A two-step process for chemically recycling plastic waste

Abstract

A two-stage process is described that involves a first stage of pyrolysis carried out in mechanically or gravity driven reactors and a second stage in a catalytic fluidized bed for upgrading the resulting vapors to convert waste plastics, polymers and other waste materials into useful chemical and fuel products, such as paraffins, olefins and aromatics such as BTX.

Description

[Technical field]

[0001] Related Applications This application claims priority to U.S. Patent Application No. 17 / 201,706, filed March 15, 2021.

[0002] The present invention relates to the conversion of waste plastics, polymers, and other waste materials into useful chemical and fuel products, such as paraffins, olefins, aromatics such as BTX, in a two-stage process involving a first stage of pyrolysis and a second stage of upgrading of the resulting steam.

[0003] sayings In 2018, the United States generated 38.5 million tons of plastic, accounting for 13.1% of MSW generation. Over 350 million tons of plastic were produced worldwide. Plastic recycling involves recovering scrap or waste plastic and reprocessing the material into useful products. However, since China banned the import of waste plastic, the recycling rate in the United States is estimated to have dropped to just 4.4%.

[0004] Recycling of plastics is difficult due to the chemical properties and low economic benefits of long-chain organic polymers. Furthermore, waste plastic materials often need to be separated into different types of plastic resins, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), etc., for separate recycling processes. Pyrolysis and catalytic pyrolysis processes are known in which waste plastics are heated to produce products such as liquid oil, gas, and carbon black.

[0005] Plas-TCat™ is a catalytic fluidized bed process that uses a zeolite catalyst to convert polymer / plastic materials, especially waste plastics that may be destined for landfills or incinerators, into a mixture of products: permanent gases, C2-C4 light olefins, C1-C4 light paraffins, C5+ hydrocarbons (benzene, toluene, and xylenes ("BTX"), aromatic and non-aromatic naphtha molecules, C11+ hydrocarbons, coke and char, and small amounts of by-products. Plastic mixtures with relatively high hydrogen to carbon molar ratios, such as polyethylene (PE), polypropylene, polystyrene, and combinations thereof, can be converted into olefins and aromatics.

[0006] US Patent No. 4,746,406 to Timmann discloses a pyrolysis reprocessing process for plastics, rubber, or other hydrocarbon materials, in which the pyrolysis gas obtained is subjected to a cooling stage at a temperature just above the freezing point of water and an overpressure of about 0.8-1.4 bar. The resulting condensate is then separated and heated to normal storage temperatures, and the superatmospheric pressure on the condensate is reduced to atmospheric pressure. The gas thereby produced, containing C1-C4 hydrocarbon compounds, is fed to the pyrolysis process as special product gas. It is reported that the proportion of aromatic compounds in the pyrolysis gas is significantly increased.

[0007] US Patent No. 8,895,790 to Narayanaswamy et al. describes a single-stage process for converting plastics to olefins and aromatics by contacting the feed mixture with a fluidized bed catalyst at 550° C. or above.

[0008] U.S. Patent Application No. 2016 / 0289569 by Baird et al. describes a process for pyrolyzing biomass into pyrolysis oil, separating and upgrading the pyrolysis oil, deoxygenating the upgraded pyrolysis oil to obtain aromatic and paraffinic products, and further upgrading the paraffinic products by aromatization.

[0009] U.S. Patent No. 10,233,395 to Ward relates to a process for converting mixed waste plastics (MWP) into petrochemicals, where the MWP stream is fed to a pyrolysis reactor, which converts the MWP into separate gas and liquid streams, and further processes the gas and liquid streams separately.

[0010] U.S. Patent No. 4,851,601 to Fukuda et al. describes a process in which plastics are pyrolyzed in a tank reactor with the addition of solids to minimize adhesion of materials to the reactor walls, and steam is reacted in a fixed bed catalytic reactor.

[0011] US Patent No. 9,040,761 to Bartek et al. describes a process for pyrolyzing biomass and plastics in a fluidized bed of heat transfer material and reacting the products with a catalyst in a second reactor to produce bio-oil. Summary of the Invention

[0012] A method for producing olefinic and aromatic hydrocarbons from waste plastics is described that includes feeding a plastic mixture to a two-stage process including a first stage in which the plastic mixture is anaerobically pyrolyzed, and a second stage in which the vapor product of the first stage is catalytically reacted to produce olefins and aromatics.

[0013] In a first aspect, the present invention provides a method for converting plastics to olefins, aromatics, or a mixture of olefins and aromatics, the method comprising: feeding a polymer or a mixture of polymers to a first pyrolysis reactor comprising a mechanically or gravity induced moving bed; anaerobically pyrolyzing the stream in the first reactor under conditions sufficient to produce a vapor raw product mixture comprising one or more olefins and paraffins; transferring the product vapor from the first pyrolysis reactor to a fluidized bed catalytic reactor, where in the presence of a catalyst the vapor mixture is converted to a product vapor mixture; and recovering the olefins or aromatics, or any combination thereof, from the product vapor mixture.

[0014] The method of the present invention may be further characterized by one or any combination of the following features, comprising: feeding a feed mixture comprising plastics to a pyrolysis reactor, wherein the feed mixture is selected from the group consisting of polyethylene, polypropylene, polyester, polyethylene terephthalate (PET), acrylonitrile-butadiene-styrene (ABS) copolymers, polyamides, polyurethanes, polyethers, polycarbonates, poly(oxides), poly(sulfides), polyarylates, polyetherketones, polyetherimides, polysulfones, polyurethanes, polyvinyl alcohols, and polymers produced by polymerization of monomers (e.g., dienes, olefins, styrenes, acrylates, acrylonitrile, methacrylates, methacrylonitrile, diacids and diols, lactones, diacids and diamines, lactams, vinyl esters, block copolymers thereof, and alloys thereof), thermosetting polymers (e.g., epoxy resins, phenolic resins, melamine resins, alkyd resins, vinyl ester resins, unsaturated polyester resins, crosslinked polyurethanes, polyisocyanurates, crosslinked elastomers (e.g., polyisoprene, polybutadiene, styrene- ... and mixtures thereof), wherein the feedstock comprises a waste plastic mixture selected from polyethylene terephthalate (PET), high density polyethylene (HDPE), polyvinyl chloride (PVC or polyvinylidene) (PVCD), low density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), or mixed resins, or any combination thereof, wherein the plastic The feed stream is first heated to at least 200°C to a molten state and filtered to remove solids, where the feed mixture is anaerobically heated to a temperature of 250-300°C to at least partially decompose the polymer in a pyrolysis reactor, where the pyrolysis reactor is one or more moving beds, single screw extruders, twin screw extruders, Auger reactors, rotary kiln reactors, or tray grate reactors, or any combination thereof, where the first pyrolysis reactor includes an inlet port and an outlet port, and the temperature is between 20°C and 100°C at or near the inlet port;or 20° C. to 50° C., and the temperature range of the hot outlet port may be from 300° C. to 700° C., such as from 325° C. to 650° C., or from 350° C. to 600° C., and wherein the residence time of the condensed phase in the first pyrolysis reactor, or in any reactor if there are multiple pyrolysis reactors (before the catalytic fluidized bed reactor), is at least 1 minute, or at least 5 minutes, or at least 10 minutes, or at least 20 minutes, or at least 30 minutes, or from 1 to 60 minutes, or from 5 to 30 minutes, or from 10 to 30 minutes, and wherein the pyrolysis reactor is two or more in series. reactor, wherein the feed is heated in a first pyrolysis reactor to a temperature of 250-300°C and the condensed phase is sent to a second pyrolysis reactor, wherein an inert gas is fed to the first pyrolysis reactor and vapor is exhausted, wherein the non-vapor products of the pyrolysis reactor, or a portion of the gas remaining after removal of the desired products, or both, are combusted to provide energy for the pyrolysis process, wherein a solid co-reactant material is fed to the pyrolysis reactor, wherein the solid co-reactant is selected from the group consisting of agricultural lime, calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, and wherein the solid co-reactant material is transferred to a combustion regenerator, wherein the carbonaceous material is reacted with air, and at least a portion of the hot solid co-reactant material is returned to a fluidized bed pyrolysis reactor, wherein a hot vapor product produced in the pyrolysis reactor is transferred to a catalytic pyrolysis reactor containing a catalyst without cooling or condensing a significant portion of the vapor product, wherein the catalytic reactor is a fluidized bed reactor, and wherein the catalytic reaction is carried out in a fluidized bed, circulating bed, bubbling bed, or laminar bed. The process is carried out in a cyclohexane reactor at an operating temperature in the range of 300° C. to 800° C., or 350° C. to 750° C., or 400° C. to 700° C., or 450° C. to 650° C., or 500° C. to 600° C., wherein the pressure is at least 0.1 MPa (1 bar), or at least 0.3 MPa (3 bar), or at least 0.4 MPa (4 bar), or 0.1 to 2.0 MPa (1 to 20 bar), or 0.1 to 1.0 MPa (1 to 10 bar), or 0.3 to 0.8 MPa (3 to 8 bar), preferably 0.4 to 0.6 MPa (4 to 6 bar),The residence time of the vapor in the catalytic pyrolysis reactor can be from 1 second to 480 seconds, or from 1 second to 240 seconds, or from 2 seconds to 60 seconds, or from 3 seconds to 30 seconds, or from 4 seconds to 15 seconds, wherein the catalyst is a solid catalyst, and the catalytic pyrolysis step includes pyrolyzing in the presence of the solid catalyst in a fluidized bed reactor to produce a fluid product stream and spent catalyst comprising coke, wherein at least 95% of the carbon in the feed is converted to coke and volatile products, and wherein the catalyst includes a zeolite, and wherein the catalyst is selected from natural zeolites, synthetic zeolites, and combinations thereof. and wherein the catalyst may be selected from ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, or combinations thereof, wherein the product vapor mixture from the catalytic conversion comprises at least 20 wt.% olefins, or at least 50 wt.% olefins, in some embodiments in the range of 20 to 90 wt.% olefins, wherein the catalyst composition comprises a crystalline molecular sieve characterized by a SAR of greater than 12 and up to 240 and a CI of 5 to 10, wherein the polymer Based on the mass in the feed, the mass yield of olefins in the product vapor mixture from catalytic conversion is at least 30%, or at least 40%, or at least 45%, or at least 50%, or at least 55%, or at least 60%, or between 20% and 90%, or between 30% and 70%, or between 45% and 60%, where the mass yield of BTX in the gaseous product mixture from catalytic conversion is at least 30%, or at least 40%, or at least 45%, or at least 50%, or at least 55%, or at least 60%, or 20%-90%, or 30%-70%, or 45%-60%, wherein the vapor product of the catalytic pyrolysis is passed through one or more solids separation devices including a cyclone, wherein the catalyst in the catalytic pyrolysis reactor is removed and regenerated by oxidation with air and returned to the catalytic pyrolysis reactor, wherein heat from the hot regenerated catalyst provides energy for the pyrolysis stage, wherein at least a portion of the gases in the product mixture are combusted in the regenerator, wherein the gaseous catalytic pyrolysis product mixture is subjected to a separation process to separate CH4, CO,and producing a gas stream rich in CH4, CO, and H2, and sending at least a portion of the gas stream rich in CH4, CO, and H2 to a regenerator and combusting it therein, wherein the gaseous catalytic pyrolysis product mixture comprises CH4 and C2-C4 paraffins, and wherein 50-100 wt. % of the CH4 and C2-C4 paraffins are combusted in the regenerator.

[0015] Chemically recycling plastics by pyrolysis in mechanically or gravity-driven reactors has many advantages: any type of plastic mixture is suitable, the long residence time in the pyrolysis reactor or reactors ensures that the plastic pieces are heated to the decomposition temperature, eliminating the need to crush the plastic particles to small sizes, pyrolysis can operate at high temperatures, the vapor products can be easily separated from the condensed phase in the pyrolysis reactor, the vapors can be reacted in a catalytic reactor and the condensed phase regenerated for recycling or combustion, inorganic impurities in the plastic mixture are separated from the hydrocarbon-based materials, and energy can be obtained from the regeneration or combustion of the condensed phase for use in the process or power generation.

[0016] The advantages of the two-stage plastic upgrading process are: a simple steam supply system to the catalytic stage, no risk of agglomeration in the fluidized bed causing defluidization or agglomeration in the bed, no need for thorough mixing of the solid or molten plastic feedstock with the catalyst particles, a much narrower residence time distribution of the pyrolysis gas in the catalytic reactor compared to the solid feedstock, thus reducing heavy products, no handover of plastic particles to the catalyst regenerator, fewer external impurities transferred to the catalytic reactor, inorganic particles embedded in the polymer such as fillers or additives are not transferred to the catalytic reactor (fillers are usually alkaline (basic) and will cause their deactivation when reacting with acidic catalysts), heat is supplied to the plastic convectively without the use of steam causing catalyst deactivation (dealuminization), a much reduced need for additional fluidization gas, easier product recovery and reduced costs. [Brief description of the drawings]

[0017] [Figure 1] Illustrates a conceptual embodiment of a process for converting mixed plastic materials into valuable products by pyrolyzing the mixed plastics and catalytically reacting the vapor products to produce olefins, aromatics, or some combination thereof. [Diagram 2] A conceptual embodiment of a process for converting mixed plastic materials into valuable products by pyrolyzing the mixed plastics and catalytically reacting the vapor products to produce olefins, aromatics, or some combination thereof is shown, where pyrolysis is performed in two reactors. [Diagram 3] FIG. 1 shows a diagram of the reactor used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Glossary With respect to aromatics, as used herein, the terms "aromatic" or "aromatic compound" are used to refer to a hydrocarbon compound or compounds that contain one or more aromatic groups, such as, for example, monoaromatic ring systems (e.g., benzyl, phenyl, etc.) and fused polycyclic aromatic ring systems (e.g., naphthyl, 1,2,3,4-tetrahydronaphthyl, etc.). Examples of aromatic compounds include, but are not limited to, benzene, toluene, indane, indene, 2-ethyltoluene, 3-ethyltoluene, 4-ethyltoluene, trimethylbenzene (e.g., 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene, etc.), ethylbenzene, styrene, cumene, methylbenzene, propylbenzene, xylene (e.g., p-xylene, m-xylene, o-xylene, etc.), naphthalene, methyl-naphthalene (e.g., 1-methylnaphthalene, anthracene, 9.10-dimethylanthracene, pyrene, phenanthrene, dimethyl-naphthalene (e.g., 1,5-dimethylnaphthalene, 1,6-dimethylnaphthalene, 2,5-dimethylnaphthalene, etc.), ethyl-naphthalene, hydrindene, methyl-hydrindene, dimethyl-hydrindene. In some embodiments, single ring aromatic compounds and / or polycyclic aromatic compounds may also be produced.

[0019] With respect to fluids, the term "fluid" refers to a gas, a liquid, a mixture of gas and liquid, or a gas or liquid containing dispersed solids, droplets, and / or bubbles. The terms "gas" and "vapor" have the same meaning and may be used interchangeably. In some embodiments, it may be advantageous to control the residence time of the fluidizing fluid within the reactor. The fluidization residence time of the fluidizing fluid is defined as the volume of the reactor divided by the volumetric flow rate of the fluidizing fluid under process conditions of temperature and pressure.

[0020] Regarding fluidized bed reactors, the term "fluidized bed reactor" is given its conventional meaning in the art and is used to refer to a reactor that includes a vessel capable of containing a particulate solid material (e.g., silica particles, catalyst particles, etc.) where a fluid (e.g., gas or liquid) passes through the particulate solid material at a sufficient velocity to suspend the solid material and cause it to behave as if it were a fluid. Examples of fluidized bed reactors are described in "Fluidization Engineering" Butterworth-Heinemann, 1991, by D. Kunii and O. Levenspiel, which is incorporated herein by reference. The term "circulating fluidized bed reactor" is also given its conventional meaning in the art and is used to refer to a fluidized bed reactor in which the particulate solid material exits the reactor, circulates through a line in fluid communication with the reactor, and is recycled back to the reactor. Examples of circulating fluidized bed reactors are described in "Fluidization Engineering" Butterworth-Heinemann, 1991, by D. Kunii and O. Levenspiel.

[0021] Bubbling and turbulent fluidized bed reactors are also known to those skilled in the art. In bubbling fluidized bed reactors, the fluid stream used to fluidize the particulate solid material operates at a flow rate low enough that bubbles and voids are observed within the volume of the fluidized bed during operation. In turbulent fluidized bed reactors, the flow rate of the fluid stream is higher than that used in bubbling fluidized bed reactors, so that bubbles and voids are not observed within the volume of the fluidized bed during operation. Examples of bubbling and turbulent fluidized bed reactors are described in Kirk-Othmer Encyclopedia of Chemical Technology (online), Vol. 11, Hoboken, NJ: Wiley-Interscience, 2001, pages 791-825, which are incorporated herein by reference.

[0022] With respect to olefins, the terms "olefin" or "olefinic compound" (also known as "alkene") are given their ordinary meaning in the art and are used to refer to any unsaturated hydrocarbon containing one or more pairs of carbon atoms joined by a double bond. Olefins include both cyclic and acyclic (aliphatic) olefins, where the double bond is located between carbon atoms that form part of a cyclic (closed ring) or open chain group, respectively. Furthermore, olefins can contain any suitable number of double bonds (e.g., monoolefins, diolefins, triolefins, etc.). Examples of olefinic compounds include, but are not limited to, ethene, propene, allene (propadiene), 1-butene, 2-butene, isobutene (2 methylpropene), butadiene, and isoprene, among others. Examples of cyclic olefins include cyclopentene, cyclohexane, and cycloheptene, among others. Aromatic compounds such as toluene are not considered olefins, but olefins containing aromatic moieties, such as benzyl acrylate or styrene, are considered olefins.

[0023] Regarding catalysts, the catalyst components useful in the context of the present invention can be selected from any catalyst known in the art or understood by those skilled in the art. A catalyst promotes and / or affects a reaction. Thus, as used herein, a catalyst lowers the activation energy (increases the rate) of a chemical process and / or improves the distribution of products or intermediates in a chemical reaction (e.g., shape-selective catalysis). Examples of reactions that can be catalyzed include dehydration, dehydrogenation, isomerization, hydrogen transfer, hydrogenation, polymerization, cyclization, desulfurization, denitrogenation, deoxygenation, aromatization, decarbonylation, decarboxylation, aldol condensation, and combinations thereof. As will be understood by those skilled in the art, the catalyst components can be considered to be acidic, neutral, or basic.

[0024] For catalytic pyrolysis, particularly advantageous catalysts include catalysts that include internal porosity selected according to pore size (e.g., mesoporosity and pore size typically associated with zeolites), e.g., average pore size of less than about 10 nm, less than about 5 nm, less than about 2 nm, less than about 1 nm, less than about 0.5 nm, or smaller. In some embodiments, catalysts having average pore sizes of about 0.5 nm to about 10 nm can be used. In some embodiments, catalysts having average pore sizes of about 0.55 nm to about 0.65 nm, or about 0.59 nm to about 0.63 nm can be used. In some examples, catalysts having average pore sizes of about 0.7 nm to about 0.8 nm, or about 0.72 nm to about 0.78 nm can be used.

[0025] In some preferred embodiments of catalytic pyrolysis, the catalyst may be selected from natural zeolites, synthetic zeolites, and combinations thereof. In certain embodiments, the catalyst may be a ZSM-5 zeolite catalyst, as will be appreciated by those skilled in the art. In some cases, such catalysts may contain acid sites. Other types of zeolite catalysts include ferrierite, zeolite Y, zeolite beta, mordenite, MCM-22, ZSM-23, ZSM-57, SUZ-4, EU-1, ZSM-11, (S)AlPO-31, SSZ-23, among others. Zeolites and other small pore materials are often characterized by their constraint index. The constraint index approximates the ratio of the cracking rate constants of normal hexane and 3-methylpentane. Methods for determining the constraint index are described in more detail in U.S. Pat. No. 4,029,716, which is incorporated by reference for details of the method.

[0026] The Constraint Index (CI) values ​​of some representative materials are as follows: [Table 1]

[0027] The CI may vary within the indicated range of 1 to 12. Similarly, other variables may affect the CI, such as crystal size, or the presence of potentially occluded exhaust contaminants and binders that are tightly bound to the crystals. Those skilled in the art will appreciate that the CI utilized herein, while providing a very useful means for characterizing the molecular sieves of interest, is approximate given the method of its determination, and that in some cases the extreme values ​​of variation may be compounded. However, the CI will have a value within the approximate range of 1 to 12 for any given molecular sieve useful herein.

[0028] In other embodiments, non-zeolitic catalysts such as WOx / ZrO2, aluminum phosphate, etc. may be used. In some embodiments, the catalyst may include a metal and / or metal oxide. Suitable metals and / or oxides include, among others, nickel, palladium, platinum, titanium, vanadium, chromium, manganese, iron, cobalt, zinc, copper, gallium, and / or any of their oxides. In some examples, promoter elements selected from rare earth elements, i.e., elements 57-71, cerium, zirconium, or combinations thereof, may be included to modify the activity or structure of the catalyst. Additionally, in some examples, the properties of the catalyst (e.g., pore structure, type and / or number of acid sites, etc.) may be selected to selectively produce desired products.

[0029] Catalysts for other processes, such as olefin alkylation, aromatization (hydrocarbon reforming), hydrogenation, hydrotreating, deoxygenation, denitrogenation, and desulfurization, are well known and can be selected for olefin conversion or other processes described herein.

[0030] With respect to plastics or polymers, the terms "plastic" and "polymer" are used interchangeably herein. A polymer is a carbon-based (at least 50 weight percent C) material composed primarily of repeating units and having a number average molecular weight of at least 100, usually greater than 1000, or greater than 10,000. Polymers include thermoplastic polymers such as polyethylene, polypropylene, polyester, polyethylene terephthalate (PET), acrylonitrile-butadiene-styrene (ABS) copolymers, polyamides, polyurethanes, polyethers, polycarbonates, poly(oxides), poly(sulfides), polyarylates, polyetherketones, polyetherimides, polysulfones, polyurethanes, polyvinyl alcohols, and polymers produced by polymerization of monomers such as dienes, olefins, styrenes, acrylates, acrylonitriles, methacrylate ... Examples of suitable feedstocks include nitrile, diacids and diols, lactones, diacids and diamines, lactams, vinyl halides, vinyl esters, their block copolymers, and their alloys, thermosetting polymers such as epoxy resins, phenolic resins, melamine resins, alkyd resins, vinyl ester resins, unsaturated polyester resins, crosslinked polyurethanes, polyisocyanurates, and crosslinked elastomers including, but not limited to, polyisoprene, polybutadiene, styrene-butadiene, styrene-isoprene, ethylene-propylene-diene monomer polymers, and blends thereof. Polymer mixtures separated from municipal solid waste or other waste streams are suitable feedstocks only if they contain only small amounts of contaminants such as S, N, O, or halogens. Polymers that produce halogenated materials upon pyrolysis, such as polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), and other halogenated polymers, are generally minimized or excluded from the feedstocks useful in this invention.

[0031] With respect to pyrolysis, the terms "pyrolysis" and "pyrolyzing" are given their conventional meaning in the art and are used to refer to the conversion of compounds such as solid hydrocarbonaceous materials, preferably without the addition of O2 or having O2, by heat, to one or more other substances, such as volatile organic compounds, gases, and coke. Preferably, the volume fraction of O2 present in the pyrolysis reaction chamber is 0.5% or less. Pyrolysis can occur with or without the use of a catalyst. "Catalytic pyrolysis" refers to pyrolysis carried out in the presence of a catalyst and can include steps described in more detail below. Examples of catalytic pyrolysis processes are outlined, for example, in Huber, GWet al, "Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysts, and Engineering," Chem. Rev. 106, (2006), pp. 4044-4098.

[0032] Regarding selectivity, the term "selectivity" refers to the production of a particular product compared to a selected product. The selectivity for a product may be calculated by dividing the amount of a particular product by the amount of some product produced. For example, if a reaction produces 75 grams of aromatic compounds and 20 grams of benzene are found among the aromatic compounds, the selectivity to benzene in the aromatic products is 20 / 75=26.7%. Selectivity can be calculated on a mass basis, as in the previous example, or on a carbon basis, where the selectivity is calculated by dividing the amount of carbon in a particular product by the amount of carbon in a selected product. For reactions involving polymers as reactants, the selectivity is on a mass basis unless otherwise specified. For reactions involving the conversion of a particular molecular reactant (such as ethene), the selectivity is the percentage (on a mass basis unless otherwise specified) of the selected product divided by all products produced.

[0033] Regarding yield, the term "yield" as used herein refers to the amount of product leaving the reactor divided by the amount of reactants entering the reactor, usually expressed as a percentage or fraction. Yields are often calculated on a mass basis, a carbon basis, or based on a particular feed component. Mass yield is the mass of a particular product divided by the weight of the feed used to prepare that product. For example, if 500 grams of polymer are fed to a reactor and 45 grams of benzene are produced, the mass yield of benzene is 45 / 500=9% benzene. Carbon yield is the mass of carbon in a particular product divided by the mass of carbon in the feed to the reactor. For example, if 500 grams of a polymer containing 90% carbon are reacted to produce 400 grams of benzene containing 92.3% carbon, the carbon yield is [(400*0.923) / (500*0.90)]=82.0%.

[0034] As in standard patent terminology, the term "comprising" means "including" and does not exclude additional components. Any aspect of the invention described in conjunction with the term "comprising" also includes narrower embodiments in which the term "comprising" is replaced with the narrower terms "consisting essentially of" or "consisting of." As used herein, the terms "includes" or "including" should not be construed as limiting the invention, but rather as reciting exemplary components.

[0035] Detailed Description of the Invention FIG. 1 shows a schematic diagram of one embodiment of the process of the present invention for converting plastic waste to olefins and aromatics. The plastic mixture 10 is introduced into an optional feed system 100 that prepares the plastic mixture for introduction into the process, for example by removing undesired feed materials 102, such as metals, minerals, halogenated materials, and / or sizing the materials to a desired size range. The steps of removing undesired feed materials and sizing can be performed in any order, i.e., either step can be performed first and the other step can be performed next. The remaining plastic mixture 101 is sent to an optional washing process 110, where the plastic mixture can be washed, for example by treating with a washing solution 112 to remove unwanted materials such as dirt, labels, coatings, etc., to produce a washed plastic mixture 111 and a spent solution 113. The washed plastic mixture 111 is sent to a pyrolysis reactor 120 along with an optional co-reactant 122, such as a heat transfer medium or getter. In the pyrolysis reactor 120, the mixture is heated to a temperature to crack the plastic into a product mixture including lighter components 121 in the vapor phase and heavier components 123 in a solid or liquid phase or a combination of solid and liquid phases, including at least a portion of the materials introduced in the co-reactant. The vapor phase pyrolysis product mixture passes through an optional solids removal system 130 which further removes solid particles entrained in the pyrolysis product vapors 121. The remaining vapor phase 131 is sent to the optional solids separator 130, or to the catalytic reactor 140 for at least a period of time that maintains the temperature of the pyrolysis product vapor at the temperature of the vapor phase upon exiting the pyrolysis reactor 120 if no solids separator is present. The vapor phase 131 is sent to the thermal catalytic reactor 140 which is packed with an aromatization catalyst, shown as catalytic product 141, effective to convert paraffins and / or olefins to aromatics. A portion of the catalyst 142 is continuously removed from the reactor 140 , separated from the product 141 , or both, and sent to a catalyst regenerator 150 .In the catalyst regenerator 150, the catalyst is oxidized by treatment with an oxygen source such as air 151, the regenerated catalyst 143 is returned to the reactor 140, and the combustion product gases 152 are vented or used to provide heat to the pyrolysis reactor or reactors. The catalyst product 141 can be separated into components such as ethylene, propylene, butenes, C1-C5 paraffins, benzene, toluene, xylenes, naphthalene, and other fractions in a separation scheme using conventional separation techniques.

[0036] Figure 2 shows a schematic diagram of another embodiment of the process of the present invention for converting plastic waste to olefins and aromatics. The plastic mixture 10 is introduced into an optional feed system 100 that prepares the plastic mixture for introduction into the process, for example by removing undesired feed materials 102, such as metals, minerals, halogenated materials, and / or sizing the materials to a desired size range. The steps of removing undesired feed materials and sizing can be performed in any order, i.e., one step can be performed first and the other step can be performed second. The remaining plastic mixture 101 is sent to an optional washing process 110, where the plastic mixture can be washed, for example by treating with a washing solution 112 to remove unwanted materials such as dirt, labels, coatings, etc., to produce a washed plastic mixture 111 and a spent solution 113. The washed plastic mixture 111 is sent to a pyrolysis reactor 120A together with an optional co-reactant 122, such as a heat transfer medium or getter. In the pyrolysis reactor 120A, the mixture is heated to an intermediate temperature to partially decompose the plastic, for example, decomposing PVC or PVDC to release HCl, or decomposing another halogenated polymer to release HCl, HBr, or HI, or releasing vapors such as NH3, HO, etc. An optional inert sweep gas 124 is fed to the reactor 120A to aid in the removal of vapors generated in the reactor and exhausted through an exit port 125. With or without a sweep gas, the vapor 125 can be treated to capture or neutralize HCL and toxic materials before being released or transported to water treatment. The vapor 125 typically contains at least 60% or at least 80% HO, and may contain HCl, halogenated carbon compounds, and other species that are more volatile than the molten polymer.The condensed phase 126 is sent to the second pyrolysis reactor 120B where they are heated and cracked into a product mixture including lighter components 121 in the vapor phase and heavier components 123 in solid or liquid phases or a combination of solid and liquid phases, including at least a portion of the materials introduced in the co-reactant, or the co-reactant can be fed directly to the second pyrolysis reactor (not shown). The vapor phase pyrolysis product mixture passes through an optional solids removal system 130 which further removes solid particles entrained in the pyrolysis product vapor 121. The remaining vapor phase 131 is sent to the catalytic reactor 140 for at least a period of time that maintains the temperature of the pyrolysis product vapor at the optional solids separator 130, or the temperature of the vapor phase upon exiting the pyrolysis reactor 120 if no solids separator is present. The vapor phase 131 is sent to the thermal catalytic reactor 140 which is packed with an aromatization catalyst, shown as catalytic product 141, effective to convert paraffins or olefins, or both, to aromatics. A portion of the catalyst 142 may be continuously removed from the reactor 140, separated from the product 141, or both, and sent to a catalyst regenerator 150. In the catalyst regenerator 150, the catalyst is oxidized by treatment with an oxygen source such as air 151, and the regenerated catalyst 143 is returned to the reactor 140, and the combustion product gases 152 are vented or used to provide heat to a pyrolysis reactor or reactors. The catalyst product 141 may be separated into components such as ethylene, propylene, butenes, C1-C5 paraffins, benzene, toluene, xylenes, naphthalene, and other fractions in a separation scheme using conventional separation techniques.

[0037] Combustible gases such as methane, ethane, propane, butane, CO and H2 can optionally be recovered from the vapor stream 125 or from the gases produced in the catalytic pyrolysis in the fluidized bed reactor. The combustible gases can provide heat to the process. Heat in the reactor 120A can also be provided by other sources such as pressure / friction and / or resistive or inductive heating.

[0038] In some embodiments, for example when recycled polymeric materials are used, impurities may be optionally removed from the feed composition prior to being fed to the reactor by an optional separation step, such as, for example, 100 in FIG. 1 or FIG. 2. In some examples, the separation step may include mechanical separation, float-sink separation, air elutriation, or other known separation processes, preferably in an automated mode. In some examples, the particle size of the solid polymeric feed composition may be reduced in a size reduction system as part of 100 prior to sending the feed to the pyrolysis reactor. In some embodiments, the average diameter of the reduced size feed composition exiting the size reduction system comprises about 50% or less, about 25% or less, about 10% or less, about 5% or less, about 2% or less of the mass average diameter of the feed composition fed to the size reduction system. The feed mixture may include a plastic mixture in which at least 85 percent by weight, or at least 90 percent by weight, or at least 95 percent by weight of the particles pass through a 0.25 inch (0.6 cm), or 0.5 inch (1.2 cm), or 1.0 inch (2.5 cm), or 1.5 inch (3.7 cm), or 2 inch (5.0 cm), or 4 inch (10.0 cm) screen. The average diameter (size) may be measured through the mesh (sieve). Larger particle feed materials may be easier to transport and less difficult to process than smaller particle feed materials. On the other hand, in some cases, it may be advantageous to feed smaller particles to the reactor. The use of a size reduction system allows for the transport of larger particle feed between the source and the process while simultaneously allowing for the feeding of smaller particles to the reactor.

[0039] Feed materials suitable for use in the present invention include polyethylene (PE), polypropylene (PP), polyacetylene, polybutylene, polyolefin, polyethylene terephthalate (PET), polybutylene terephthalate, polyester, copolyester, polycarbonate, polyurethane, polyamide, polystyrene (PS), polyacetal, epoxy, polycyanurate, polyacrylic acid, polyurea, vinyl ester, polyacrylonitrile, polyamide, polyurethane, polyether, polycarbonate, poly(oxide), poly (sulfides), polyarylates, polyetherketones, polyetherimides, polysulfones, polyurethanes, polyvinyl alcohol, polyvinyl chloride (PVC), polyvinyl dichloride (PVDC), polyvinyl acetate, nylons, copolymers such as ethylene-propylene, acrylonitrile-butadiene-styrene (ABS), nitrile rubber, natural and synthetic rubber, tires, styrene-butadiene, styrene-acrylonitrile, styrene-isoprene, styrene-maleic anhydride, ethylene vinyl acetate, nylon 12 / 6 / 66, This may include all types of polymeric materials, including filled polymers, polymer composites, plastic alloys, other polymeric materials, and polymers or plastics dissolved in solvents (even those obtained from the polymer or plastic manufacturing process as waste or discarded materials), post-consumer recycled polymeric materials, materials separated from waste streams such as municipal solid waste, and polymers produced by polymerization of monomers, such as dienes, olefins, styrenes, acrylates, acrylonitrile, methacrylates, methacrylonitrile, diacids and diols, lactones, diacids and diamines, lactams, vinyl esters, block copolymers thereof, and alloys thereof, thermosetting polymers, such as epoxy resins, phenolic resins, melamine resins, alkyd resins, vinyl ester resins, unsaturated polyester resins, crosslinked polyurethanes, polyisocyanurates, and crosslinked elastomers, including, but not limited to, polyisoprene, polybutadiene, styrene-butadiene, styrene-isoprene, or any combination thereof.The present invention includes subcombinations of these materials as needed or available from a particular location, and the invention can be described as including one or any combination of these materials.

[0040] In any method, the pyrolysis reactor 120, or 120A, or 120B, or two or more of them, may be moving bed reactors, where the feed material is propelled along the length of the reactor by mechanical or gravitational means, or both mechanical and gravitational means. Typical examples of reactors suitable for the pyrolysis reactors 120, 120A, and 120B include single screw extruders, twin screw extruders, Auger reactors, rotary kiln reactors, or staged grate reactors. In any embodiment, the pyrolysis reactor has a means for separating condensed materials, such as solids or liquids or both, from the vapor product, and an outlet for the condensed phase that is separate from the outlet for the vapor phase. In any embodiment, the pyrolysis reactor has multiple heating zones, with the temperature being successively higher in later zones. In some embodiments, the pyrolysis reactor is fitted with a gas outlet in a region of the reactor where the temperature of the material in the reactor is below 300°C or between 250°C and 300°C so that products generated at lower temperatures, such as steam, HCl, NH3, or other materials, can be removed from the reactor. In one embodiment, a separation screen is fitted immediately downstream of the gas outlet in the pyrolysis reactor to at least partially prevent gases generated at lower temperatures from entering the hotter portion of the reactor along with the molten and solid materials. In one embodiment, a gas inlet for introducing hot inert or recycle gases, such as CH4, H2, CO, CO2, and gases containing any of C2-C4 paraffins or olefins, or mixtures, is fitted immediately downstream of the gas vent and optional screen.

[0041] In some embodiments, the pyrolysis reactor comprises two or more reactors 120A and 120B in series, etc., where the feed is heated to a temperature of 250° C.-300° C. in the first reactor 120A, and the hot condensed phase, i.e., solids and liquids, is sent from the first reactor to the second reactor 120B, and vapor is exhausted without entering the second reactor. Optionally, instead of or in addition to being fed to the pyrolysis reactor 120A, a solid co-reactant 122 can be fed to the pyrolysis reactor 120B.

[0042] When an Auger reactor is utilized, embodiments of the invention include a helical auger, optionally with different pitch dimensions in different portions of the auger, to tailor the velocity of the condensed phase from the inlet to the outlet of the reactor. In this embodiment, the flight thickness and shaft diameter can also be variable dimensions along the length of the auger to control the flow rates of the vapor and condensed phases. Augers with paddled, or cut, or folded flights are also contemplated within the scope of these embodiments.

[0043] In embodiments, when a rotary kiln reactor is utilized, the kiln cylinder can be fitted with lifters, such as helical lifters attached to the cylinder wall, or plate lifters, folded lifters, or segmented lifters extending from the cylinder wall. The rotary kiln reactors contemplated herein can also be tilted either up or down toward the exit end of the kiln, depending on the desired residence time and flow rate of the condensed phase in the kiln, thus utilizing gravity to control the residence time of the condensed phase. It is also contemplated that the rotational speed of the rotary kiln reactor can be adjusted as desired, for example, between 20 revolutions per minute and 0.2 revolutions per minute, depending on the nature of the feed mixture and the co-reactants added, to provide thorough mixing and high heat transfer. The rotary kiln reactors contemplated in those embodiments can be externally heated by combustion of process waste gases, such as CH4, C2-C4 paraffins, H2, CO, etc., recycled from product separation or natural gas, or electrically.

[0044] In any embodiment, the temperature profile within the pyrolysis reactor ranges from a low temperature near the feed inlet port to a high temperature at the outlet port or ports. The temperature range at or near the inlet port can be from 20° C. to 225° C., e.g., from 20° C. to 100° C., or from 20° C. to 50° C., and the temperature range at the high temperature outlet port can be from 300° C. to 700° C., e.g., from 325° C. to 650° C., or from 350° C. to 600° C.

[0045] In embodiments where solid co-reactant material is fed to the pyrolysis reactor, the solid co-reactant material is optionally transferred to a combustion regenerator where the carbonaceous material reacts with air and at least a portion of the hot solid co-reactant material is returned to the pyrolysis reactor. In one embodiment of the present invention, the hot flue gas exiting the solid co-reactant regenerator is sent to a catalytic heater to heat the catalyst in the catalytic pyrolysis reactor.

[0046] In some embodiments, vapors exiting the pyrolysis reactor or reactors may be passed through filters to remove fines and to capture compounds such as NH3, HS, COS, or metal vapors such as Hg that may poison the catalyst in the catalytic reactor. These may be mesh filters and / or beds of absorbent particles such as activated carbon.

[0047] In any method, the vapors exiting the pyrolysis reactor can be passed through an optional solids separation device, such as a cyclone or screen, to remove entrained solids, while maintaining the temperature of the vapor at least the same temperature as the temperature of the vapor at the outlet of the pyrolysis reactor, i.e., not allowing the vapor to cool significantly before being sent to the catalytic pyrolysis reactor. After exiting the anaerobic pyrolysis reactor 120A, the vapor product preferably does not come into contact with cold surfaces that could condense the product, and preferably the surfaces are maintained at a temperature of at least 300°C, at least 325°C, or at least 350°C, or within 25°C or 50°C of the temperature exiting the reactor 120A. Preferably, in any embodiment, the temperature of the vapor is maintained at a temperature at least 2°C, or at least 3°C, or at least 5°C, or at least 10°C higher than the temperature of the vapor at the outlet end of the pyrolysis reactor.

[0048] In any method, the catalytic reactor 140 can be a fluidized bed reactor, where the catalyst is a solid catalyst, and the catalytic pyrolysis step includes pyrolyzing in the presence of the solid catalyst in the fluidized bed reactor to produce a fluid product stream 141 and a coke-containing spent catalyst 142, where at least 95% of the carbon in the steam feed is converted to coke and volatile products, at least a portion of the coke-containing spent catalyst is transferred to a regenerator 150 where the coke reacts with oxygen or air to form a hot regenerated catalyst, and at least a portion of the hot regenerated catalyst 143 is returned to the fluidized bed reactor, where heat from the hot regenerated catalyst provides energy for the pyrolysis step.

[0049] In any method, the catalytic pyrolysis step may include pyrolysis in the presence of a fluidized bed catalyst. The catalytic pyrolysis reactor may include a fluidized bed, circulating bed, bubbling bed, or riser reactor operating at temperatures ranging from 300° C. to 800° C., or 350° C. to 750° C., or 400° C. to 700° C., or 450° C. to 650° C., or 500° C. to 600° C. The vapor residence time in the catalytic pyrolysis may be from 1 second to 480 seconds, or from 1 second to 240 seconds, or from 2 seconds to 60 seconds, or from 3 seconds to 30 seconds, or from 4 seconds to 15 seconds. The pressure in the catalytic pyrolysis reactor may be at least 0.1 MPa (1 bar), or at least 0.3 MPa (3 bar), or at least 0.4 MPa (4 bar), or from 0.1 to 2.0 MPa (1 to 20 bar), or from 0.1 to 1.0 MPa (1 to 10 bar), or from 0.3 to 0.8 MPa (3 to 8 bar), preferably from 0.4 to 0.6 MPa (4 to 6 bar), the pressure being absolute.

[0050] The design and conditions of the fluidized bed reactor may be those known in the art. A fluidizing gas may be required at start-up, and during steady state operation, the fluidizing gas may comprise part of the vapor stream 126 and may optionally be piped to the bottom of the fast catalytic pyrolysis fluidized bed reactor. Recycle gas from the process may be used as the fluidizing gas.

[0051] For catalytic pyrolysis, useful catalysts include catalysts that include internal porosity selected according to pore size (e.g., mesoporosity and pore sizes typically associated with zeolites), e.g., average pore sizes less than 10 nm, less than 5 nm, less than 2 nm, less than 1 nm, less than 0.5 nm, or smaller. In some embodiments, catalysts having average pore sizes of 0.5 to 10 nm can be used. In some embodiments, catalysts having average pore sizes of 0.5 to 0.65, or 0.59 to 0.63 nm can be used. In some examples, catalysts having average pore sizes of 0.7 to 0.8 nm, or 0.72 to 0.78 nm can be used.

[0052] Particularly advantageous catalyst compositions in the catalytic pyrolysis fluidized bed reactor of the present invention include crystalline molecular sieves characterized by a SAR (silica to alumina, SiO2:Al2O3 mass ratio) of greater than 12 or between 12 and 240, and a CI (constraint index) of 1 to 12. Non-limiting examples of such crystalline molecular sieves are those having the structure of ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, or combinations thereof. In one embodiment, the catalyst composition includes crystalline molecular sieves characterized by a SAR of greater than 12 to 240 and a CI of 5 to 10, such as molecular sieves having the structure of ZSM-5, ZSM-11, ZSM-22, ZSM-23, or combinations thereof. Methods for determining CI are more fully described in U.S. Pat. No. 4,029,716, the details of which are incorporated herein by reference.

[0053] The molecular sieve or catalyst composition containing same used herein may be heat treated at elevated temperatures. This heat treatment is generally carried out by heating at a temperature of at least 370°C for at least 1 minute, generally up to 20 hours (usually in an oxygen-containing atmosphere, preferably air). For heat treatment, atmospheric pressure is preferred for convenience, although subatmospheric pressures may also be used. Heat treatment may be carried out at temperatures up to about 925°C. Heat treated products are particularly useful in the process of the invention.

[0054] For the catalyst compositions useful in the present invention, suitable molecular sieves can be used in combination with a carrier or binder material, such as, for example, a porous inorganic oxide carrier or a clay binder. Non-limiting examples of such binder materials include alumina, zirconia, silica, magnesia, thoria, titania, boria, and combinations thereof, typically in the form of dry inorganic oxide gels and gelatinous precipitates. Suitable clay materials include, by way of example, bentonite, diatomaceous earth, and combinations thereof. The relative proportion of suitable crystalline molecular sieves in the overall catalyst composition can vary widely, with the molecular sieve content ranging from 30 to 90 weight percent of the composition, more typically from 40 to 70 weight percent. The catalyst composition can be in the form of extrudates, beads, or fluidized microspheres.

[0055] The molecular sieves used herein or catalyst compositions containing same may have the original cations at least partially replaced by ion exchange with hydrogen, or hydrogen precursor cations, or non-noble metal ions of Group VIII of the Periodic Table, i.e., nickel, iron, or cobalt, or zinc, or gallium, or combinations thereof, according to techniques well known in the art.

[0056] In the process of regenerating catalysts obtained from catalytic pyrolysis, heat is generated by oxidation of coke, char, and other materials in a catalyst regenerator, which can be used in the process or converted into electricity for export. In one set of embodiments, an oxidant is fed to the regenerator via a stream shown as 151 in FIG. 1. The oxidant can come from any source, including, for example, tank oxygen, air, steam, etc., among others. In the regenerator, the catalyst and the oxidant react to reactivate the catalyst and generate heat. The solid mixture containing the deactivated catalyst can contain residual carbon and / or coke, as well as coke or char from the process, which can be removed by reaction with the oxidant in the regenerator. In some embodiments, a portion of the gaseous products from the catalytic pyrolysis process is fed to a catalyst regenerator and combusted with the solid materials. The gaseous products can be initially separated into an olefin-rich stream and an olefin-lean stream, and at least a portion of the olefin-lean stream can be fed to the catalyst regenerator. The regenerator in FIG. 1 includes a vent stream 152, which can contain regenerated reaction products, residual oxidant, etc.

[0057] In some embodiments of the process, at least a portion of the non-vapor materials 123 removed from the pyrolysis reactor 120 may be recycled to the feed of the pyrolysis reactor 120 as part of the optional co-reactant 122. In some embodiments of the process, the optional co-reactant 122 may include a solid material that reacts with the sulfur or nitrogen compounds to capture the sulfur or nitrogen species in the solid phase. The solid material in the optional co-reactant 122 may include one or more materials selected from agricultural lime, calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, limestone, or hydrotalcite, or any combination thereof. EXAMPLES

[0058] Examples 1 to 10 The drop tube reactor for the two-stage chemical conversion of plastics comprises a quartz reactor tube (ACE Glass) with a quartz frit (40-90 μm) welded to the center of the tube. Figure 3 shows the configuration of the drop tube reactor. The sample cell (10 mm outer diameter, 8 mm inner diameter, 25 mm long, quartz, made by TGP) is filled with the feedstock using two pieces of quartz wool (TGP). As shown in Figure 3, the sample cell was placed in a reactor cap (borosilicate, ACE Glass) and held with a stopper (1 / 4 inch (6 mm) aluminum rod, McMaster). The reactor cap and quartz reactor were then assembled and placed in a fixed-bed reactor system. The bottom of the reactor was connected to a condenser (borosilicate) filled with a perforated stainless steel packing (ACE Glass) immersed in an ice-water bath (0 °C). A heating mantle was applied between the bottom of the reactor and the top of the condenser to prevent condensation before the condenser. The heating mantle was set to 210° C. during the reaction.

[0059] In the reactor, a small sample (1.5 g) of ZSM-5 catalyst was placed on top of the quartz frit. The feedstock (100 mg for each run) was sealed in the sample cell with quartz wool. The catalyst / feedstock weight ratio was about 15. Before the contents of the sample cell were dropped into the reactor, the catalyst was calcined at 550 °C for 20 min under 100 mL / min air flow (heating rate = 12 °C / min). After calcination, the reactor was cooled to the reaction temperature (500 °C). During cooling, the condenser was filled with 10 mL of solvent (ethyl acetate for plastic conversion, acetone for biomass conversion) and held for 10 min for temperature lineout. The reactor system was then purged with a helium flow of 75 mL / min for 20 min to remove air and to purge the gas collection lines. The sample cell with the feedstock was dropped into the reactor by withdrawing the stopper rod to start the reaction.

[0060] A 10 min holding period was used to complete the reaction. The gas products, consisting mostly of permanent gases and C1-C3 olefins and paraffins, were collected in a gas bag. The liquid products (mainly C 4+) was collected in the condenser. After the reaction, the temperature was increased to 650 °C without gas flow. The solid products including coke and char remaining in the reactor were then combusted at 650 °C for 10 min under 50 mL / min air flow. The gas products during combustion were collected in a second gas bag. Additionally, 3 mL of solvent was added to the condenser to extract any products remaining on the top of the condenser. Then, all the liquid in the condenser was transferred to a 20 mL sample vial. A weighed amount of internal standard (dioxane, typically 3000-5000 mg, Sigma-Aldrich) was added to the sample vial. The condenser was washed with acetone and dried in a drying oven. It should be noted that a small amount of liquid was retained in the condenser due to hold-up in the packing. Therefore, the weight of the condenser with and without liquid product was measured to determine the total amount of liquid product. Liquid samples were analyzed for hydrocarbons and oxygenates by GC-FID (Shimadzu 2010Plus gas chromatograph with flame ionization detector). Gas bag samples were analyzed using an Agilent GC 7890B gas chromatograph.

[0061] The results of the runs for the various feeds are shown in Table 2. The remainder of the products not listed in Table 2 includes water, inert solids, and minor components that are not easily recovered due to combustion.

[0062] Examples 1-11 show that two-stage pyrolysis followed by catalytic pyrolysis produces high yields of olefins and aromatics from plastics. The olefin yield is at least 2% in all cases, and the BTX yield is at least 10.08% in all cases. Examples 1, 2, 3, 4, and 9 show that for polymers without fillers (tires) or heteroatoms (PET, nylon), the BTX yield is at least 32.88%, the olefin yield is at least 5.58%, and the coke and char yield is less than 5% of the feed mass, and often less than 2%. The olefin yield in two-stage pyrolysis / catalysis of polyolefins (Examples 1, 2, 3, 4) is at least 10.43%, and for linear unbranched polyolefins (Examples 1, 2, and 3) is at least 17.25%. The yield of aromatics in the two-stage pyrolysis / catalysis of polyolefins (Examples 1, 2, 3, 4) is at least 32.88%, and for linear unbranched polyolefins (Examples 1, 2, and 3) the yield is at least 45.6%.

Claims

1. 1. A process for producing olefins and aromatic compounds, comprising the steps of: feeding a plastics-containing stream into a first pyrolysis reactor comprising a mechanically or gravity-induced moving bed; anaerobically pyrolyzing the stream in the first reactor at a temperature greater than 350°C; preparing a raw vapor product, said raw vapor product at said temperature exiting said first reactor at a first temperature; passing the raw vapor product produced in the first pyrolysis reactor to a second reactor containing a fluidized bed having a catalyst while maintaining the temperature of the vapor at least 2° C. above the first temperature; catalytically reacting the vapor product from the pyrolysis with the catalyst in the fluidized bed reactor to form a product vapor mixture; and recovering olefins, or aromatics, or any combination thereof, from the product vapor mixture.

2. 10. The process of claim 1, wherein the first pyrolysis reactor comprises a moving bed, a single screw extruder, a twin screw extruder, an Auger reactor, a rotary kiln reactor, or a staged grate reactor.

3. 3. The process of claim 2, wherein the first reactor includes an inlet port and an outlet port, and the temperature at or near the inlet port is between 20° C. and 225° C., and the temperature range of the outlet port is between 300° C. and 700° C.

4. 10. The process of claim 1, wherein the first pyrolysis reactor comprises two or more reactors in series.

5. 5. The process of claim 4, wherein the feed stream is heated to a temperature of 250-300° C. in the first pyrolysis reactor and the condensed phase is sent to a second pyrolysis reactor.

6. 10. The process of claim 1, wherein an inert gas is fed to the first pyrolysis reactor.

7. 10. The process of claim 1, wherein a solid co-reactant material is fed to the first pyrolysis reactor.

8. 8. The process of claim 7, wherein the solid co-reactant material is transferred to a combustion regenerator, where the carbonaceous material reacts with air, and at least a portion of the hot solid co-reactant material is returned to the first pyrolysis reactor.

9. 8. The process of claim 7, wherein the solid co-reactant fed to the first reactor comprises agricultural lime, calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, limestone, hydrotalcite, or any combination thereof.

10. 9. The process of any of claims 2, 3, 6, 7 and 8, wherein the catalyst in the fluidized bed reactor comprises a zeolite.

11. 9. The process of any of claims 2, 3, 6, 7 and 8, wherein the plastic feed stream is first heated to at least 200°C to a molten state and filtered to remove solids.

12. 9. The process of any of claims 2, 3, 6, 7 and 8, wherein the product vapor mixture from the fluidized bed catalytic reactor comprises at least 20 weight percent BTX.

13. 9. The process of any of claims 2, 3, 6, 7 and 8, wherein the product vapor mixture is passed through one or more solids separators.

14. 14. The process of claim 13, wherein the catalyst in the fluidized bed catalytic pyrolysis reactor is removed, regenerated by oxidation with air in a regenerator, and returned to the catalytic pyrolysis reactor.

15. 15. The process of claim 14, wherein heat recovered from the catalyst regenerator is used to heat the feedstock, the first pyrolysis reactor, or catalytic pyrolysis in the fluidized bed reactor, or some combination thereof.

16. 15. The process of claim 14, wherein the product vapor mixture comprises CH4 and C2-C4 paraffins, and 50 to 100 mass percent of the CH4 and C2-C4 paraffins is combusted in the regenerator.

17. 14. The process of claim 13, wherein the product vapor mixture from the fluidized bed catalytic reactor comprises at least 20 weight percent olefins.

18. 2. The process of claim 1, wherein the mass yield of BTX in the product vapor mixture from the catalytic conversion is at least 30% BTX based on the mass in the stream.

19. 20. The process of claim 18, wherein benzene, toluene, or xylenes are separated from the product vapor mixture.

20. 9. The process of claims 2, 3, 6, 7 and 8, wherein at least a portion of the aromatic products in the product vapor mixture is hydrogenated to produce naphthenes.

21. 2. The process of claim 1, wherein the first pyrolysis is carried out by first heating the feed to a temperature of 250-300°C and holding at that temperature while steam is removed, after which the molten plastic waste is pyrolyzed at a higher temperature.

22. 9. The process of any of claims 2, 3, 6, 7 and 8, wherein the feedstock comprises a waste plastic mixture selected from polyethylene terephthalate (PET), high density polyethylene (HDPE), polyvinyl chloride (PVC), polyvinylidene (PVCD), low density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), mixed resins, or any combination thereof.

23. 9. The process of any of claims 2, 3, 6, 7 and 8, wherein the catalyst in the fluidized bed reactor comprises ZSM-5.

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