Use of metal-free carbon materials for converting plastics to C2-C4 olefins and / or hydrocarbons under direct induction heating, and method thereof

Abstract

The present invention refers to the use of metal-free carbon materials for converting plastics into C2-C4 olefins and / or other hydrocarbons under direct induction heating at temperatures up to 800°C. The present invention also relates to a process for converting plastics into C2-C4 olefins and / or other hydrocarbons, comprising a step of reacting under direct induction heating at a temperature of up to 800°C with a metal-free carbon material as defined in any one of the claims.

Description

[Technical Field]

[0001] The present invention refers to the use of materials for converting plastics into C2-C4 olefins and / or other hydrocarbons, as well as to processes for converting plastics into C2-C4 olefins and / or other hydrocarbons.

[0002] The present invention therefore has utility in the plastics and chemical industries, particularly in the area of ​​recycling.

[0003] In the following description, reference numbers in brackets ([ ]) refer to the list of references at the end of the text. [Background technology]

[0004] Plastics represent one of the major commodities for everyday use in almost every sector, ranging from industrial packaging to healthcare and composite materials for transportation and storage. It was estimated that approximately 380 million tons of petroleum-based plastics were produced in 2015. The majority of these are used for packaging (primarily disposable), while others end up in construction, automobiles, electrical equipment, and many other applications. Given annual growth rates, this amount is projected to double by 2035. The disposability of plastics as a commodity (40%) is one of the main contributors to CO2 emissions and poses environmental and health problems, as approximately 90% of waste plastics are currently discarded or landfilled, while only a small amount is recycled. Additionally, a large portion of waste plastic ends up in rivers and oceans, posing a problem for the natural environment.

[0005] New legislation and environmental initiatives will significantly contribute to the increased recycling of waste plastics to produce new plastics or feedstock for liquid fuels for transportation and petrochemicals. While academic interest in the conversion of plastics to fuel (PTF) has never been greater, industrial interest has also been growing since the last few years. More recently, several announcements from various industries about the establishment of new plants to convert waste plastics into valuable gas / liquid components have contributed to renewed interest in the process.

[0006] Plastic waste itself is contaminated by other products, so prior sorting and cleaning are necessary before starting the recycling process. Today, depending on the quality and purity of the plastic waste, different recycling processes can be used: (i) reuse (directly from the waste plastic), (ii) reprocessing or mechanical recycling, (iii) depolymerization to monomeric raw materials (not for all types of waste plastics), (iv) conversion of waste plastics to hydrocarbon raw materials, and finally (v) energy recovery through incineration. Recycling efficiency also depends on the nature of the various additives present in the plastic.

[0007] Conversion of plastics to liquid or gaseous hydrocarbons also allows for the recycling of solid waste fractions that cannot be reused or recycled by mechanical or depolymerization processes, avoiding landfill or incineration. Recycling waste plastics allows for significant reductions in greenhouse gas (GHG) emissions compared to incineration. In addition to converting waste plastics to liquid fuels, other research has also aimed at converting such waste materials into light olefins, which are of high interest as base chemicals, i.e., feedstock monomers, for the production of plastics. However, the direct conversion of waste plastics to light olefins is not a straightforward process, so indirect routes have been developed via the conversion of waste plastics to intermediate hydrocarbons and the further conversion of these chemicals to light olefins. Onwudili et al. (Onwudili et al., 2019([1])) studied the conversion of plastic mixtures (HDPE, LDPE, PP, PS, and PET) to polyolefin vapors by FCC (fluid catalytic cracking) using Y-zeolite at 500 °C and ZSM-5 zeolite at 600 °C. The amount of C2-C4 olefins obtained remains relatively low at about 21 wt%.

[0008] The depolymerization of polyolefins into their monomeric components, known as plastics to olefination (PTO), requires relatively harsh pyrolysis conditions and results in a complex mixture of hydrocarbons. Generally, pyrolysis of polyolefins at temperatures ≦500°C results in the formation of C 10 ~C 40While milder conditions produce a paraffinic mixture with carbon chain lengths in the range of 0.1 to 1.5, harsher conditions produce more aromatic compounds, ultimately producing olefin-rich gas and charcoal under even harsher conditions (≥700 °C) (Lopez et al., 2017([2]); Dogu et al., 2021([3])). To maximize the olefin fraction, the aliphatic compounds produced under milder conditions can be further processed to obtain light olefins by steam cracking (FCC), which can produce olefins with a yield of 65 wt%. Synova technology is based on the use of a high-temperature fluidized sand bath to crack plastic waste to produce liquids and tar, which are further cracked to produce olefin-rich gas. Anellotech and BioBTX have developed pyrolysis using acidic zeolites to convert plastic pyrolysis vapors into light olefins and waxes. However, catalyst deactivation requires complex reactor design and frequent catalyst regeneration (J.-P. Lange, Managing Plastic Waste-Sorting, Recycling, Disposal, and Product Redesign, ACS Sustain. Chem. Eng., 2021, 9, 15722-15738 https: / / doi.org / 10.1021 / acssuschemeng.1c05013([4])).

[0009] In addition, to reduce GHG emissions in the chemical industry, it is highly desirable to replace the conventional method of operating catalytic processes, i.e., the combination of large gas burners and metal catalysts, with entirely new ones. Replacing natural gas burners with electric heating systems has attracted significant industrial interest in recent years. For example, recent consortia restructuring several petroleum industries are developing novel steam crackers that operate on electricity (Layritz et al., 2021([5])), electrocatalysis (Schiffer et al., 2017([6])), or intermediate heating modes using electricity, such as microwave, plasma, or induction heating (Jie et al., 2020([7]); Zhou et al., 2021([8])). It is also desirable to replace conventional supported metal or zeolite-based catalysts with metal-free alternatives, which reduce production costs and environmental impacts (recycling or disposal of spent catalysts). Last but not least, the ability to produce chemicals using electricity directly or indirectly is also a clever way to store excess electrical energy from renewable sources and can aid in improving energy harvesting from solar and wind power.

[0010] Induction heating (IH) has been widely developed in the manufacturing of industrial metal workpieces (joining, welding, sintering) in several industries. Heat is generated directly inside the target material, thus significantly reducing energy loss through conduction or thermal radiation (Wang et al., 2019([9])). In such processes, heat can be induced within the target area without excessively heating the entire large-volume oven. Therefore, in the case of catalytic processes, thermal decomposition of reactants and products, which would form unwanted amorphous carbon or by-products, can be avoided. In recent years, IH mode has been reported as an efficient heating mode for operating catalytic processes with significantly improved performance (Wang et al., 2019([9])). In addition to the above advantages, IH is also an environmentally friendly heating method for operating catalytic processes because it can be operated using excess renewable energy (RE) sources instead of using conventional fuel burners to add heat to the reactor, which contributes to reducing CO2 emissions from the process. The faster heat generation in the system can also reduce energy losses during the long start-up time when using conventional indirect heating modes. The rapid cooling of the exiting gaseous effluent due to the targeted heating of the IH also significantly reduces the cost of the process by avoiding the cooling system at the outlet of the catalyst section.

[0011] The most commonly used catalysts for either PTF or PTO (plastic olefination) conversion are based on acidic zeolites, i.e., ZSM5 and USY, which operate via acidic cracking to generate liquid or gaseous hydrocarbons from pyrolysis polymer vapors. Recent research has also pointed to the use of acidic carbon-based catalysts for converting post-industrial waste plastics into jet fuel (Y. Zhang, D. Duan, H. Lei, E. Villota, R. Ruan. Jet fuel production from waste plastics via catalytic pyrolysis with activated carbons. Appl. Energy 251, 113337 (2019)). Summary of the Invention [Problem to be solved by the invention]

[0012] However, there is a need for alternative processes that are easy to use, highly selective, and energy efficient. The present invention meets these and other needs. [Means for solving the problem]

[0013] Applicants have surprisingly discovered that metal-free carbon materials can be used in PTF and PTO processes.

[0014] More particularly, the applicant surprisingly reports the use of metal-free carbon materials in combination with medium temperature direct induction heating for the direct conversion of plastics (e.g. waste plastics) into light olefins, particularly ethylene and propylene, or into liquid hydrocarbons, particularly fuel oil, and / or other hydrocarbons such as paraffinic gaseous C1-C5 hydrocarbons.

[0015] The metal-free carbon materials used in the present invention are particularly advantageous because they are highly resistant to deactivation in the presence of impurities contained in plastics (e.g., waste plastics) and have low production costs compared to other materials. In addition, due to their chemical inertness, these carbon materials can be advantageously regenerated by chemical treatment to remove accumulated impurities.

[0016] In addition, the metal-free carbon material is heat-activated by direct induction heating, opening new avenues for developing charging processes for recycling plastics (e.g., waste plastics).

[0017] The combination of carbon materials and induction heating offers several advantages, as discussed below.

[0018] One of these advantages is that the carbon material can be arranged in a fixed-bed configuration, allowing eddy currents resulting from the interaction between the metal-free carbon material and the magnetic field to generate heat uniformly on the outer surface of the carbon where the reaction occurs. The high thermal conductivity of such carbon materials also contributes to high heat transfer within the solid bed, which, combined with high heating rates, allows for maintaining bed temperatures during the highly endothermic PTF or PTO process. This is a significant advantage over prior art heating methods, such as microwave (MW) heating. Within a fixed bed, particles are in contact with each other and have high heat absorption adjacent to the MW antenna. As a result, only a small area around the MW antenna is actually heated, resulting in localized hot spots that adversely affect process selectivity. To distribute heat throughout the reaction section, fluidization is required, resulting in uniform heat distribution. However, the use of a fluidized bed induces excessive energy consumption for material movement and also generates fine particles due to catalyst attrition, which can affect material integrity.

[0019] Another advantage is that the present invention can be realized in a two-stage process: in a first-stage reactor, plastic pre-cracking (also called vaporization / liquefaction) occurs; and the plastic vapor / liquid or pre-cracked product is swept by an inert gas toward the reaction stage over the solid material heated by induction heating. Advantageously, the pre-cracking stage produces liquid and / or gaseous products. Such a two-stage process facilitates temperature control of both the pre-cracking and reaction stages. As demonstrated by the present applicant, both model and actual industrial waste plastics, including intermediate products from plastic recycling processes, can be used in the PTO or PTF process of the present invention.

[0020] Another advantage is that the precracking step and reaction temperature can be decoupled, thereby allowing the reaction temperature to be adjusted to tailor either liquid or light olefinic products depending on the downstream application.

[0021] Accordingly, in a first aspect, the present invention provides use of a metal-free carbon material for converting plastics into C2 to C4 olefins and / or other hydrocarbons under direct induction heating at a temperature of 800°C or less, preferably 700°C or less, more preferably 600°C or less, or strictly less than 600°C, or 550°C or less, or 500°C or less, for example 400-600°C, or 450-550°C, or 450-500°C.

[0022] In a second aspect, the present invention provides a process for converting plastics into C2-C4 olefins and / or other hydrocarbons, comprising a step of reacting a plastic under direct induction heating using a metal-free carbon material at a temperature of 800°C or less, preferably 700°C or less, more preferably 600°C or less, or strictly below 600°C, or 550°C or less, or 500°C or less, for example, 400-600°C, or 450-550°C, or 450-500°C. Hereinafter, this step may be referred to as the "cracking step."

[0023] "Metal-free carbon material," as used herein, refers to a material that is substantially free of metals, or preferably completely free of metals. By "substantially free," we mean that the material may contain trace amounts of impurities, including metals, metal oxides, and / or zeolites. For example, the carbon material may contain less than 3000 ppm (0.3 wt.%), less than 2000 ppm, less than 1000 ppm, less than 500 ppm, less than 200 ppm, less than 100 ppm, less than 50 ppm, less than 20 ppm, or even less than 1 ppm of metals, based on the total weight of the material.

[0024] "Metal," as used herein, refers to any element that forms a metallic structure under normal conditions and is recognized in the Periodic Table of the Elements as a metal, including alkali metals, alkaline earth metals, transition metals, lanthanides, actinides, and post-transition metals.

[0025] "Carbon material," as used herein, refers to a material that is primarily composed of carbon. For example, the material may be composed of more than 50% by weight carbon, at least 80% by weight carbon, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 98% by weight, at least 99% by weight, at least 99.5% by weight, at least 99.9% by weight, or at least 99.99% by weight carbon. As such, carbon material, as used herein, can include carbon and non-carbon components, as described in more detail below.

[0026] "Carbon" or "carbon component" as used herein refers to a component including graphite, graphene, carbon black, acetylene black, pyrolytic carbon, activated carbon, and any combination thereof. In particular, the carbon portion of a carbon material may be selected from the group including or consisting of graphite, graphene, carbon black, acetylene black, pyrolytic carbon, activated carbon, and any combination thereof.

[0027] Carbon materials may also contain elements that are non-carbon, as long as they do not qualify as "metals" according to the above definition. Carbon materials may contain one or several non-carbon elements or components selected from, for example, Na, K, Si, S, N, and O. In particular, carbon materials of the present invention may contain one or several non-carbon elements selected from the group consisting of Na, K, Si, S, N, and O, and mixtures thereof.

[0028] The inventors have demonstrated herein that the use of metal-free carbon materials, particularly those free of additives or promoters, in combination with induction heating is advantageous for preparing C2-C4 olefins because the metal-free carbon materials exhibit greater resistance to deactivation by encapsulation with supported carbon or coke precursors when encountered with zeolitic materials, and better chemical stability in the presence of organic or inorganic impurities present in the processed polymer. Advantageously, spent carbon-based materials can be regenerated by chemical leaching without significant loss of activity due to their high chemical inertness compared to other catalysts or materials. Advantageously, the metal-free carbon materials can serve to accelerate the conversion process.

[0029] As such, the present invention is based on the combined use of a metal-free carbon material and induction heating for preparing C2-C4 olefins from plastics (e.g., waste plastics). In particular, the present invention relates to such a combination, in which the temperature of the induction heating is 800°C or less. According to an advantageous embodiment, the present invention relates to such a combination, in which the metal-free carbon material is arranged in a packed bed. According to an advantageous embodiment, the present invention relates to such a combination, in which the metal-free carbon material is rolled carbon felt. These embodiments are detailed more precisely below.

[0030] In this application: - The phrase "included between" is to be understood as including the limits. Any description, even if made in relation to a particular embodiment, is applicable and compatible with other embodiments of the invention. -When an element or component is said to be included in and / or selected from a listed list of elements or components, it is to be understood that in the relevant embodiments expressly contemplated herein, the element or component can be any one of the elements or components individually listed, or can be selected from a group consisting of any two or more of the elements or components explicitly listed, and any element or component listed in a list of elements or components can be excluded from that list. - As used herein, any recitation of numerical ranges by endpoints includes all numbers subsumed within the recited range, as well as the endpoints of the range and equivalents thereof.

[0031] In some embodiments, the metal-free carbon material has a surface area of ​​at least 0.10 m as determined by ASTM-D-3663 (Standard Test Method for Surface Area of ​​Catalysts and Catalyst Carriers, 2020). 2 / g, e.g., 0.10 to 2000 m 2 / g, 0.20~1500m 2 / g, 0.50 to 1000m 2 / g, 1.0-900m 2 / g, 4.0-400m 2 / g.

[0032] In some other embodiments, the metal-free carbon material has a surface area of ​​0.10 to 30.0 m, as determined by ASTM-D-3663 (Standard Test Method for Surface Area of ​​Catalysts and Catalyst Carriers, 2020). 2 / g, 0.20-20.0m 2 / g, or 0.5 to 6.0 m 2 / g, or 1.0 to 3.0 m 2 / g BET surface area.

[0033] Advantageously, there is no technical limit to the maximum BET value. A very high BET value implies the presence of micropores that have no specific function but do not interfere with the reaction. In some preferred embodiments, the BET surface area of ​​the metal-free carbon material is as small as possible, e.g., 30.0 m 2 / g or less, 20m 2 / g, less than 6.0m 2 / g, less than 8.0m 2 / g or 6.0m 2 / g or even less. The inventors have surprisingly found that the smaller the BET surface area, the less energy is required to heat the metal-free carbon material. While not wishing to be bound by a particular mechanism of action, in such cases, the high intrinsic thermal conductivity of the carbon material can result in high heat dissipation within it. It can also shift the conversion products to C2-C4 olefins. In the case of the PTO process, the results seem to indicate that the external surface area, i.e., the exposed geometric surface, is a key factor for converting plastics to light olefins. Advantageously, the metal-free carbon material is non-porous or low-porosity, i.e., characterized by the absence or minimal pore network due to its small specific surface area. In this embodiment, the material can have a pore size greater than 500 nm, greater than 1 μm, greater than 3 μm, or even greater than 5 μm, as measured by ASTM D4284 (Standard Test Method for Determining Pore Volume Distribution of Catalysts and Catalyst Carriers by Mercury Intrusion Porosimetry).

[0034] In some embodiments, the carbon material has a geometric structure that allows for good connectivity between its primary particles, and therefore the high intrinsic thermal conductivity of the carbon material allows for high heat dissipation within its matrix. The geometric surface of the carbon material can be, for example, about 1.10 -2 m 2 / g or more, or approximately 1.10 -3 m 2 / g or more, or preferentially about 1.10 -1 m 2 / g or more, and up to 2m 2 The geometric surface can be measured by any means or method known to those skilled in the art, for example, by X-ray computed microtomography (Moncada Quintero et al., "Investigating mass transfer coefficients in lean methane combustion reaction through the morphological and geometric analysis of structured open cell foam catalysts," Chemical Engineering Science, Volume 281, 5 November 2023, 119138 (

[18] )).

[0035] As detailed above, several forms of carbon can be used in the present invention. In some preferred embodiments, the carbon material is selected from the group including or consisting of graphite, graphene, carbon black, acetylene black, pyrolytic carbon, activated carbon, and any combination thereof. Such carbon materials can be produced in different sizes and shapes, as described below.

[0036] The term "graphite," as used herein, refers to a crystalline form of elemental carbon whose atoms are arranged in a hexagonal structure. Graphitic carbon possesses the characteristic, as determined by X-ray diffraction, of an ordered three-dimensional graphitic crystalline structure consisting of layers of hexagonally arranged carbon atoms stacked parallel to one another. The term graphite, as used herein, includes both natural graphite, i.e., graphite in its natural, essentially geologically occurring, crystalline form, and synthetic graphite, i.e., synthetically prepared or processed graphite. Examples of natural graphite include so-called amorphous (nanocrystalline) graphite, flake graphite, and vein graphite. Examples of synthetic graphite include pyrolytic graphite, highly oriented pyrolytic graphite (HOPG), and synthetic flake graphite. The term "synthetic graphite," as used herein, unless further limited, is intended to include unexpanded graphite.

[0037] The term "graphene," as used herein, refers to a polycyclic aromatic molecule having carbon atoms covalently bonded to one another in the same plane. The covalently bonded carbon atoms can form a six-membered ring as a repeating unit, and may also include five- and / or seven-membered rings. Multiple graphene layers are referred to in the art as graphite. Thus, graphene may be a single layer or may include multiple graphene layers stacked on top of other graphene layers. Graphene generally has a maximum thickness of about 100 nanometers (nm), specifically about 5 nm to about 90 nm, and more specifically about 20 nm to about 80 nm. Graphene can also be used in the form of expanded graphite, in which the graphite structure is partially expanded by incorporating molecules such as HNO3 or KOH between the layers to create a highly accessible graphite-like structure.

[0038] As used herein, the term "carbon black" refers to a form of carbon with a short-range ordered structure and a high surface area to volume ratio, although lower than that of activated carbon. Carbon black is a material produced by the incomplete combustion of coal, coal tar, vegetable matter, or petroleum products (including fuel oil, fluid catalytic cracking tar, and ethylene cracking).

[0039] The term "acetylene black" as used herein refers to carbon black produced by the thermal decomposition of acetylene, which has a higher purity than many other carbon blacks, fewer impurity factors, a higher degree of crystallinity, and a more developed structure.

[0040] The term "pyrolytic carbon" refers to any form of carbon, whether ceramic or carbonaceous, obtained by pyrolysis of an organic feedstock or by decomposition of gaseous hydrocarbons at high temperatures on a host substrate.

[0041] As used herein, the term "activated carbon" refers to a form of carbon with small, low-volume pores that increase the surface area available for adsorption or chemical reaction. It can be produced from a variety of sources, such as bamboo, coconut shells, willow peat, wood, coir, lignite, coal, and petroleum pitch, which are pyrolyzed and subjected to a subsequent activation process aimed at creating micropores. Carbon activation can be engineered by any method known to those skilled in the art.

[0042] The carbon material used in the present invention may have different forms. The form or type of the carbon material is not particularly limited and may include, for example, granules, felts, fibers such as nanofibers, filaments, 2D or 3D fabrics, foams such as open-cell foams, 3D printed structures, extrudates such as spheres, cloths, monoliths, honeycombs, rods, sticks and particles, tubes such as nanotubes, rings, trilobes, tablets and nanotablets, and any combination thereof.

[0043] For example, the carbon material may be commercially available graphite felt. The term "graphite felt" (GF) as used herein refers to a woven material primarily composed of randomly oriented and entangled carbon filaments or fibers that has been subjected to a graphitization process, which may require heat treatment of the carbon felt at high temperatures, such as in the range of about 2600°C to about 3300°C. During the graphitization process, the randomly oriented and entangled carbon filaments or fibers can be converted into an ordered graphite structure. The structuring of the as-synthesized graphite felt was achieved by a known process called needlepunching. Preferred examples of carbon materials for use in the present invention include graphite felts preferably having the following dimensions: a fiber diameter of about 10 μm and lengths up to several millimeters. The fibers become highly entangled following the synthesis process, providing a high frequency contact surface for the reactants.

[0044] Another example of a carbon material is carbon felt. As used herein, the term "carbon felt" (CF) refers to a woven material primarily comprising randomly oriented and entangled carbon filaments or fibers. Carbon felt suitable for use in the present invention is commercially available, without limitation, from, for example, Avcarb or Cera Materials. Advantageously, the carbon felt may have a thickness of about 2 mm to about 20 mm. For example, the carbon felt may have a thickness of about 4 mm to about 15 mm, about 6 mm to about 10 mm, or about 2 mm to about 6 mm. For example, a carbon felt may have a thickness of 0.19 mm with 10 μm diameter fibers. 2 / g geometric surface area, approximately 2.1 g / cm 3 density, and 4m 2 / g, or 1.9 m if the carbon has 90% porosity. 2 / g BET.

[0045] CF can also be used in different configurations, e.g., by itself, flat, or in a "rolled" configuration, to provide different surface contact and length depending on the downstream application. "Rolled CF" herein refers to carbon felt wrapped around a shaft. Rolled CF can have any size, e.g., a diameter ranging from 20 to 2000 mm, preferably from 40 to 1000 mm, and most preferably from 100 to 800 mm, and a length ranging from 30 to 3000 mm, preferably from 100 to 2000 mm, and most preferably from 300 to 800 mm.

[0046] Another example of a carbon material is a "carbon nanotube" or "CNT," which can refer to a hollow, cylindrical or tubular carbon structure defining a cavity therein that may be empty or filled with another material. CNTs may be closed at one or both ends. CNTs can be conceptualized as rolled graphene sheets with a hexagonal lattice of carbon molecules, with the bottom exposed. Depending on the degree of rolling and the method of forming the original graphene sheet, carbon nanotubes of different diameters and internal shapes can be formed. Carbon nanotubes formed by rolling a single sheet to form the aforementioned cylinder are referred to as "single-walled" carbon nanotubes. Carbon nanotubes formed by rolling two or more sheets of graphene, with a structure resembling a series of concentric cylinders with increasing diameter from the center to the periphery, are referred to as "multi-walled" carbon nanotubes. Carbon nanotubes suitable for use in the present invention include single-walled and multi-walled carbon nanotubes. In certain embodiments where the carbon nanotube is a multi-walled carbon nanotube, the multi-walled carbon nanotube contains two or more graphite layers, e.g., 2 to 20 or 5 to 50. In certain embodiments, carbon nanotubes used herein have a high aspect ratio, i.e., a length-to-diameter ratio, preferably 10 to 10,000,000 to 1, e.g., 100 to 10,000 to 1. In certain embodiments, carbon nanotubes used herein have an average outer diameter of about 2 to 100 nm, e.g., about 5 to 50 nm, e.g., about 8 to 30 nm, e.g., about 20 nm. The average inner diameter of carbon nanotubes used herein can be about 0.5 to 100 nm, or about 1 nm to 50 nm.

[0047] Another example of a carbon material is a "carbon nanofiber" or "CNF," which includes a carbon-containing material having a solid cylindrical shape with exposed cylindrical surfaces and little or no voids (meaning there is no hollow center, although some small channels may be present). Carbon nanofibers may be similar to carbon nanotubes (CNTs), but may contain a solid core rather than a hollow center and more reactive exposed cylindrical surfaces rather than a basal surface. Carbon nanofibers may be formed by any method known in the art, including deposition of carbon-containing vapors, such as by catalytic chemical vapor deposition (CCVD), which deposits carbon in the presence of a transition metal catalyst on a macroscopic substrate using various gaseous carbon sources, or other methods of forming carbon nanofibers known in the art.

[0048] Advantageously, the carbon nanofibers may have a length of about 100-1000 nm, e.g., about 150-500 nm. In certain embodiments, the carbon nanofibers used herein may have an aspect ratio, i.e., the ratio of length to outer diameter, of preferably greater than about 10, e.g., greater than about 50, or greater than about 100, or greater than about 1000, or greater than about 2000.

[0049] Advantageously, the carbon nanofibers used herein may have an average diameter of less than 1000 nm. In certain embodiments, the carbon nanofibers have an average diameter of less than 500 nm, for example less than 300 nm.

[0050] It is worth noting that both CNTs and CNFs can be grown on macroscopic substrates such as ceramic or oxides, i.e., silicon carbide, silica, alumina, and combinations thereof, or on other host substrates such as activated carbon or graphite and even carbon felt. Such structural composites can allow for control of flow patterns within the solid bed and increased surface contact between reactants and solids.

[0051] Other examples of suitable forms of carbon material include grains with an average particle size of 0.1 to 5 mm, extrudates with an average particle size of 1 to 5 mm and lengths up to 2, 3, 4, 5, 6 mm or more, trilobes with an average particle size in the range of 1 to 5 mm and lengths of 1 to 10 mm, foams with ppi (pores per inch) in the range of 60 to 5 ppi, honeycombs with cpsi (cells per square inch) in the range of 5 to 900, and tubes with aspect ratios of approximately 5:1 (meaning 1 mm diameter x 5 mm length), 3:1, or 2:1, depending on the diameter of the material.

[0052] In some embodiments, the metal-free carbon material is not mixed with the plastic to be converted. For example, the metal-free carbon material can be arranged as a packed bed (sometimes called a fixed bed), preferably with a 3D-connected structure, to favor good continuity of material within the entire reaction zone. Thus, preferred forms include felts, fibers such as nanofibers, filaments, 2D or 3D fabrics, foams such as open-cell foams, 3D-printed structures, extrudates such as spheres, cloths, monoliths, and honeycombs, rods, sticks, and particles, tubes such as nanotubes, rings, trilobes, tablets, and nanotablets. More preferably, the form is felt, most preferably rolled felt with an interconnected structure and variable length depending on the reaction conditions. Such interconnected structure allows for rapid heat vectorization throughout the packed bed matrix, thereby reducing the overall power input from the inductor for a given reaction temperature.

[0053] As mentioned above, the carbon material may be a combination of at least two materials as defined above.

[0054] In some embodiments, the metal-free carbon material is supported by a structure (also called a substrate or support structure) while being used to prepare the reaction product. Such a structure may be a non-carbon structure made of, for example, alumina, silica, silicon carbide, other oxides or ceramics, or a combination thereof. Such a support structure functions to physically support the metal-free carbon material. Because the support structure is not an inductively active material, it does not participate in the conversion reaction. Therefore, if present, the support structure does not have a heating or catalytic effect. As an example, a graphene coating can be formed on the support structure, providing high electrical connectivity to the carbon material and allowing efficient heating under induction mode. In contrast, a support structure alone cannot be heated by induction heating. The coating layer on the surface of the support structure also allows heat generation resulting from induction heating to occur exclusively on the material surface where the reaction occurs. Graphene coatings can also be applied to activated carbon structures to improve electrical connectivity. Such connectivity significantly improves heat recovery from the induction coil, resulting in a temperature increase in the composite material. Optionally, such better connectivity may reduce the heating power delivered to the carbon material.

[0055] "Plastic" is to be understood in its broadest sense herein. In particular, plastic refers herein to any synthetic material made from organic polymers that can be molded into a shape while soft and then become rigid or slightly elastic. This includes, for example, high density polyethylene (HDPE) and low density polyethylene (LDPE), polypropylene, polystyrene, mixed waste plastics from industrial waste, such as low density polyethylene, PET, PVC and polystyrene-containing solid residues, plastic-containing solid residues, C 15 ~C 45 or C 20 ~C 40The product may be at least one selected from intermediate products from plastic recycling processes, such as wax, and polymers previously pre-cracked with short contact times at temperatures between 300° C. and 600° C. The fact that the process of the present invention can be implemented on intermediate products from plastic recycling processes makes it possible to use the process of the present invention to recycle tires, crude oil, and kerosene.

[0056] "C2-C4 olefin" herein refers to at least one aliphatic alkene selected from ethylene, propylene, and butylene. Preferably, it can be ethylene and / or propylene. According to the present invention, plastics can be converted to one specific olefin or to a mixture of olefins. In some cases, the conversion may not be complete, and possible traces of diolefins may occur, such as diolefins made from ethylene, propylene, and butylene.

[0057] "Other hydrocarbons" as used herein refers to any hydrocarbon other than a C2-C4 olefin, such as a hydrocarbon having at least 5 carbon atoms (C 5+ (also called), for example, C5~C 10 or fuel oil, and / or paraffinic gaseous C1-C4 hydrocarbons. It may refer to a mixture of at least two of these hydrocarbons.

[0058] "Direct induction heating," as used herein, refers to a process in which carbon materials are directly heated by electrical currents generated on their surfaces through interaction with an electromagnetic field applied by an inductor. In one embodiment of the present invention, carbon materials may be heated by generating an alternating electromagnetic field in a reaction zone containing the carbon material, where the alternating electromagnetic field passes through the reaction zone, thereby generating electrical currents in the carbon material and heating it. Advantageously, the high intrinsic thermal conductivity of the carbon material allows for rapid heat transfer from the outer surface to the core of the material. The high intrinsic electrical and thermal conductivity of carbon or carbon-coated materials also allows for the reaction temperature to be maintained at a set temperature despite the highly endothermic nature of the reaction, advantageously avoiding the production of long-chain liquid hydrocarbons due to temperature drops within the bed.

[0059] Advantageously, the step of direct induction heating may be carried out at a reaction pressure between 0.5 and 20.0 bar, for example between 1 and 5.0 bar.

[0060] The present invention relates to a process for converting plastics into C2-C4 olefins and / or other hydrocarbons, which comprises reacting them under direct induction heating with metal-free carbon materials at temperatures up to 800°C.

[0061] The present invention also generally relates to a process for preparing C2-C4 olefins and / or other hydrocarbons, comprising reacting a metal-free carbon material under direct induction heating at a temperature of 800°C or less.

[0062] The reaction process may also be referred to herein, without distinction, as the "cracking process," the "induced cracking process," or the "cracking stage."

[0063] The process of the present invention can also be implemented as a two-stage process. In fact, this process can include a first step (also referred to as the "first stage") in which the plastic is pre-cracked before the cracking step requiring induction heating. The first stage can be carried out in the absence of metal-free carbon materials. Alternatively, the first stage can be carried out in the presence of some material capable of recovering heat from the oven to improve heat transfer to the plastic, while in the second stage, steam and / or liquid is swept toward the metal-free carbon material, where the cracking step takes place under direct induction heating. The liquid produced in the first stage can be in gas form at the outlet temperature of that stage. Such temperatures can range from 200°C to 600°C, in particular, to allow the heavy hydrocarbons to remain in gas form as they flow either downward or upward to the induction cracking stage.

[0064] The pre-cracking step is advantageously 15 ~C 45 or C 20 ~C 40 This allows for the production of polymer fragments with short chains such as olefins. It is also possible to vaporize plastics (e.g., waste plastics) to produce a mixture of liquid and gas. Note that the gas fraction can be increased by increasing the residence time of the polymer in this first precracking stage. The gas fraction can also be increased by increasing the temperature at the outlet of the precracking stage, since at high temperatures the liquid long-chain hydrocarbons are converted into the gas fraction of the outlet mixture, thus containing approximately 90% by weight liquid and 10% by weight gas, preferably 50% by weight liquid and 50% by weight gas, and most preferably 20% by weight liquid and 80% by weight gas.

[0065] The first optional step can be carried out by any method commonly used by those skilled in the art to pre-crack plastics, such as Joule heating, induction heating and / or microwave heating. The pre-cracking step can be carried out in the presence of silicon carbide (SiC), metal beads or any heat-conducting material.

[0066] The precracking conditions can be determined by those skilled in the art depending on the nature and amount of plastic, the presence of a heat-conducting material, and the type of heating method. The temperature of the first step can be 300°C to 600°C, 350°C to 550°C, 400°C to 540°C, or 450°C to 500°C, advantageously about 500°C, and preferentially about 450°C. For example, if Joule heating is used, the temperature can be 450°C to 600°C. Alternatively, if induction heating is used, the temperature can be 450°C to 500°C. The duration of the first step can be 5 to 100 minutes, preferably 15 to 60 minutes, for example, about 30 minutes. For example, the precracking step can be realized in the first-stage reactor. The plastic vapor / liquid can then be swept with an inert gas, such as argon, helium, or nitrogen, toward the solid material in the second-stage reactor, where the cracking process takes place. C2-C4 olefins and / or other hydrocarbons are then obtained during the cracking step. In other modes of operation, other gases such as hydrogen or other light hydrocarbons may also be used as the sweep gas.

[0067] The first step of precracking can be advantageous compared to a process without the first step because it shifts the reaction conversion to obtain olefins rather than other hydrocarbons, thus resulting in higher levels of C2-C4 olefins than other hydrocarbons.

[0068] In one embodiment, the first step comprises: 15 ~C 45 Or C 20 ~C 40They can even be replaced by direct cracking of polymers with short chains and / or polymers previously distilled at temperatures between 200 and 500 °C. These polymers may also be intermediate products from plastic recycling processes.

[0069] In one aspect, the present invention also relates to a process for preparing C2-C4 olefins and / or other hydrocarbons, comprising reacting with a metal-free carbon material under direct induction heating at a temperature of 800°C or less. In such a process, the input material may be a plastic material as described above. For example, the plastic material may be a C2-C4 olefin, sometimes called wax. 15 ~C 45 Olefin or C 20 ~C 40 As such, the present invention also provides a mixture of C 15 ~C 45 Olefin or C 20 ~C 40 It also relates to a process for converting olefins to C2-C4 olefins and / or other hydrocarbons, preferably C2-C4 olefins.

[0070] The process can be operated in a continuous mode, so the operating times of the different steps depend on the amount of plastic to be processed. For example, the time for the "cracking step" can take from 2 to 20 minutes, for example about 10 minutes.

[0071] Depending on the nature of the carbon in the cracking process, i.e., non-porous or porous, the liquid to gas fraction can be adjusted by changing the reaction conditions. For example, as illustrated in the examples, non-porous materials under certain reaction conditions can produce a gas fraction as the main fraction, with the majority being light olefins as the main product, while porous materials produce a higher liquid fraction relative to the gas fraction, with the liquid fraction ranging from C6 to C8 depending on the reaction temperature. 25 is.

[0072] Advantageously, at the end of the cracking step, the liquid hydrocarbons obtained (also referred to as the "liquid fraction") may be condensed and / or the gaseous products obtained (also referred to as the "gas fraction") may be subjected to gas chromatography for analysis. Advantageously, the gas fraction may comprise at least 5.0 mol% of unsaturated C2-C4 hydrocarbons, preferably at least 30.0 mol% or preferably at least 50.0 mol% or preferably at least 70.0 mol% of unsaturated C2-C4 hydrocarbons.

[0073] Advantageously, the liquid fraction produced on the porous carbon material may itself be used in another chemical process, i.e. as a fuel for transportation, or may be recycled onto the carbon material to be further cracked into light olefins, i.e. C2-C4 olefins.

[0074] In some embodiments, the present invention provides a process for converting plastics into C2-C4 olefins and / or other hydrocarbons, comprising: -precracking the plastic; reacting the metal-free carbon material under direct induction heating at a temperature of -800°C or less; The present invention relates to a process including:

[0075] In some embodiments, the present invention provides a process for converting plastics into C2-C4 olefins and / or other hydrocarbons, comprising: - a pre-cracking step of the plastic, carried out by induction heating, Joule heating or microwave heating at temperatures ranging from -300°C to 600°C; reacting the metal-free carbon material under direct induction heating at a temperature of -800°C or less; The present invention relates to a process including:

[0076] In some embodiments, the present invention provides a process for converting plastics into C2-C4 olefins and / or other hydrocarbons, comprising: - pre-cracking of the plastic, carried out on metal beads or any heat-conducting material mixed with the plastic; reacting the metal-free carbon material under direct induction heating at a temperature of -800°C or less; The present invention relates to a process including:

[0077] In some embodiments, the present invention provides a process for converting plastics into C2-C4 olefins and / or other hydrocarbons, comprising: -precracking the plastic; reacting the metal-free carbon material under direct induction heating at a temperature of -800°C or less; Including, It concerns a process in which during the precracking step, the plastic is precracked in a first stage reactor, while the vapors and / or liquids produced in the first section, which later become gaseous at temperatures between 200°C and 400°C, are swept by a gas flow towards the material in a second stage reactor where the cracking process takes place.

[0078] The present invention is further illustrated by the following examples in conjunction with the accompanying drawings, which should not be construed as limiting. [Brief explanation of the drawings]

[0079] [Figure 1] Figure 1 shows the selectivity (wt%) of a plastics olefination (PTO) process on a flat carbon felt (CF) material as a function of reaction temperature under direct induction heating to convert a model HDPE. (A-B) Distribution of gaseous and liquid products (H2 and Cn), (C-D) Distribution of gaseous products (H2 and C1-C7). Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), CF weight = 0.54 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C, CF temperature = variable. [Figure 2]Figure 1 shows the selectivity (wt%) of a plastics olefination (PTO) process on a planar carbon felt (CF) material as a function of reaction temperature under indirect Joule heating to convert a model HDPE. (A, B) Distribution of liquid and gaseous products (H2 and Cn (including nearly solid wax)), (C, D) Distribution of gaseous products (H2 and C1–C7). Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), CF weight = 0.54 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min), CF temperature = variable. [Figure 3A] Figure 1 shows the selectivity (wt%) of a plastics olefination (PTO) process using rolled CF material to convert model HDPE: (A, C) as a function of reaction temperature, and (B, D) the saturated fraction of gaseous products in the C1-C7 range versus C2-C4 olefins as a function of reaction temperature under direct induction heating. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), rolled CF weight = 1.2 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min), CF temperature = variable. [Figure 3B] Figure 1 shows the selectivity (wt%) of the plastics olefination (PTO) process for converting model HDPE using rolled CF material: (E) as a function of reaction temperature, and (F) the saturated fraction of gaseous products in the C1-C7 range versus C2-C4 olefins as a function of reaction temperature under direct induction heating. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), rolled CF weight = 1.2 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min), CF temperature = variable. [Figure 4]Figure 1 shows the selectivity (wt%) of the plastics olefination (PTO) process for CF materials, namely, flat and rolled CF materials, operated under induction heating at 550 °C for flat CF and 500 °C for rolled CF to convert model HDPE plastic to light olefins. (A, C) Product distribution. (B, D) Olefins versus gaseous saturated C2-C4 fraction. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), CF weight = 0.54 g (flat CF) and 1.2 g (rolled CF), reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min). [Figure 5] Figure 1 shows the selectivity (wt%) of the plastics olefination (PTO) process using industrial mixed polymer waste materials, namely, flat and rolled CF materials, operated under induction heating at 550 °C for flat CF and 500 °C for rolled CF, to convert industrial mixed waste plastics to light olefins. (A, C) Product distribution and C2-C4 fractions for rolled CF materials. (B, D) Product distribution and C2-C4 fractions for flat CF materials. Reaction conditions: industrial mixed plastics weight = 6 g (mixed with 2 g of SiC to improve heat transfer), CF weight = 0.54 g (flat CF) and 1.2 g (rolled CF), reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min). [Figure 6A] Figure 1 shows cycle tests of a plastics olefination (PTO) process using rolled CF material (26 mm diameter, 15 mm height) operated under induction heating mode to convert industrial mixed waste plastics to light olefins at 450 °C. (A, B) Product distribution as a function of cycle test. (D, E) Olefins versus saturated C2-C4 fraction as a function of cycle test (cycle 1, cycle 3, and cycle 9). Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), CF weight = 1.2 g (rolled CF), reactor diameter = 26 mm, argon flow rate = 15 mL / min or 30 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min). [Figure 6B] Figure 1 shows cycle tests of a plastics olefination (PTO) process using rolled CF material (26 mm diameter, 15 mm height) operated under induction heating mode to convert industrial mixed waste plastics to light olefins at 450 °C. (C) Product distribution as a function of cycle test. (F) Olefins versus saturated C2-C4 fraction as a function of cycle test (cycle 1, cycle 3, and cycle 9). Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), CF weight = 1.2 g (rolled CF), reactor diameter = 26 mm, argon flow rate = 15 mL / min or 30 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min). [Figure 7] Figure 1 shows (A) the distribution of gas and liquid fractions and (B) the distribution of olefin C2–C4 fractions as a function of cycles during a PTO process using rolled CF material (26 mm diameter, 15 mm height) operated under induction heating (IH) mode at 450 °C to convert industrial mixed waste plastics to light olefins. Reaction conditions: 6 g of mixed waste plastics (mixed with 2 g of SiC to improve heat transfer) was used for each cycle, 1.2 g of CF (rolled CF), 26 mm reactor diameter, 30 mL min-1 argon flow rate, and 450 °C vaporization temperature. [Figure 8A] Figure 1 shows the selectivity (wt%) of a plastics-to-fuel (PTF) process using a model HDPE polymer on a 3 mm pellet of MESOC+ material under direct induction heating (500 °C) and indirect Joule heating modes (500 °C and 550 °C). (A, B) Distributions of liquid and gaseous products (H2 and Cn) and gaseous products (H2 and C1–C7) under direct induction heating. (C, D) Distributions of liquid and gaseous products (H2 and Cn (including solid wax)) and gaseous products (H2 and C1–C7) under indirect Joule heating. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), MESOC+ weight = 3 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min). [Figure 8B] Figure 1 shows the selectivity (wt%) of a plastics-to-fuel (PTF) process using a model HDPE polymer on a 3 mm pellet of MESOC+ material under direct induction heating (500 °C) and indirect Joule heating modes (500 °C and 550 °C). (E, F) Distribution of liquid and gaseous products (H2 and Cn (including solid wax)) and gaseous products (H2 and C1–C7) under indirect Joule heating. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), MESOC+ weight = 3 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min). [Figure 9] Figure 1 shows the plastics-to-fuel (PTF) process (selectivity (wt%)) for (A, B) 3 mm pellets of MESOC+ and (C, D) 1 mm pellets of MESOC+ material under induction heating at 500 °C. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), MESOC+ weight = 3 g, reactor diameter = 26 mm, argon flow rate = 15 mL min-1, HDPE vaporization temperature = 450 °C (heating rate of 20 °C min-1). [Figure 10] This figure shows the selectivity (wt%) of a plastics-to-fuel (PTF) process using model HDPE polymers (A, B) and industrial blended polymers (C, D) on 3 mm pellets of MESOC+ material under direct induction heating. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), MESOC+ weight = 3 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min), MESOC+ temperature = 500 °C. [Figure 11A]Figure 1 shows cycle testing of the plastics-to-fuel (PTF) process (selectivity (wt%)) for 3 mm pellets of MESOC+ material operated under induction heating at 500 °C to convert model HDPE into fuel. (A, C) Product distribution as a function of the number of cycles (A-B: cycle 1, C-D: cycle 2). (B, D) Olefins versus saturated C2-C4 fractions as a function of the number of cycles. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), MESOC+ weight = 3 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min). [Figure 11B] Figure 1 shows cycle testing of the plastics-to-fuel (PTF) process (selectivity (wt%)) for 3 mm pellets of MESOC+ material operated under induction heating at 500 °C to convert model HDPE into fuel. (E) Product distribution as a function of the number of cycles (E-F: cycle 3). (F) Olefins versus saturated C2-C4 fraction as a function of the number of cycles. Reaction conditions: HDPE weight = 6 g (mixed with 2 g of SiC to improve heat transfer), MESOC+ weight = 3 g, reactor diameter = 26 mm, argon flow rate = 15 mL / min, HDPE vaporization temperature = 450 °C (heating rate of 20 °C / min). [Figure 12A] These graphs show the plastic olefination (PTO) process of HDPE under different conditions. A) The results of the PTO process on a rolled carbon felt (CF) catalyst in a two-step process. The top graph shows the yield (wt%) of H2 and Cn (C5-C40) produced (Graphs A and B) or H2, C5, and wax (Graph C). The bottom graph shows the yield (wt%) of H2 and C1-C7 (Graphs A, B, and C). [Figure 12B]A) HDPE plastic olefination (PTO) process under different conditions. B) Results of the PTO process on a rolled carbon felt (CF) catalyst in a one-step process. The top graph shows the yield (wt%) of H2 and Cn (C5-C40) produced (Graphs A and B) or H2, C5, and wax (Graph C). The bottom graph shows the yield (wt%) of H2 and C1-C7 (Graphs A, B, and C). [Figure 12C] Figure 1 shows the plastic olefination (PTO) process of HDPE under different conditions. Figure 2 shows the results of the PTO process on a metal catalyst in a one-step process. The top graph shows the yield (wt%) of H2 and Cn (C5-C40) produced (graphs A and B) or H2, C5, and wax (graph C). The bottom graph shows the yield (wt%) of H2 and C1-C7 (graphs A, B, and C). [Example]

[0080] Example 1: Materials for carrying out the process of the present invention The apparatus for carrying out the present invention includes a first section, a polymer supply section, which can contain a polymer weighing approximately 5-100 g. The reservoir of this polymer supply section is supplied with an argon flow (30 mL min ) to avoid any air intrusion in the reservoir. -1 The polymer extrudate was continuously flushed with 15-60 mL min , maintained at 450 °C. -1The polymer vapors were fed to a vaporization stage located within an electric furnace (Joule heated) that was continuously flushed with an argon flow at various flow rates ranging from 0.01 to 0.01. The polymer vapors produced in this stage were conveyed to a reaction section (also referred to as the "cracking stage") operated under either direct non-contact induction heating ("IH") or indirect Joule heating ("JH") at different temperatures. The reaction products were then passed through a trap maintained at 16°C to condense the liquid hydrocarbons, while the gaseous products were directed to gas chromatography (GC) for analysis. The reaction products were analyzed online by two VARIAN 3800 gas chromatographs. The first one was equipped with two detectors: a thermal conductivity detector (TCD) connected to an Agilent J&W DB-1 column and a flame ionization detector (FID) connected to an Agilent J&W CarboBOND column, to measure H2 / CH4 and C. 12 A second one equipped with an FID detector connected to a Restek RT alumina BOND column was used to separate the lighter hydrocarbons such as C2H2, C2H4, and C2H6 from the other hydrocarbons up to C7. A calibration curve was used to separate CH4, H2, the C2 fraction, C6H6, C7H8, and C8H. 10 , and C 10 H8 was quantified. The Dietz factor method was used to calculate other hydrocarbons using FID integrated area.

[0081] The IH experiment was performed using a spiral induction coil with six turns (L = 1.05 m, coil net resistance = 2.066 × 10 -3Experiments were carried out in an EasyHeat® 8310 induction heater (10 kW, Ambrell Ltd) equipped with a 1000 Ω (1000 Ω) and an external cooling chiller using a recirculating water / glycerol (10%) mixture as the cooling medium. In a typical experiment, one quartz reactor containing material similar to that used for JH was placed inside the induction furnace coil. Real-time temperature control / regulation was ensured by a PID system (proportional-integral-derivative controller, Eurotherm model 3504) focused at the center of the material bed and connected to a laser pyrometer (Optris®, power <1 mW, positioned approximately 30 cm from the material) capable of operating in the range of 150–1000 °C. The heating / cooling rate allowed by the system was approximately 300 °C min within the temperature range of 160–300 °C. -1 It is noteworthy that the inductor operated at a frequency of 263 kHz, which generated a much lower magnetic field compared to those operating at lower frequencies, i.e., <10 kHz. In fact, the magnetic field resulting from low-frequency induction is more permeable to surrounding materials. However, to further reduce the operator's exposure to magnetic fields, the device was located inside a Faraday cage surrounded by a metal mesh.

[0082] For indirect Joule heating, the material was located in an electric oven set at the reaction temperature and controlled by a thermocouple inserted in the ceramic section of the oven.

[0083] For the PTO and PTF processes, both model plastics, namely high density polyethylene (HDPE) and industrial mixed plastics, namely low and high density polyethylene (LDPE) and polystyrene (PS) containing solid residues, were examined.

[0084] In this study, we investigated two types of carbon materials: (i) low-specific surface area 4 m2, consisting of entangled carbon microfilaments (with an average diameter of about 10 μm and lengths up to several hundred micrometers); 2 / g of nonporous carbon felt (commercially available from MERSEN Com.), and (ii) a specific surface area of ​​300 m2 We used industrially produced porous carbon (MESOC+, commercially available from SICAT SARL) with a capacity of 1 / g and consisting of a large mesoporous network. The various properties of these carbon-based materials are listed in Tables 1 to 3.

[0085] Properties of various carbon materials used in the process [Table 1]

[0086] Detailed characteristics of carbon felt according to the purchaser are summarized in Table 2.

[0087] Properties of carbon felt in its initial state (information provided by the supplier) [Table 2]

[0088] Detailed characteristics of MESOC+ according to purchasers are summarized in Table 3.

[0089] Typical properties of fresh MESOC+ (information provided by supplier for 3mm pellets) [Table 3]

[0090] Example 2: Polymer Cracking Process PTO for non-porous carbon felt material Carbon felt (CF) purchased from Mersen Co. was used without any pretreatment. CF is composed of entangled microfilaments with an average diameter of approximately 10 μm and lengths up to several hundred micrometers. CF microfilaments are very smooth with few internal pores and roughness, which is consistent with their low specific surface area. This material also exhibits a high effective porosity, up to approximately 90% by volume.

[0091] When used as a metal-free material, CF can be directly cut into flat disks (flat CF shown) or cut into sheets that can be further rolled up to form a cylindrical shape (rolled CF shown). Rolled CF material appears to be a very good configuration for use as a carbon material for plastic conversion processes because its length can be easily adjusted, allowing the bed height to be adapted to control the contact time and exposed surface to plastic vapors / liquids, thereby improving the yield of light olefins. In fact, such bed height control is very efficient in the case of rolled CF configurations, because placing rolled CF pieces in a reactor results in uniform heating of the solid bed. In fact, the tight contact between the rolled CF pieces prevents local overheating, which would otherwise lead to uneven temperature distribution within the solid bed and excessive decomposition of intermediate compounds to carbon.

[0092] PTO process for model HDPE plastic waste In this example, the conversion of model waste plastic (HDPE) to light olefins is carried out on CF material under both direct induction heating (invention) and indirect radiant Joule heating (comparison). The results obtained as a function of reaction temperature are shown in Figures 1-4.

[0093] The cracking performance for the planar CF material operated under IH mode increases from 500 °C to 550 °C, i.e., the gas fraction increases from 53% to 76% (Figure 1A-B). As shown in Figure 1A-B, the liquid fraction is mostly C. 19 ~C 30 It consists of long chain hydrocarbons ranging from C 30 ~C 35The fraction of long-chain hydrocarbons is small. The small fraction of long-chain hydrocarbons can be attributed to the high porosity of the CF material, i.e., 90% void volume, which can favor the bypass of some of the polymer vapor during the test. It can be observed that a blank test carried out under Joule heating using quartz wool rather than CF alone results in long-chain hydrocarbons (C>30) that cannot be dissolved in any solvent, leaving no trace of hydrocarbons with a carbon chain of less than 30.

[0094] The C2–C4 olefins versus saturated gas fraction obtained as a function of reaction temperature for planar CF material under IH also shows the same trend with a yield of 33% C2–C4 olefins at 500 °C and 51% at 550 °C ( Figure 1C–D ).

[0095] It is worth noting that the color of the liquid hydrocarbons produced also changes as a function of reaction temperature, i.e., becomes darker as the reaction temperature increases. This color change may be due to the presence of polyolefins or aromatic compounds in the product. It is expected that such products may be advantageous at higher reaction temperatures.

[0096] The PTO process as a function of reaction temperature was also performed on the CF material operated under indirect Joule heating (comparison), and the results are shown in Figures 2A–D. At 500 °C, only wax was obtained on the CF material, and the results are not reported because the wax is barely soluble in the solvent for GC analysis. The product distribution is fundamentally different under JH mode, as the gas fraction constitutes only 23 wt% and 39 wt% at reaction temperatures of 550 °C and 600 °C, respectively (Figures 2A and B). Among the gas fraction, C2–C4 olefins predominate. Their absolute weight percentages are 12 wt% and 22 wt% at 550 °C and 600 °C, respectively, based on the initial weight of the waste plastic. The liquid fraction recovered at the reactor outlet is mostly composed of wax, which is insoluble, as shown in the digital photographs presented in the insets of Figures 2A and B.

[0097] These results clearly support the high efficiency of the direct induction heating mode for operating carbon materials for PTO processes at low reaction temperatures. The high PTO efficiency observed for CF materials under induction heating can be attributed to several factors: (i) the high-temperature maintenance efficiency resulting from the high heating rate of induction heating, i.e., several hundred degrees per minute, to maintain the material temperature for the endothermic cracking reaction; and (ii) better temperature uniformity throughout the solid bed, since heat is generated directly within the material body rather than through indirect convection / conduction, as encountered with indirect Joule heating modes. In fact, carbon felt is well known as an insulating shielding material to prevent heat transfer in high-temperature ovens. Therefore, carbon filaments exhibit high heat transfer along their filamentary structure, but not between the filaments due to the presence of large voids in the material. In the case of induction heating, the entire solid volume can be heated, whereas in the case of JH heating, heat is transferred along the outer filaments toward the core of the solid bed, which is more susceptible to the influence of the material's filamentary structure. Such heat resistance can be avoided with induction heating because, as mentioned above, heat is generated directly through the material body, and heat distribution throughout the carbon microfilaments is much faster due to the microfilament's small diameter, remaining within the range of depth penetration for eddy currents, i.e., within a few micrometers from the outer surface. The high aspect ratio (length to diameter) of the carbon microfilaments that make up the CF material also contributes to rapid heat conduction along the filaments and throughout the material matrix, thus greatly improving the reaction process. Comparing the results in Figures 1 and 2 conclusively demonstrates the advantages of operating the PTO process in direct, non-contact induction heating mode.

[0098] Effect of the macroscopic shape of CFs In this data set, rolled CF material was used instead of flat CF material, and the results as a function of reaction temperature are shown in Figure 3. At a reaction temperature of 500 °C, the majority of the starting plastic was converted to light hydrocarbons (Figures 3C and 3D), which differs from the lower reaction temperatures, i.e., 450 °C, where some liquid fraction was observed (Figures 3A and 3B). At 500 °C, the C2–C4 olefin fraction accounted for 46% of all hydrocarbon products (Figure 3D). This fraction consisted primarily of ethylene and propylene, while methane accounted for approximately 13 wt%. Increasing the reaction temperature from 500 °C to 550 °C resulted in a sharp increase in cracking products, with methane accounting for a significant portion, i.e., 29 wt% (Figure 3F), and a corresponding significant decrease in light olefins. Ethylene remained the predominant light olefin, accounting for approximately 22 wt% (Figure 3F). The obtained results show that rolled CF exhibits higher cracking performance at the same reaction temperature compared to its planar counterpart (with the same apparent volume). Such results may be due to the orientation of the CF in the induction coil, i.e., circular rolling, which may be favorable for the circulation of eddy currents from the induction heating furnace within the CF pieces, resulting in higher heat recovery rates and temperature uniformity within the solid bed.

[0099] The PTO results obtained with flat and rolled CF materials are compared in Figure 4. The results show that the same cracking and production of C2-C4 olefins is obtained on the rolled CF material at a lower reaction temperature, i.e., 500 °C vs. 550 °C, compared with the flat CF material, so the rolled CF exhibits higher PTO performance compared to the flat CF material (Figures 4B and D). Also, the production of higher grade, i.e., >C 25The amount of hydrocarbons was significantly lower on the rolled CF material, confirming the high efficiency of the rolled CF material in decomposing long-chain polymers passing through it, even at low temperatures (Figure 4A and C). Such results may be attributed to the difference in the density of carbon microfilaments between the two structures. Indeed, for CF fabricated by the needle-punched process, it should be expected to have more bypass channels within the planar structure material compared to the rolled one with exposed sides. The circular orientation of the rolled CF material also favors induced currents and improves axial heat transfer.

[0100] PTO process for post-industrial plastic waste In this example, the PTO process was investigated on CF materials, namely flat and rolled CF materials, using a mixture of plastic waste from different industrial sources (Table 4). The waste plastics were heat treated at 250°C under argon to melt the polymer and determine the exact amount of inorganic solids in the samples.

[0101] Composition and origin of industrial mixed polymer waste. PE accounts for >50 wt%, PS accounts for <20 wt%, and other components are non-plastic solid waste. [Table 4]

[0102] The results show that the CF materials, regardless of their shape and configuration, exhibit high cracking performance when operated under IH mode to convert industrial mixed polymers into liquid and gaseous hydrocarbons (Figure 5A and B). Both materials also exhibit high selectivity to C2–C4 olefins at reaction temperatures as low as 500 °C (Figure 5C and D). The C2–C4 olefin fraction reached approximately 43% on the rolled CF material at 500 °C, but approximately 49% on the flat CF material at 550 °C. In both cases, ethylene and propylene are the major products of this C2–C4 olefin fraction. The very similar results obtained with both CF materials when operating the PTO process with industrial mixed polymers can be attributed to the lower density and easier cracking of the latter compared to the model polymer, i.e., the mixture of LDHP and HDPE instead of pure HDPE.

[0103] The results obtained in various tests involving model HDPE and mixed industrial waste plastics are summarized in Table 5 and compared with results reported in the literature.

[0104] [Table 5]

[0105] Stability as a function of cycle testing The suitability of the CF material for converting mixed industrial waste to light olefins was investigated, and the results are shown in Figure 6. Cyclic tests are carried out on rolled CF material at 450 °C (because according to our previous results, this temperature is the most suitable for carrying out the PTO process on such material).

[0106] The results show that the rolled CF material exhibits high and stable PTO activity as a function of cycle testing using industrial mixed polymers. This high stability can be attributed to the following fact: the process was carried out in two stages: first, waste polymer was vaporized in the upper heated bed, followed by cracking of the polymer vapor in the second reactor containing the CF material. The polymer vapor passed through a quartz wool plug, which acted as a scavenger or filter, blocking impurities from the polymer waste and preventing excessive carbon material deactivation. By operating in these separate sections, the majority of impurities contained in the waste plastic feedstock remained in the first heated bed, while much less impurities (mostly in gaseous form) passed through the reactor, which may contribute to its stability as a function of cycle testing. In addition, a 1 mm layer of MESOC+ extrudate (2 mm long) was added on top of the rolled CF material, slightly offset from the induction coil at a temperature of approximately 450 °C, to act as a scavenger layer and to better vaporize the adsorbed polymer vapor. It is noteworthy that at this temperature, i.e., 450°C, the MESOC+ sample exhibits very low activity without any ability to produce light olefins. The gas, liquid and solid residue fractions obtained after each cycle at 450°C are shown in Figure 7, confirming the high stability of the rolled CF material for the PTO process.

[0107] The weight of the deposited solid residue as a function of the cycle test is also measured. The results show that the weight of the carbon material increases slightly by about 0.6±0.3 wt.% after each cycle when the first five cycle tests are performed at 500°C.

[0108] PTF for porous carbon materials Porous carbons representing MESOC+ have been produced on an industrial scale by Sicat SARL (www.sicatcatalyst.com) in the form of extrudates with different macroscopic shapes. For the PTF process, MESOC+ extrudates with diameters of either 1 mm or 3 mm and lengths of 2–4 mm were used. Low-resolution SEM micrographs performed on MESOC+, taken at different angles, demonstrate the roughness of its surface. Medium-resolution SEM micrographs demonstrate the presence of macropores within the material, as well as a highly mesoporous structure that may favor the adsorption and cracking of pyrolytic polymer vapors.

[0109] PTF process for model HDPE plastic waste In this section, the conversion of model waste plastic (HDPE) to HCs is performed on MESOC+ material under both direct induction heating (present invention) and indirect radiative Joule heating (comparison). The results are shown in Figure 8. At the same reaction temperature of 500 °C, 3 mm of MESOC+ exhibits lower cracking activity than CF material (i.e., flat or rolled). However, it is noteworthy that the performance obtained with 3 mm of MESOC+ under IH remains much higher than under JH mode, even at high temperatures (Figure 8A vs. Figures 8C and E). Such results can again be explained by the higher heat maintained within the carbon bed. Cracking of long polymer chains is an endothermic process, and therefore the efficiency of the solid material is strongly influenced by the effective temperature distribution within the bed and on the carbon surface where the reaction occurs. At high cracking rates, the material temperature may decrease, and therefore the cracking performance may decrease, which is the starting point for the formation of long-chain hydrocarbons or waxes. The low heat delivery rate using the indirect heating mode does not allow for maintaining an optimum bed temperature, unlike induction heating, which generates heat directly inside the body of material.

[0110] However, the 3 mm MESOC+ material yielded mostly saturated fractions and C6-C 20 It is noteworthy that the production of liquid hydrocarbons in the range of C 2= ~C4= This is different from that obtained with non-porous CF materials operated under similar reaction conditions, where olefins (C6-C8) dominated. Such results can be explained by the following facts: (i) unlike non-porous CF, the porosity of MESOC+ may favor the diffusion of pristine light olefins into the interior of the material's pores, thus favoring the recombination of light olefins to form long-chain olefins or aromatic compounds; (ii) 3 mm MESOC+ also exhibits a longer diffusion distance compared to that of CF, i.e., 3 mm vs. 10 μm diameter, which may induce an internal temperature gradient within the extrudate, resulting in poor cracking performance. Such a hypothesis was investigated by modifying 3 mm MESOC (3 mm diameter) with 1 mm MESOC+ (1 mm diameter). The results of the comparison are shown in Figure 9. The results indicate that the smaller carbon material, i.e., 1 mm MESOC+, is more favorable for the diffusion of C6-C8. 15 The results show improved selectivity in light olefins, although some liquid hydrocarbons in the range of 0.05 to 0.25 are still observed. At 3 mm MESOC+, long chain hydrocarbons are limited to a maximum of >C. 23 However, in the case of 1mm MESOC+, the maximum C 15Only hydrocarbons containing up to 10 ... However, it is worth noting that the liquid hydrocarbons produced from the pyrolysis of waste plastics also have interesting uses, as the products can be converted into other fuel fractions, namely gasoline, diesel and jet fuel, with low sulfur content.

[0111] PTF process for industrial plastic waste Cracking of plastics over MESOC+ material was also investigated using mixed plastic waste from different industrial sources (Table 4). The results (Figure 10) show that the 3 mm MESOC+ material operated in IH mode exhibits high cracking performance and even high selectivity for light olefin formation from post-industrial mixed plastic waste at relatively low reaction temperatures (Figures 11C and 11D). The formation of a smaller proportion of long-chain liquid fractions may be due to the lower vaporization temperature of the mixed polymer containing LDPE, which can generate a larger amount of polymer vapor at the same pyrolysis temperature compared to model HDPE.

[0112] Stability as a function of cycle testing The stability of the 3 mm MESOC+ material for converting model HDPE to light olefins and fuels was investigated, and the results are shown in Figure 11. The 3 mm MESOC+ exhibits intermediate behavior with a gas fraction of approximately 55% and a liquid fraction reaching approximately 42% in all cycle tests. However, in cycle #3, the long chain (i.e., >C 17 It can be noted that a slight increase in ethylene and propylene hydrocarbons can be observed, which may be due to partial plugging or encapsulation of some active sites at the origin of the cracking process (Figure 11E). According to the results, the 3 mm MESOC+ material is capable of converting waste plastics into liquid and gaseous hydrocarbons for downstream applications such as polymer processing (ethylene and propylene fractions) or liquid feedstock for transportation or petrochemical processing. The C2-C4 fraction decreases from 38% to 28% from cycle #1 to cycle #2 and remains unchanged in cycle #3, whereas the C2-C4 olefin fraction increases from 15% to 17% and 20% in cycles #1, #2, and #3. The obtained results again confirm the ability of the MESOC+ material to convert waste plastics into hydrocarbons that can be used in many petrochemical processes.

[0113] conclusion In summary, we have reported the efficient use of metal-free carbon materials in combination with direct induction heating to convert either model or industrial mixed plastics (e.g., waste plastics) into C2-C4 light olefin fractions, particularly on nonporous CF materials, and into liquid hydrocarbons, particularly on porous MESOC+ materials. The results demonstrate that either nonporous or porous carbon materials, such as carbon felt, are efficient for such direct conversion at relatively low temperatures under induction heating. The carbon materials also exhibit high stability as a function of cycle testing, again confirming their interest in such processes. In this conversion process, the carbon material is directly heated by eddy currents generated on the material's surface by interaction with an electromagnetic field provided by an inductor. The high intrinsic thermal conductivity of carbon-based materials significantly improves heat transfer from the outer surface to the core of the material. Heat transfer is expected to be more efficient in the case of carbon felt due to the relatively small diameter, i.e., 10 μm, of carbon microfilaments, which remain within the range of depth penetration for eddy currents, compared to mesoporous materials with larger diameters ≥ 1 mm. Such high heat transfer in the carbon felt may further explain the greater production of light olefins from plastic waste compared to that observed with larger-sized mesoporous carbons, where temperature gradients within the pellets may hinder the cracking reaction and result in the formation of a larger liquid fraction under the same reaction conditions. The difference in light olefin yield between CF and MESOC+ materials may also be due to diffusion phenomena between the two materials due to their pore and geometric structures. Induction heating also provides a simple method for directly heating materials without the excessive energy losses due to convection and conduction typically observed in the case of indirect Joule heating. This result also suggests that carbon materials with smaller dimensions, i.e., macroscopic host substrates decorated with carbon nanotubes or nanofibers, can also be efficiently heated using induction heating to perform PTO or PTF processes.

[0114] Nonporous carbon felt (CF) exhibits high selectivity for C2–C4 olefins, essentially consisting of ethylene and propylene fractions, at reaction temperatures ranging from 450 to 550 °C for both model waste plastics (HDPE) and mixed industrial waste plastics containing impurities. The C2–C4 olefin yield can be finely tuned by modifying operating parameters such as temperature or contact time. This material also exhibits high stability as a function of cycle testing using mixed industrial waste plastics, highlighting the advantages of using such metal-free carbon materials. Along with the C2–C4 olefin fraction, other liquid hydrocarbons are also produced from the waste plastics, which can be further used in other downstream applications or recycled at the top of the reactor to obtain light olefin fractions.

[0115] The MESOC+ porous carbon material had a lower light olefin yield and a higher proportion of C5-C6, accounting for approximately 50%. 20 The mesoporous carbon material also exhibits high stability as a function of cycle testing, which again confirms its interest for such processes.

[0116] It is noteworthy that, compared with linear or branched hydrocarbons, the production of aromatic compounds was very low on both nonporous and porous carbon materials at reaction temperatures ≦500°C. This may be due to the strong acidity present on zeolite catalysts but absent on the carbon materials. This result is very interesting because the formation of aromatic compounds contributes to an enhanced hydrogen pool that can react with unstable intermediate olefins to produce saturated products. The results showed that nonporous carbon materials, i.e., carbon felts, lacking internal pores and possessing very low specific surface areas, primarily produced a higher proportion of light olefins. This may be due to the high desorption rate of light olefin intermediates and the lower rate of aromatic formation, which reduces the proportion of hydrogen available for hydrogenation of such intermediates. On the other hand, porous carbons, which can induce longer residence times, resulted in a higher proportion of liquid fraction and a lower proportion of light olefin fraction (in the gaseous product).

[0117] Example 3: Comparison of HDPE plastic olefination processes using rolled carbon felt or metal chips The first experiment (comparative) was carried out using a metal tip made of an alloy of Fe and Ni in the form of a metal spring with the following dimensions: length 50 mm, diameter 4 mm, which was inductively heated to 500°C and then the polymer extrudate was dropped directly into the reaction zone, the results of which are shown in Figure 12C.

[0118] A second experiment (the present invention) is carried out under the same conditions using rolled carbon felt (CF) as the metal-free carbon material, and the results are shown in Figure 12B.

[0119] T1 refers to the stream temperature before entering the reactor inlet, and T2 refers to the conversion reaction (or "cracking") temperature. In both experiments, T1 = 25°C and T2 = 500°C.

[0120] Reaction conditions: M = 1.7 g for CF (H = 40 mm), 4 g for metal (H = 35 mm); M HDPE =20g;F AR =30mL.min-1 Feedstock for CF and metal chips dropped directly onto the catalyst = 5g HDPE .h -1

[0121] The result of the conversion is shown in Figure 12C.

[0122] In both experiments, the gas fraction represents 64%, the liquid fraction represents 33%, and the residue represents 3%. However, the experiment using metal chips converted the polymer extrudate to about 99.46 wt% wax and about 0.54 wt% C2-C4 olefins, whereas the experiment using rolled CF converted the polymer extrudate to about 42 wt% C2-C4 olefins.

[0123] These results show that the inductively heated PTO process using a metal catalyst does not make it possible to obtain C2-C4 olefins, in contrast to the metal-free carbon material used in the process of the present invention.

[0124] Example 4: Comparison of HDPE plastic olefination processes using rolled carbon felt in one or two steps Two experiments are carried out using rolled CF: a one-step conversion reaction (i.e., a direct cracking step) or a two-step conversion reaction (i.e., a first stage of precracking, then a cracking step using metal-free carbon material).

[0125] T1 refers to the stream temperature or first stage temperature (if present), and T2 refers to the conversion reaction (or "cracking") temperature. For the one-step process, T1 = 25°C and T2 = 500°C. For the two-step process, T1 = 450°C and T2 = 500°C.

[0126] Reaction conditions: M = 1.7 g of rolled CF (H = 40 mm); M HDPE =20g;T HDPE = 450℃(JH);F AR =30mL.min -1Feedstock for CF catalyst in two steps: First step: pyrolysis by Joule heating ("JH") and second step catalysis = 10 g HDPE .h -1 Feedstock for CF dropped directly onto catalyst = 5g HDPE .h -1 .

[0127] The results for the one-step process are shown in Figure 12B, and the results for the two-step process are shown in Figure 12A.

[0128] In the one-step process, the gas fraction represents 64 wt%, the liquid fraction represents 33 wt%, and the residue represents 3 wt%. In the two-step process, the gas fraction represents 69 wt%, the liquid fraction represents 23 wt%, and the residue represents 8 wt%. The one-step process converts the polymer extrudate to about 42 wt% C2-C4 olefins, while the two-step process converts the polymer extrudate to about 48 wt% C2-C4 olefins.

[0129] These results show that the presence of the first stage is beneficial in improving the conversion of C2-C4 olefins.

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Claims

1. Plastics are heated under direct induction heating at temperatures below 800°C. ２ ~C ４ Use of metal-free carbon materials for the conversion of olefins and / or other hydrocarbons.

2. 2. Use according to claim 1, wherein said temperature is strictly less than 600°C.

3. The metal-free carbon material has a thickness of at least 0.10 m as determined by ASTM-D-3663(2020). ２ / g up to 2000m ２ 3. The use according to claim 1 or 2, wherein the surface area is a BET surface area of ​​up to 1 / 2 g.

4. 4. The use according to claim 1, wherein the carbon of the metal-free carbon material is selected from the group comprising graphite, graphene, mesoporous carbon, carbon black, acetylene black, pyrolytic carbon, activated carbon, and any combination thereof.

5. 5. The use according to any one of claims 1 to 4, wherein the metal-free carbon material has a morphology selected from among granules, felts, such as rolled felts, fibres, such as nanofibers, filaments, 2D or 3D fabrics, foams such as open-cell foams, 3D printed structures, spheres, cloths, monoliths such as honeycombs, extrudates, rods, sticks and particles, tubes, such as nanotubes, rings or trilobes, tablets, nanotablets, and any combination thereof.

6. 6. The use according to any one of claims 1 to 5, wherein the metal-free carbon material is supported by a non-carbon structure.

7. Plastic C ２ ~C ４ 1. A process for converting olefins and / or other hydrocarbons, comprising: - optionally pre-cracking said plastic; reacting under direct induction heating using a metal-free carbon material as defined in any one of the preceding claims at a temperature of -800°C or lower; The process includes:

8. 8. The process of claim 7, wherein the pre-cracking step, if present, is carried out at a temperature ranging from 300°C to 600°C.

9. 9. The process of claim 7 or 8, wherein the pre-cracking step, if present, is carried out under induction heating, Joule heating or microwave heating.

10. 10. The process of any one of claims 7 to 9, wherein, if present, the pre-cracking step is performed on silicon carbide, metal beads or any thermally conductive material mixed with the plastic.

11. 11. The process according to any one of claims 7 to 10, wherein during the precracking step, the plastic is precracked in a first stage reactor, while the vapors and / or liquids produced in the first section are swept by a gas flow towards the material in a second stage reactor where the cracking process takes place.

12. The plastics include high-density and low-density polyethylene, polypropylene, polystyrene, mixed industrial waste plastics, such as low-density polyethylene, PET, PVC and polystyrene-containing solid residues, plastic-containing solid residues, C １５ ~C ４５ 12. The use according to any one of claims 1 to 6 or the process according to any one of claims 7 to 11, wherein the at least one plastic is selected from among waxes and polymers distilled at temperatures between 200°C and 500°C.

13. 13. The use according to any one of claims 1 to 6 or 12, or the process according to claims 7 to 11, wherein the metal-free carbon material used in the reaction step is not mixed with the plastic material to be converted.

14. 14. The use or process of claim 13, wherein the metal-free carbon material is arranged in a packed bed.

15. Said C ２ ~C ４ The olefin is at least one selected from ethylene, propylene, and butylene, and diolefins prepared from ethylene, propylene, and butylene, and the other hydrocarbon is C ５＋ Liquid hydrocarbons and / or paraffinic gaseous C １ ~C ４ 15. The use according to any one of claims 1 to 6 or 12 to 14, or the process according to any one of claims 7 to 11, wherein the hydrocarbon is a hydrocarbon.

16. Said C ５＋ 16. The use according to any one of claims 1 to 6 or 12 to 15, or the process according to any one of claims 7 to 11, wherein the liquid hydrocarbon is a fuel oil.

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