product distribution. However, using the acid catalyst promotes the formation of aromatics, methane and coke each of which are undesirable. In the case when the acid catalyst is a microporous material such as a zeolite or silicoaluminophosphate, increased yield of aromatics, coke and methane at the expense of C2 - C4 olefin. Surprisingly, when the microporous acid catalyst has pore openings in the range between 0.3 nm and less than 0.45 nm, the C2-C4 yield increases while only a slight increase in methane and coke are observed. Increasing C2-C4 yield is highly desired in the recycling of plastic wastes.

[0055] As provided herein, the acid catalyst is a microporous material. In an embodiment, the zeolite is an 8-ring zeolite or zeolitic material. In an embodiment, the acid catalyst is a small pore size zeolite (8R) comprising between 0.3 nm and less than 0.45 nm micropores. In an embodiment, the acid catalyst is a Si-rich aluminosilicate zeolite having a Si / Al ratio greater than 5. In an embodiment, the acid catalyst is an aluminosilicate zeolite comprising 0.38 nm micropores.

[0056] In an embodiment, the acid catalyst is chabazite (CHA), as defined by the International Zeolite Associate (IZA). According to the IZA structure database, the poreopening of CHA is ~ 0.38 nm. More specifically, in an embodiment, the acid catalyst is SSZ-13, a Si-rich (Si / Al is greater than 5) small pore zeolite (chabazite topology). This zeolite is described in US Pat. No. 4,544,538 (the ‘538 patent). In US Pat. No. 4,544,538, the SSZ-13 molecular sieve is prepared in the presence of N,N,N-trimethyl-l-adamantammonium cation which serves as a structure directing agent (“SDA”), also known as on organic template. See US Pat. No. 4,544,538 at Col. 2, 1. 42 through Col. 4, 1. 25, incorporated by reference. Tables 1 and 2 of the '538 patent provide the X-ray powder diffraction patterns before and after calcination, respectively. Further, methods of preparing the SSZ-13 zeolite are provided. See, US Pat. No. 4,544,538 at Col. 4, 1. 26 through Col. 5, 1. 38, incorporated by reference. The CHA catalyst is substantially proton exchanged and calcined to convert it to the proton form, having a residual alkali amount (expressed in A2O wt.%, where A is the alkali metal such as Na, K, or a combination thereof) of less than 5,000 ppm, less than 1,000 ppm, and less than 500 ppm. The BET surface area of the CHA catalyst is greater than 200 m2 / g, greater than 300 m2 / g, and greater than 500 m2 / g. The Si / Al ratio is greater than 5, greater than 10, and greater than 20. The CHA catalyst can be in the form of neat zeolite, or optionally formulated with a binder to form extrudates or spray dried into spherical particles. The amount of binder is in the range of 5 wt.% to 60 wt.%, 20 wt.% to 50 wt.%, and / or 30 wt.% to 40 wt.%.

[0057] In another embodiment, the acid catalyst is an 8-ring silicoaluminophosphate (“SAPO”) having the structure code CHA as defined by the International Zeolite Associate (IZA). According to the IZA structure database, the pore-opening of CHA is ~ 0.38 nm. In an embodiment, the acid catalyst is SAPO-34. The SAPO molecular sieves contain a three- dimensional microporous crystalline framework structure of [SiO?], [AIO2] and [PO2] corner sharing tetrahedral units which are generally synthesized by the hydrothermal crystallization of a reaction mixture of silicon-, aluminum- and phosphorus-sources and at least one templating agent. For example, the synthesis of silicoaluminophosphate SAPO-34 is described in US Pat. No. 4,440,871, Col. 4. 1. 50 to Col. 8, 1. 58 & Examples 32-38, incorporated by reference. Conveniently, the silicoaluminophosphate molecular sieve has a silica to alumina molar ratio from about 0.15 to about 0.22, from about 0.17 to about 0.21, such as from about 0.18 to about 0.19. The SAPO-34 catalyst is substantially proton exchanged and calcined to convert it to the proton form, having a residual alkali amount (expressed in A2O wt.%, where A is the alkali metal such as Na, K, or a combination thereof) of less than 5,000 ppm, less than 1,000 ppm, and less than 500 ppm. The BET surface area of the SAPO-34 catalyst is greater than 200 m2 / g, greater than 300 m2 / g, and greater than 500 m2 / g. The SAPO-34 catalyst can be in the form of neat molecular sieve, or optionally formulated with a binder to form extrudates or spray dried into spherical particles. The amount of binder is in the range of 5 wt.% to 60 wt.%, 20 wt.% to 50 wt.%, and 30 wt.% to 40 wt.%.

[0058] In another embodiment, the acid catalyst is an 8-ring silicoaluminophosphate (SAPO) having the structure code AEI as defined by the International Zeolite Associate (IZA). According to the IZA structure database, the pore-opening of AEI is ~ 0.38 nm. In an embodiment, the acid catalyst is SAPO-18. The silicoaluminophosphate SAPO molecular sieves contain a three-dimensional microporous crystalline framework structure of [SiO2], [AIO2] and [PO2] comer sharing tetrahedral units; which are generally synthesized by the hydrothermal crystallization of a reaction mixture of silicon-, aluminum- and phosphorus- sources and at least one templating agent. For example, the synthesis of silicoaluminophosphate SAPO-18 has been reported in several publications, including J. Chen et al. in Catalysis Letters , v.28, pp. 241-248 (1994) and US Pat. No. 5,609,843, Col. 1, 1. 4 to Col. 6, 1. 40, incorporated by reference. Conveniently, the silicoaluminophosphate molecular sieve has a silica to alumina molar ratio from about 0.15 to about 0.22, more preferably from about 0.17 to about 0.21, such as from about 0.18 to about 0.19. The SAPO-18 catalyst is substantially proton exchanged and calcined to convert it to the proton form, having a residual alkali amount (expressed in A2O wt.%, where A is the alkali metal such as Na, K, or acombination thereof) of < 5,000 ppm, preferably < 1,000 ppm, and more preferably < 500 ppm. The BET surface area of the SAPO-18 catalyst is > 200 m2 / g, preferably > 300 m2 / g, and more preferably > 500 m2 / g. The SAPO-18 catalyst can be in the form of neat molecular sieve, or optionally formulated with a binder to form extrudates or spray dried into spherical particles. The amount of binder is in the range of 5 wt.% to 60 wt.%, 20 wt.% to 50 wt.%, and 30 wt.% to 40 wt.%.

[0059] In another embodiment, the acid catalyst is a combination of 8-ring silicoaluminophosphates (SAPO) having the structure code CHA and AEI as defined by the International Zeolite Associate (IZA). In an embodiment, the acid catalyst is a combination of S APO-34 and SAPO-18, either by physical mixture or intergrowth. The mixture or intergrowth of CHA / AEI has the weight ratio of 5 / 95 to 95 / 5, or 30 / 70 to 70 / 30. The synthesis of CHA / AEI intergrowth is disclosed in US Pat. No. 7,622,624, Col. 5, 11 to Col. 5, 1. 52, incorporated by reference. Conveniently, the silicoaluminophosphate molecular sieve has a silica to alumina molar ratio from about 0.15 to about 0.22, from about 0.17 to about 0.21, such as from about 0.18 to about 0.19. The combination of SAPO-34 / SAPO-18 catalyst is substantially proton exchanged and calcined to convert it to the proton form, having a residual alkali amount (expressed in A2O wt.%, where A is the alkali metal such as Na, K, or a combination thereof) of less than 5,000 ppm, less than 1,000 ppm, and less than 500 ppm. The BET surface area of the SAPO-34 / SAPO-18 catalyst is greater than 200 m2 / g, greater than 300 m2 / g, and greater than 500 m2 / g. The SAPO-34 / SAPO-18 catalyst can be in the form of neat molecular sieve, or optionally formulated with a binder to form extrudates or spray dried into spherical particles. The amount of binder is in the range of 5 wt.% to 60 wt.%, or 20 wt.% to 50 wt.%, or 30 wt.% to 40 wt.%.Zeolites and Zeolitic Materials

[0060] Zeolites and their isotypes are classified by the Structure Commission of the International Zeolite Association according to the rules of the IUPAC Commission on Zeolite Nomenclature. According to this classification, framework type zeolites and other crystalline microporous molecular sieves, for which a structure has been established, are assigned a three- letter code and are described in the “Atlas of Zeolite Framework Types”, eds. Ch. Baerlocher, L.B. McCusker, and D.H. Olson, Elsevier, Sixth Edition, 2007, which is hereby incorporated by reference.

[0061] Certain zeolites comprise an inorganic framework type where the silicon tetrahedral atoms are connected by oxygen atoms with the four next-nearest tetrahedral atoms. The term “silicate”, as used herein, refers to a substance comprising silicon and oxygen atoms alternatelybonded to each other (z.e., -O-Si-O-Si-), and optionally comprise other types of atoms within the inorganic framework type, including boron, gallium, aluminum, or other metals (e.g., transition metals, such as titanium, vanadium, or zinc). Atoms other than silicon and oxygen in the framework occupy a portion of the lattice sites that would be otherwise occupied by silicon atoms in an ‘all-silica’ framework (also referred to as “silicate”). Thus, the term “framework silicate” or “zeolite framework silicate” refers to an atomic lattice comprising silicate, borosilicate, gallosilicate, ferri silicate, aluminosilicate, titanosilicate, zincosilicate, vanadosilicate, and the like. As noted above, the framework structure within a zeolite determines the size of the pores or channels. The pore or channel size determines the type of process for which a given zeolite is applicable. Currently, there are more than 200 known zeolite framework silicates recognized by the Structure Commission of the International Zeolite Association, providing a range of pore geometries and orientations defined.

[0062] The zeolite framework silicate is commonly characterized in terms of ring size, wherein the ring size refers to the number of silicon atoms (or alternative atoms, such as those listed above) that are tetrahedrally coordinated with oxygen atoms in a loop to define a pore or channel within the interior of the zeolite. For example, an “8-ring” zeolite refers to a zeolite having pores or channels defined by 8 alternating tetrahedral atoms and 8 oxygen atoms in a loop. The pores or channels defined within a given zeolite are symmetrical or asymmetrical depending upon various structural constrains that are present in the framework silicate.

[0063] Zeolites and silicoaluminophosphate (SAPO) are classified as having small, medium, large, and extra-large pore structures for pore windows delimited by 8, 10, 12, and more than 12 T-atoms, respectively. Extra-large pore zeolites (>12R) include, for example, AET (14R, e.g., ALPO-8), SFN (14R, e.g., SSZ-59), VFI (18R, e.g., VPI-5), CLO (20R, e.g., cloverite), and ITV (30R, e.g., ITQ-37) framework type zeolites. Extra-large pore zeolites generally have a free pore diameter of larger than about 0.8 nm. Large pore zeolites (12R) include, for example, LTL, MAZ, FAU, EMT, OFF, MTW, *BEA, MOR, and SFS framework type zeolites, e.g., mazzite, offretite, zeolite L, zeolite Y, zeolite X, omega, ZSM-2, ZSM-12, zeolite T, Beta, and SSZ-56. Large pore zeolites generally have a free pore diameter of 0.6 nm to 0.8 nm. Medium (or intermediate) pore size zeolites (10R) include, for example, MFI, MEL, *MRE, EUO, MTT, MFS, AEL, AFO, HEU, FER, MWW, and TON framework type zeolites, e.g., ZSM-5, ZSM-11, ZSM-48, ZSM-22, ZSM-23, ZSM-35, MCM-22, MCM-49, silicalite-1, and silicalite-2. Medium pore size zeolites generally have a free pore diameter of 0.45 nm to 0.6 nm. Small pore size zeolites (8R) include, for example, DDR, CHA, SSZ-13, RTH, ERI, KFI, LEV, and LTA framework type zeolites, e.g., ZK-4, SAPO-18, SAPO-34, SAPO-35,ZK-14, SAPO-42, ZK-21, ZK-22, ZK-5, ZK-20, zeolite A, chabazite, and A1P0-17. Small pore size zeolites generally have a free pore diameter of 0.3 nm to less than 0.45 nm.

[0064] Molecular sieve materials, both natural and synthetic, can be used as adsorbents and have catalytic properties for hydrocarbon conversion reactions. Certain molecular sieves, such as zeolites, AlPOs, and mesoporous materials, are ordered, porous crystalline materials having a definite crystalline structure as determined by X-ray diffraction (“XRD”). Molecular sieves can be ordered and produce specific identifiable XRD patterns. Within certain molecular sieve materials are cavities interconnected by channels or pores. Within a particular type of molecular sieve, the pores are generally uniform in size. Pore size determines whether a molecule can travel within the molecular sieve and be adsorbed or rejected.

[0065] Molecular sieves are utilized in a variety of industrial processes, e.g., cracking, hydrocracking, disproportionation, alkylation, oligomerization, and isomerization. Molecular sieves, including naturally occurring or the synthetic crystalline molecular sieves, can find application in catalysis and adsorption.

[0066] Synthesis of molecular sieve materials (zeolites) typically involves hydrothermal crystallization from a synthesis mixture comprising sources of all the elements present in the molecular sieve (or zeolite) such as sources of silica but also of alumina etc. In many cases a structure directing agent (“SDA”) is also present. Structure directing agents are compounds which are believed to promote the formation of a molecular sieve, and which are thought to act as templates around which certain molecular sieve structures can form and which thereby promote the formation of the desired molecular sieve. Various compounds have been used as structure directing agents including various types of quaternary ammonium cations. Typically, molecular sieve (zeolite) crystals form around structure directing agents with the structure directing agent occupying pores in the molecular sieve once crystallization is complete. The “as-synthesized” (or “as-made”) molecular sieve will therefore contain the structure directing agent in its pores so that, following crystallization, the “as-synthesized” molecular sieve is subjected to a treatment step such as a calcination step to remove the structure directing agent.

[0067] Synthesis of molecular sieve materials (zeolites) typically involves hydrothermal crystallization from a synthesis mixture comprising sources of all the elements present in the molecular sieve (or zeolite) such as sources of silica but also of alumina etc. In many cases a structure directing agent (“SDA”) is also present. Structure directing agents are compounds which are believed to promote the formation of a molecular sieve, and which are thought to act as templates around which certain molecular sieve structures can form and which thereby promote the formation of the desired molecular sieve. Various compounds have been used asstructure directing agents including various types of quaternary ammonium cations. Typically, molecular sieve (zeolite) crystals form around structure directing agents with the structure directing agent occupying pores in the molecular sieve once crystallization is complete. The “as-synthesized” (or “as-made”) molecular sieve will therefore contain the structure directing agent in its pores so that, following crystallization, the “as-synthesized” molecular sieve is subjected to a treatment step such as a calcination step to remove the structure directing agent.

[0068] For instance, US Pat. No. 3,308,069 and J.B. Higgins et al., Zeolites, v.8, pp. 446-448 (1988) disclose the preparation and characterization of zeolite Beta, a large pore zeolite of *BEA framework type, which exhibits a three-dimensional pore system formed by 12-membered ring channels. Zeolite Beta was first crystallized from a reaction mixture containing the tetraethylammonium ion (US Pat. No. 3,308,069). US Pat. No. 11,180,430 B2 discloses the preparation of zeolite Beta, in particular zeolite Beta having a high external specific surface area, using l,r-(pentane-l,5-diyl)bis(l-pentylpiperidinium), and their use in olefin oligomerization processes.

[0069] Beta zeolite (also “P-zeolite”) is an aluminosilicate that consists of two distinct polymorph structures consisting of a three-dimensional network of 12-ring pores. The polymorphs grow as two-dimensional sheets, and the structure randomly alternates between the two types of sheets. As taught in the prior art, P-zeolite has been found to increase gas fractions and reduce liquid oil, however strong secondary reactions can occur to form high quantities of residue and wax, dependent on the plastic feedstock. See Mark, L. et al., The Use of Heterogenous Catalysis in the Chemical Valorization of Plastic Waste ChemSusChem, v.13, pp. 5808-5826 (2020) citing K. Li, S. et al., Energies, 2016, v.9, pg. 431 & C. Ma, et al., Fuel Process. Technol., 2017, v.155, pp. 32-41. For example, P-zeolite could somewhat improve selectivity towards gaseous products while drastically reducing liquid oil products for the pyrolysis of HIPS. However, most of the cracked products underwent severe cross-linking reactions following cracking to produce yellowish brown wax that coated the reactor walls. Id.

[0070] Another class of zeolites that are commonly used for plastic conversion are ZSM-5 catalysts. These zeolites are MFI (silicalite-1) structured porous aluminosilicate zeolites that have been reported to have increased cracking activity for polyolefins in particular polyethylene that results in a decrease in the heavy oil fraction, reduction in wax production, minimization in char production, and an increase in light hydrocarbon content in the liquid and gas produced. Mark, L. et al., The Use of Heterogenous Catalysis in the Chemical Valorization of Plastic Waste, ChemSusChem, v.13, pp. 5808-5826 (2020) at pg. 5822.

[0071] Other types of zeolitic materials that can be used in plastic conversion include amorphous (non-zeolite) solid acids (such as used in amorphous silica-alumina. See e.g., Busca, G., Silica-Alumina Catalytic Materials: A Critical Revie , v. 357, pp. 621-629 (2020).Reaction Yield

[0072] Polyolefins can be pyrolyzed under pyrolysis conditions to form olefin monomers. Although the pyrolysis conditions can modify the selectivity for the olefin monomers, the pyrolysis reaction generates a mixture of olefin monomers as the olefin product. This can correspond to a mixture including C2-C4 (“C2-C4”) olefins, a mixture including C2-C3 (“C2-C3”) olefins, or a mixture including C2 olefins, C3 olefins, optionally C4 olefins, and one or more additional olefins (such as C5 or C6 olefins).

[0073] Although pyrolysis conditions can modify selectivity for olefin monomers, a pyrolysis reaction generates a mixture of olefin monomers. For example, the present process that utilizes an acid catalyst comprising microporous material such as a zeolite having a pore opening between 0.3 nm and less than 0.45 nm in diameter to produce an olefin product such as a mixture of C2-C4 (“C2-C4”) olefins, a mixture including C2-C3 olefins, or a mixture including C2 olefins, C3 olefins and optionally C4 olefins. The C2-C4 olefins produced are primarily in a gas phase. Further, as described herein, the pyrolysis process can produce C5 to C20+ (“Cs to C20+”) olefins. The pyrolysis products of Cs to C20+ olefins are produced in a liquid phase. The pyrolysis products in the liquid phase can be less than or equal to 80 wt.%, 75 wt.%, 70 wt.%, 60 wt.%, 50 wt.% or 45 wt.% of the total weight of olefin product produced. Similarly, the pyrolysis products in the gas phase can be less than or equal to 50 wt.%, 45 wt.%, 40 wt.%, 35 wt.%, 30 wt.%, 25 wt.% or 20 wt.% of the total weight of olefin product produced.

[0074] Additionally, or alternately, a solvent or carrier can be added to the polyolefin feedstock. For introduction into the pyrolysis reactor, it can be convenient for the polyolefm / polymer produced from plastic waste to be in the form of a solution, slurry, or other fluid-type phase. If a solvent is used to at least partially solvate the polyolefins, any convenient solvent can be used. Examples of suitable solvents can include (but are not limited to) a wide range of petroleum or petrochemical products. For example, some suitable solvents include crude oil, naphtha, kerosene, diesel, and oils. Other potential solvents can correspond to naphthenic and / or aromatics solvents, such as toluene, benzene, methylnaphthalene, cyclohexane, methylcyclohexane, and mineral oil. Still other solvents can correspond to refinery fractions, such as a gas oil fraction or naphtha fraction from a steam cracker product. If a carrier is used, the carrier can correspond to a liquid or gas phase carrier, such as steam.

[0075] A diluent gas stream is typically inert but can be a hydrocarbon gas. Steam can be a diluent gas stream. The amount of steam is 50 wt.% or lower relative the amount of plastic waste, or 40 wt.% or 30 wt.% or lower. In an embodiment, the amount of steam co-fed with the plastic waste is 30 wt.% or less. The diluent gas stream separates reactive olefin products from each other to preserve the selectivity to light olefins thus avoiding oligomerization of light olefins to higher olefins or over cracking to light gas. The absence of oxygen, however, is critical. The polyolefin feedstock is optionally preheated to high temperature before it is fed to the pyrolysis reactor or heated to pyrolysis temperature after entering the pyrolysis reactor.Olefin Product - Polyethylene & Other Polyolefins

[0076] Polyolefin polymers are commonly used in a wide variety of industrial and consumer applications. In some instances, substantial quantities of plastic waste are available that correspond to a single type of polyolefin, but more typically polyolefin waste corresponds to a mixture of polyethylene, polypropylene, and / or other polymer chains based on small olefins.

[0077] Polyethylene is used widely in various consumer and industrial products including bags, films, geomembranes, and bottles. Polyethylene can be produced as high-density polyethylene (HDPE, approximately 0.940 to approximately 0.965 g / cm3), linear low-density polyethylene (LLDPE, approximately 0.915 to approximately 0.940 g / cm3) and low-density polyethylene (LDPE, <0.930 g / cm3), each having a chemical formula of (C2H4)n where n is a number one or greater, but with different molecular structure. HDPE has a low degree of branching with short side chains while LDPE has a very high degree of branching with long side chains. LLDPE is a substantially linear polymer with significant numbers of short branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins. US Pub. App. No. 2021 / 0332299

[0021] ,

[0078] Low density polyethylene (“LDPE”) is produced via radical polymerization at a temperature between 150°C and 300°C and pressure of 1,000-3,000 atm (101-304 MPa). This process uses a small amount of oxygen and / or organic peroxide initiator to produce polymer with about 4,000-40,000 carbon atoms per the average polymer molecule, and with many branches. High density polyethylene (“HDPE”) is manufactured at relatively low pressure (10-80 atm, 1-8 MPa) and 80-150°C temperature in the presence of a catalyst. Id. at

[0023] , Present Methods as Used in connection with Other Recycling Processes

[0079] The present processes are not limited to producing a type of polyolefin, a polymer or group of polymers. However, to optimize melting of plastic wastes and depending on the type of polymers in the plastic wastes, separate flows can be required for different polymers.For example, the condensation polymers PET are mechanically recycled and are removed from the plastic material prior to pyrolysis or chemically recycled by an alternative process such as hydrolysis. In another example, because PVC generates HC1 at pyrolysis, PVC is typically removed from the plastic material. However, a small presence of PVC in the plastic material is acceptable. Alternative processes include chemical recycling by different processes (i.e., hydrolysis) of other polymers such as polyesters and polyamides.

[0080] In an embodiment, the present process includes a step of selecting plastic wastes containing polyolefins such as polyethylene and / or polypropylene. Plastic wastes are passed through the pyrolysis plastic wastes reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent can be separated into off gas, pyrolysis product, (i.e., comprising polyolefin, naphtha, diesel, and heavy fractions) and char. In an embodiment, the pyrolyzed effluent is a pyrolysis feedstock to a pyrolysis unit.

[0081] In an embodiment, the present process is integrated as a continuous process for converting plastic wastes comprising polyethylene into a recycle stream used in polyethylene polymerization. This process comprises the step of selecting plastic wastes containing polyethylene and / or polypropylene and then passing the plastic wastes through the pyrolysis plastic wastes reactor to thermally crack at least a portion of the plastic wastes and produce the pyrolyzed effluent which is further processed.

[0082] In an embodiment, the present processes can be incorporated into an oil refinery where a single use waste plastic such as polyethylene or polypropylene is in fluidic communication with a steam cracker for ethylene production allowing for a “cyclical economy.” Also, in an integrated process, the pyrolysis product in the form of a naphtha stream can be used as a steam cracker feedstock for ethylene generation and subsequent polyethylene production.

[0083] Aspects of the disclosure are described in greater detail by way of specific examples. The following examples are offered for illustrative purposes and are not intended to limit the disclosure in any manner. Those of skill in the relevant art will readily recognize a variety of parameters can be changed or modified to yield essentially the same results.ADDITIONAL EMBODIMENTS

[0084] Embodiment 1. A catalytic pyrolysis process for conversion of a plastic waste to an olefin product comprising the steps of: introducing the plastic waste into a pyrolysis unit; andpyrolyzing at least a portion of the plastic waste in the presence of an acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter to form the olefin product comprising a liquid olefin product and a gas olefin product, wherein the gas olefin product comprises C2 olefin, C3 olefin, and C4 olefin and the liquid olefin product comprises C9+ olefin.

[0085] Embodiment 2. The process of embodiment 1, wherein the plastic waste is a postconsumer waste and / or a post-industrial waste.

[0086] Embodiment 3. The process of embodiment 2, wherein the post-consumer waste comprises a waste plastic, a waste rubber, a textile, modified cellulose, wet-laid products, and / or combinations thereof.

[0087] Embodiment 4. The process of embodiment 3, wherein the plastic waste comprises at least 30 wt.% of polyethylene and / or polypropylene.

[0088] Embodiment 5. The catalytic pyrolysis process of embodiment 1, wherein the pyrolysis unit is at a temperature of 550°C or less.

[0089] Embodiment 6. The catalytic pyrolysis process of embodiment 1, wherein the pyrolysis unit is at a pressure of 15 psig to 75 psig.

[0090] Embodiment 7. The catalytic pyrolysis process of embodiment 1, where the plastic waste is co-fed with 30 wt.% steam or less.

[0091] Embodiment 8. The process of embodiment 1, wherein at least 45 wt.% of the olefin product is the gas olefin.

[0092] Embodiment 9. The process of embodiment 1, wherein less than 10 wt.% of the olefin product is the liquid olefin.

[0093] Embodiment 10. The process of embodiment 1, wherein the olefin product further comprises less than 10 wt.% aromatics such as benzene, toluene, and xylenes.

[0094] Embodiment 11. The process of embodiment 1, wherein the olefin product further comprises less than 5.0 wt.% of methane.

[0095] Embodiment 12. The process of embodiment 1, wherein the plastic waste is catalytically pyrolyzed in the absence of oxygen.

[0096] Embodiment 13. The process according to embodiment 1, wherein the pyrolysis unit comprises a fluidized bed reactor, a transported bed reactor, an ablative (vortex) reactor, an extruder reactor, a microwave reactor, a fixed bed reactor, a vacuum reactor, an autoclave reactor, a rotary kiln, or a tubular reactor.

[0097] Embodiment 14. A catalytic pyrolysis process for conversion of a plastic waste to an olefin product comprising the steps of: heating the plastic waste to provide a liquid plastic waste; and pyrolyzing the liquid plastic waste with an acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter to produce the olefin product comprising greater than 35 wt.% C2-C4 olefins, less than 30 wt.% of C9+ olefins, less than 10 wt.% aromatics, and less than 5 wt.% methane.

[0098] Embodiment 15. The process of any one of the preceding embodiments, wherein the plastic waste comprises at least 30 wt.% of polyethylene and / or polypropylene.

[0099] Embodiment 16. The process of any one of the preceding embodiments, wherein the acid catalyst is a microporous material comprising a pore opening is 0.38 nm in diameter.

[0100] Embodiment 17. The process of any one of the preceding embodiments, wherein the acid catalyst is an 8-ring zeolite.

[0101] Embodiment 18. The process of any one of the preceding embodiments wherein the acid catalyst is chabazite (CHA).

[0102] Embodiment 19. The process of any one of the preceding embodiments, wherein the acid catalyst is an 8-ring silicoaluminophosphate (SAPO).

[0103] Embodiment 20. The process of any one of the preceding embodiments, wherein the acid catalyst is selected from SAPO-34, SAPO- 18, or a combination thereof.EXAMPLESGeneral Procedure

[0104] Pyrolysis experiments were performed in a thermogravimetric analysis with gas chromatography and mass spectrometry TGA-IST-GC / MS instrument. In the gas analysis by the GC / MS, the molecular composition and information about the molecular structure of the same can be determined. The 1ST interface allows a single thermogravimetric analysis (“TGA”) measurement to be divided into separate GC / MS experiments.

[0105] About 10 mg of plastic sample was loaded in an alumina TGA pan. Under flowing helium (75 cc / min), the pan was first heated to 200°C and held for 5 minutes to allow the plastic sample (solid plastic) to melt. Subsequently, temperature was ramped at a rate of 200°C / min to 700°C and held for 10 minutes. The evolved gas from the polymer sample first passed through a PTFE tubing immersed in an iso-propanol / dry-ice cold trap (-80°C) to knock out C9+ products. Non-condensed gas was collected downstream with pre-defined time intervals in a 16-port sampling valve fitted with 250 pL sampling loops. The gas samples were analyzed by the in-line GC / MS. The GC / MS was calibrated with gas standards containing the expectedproducts from pyrolysis. The C9+ liquid collected in the PTFE tubing was weighed. The solid residue left in the TGApan was further subjected to an oxidation step using 8% Ch / Ar at 700°C to determine the char / coke and ash contents. The amounts of gas, liquid, and coke were added and normalized to 100% to determine yields for each fraction.

[0106] In experiments where an acid catalyst was utilized, the catalyst was first calcined on the TGA at 550°C under 8% Ch / Ar for 1 hour, then 5 mg of the calcined catalyst was mixed with 10 mg of polymer sample in the TGA pan; and the pyrolysis experiment was performed in the same manner as described above.Example 1Acid Catalyzed Pyrolysis of HDPE (XP1000)

[0107] The pyrolysis experiment was performed in the same manner as described in the general procedure above. Acid catalysts were calcined on the TGA at 550°C under 8% Ch / Ar for 1 hour. Then 5 mg of the calcined acid catalyst was mixed with 10 mg of HDPE in the TGApan. The following zeolites and one silicoaluminophosphate were employed, specifically, beta (BEA), USY (CBV760), and MFI zeolite sheets (EMM-30), each having pore size greater than 0.5 nm, to provide comparative examples, and SSZ-13 chabazite and SAPO-34. The SSZ- 13 chabazite catalyst used in this example is in the proton-exchanged form, having a silica to alumina (SiCh / AhCh) molar ratio in the range of 13-15 (Si / Al ratio of 26-30), a BET surface area of greater than 600 m2 / g, crystallize sizes in the range of 0.5 micron to 1 micron, and a Na?O level of less than 500 ppm. The SAPO-34 (having the chabazite structure) catalyst used in this example is in the proton-exchanged form, having Si / Al / P atomic ratio of 0.15 / 0.78 / 0.63, a BET surface area of greater than 550 m2 / g, a mean particle size of ~ 2 micron, and an alkali level (Na2O+K2O) of less than 200 ppm.

[0108] As shown in FIG. 1, for the acid catalysts, the weight loss starts and finishes at lower pyrolysis temperatures, indicating acid catalysts shift the pyrolysis temperature lower. Acid catalysts reduced the liquid yield compared with thermal pyrolysis. As shown in FIG. 2, in the comparative examples (MFI sheets, USY and BEA), the amounts of C2-C4 olefins are lower and the amounts of aromatics are higher. However, using the SSZ-13 CHA acid catalyst, the C2-C4 olefins yield increases, and liquids yield decreases, with only slight increases in methane, aromatics (BTX - benzene, toluene, and xylenes), and coke yield. FIG. 2.

[0109] Detailed product distributions in (wt.%), is shown in FIG. 3. For the example where the SSZ-13 CHA as the acid catalyst, the increase in C2-C4 olefin is largely contributed by the increase of propylene (C3 olefin) and butenes (C4 olefin).Example 2Acid Catalyzed Pyrolysis of LLDPE (F3D4)

[0110] CHA catalyst was calcined on the TGA at 550°C under 8% Ch / Ar for 1 hour. Then 5 mg of the calcined CHA catalyst was mixed with 10 mg of LLDPE in the TGA pan. The pyrolysis experiment was performed in the same manner as described above.

[0111] Weight loss started and finished at lower pyrolysis temperatures, indicating that an acid catalyst shifts the pyrolysis temperature lower. FIG. 4. CHA also reduced the liquid yield compared with thermal pyrolysis. FIG. 5. Furthermore, the C2-C4 olefins yield increased, liquids yield decreased, and there were only slight increases in methane and coke yield, while the amounts of aromatics (BTX - benzene, toluene, and xylenes) decreased.

[0112] Detailed product distributions in wt.% are shown in FIG. 6. The increase in C2-C4 olefin is largely contributed by the increase of propylene (C3 olefin) and butenes (C4 olefin).Example 3Acid Catalyzed Pyrolysis of Polypropylene

[0113] CHA catalyst was calcined on the TGA at 550°C under 8% Ch / Ar for 1 hour. Then 5 mg of the calcined CHA catalyst was mixed with 10 mg of polypropylene in the TGA pan. The pyrolysis experiment was performed in the same manner as described above.

[0114] Weight loss started and finished at lower pyrolysis temperatures, indicating that an acid catalyst shifts the pyrolysis temperature lower. FIG. 7. CHA also reduced the liquid yield compared with thermal pyrolysis. FIG. 8. Furthermore, the yield of C2-C4 olefins increased and liquids yield decreased. Further, there were only slight increases in coke yield and the amount of methane is comparable to thermal pyrolysis without an acid catalyst. The amounts of aromatics (BTX - benzene, toluene, and xylenes) decreased. Detailed product distributions in wt.% are shown in FIG. 9. The increase of C2-C4 olefin is largely contributed by the increase of butenes (C4 olefin).

[0115] Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

Claims

CLAIMSWe claim:

1. A catalytic pyrolysis process for conversion of a plastic waste to an olefin product comprising the steps of: introducing the plastic waste into a pyrolysis unit; and pyrolyzing at least a portion of the plastic waste in the presence of an acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter to form the olefin product comprising a liquid olefin product and a gas olefin product, wherein the gas olefin product comprises C2 olefin, C3 olefin, and C4 olefin and the liquid olefin product comprises C9+ olefin.

2. The process of claim 1, wherein the plastic waste is a post-consumer waste and / or a post-industrial waste.

3. The process of claim 2, wherein the post-consumer waste comprises a waste plastic, a waste rubber, a textile, modified cellulose, wet-laid products, and / or combinations thereof.

4. The process of claim 3, wherein the plastic waste comprises at least 30 wt.% of polyethylene and / or polypropylene.

5. The catalytic pyrolysis process of claim 1 , wherein the pyrolysis unit is at a temperature of 550°C or less.

6. The catalytic pyrolysis process of claim 1, wherein the pyrolysis unit is at a pressure of 15 psig to 75 psig.

7. The catalytic pyrolysis process of claim 1, where the plastic waste is co-fed with 30 wt.% steam or less.

8. The process of claim 1, wherein at least 45 wt.% of the olefin product is the gas olefin.

9. The process of claim 1, wherein less than 10 wt.% of the olefin product is the liquid olefin.

10. The process of claim 1, wherein the olefin product further comprises less than 10 wt.% aromatics such as benzene, toluene, and xylenes.

11. The process of claim 1, wherein the olefin product further comprises less than 5.0 wt.% of methane.

12. The process of claim 1, wherein the plastic waste is catalytically pyrolyzed in the absence of oxygen.

13. The process according to claim 1, wherein the pyrolysis unit comprises a fluidized bed reactor, a transported bed reactor, an ablative (vortex) reactor, an extruder reactor, a microwave reactor, a fixed bed reactor, a vacuum reactor, an autoclave reactor, a rotary kiln, or a tubular reactor.

14. A catalytic pyrolysis process for conversion of a plastic waste to an olefin product comprising the steps of: heating the plastic waste to provide a liquid plastic waste; and pyrolyzing the liquid plastic waste with an acid catalyst comprising a microporous material having a pore opening between 0.3 nm and less than 0.45 nm in diameter to produce the olefin product comprising greater than 35 wt.% C2-C4 olefins, less than 30 wt.% of C9+ olefins, less than 10 wt.% aromatics, and less than 5 wt.% methane.

15. The process of any one of the preceding claims, wherein the plastic waste comprises at least 30 wt.% of polyethylene and / or polypropylene.

16. The process of any one of the preceding claims, wherein the acid catalyst is a microporous material comprising a pore opening is 0.38 nm in diameter.

17. The process of any one of the preceding claims, wherein the acid catalyst is an 8-ring zeolite.

18. The process of any one of the preceding claims, wherein the acid catalyst is chabazite (CHA).

19. The process of any one of the preceding claims, wherein the acid catalyst is an 8-ring silicoaluminophosphate (SAPO).

20. The process of any one of the preceding claims, wherein the acid catalyst is selected from SAPO-34, SAPO- 18, or a combination thereof.

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