WO2024231394A1 - Method for converting plastic into hydrocarbon(s) - Google Patents

Abstract

The invention concerns a method for converting into hydrocarbon(s) a solid or liquid substrate (11) selected among substrates formed of plastics material and heavy oils, by a conversion reaction of hydrogenolysis and/or pyrolysis, occurring in a given temperature range. This method comprises contacting, in a reactor (10), the substrate (11) and a microscale heating element (12) formed of a ferromagnetic metal compound, under an oxygen-free atmosphere (23), and heating this heating element (12), at a temperature within said temperature range, by electromagnetic induction by means of a magnetic field inductor (18) external to the reactor (10).

Description

PROCESS FOR THE TRANSFORMATION OF PLASTIC INTO HYDROCARBON(S)

The present invention falls within the general field of recycling plastic materials.

More particularly, the present invention relates to a method for transforming a plastic substrate or a heavy oil into hydrocarbon(s), using the electromagnetic induction heating technique. The invention also relates to the use, for such a transformation, of a micrometric heating element formed from a ferromagnetic metal compound.

Plastic waste, a major cause of pollution in landfills and oceans, is a global concern, primarily due to the enormous rate of production and the long lifespan of the materials that constitute it. For example, the global production capacity of polyethylene, the most widely used category of plastics, in a wide variety of areas ranging from garbage bags to bubble wrap to hip replacements, is 80 million tons per year. Polyethylene molecules are, as their name suggests, composed of several molecules of ethylene (C2H4). Polyethylene chains can be linear or branched, the degree of branching affecting the rigidity, density, and strength of the material. Generally speaking, the polyethylene produced is chemically inert and resistant to decomposition. It represents approximately 60% of the plastics found in landfills, where it decomposes very slowly, if at all.

Several types of plastic recycling streams have been developed and are constantly being improved to cope with the huge amount of plastic waste generated by industry.

Mechanical recycling currently efficiently processes collected plastic waste, it displays very good yields and benefits from a good establishment in the sorting sector. However, it has several limitations. On the one hand, it is not suitable for separating polymers from plastic components and their additives, for example dyes. On the other hand, although the sector is progressing rapidly, the physical characteristics of the material resulting from recycling are often degraded compared to the original material. Recycled plastic is therefore still often used for purposes other than its initial use, particularly in the construction and building sector. The combination of these factors limits the scale at which plastic is recycled, especially since it is still often less expensive to use virgin raw materials to produce plastic articles.

To take a step towards a circular economy, it is necessary to process the portion of collected plastics that mechanical recycling is unable to handle satisfactorily.

Several chemical recycling techniques, distinct in their method and the structure of the product obtained at the output, have been proposed in order to complement mechanical recycling and avoid resorting to incineration or landfill. Among these techniques, we can cite:

- dissolution, which allows the recovery, using a solvent, of polymer chains, which can be used to create new plastics,

- chemical depolymerization, allowing a return to the monomer stage by using a chemical solvent, these monomers being able to be used subsequently to form new polymer chains,

- biochemical conversion, which corresponds to a chemical depolymerization in which chemical agents are replaced by enzymes,

- pyrolysis or gasification, i.e. thermal depolymerization, which allows hydrocarbons to be recovered in liquid and/or gaseous state, depending on the length of their chain, by means of heat treatment processes. Reinjected into a steam cracker, part of these hydrocarbons can be used to form new plastics, by thermal cracking, catalytic cracking or hydrocracking, in the presence of a catalyst and hydrogen.

The transformation of plastic into fuel by pyrolysis is a process that has been known and industrially developed for more than ten years. However, this process is energy-intensive and does not allow the selectivity of the products formed to be controlled.

Document US 2022/055902 for example describes the transformation of thermoplastic polymers into short-chain hydrocarbons, C6-C10, by pyrolysis in a high temperature oven, the hydrocarbons obtained then being treated by magnetic induction heating, in the presence of large heating elements such as rods or plates, to form carbon nanotubes.

In general, the processes for recycling plastic materials proposed by the prior art are expensive to implement and energy-intensive, and/or they produce low-quality compounds that are difficult to use. Their effectiveness may also be limited to certain plastics. For example, biochemical conversion, while effective for recycling polyethylene terephthalate, is much less effective for the most commonly used plastics, namely polyethylene and polypropylene.

WO 2023/064741 describes a process for depolymerizing plastics using radiofrequency induction heating, using a catalyst and a magnetic susceptor in the form of Fe3O4 nanoparticles, with a size between 50 and 100 nm. This process makes it possible to depolymerize plastics into C2-C20 alkanes and alkenes.

US 2013/303810 describes a method for depolymerizing a plastic substrate such as a polyolefin, into materials with a lower boiling point. This method comprises a step of heating the substrate by magnetic induction using steel balls.

The present invention aims to remedy the drawbacks of the processes proposed by the prior art for the recycling of plastic waste, in particular the drawbacks set out above, by proposing such a process which makes it possible to produce high added value compounds, and in particular methane, preferably with a high yield and high specificity, in an economical manner and in particular with low energy consumption.

It has now been discovered by the present inventors that such results can be achieved by a method using an electromagnetic induction heating mode, in the presence of a micrometric-sized heating element mixed with the plastic substrate to be transformed. Such a method is particularly energy-efficient and it has great versatility, in the sense that it allows, by the choice of suitable operating conditions, to direct the transformation of plastic materials into different reaction products targeted, in particular in hydrocarbon(s) with a more or less long chain. Surprisingly, the present inventors have in particular discovered that the implementation of such a process according to specific operating conditions also makes it possible to form methane with controlled selectivity, and in particular as the largely majority product of the reaction, this with a high yield, including in the absence of a catalyst compound for the plastic transformation reaction, and/or when the heating element is simple steel wool.

Thus, according to the present invention, there is proposed a process for transforming into hydrocarbon(s) a solid or liquid substrate chosen from substrates formed from plastic material(s) and heavy oils, by a transformation reaction occurring in a given temperature range. This process comprising steps of:

- bringing into contact, in a reactor, this substrate and an element, called a heating element, in micrometric form, that is to say in the form of entity(ies) all of whose dimensions are greater than or equal to 1 pm, and at least one dimension is between 1 and 1000 pm, this element being formed of a ferromagnetic metallic compound, this under an atmosphere devoid of oxygen,

- and, still under said oxygen-free atmosphere, heating this heating element by electromagnetic induction using a magnetic field inductor external to the reactor, this heating being carried out at a temperature within said temperature range.

In the present description, by external to the reactor, it is meant that the magnetic field inductor is not located in the atmosphere of the reactor, in the sense that it is located outside the reaction zone of the reactor, in which the substrate and the heating element are brought into contact with each other, under the oxygen-free atmosphere. The magnetic field inductor may be placed so as to surround the reactor or so as to be contained in the reactor (for an annular type reactor for example), as long as it remains external to the internal atmosphere of said reactor.

In this description, micrometric shape means that the heating element is in the form of entity(ies) all of which dimensions are greater than or equal to 1 pm, and at least one dimension is between 1 and 1000 pm.

The heating element used in the method according to the invention is formed of at least one, i.e. one or more, ferromagnetic metal compounds. It may also contain other compounds, which may or may not be inert with respect to the transformation reaction to be carried out. In alternative embodiments of the invention, the heating element is made up of one or more, preferably a single, ferromagnetic metal compound(s).

A heavy oil is defined in the present description, in a conventional manner in itself, as a hydrocarbon or a mixture of hydrocarbons with a high boiling point, comprising at least 12 carbon atoms, such as octadecane. When the substrate is a heavy oil, its transformation according to the invention aims at the formation of so-called lower hydrocarbon(s), that is to say comprising a much smaller number of carbon atoms, in particular a number of carbon atoms between 1 and 4, with a much lower boiling point.

The type of reaction for transforming the substrate into hydrocarbon(s), which the method according to the invention makes it possible to carry out, varies according to the operating conditions used, and in particular the atmosphere in the reactor during the heating step. As indicated above, this atmosphere is devoid of oxygen. The atmosphere in the reactor during the heating step may be of the inert type. The reaction for transforming the substrate, referred to as pyrolysis or thermolysis, is then caused solely by heat. Otherwise, the atmosphere in the reactor during the heating step may be of the reducing type, and in particular based on dihydrogen. The transformation reaction is in this case a hydrogenolysis, which may, depending on the operating conditions applied, be combined with pyrolysis. The reaction products obtained at the end of the transformation reaction are different depending on the type of reaction, and the mechanism(s) it implements. They are also different depending on whether or not the method according to the invention uses, in addition to the micrometric heating element, a catalyst for the transformation reaction. As examples, a hydrogenolysis reaction of a polymer plastic, in the presence of a catalyst for this reaction, will lead to obtaining a mixture of oligomers, alkanes, in particular methane, olefins, and coke, distributed in gaseous, liquid and solid phases. A pyrolysis reaction, thermal and/or catalytic, under an inert atmosphere, will lead to a mixture of gaseous alkanes, liquid fuels and carbonaceous materials.

The temperature range at which the transformation reaction occurs depends on the type of reaction, and in particular on the atmosphere used in the reactor and on the presence or absence of a reaction catalyst in the latter, as well as on the chemical nature of the substrate. It is within the skills of a person skilled in the art to know how to determine this temperature range depending on the particular substrate to be recycled and the desired reaction products (determining the type of transformation reaction to be used, pyrolysis and/or hydrogenolysis, and the choice of the possible catalyst, or the absence of a catalyst). This temperature range is typically between 300 and 650 °C. For any temperature range targeted, it is also within the skills of a person skilled in the art to know how to determine the operating parameters to be used for applying the magnetic field in the reactor, so as to reach an adequate temperature in the latter, causing the transformation reaction to take place. In determining these operating parameters, the person skilled in the art will also take into account the characteristics of the particular heating element used, in particular its specific absorption rate (SAR) and its quantity present in the reactor. The SAR is a parameter well known in itself, defining the heating capacity of a magnetic or electrically conductive material subjected to an alternating magnetic field.

In all its embodiments, whatever the type of transformation reaction, the process according to the invention advantageously makes it possible to obtain, from plastic material or heavy oil, one or more gaseous hydrocarbons, i.e. C1-C4, with high added value, and even more so in the case of methane, which is systematically obtained at the end of the process, with good yield and good selectivity, unlike the processes of the prior art using, not micrometric-sized heating elements, but nanometric-sized heating elements or millimetric (such as balls). In this respect, the process according to the invention makes it possible in particular, in particular embodiments, to form, from plastic material or heavy oil, methane with a high yield, but also with a very high selectivity, methane even being able, under certain conditions, to be the only gaseous product of the reaction. In particular, such selectivity with respect to methane can advantageously, and in a particularly surprising manner, be obtained without using a catalyst for the substrate transformation reaction, in the presence of a dihydrogen atmosphere, including by means of simple steel wool as a heating element. The process according to the invention also leads to the production of solid reaction product(s), and can lead, depending on the operating parameters applied, to the production of liquid reaction product(s). In particular embodiments of the invention, using a catalyst for the specific transformation reaction, such as ruthenium, the process according to the invention can advantageously make it possible to obtain saturated alkanes with a longer chain than gaseous hydrocarbons, typically C5-C30, in liquid form, also with high added value.

The method according to the invention is particularly energy-efficient, even when the transformation reaction only involves pyrolysis. In this respect, it takes advantage of the property of ferromagnetic metal compounds to rise in temperature when they are subjected to an electromagnetic field, under the effect of their own magnetic moment. When implementing the heating step of the method according to the invention, only the heating element is heated. Under the effect of the electromagnetic field applied to the reactor, its temperature rises rapidly, locally reaching a temperature within the temperature range at which the transformation reaction according to the invention occurs. As indicated above, it is within the skills of a person skilled in the art to determine the characteristics of the magnetic field to be applied as a function of the temperature range that it is intended to obtain (typically, a temperature range in the interval between 300 and 650°C), as well as the particular ferromagnetic metal compound(s) forming part of the heating element used according to the invention, and the quantity of heating element used. Advantageously, the transformation reaction therefore occurs at the surface of the heating element, without the reaction medium as a whole reaching the temperature necessary for the intended transformation reaction, including when the substrate is initially in solid form (local heating at the surface of the heating element having the first effect of causing the solid plastic materials in contact with it to melt, with the consequence of increasing the contact surface between the heating element and the liquefied substrate).

The low energy consumption of the process according to the invention is advantageously proven even in the absence of a reducing atmosphere in the reactor, and in the absence of a catalyst. In such configurations, it is particularly inexpensive to implement, due to the low cost of reagents to be used.

The reactor preferably does not contain any element formed from a ferromagnetic metallic compound whose size is not micrometric.

The micrometric heating element is preferably free in the reactor, in the sense that it is not held there in a fixed manner.

Preferably, the reactor used in the method according to the invention is formed from non-ferromagnetic material, for example glass, quartz, silicon carbide or any other non-metallic solid material compatible with exposure to a magnetic field and with the temperatures involved.

The method according to the invention may also meet one or more of the characteristics described below, implemented in isolation or in each of their technically effective combinations.

The substrate that the method according to the invention aims to transform, when it is formed from plastic material(s), may initially be in solid form, in particular in the form of solid fragments, for example fragments of plastic bottles. It is preferably in liquefied form. Thus, the method according to the invention may comprise an initial step of liquefaction of the substrate, before its introduction into the reactor, or carried out directly in the reactor. Such a step may be carried out by any conventional heating technique in itself. As an example, particularly advantageous from the point of view of the ecological footprint of the method, the step of Liquefaction can be achieved by heating with solar energy. The heating temperature to be applied depends on the particular plastic material to be liquefied, more specifically on its melting temperature, and its determination for each given substrate is within the skill of the art. Typically, the melting temperature of plastic materials is between 90 and 200 °C.

When formed from plastic material(s), the substrate may in particular be formed from polyolefin, such as polyethylene or polypropylene, from a copolymer based on, i.e. comprising units of, polyolefin, such as polyethylene terephthalate, from polyester, from polystyrene, or from any of their mixtures. Of course, the reaction products in solid form, and where appropriate in liquid form, obtained at the end of the implementation of the method according to the invention, depend on the initial plastic material(s) used.

The micrometric heating element can be selected from particle powders based on the ferromagnetic metal compound with a size of between 1 and 1000 pm, and wires based on the ferromagnetic metal compound having a wire diameter of between 1 and 1000 pm.

By particles of size between 1 and 1000 pm, it is meant that all the dimensions of the particles are between 1 and 1000 pm. Preferably, the particles are of size between 1 and 100 pm, more preferably between 1 and 50 pm, and preferentially between 1 and 10 pm. Each of the particles may be formed of one or more ferromagnetic metal compounds, and contain only this or these compounds, or may contain additional constituents for example a catalyst for the targeted transformation reaction, such as cobalt, nickel, copper, ruthenium, rhodium, palladium, platinum or any other catalytic compound, or any alloy of one or more of these compounds.

Preferably, the heating element is a set of wires each formed from one or more ferromagnetic metal compounds, preferably composed for at least 90% by weight of one or more, preferably only one, ferromagnetic metal compound(s). In particular embodiments of the invention, each of these wires has a wire diameter between 1 and 1000 pm, preferably between 10 and 1000 pm, more preferably between 20 and 500 pm, preferably between 50 and 200 pm, and for example between 50 and 100 pm, and a wire length preferably of a few centimeters. In preferred embodiments of the invention, the heating element is in the form of straw, that is to say a tangle of such wires.

The ferromagnetic metal compound used in the method according to the invention, or each ferromagnetic metal compound used in the method according to the invention, is preferably chosen from those having a magnetic anisotropy less than or equal to 8.10 ⁴ J. nr ³ , preferably less than or equal to 3.10 ⁴ J.nr ³ .

Each of these compounds is preferably chosen from iron, cobalt, nickel, and their oxides, carbides and/or alloys, as well as amorphous ferromagnetic materials.

In particular embodiments of the invention, the ferromagnetic metal compound is chosen from iron and its alloys, in particular alloys of iron and carbon, for example of the Fe/Cx type, such as Fe2.2C, FeaC, FesC2, alloys of iron and cobalt, and alloys of iron and nickel. Alloys containing at least 50%, preferably at least 80%, by weight of iron are particularly preferred in the context of the invention, in particular in the context of an implementation of a heating element in the form of wires.

Otherwise, the ferromagnetic metal compound used according to the invention may, when it is in powder form, be chosen from iron oxides, such as magnetite or maghemite, or from ferromagnetic ceramics based on iron oxide(s).

In particularly preferred embodiments of the invention, the heating element is steel wool, in particular as commonly referred to as "superfine", comprising an entanglement of wires composed of at least 90% by weight of iron, and whose average wire diameter is between 10 and 1000 μm, preferably between 20 and 500 μm, more preferably between 50 and 200 μm, for example between 50 and 100 μm, and the length of the wires is a few centimeters, for example between 1 and 10 cm. In addition to constituting a high-performance heating element when it is subjected to a field magnetic, iron wool has the advantages of low cost and long service life. It is also easily recoverable, in particular separable from other components in the reactor, and non-polluting. In particular embodiments of the invention, the magnetic field generated by the magnetic field inductor, for the heating step of the process, has an amplitude of between 1 and 80 mT and a frequency of between 30 and 500 kHz.

The amplitude of the magnetic field is preferably between 1 and 50 mT, more preferably between 25 and 40 mT, preferentially between 27 and 40 mT, even more preferentially between 29 and 40 mT, and for example between 29 and 35 mT.

The power is preferably between 2 and 5 kW, preferably between 2 and 4 kW, and for example between 2.6 and 3.8 kW.

The frequency of the applied magnetic field is preferably between 50 and 400 kHz, more preferably between 100 and 300 kHz.

Such characteristics of the magnetic field advantageously make it possible to bring the heating element according to the invention to a temperature allowing the targeted substrate transformation reaction to occur.

As set out above, in particular embodiments of the invention, the atmosphere in the reactor, for the heating step, may be an inert atmosphere, for example an argon atmosphere, preferably at atmospheric pressure. The process according to the invention may then be described as a process for pyrolysis, or thermolysis, of the substrate. Such an embodiment results in the production of gaseous hydrocarbons, in particular in the form of a mixture of methane, ethane and propane, and saturated liquid hydrocarbons, in particular in C10-C40.

In alternative embodiments of the invention, the atmosphere in the reactor, for the heating step, is a reducing atmosphere. This atmosphere may in particular comprise dihydrogen. It preferably consists of dihydrogen. The process according to the invention can then be expressed in terms of a process of hydrogenolysis, where appropriate coupled with pyrolysis, of the substrate. The dihydrogen pressure in the reactor is then preferably at least 3 bars, preferably at least 5 bars, and for example between 5 and 10 bars. Generally speaking, a higher dihydrogen pressure in the reactor reduces the duration of the heating step necessary for the formation of the targeted products.

An implementation of the process under a dihydrogen atmosphere leads in particular to the formation of a larger gaseous fraction of hydrocarbons than when the process is implemented under an inert atmosphere. In addition, it advantageously makes it possible to obtain methane with a high yield, as well as better control of the selectivity of the reaction with respect to the formation of methane, compared with other gaseous hydrocarbons likely to be formed from the substrate.

In particular, in the embodiments of the method in which the atmosphere in the reactor is based on dihydrogen, this methane yield and this selectivity with respect to methane are all the higher, including when the reaction medium is devoid of a catalyst for the transformation reaction, and including when the heating element consists of simple steel wool, when the mass ratio of the heating element relative to the substrate, in the reactor, is greater than or equal to 0.2. The selectivity with respect to methane, relative to other gaseous hydrocarbons, is particularly high, and may in particular be 100%, when the heating element/substrate mass ratio is greater than or equal to 0.25, preferably greater than or equal to 0.3, in particular when the reaction medium is devoid of a catalyst for the transformation reaction and/or the heating element consists of steel wool, in particular as defined above.

The invention does not, however, exclude the possibility that the heating element/substrate mass ratio in the reactor is less than 0.2, the heating step then preferably being carried out in the presence, in the reactor, of a catalyst for the transformation reaction, in contact with the substrate and the heating element.

Generally speaking, the higher the quantity of heating element in the reactor, the more the duration of the heating step required to form the desired products will be reduced.

In particular embodiments of the invention, a catalytic metal compound, catalyst for the transformation reaction, is used contact, in the reactor, with the substrate and the heating element during the heating step.

Such a catalytic metal compound may be selected from manganese, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, iridium and/or tin, or any alloy of one or more of these metals.

The mass rate of “catalytic metal compound/ferromagnetic metal compound”, for example “platinum/iron” (Pt/Fe), is then preferably between 0.1 and 2%.

The catalytic metal compound is preferably present in the reactor in solid form. It can be implemented as is, in powder form for example, or be deposited on a solid support, such as a support made of silicon oxide, cerium oxide, aluminum oxide, titanium oxide or zirconium oxide, or any of their mixtures. For example, the catalytic metal compound can be implemented deposited on a support based on silicon oxide and aluminum oxide, such as the product marketed under the name Siralox by the company Sasol.

In particular embodiments of the invention, the catalytic metal compound is platinum, preferably deposited on a solid support, in particular as defined above. Such a characteristic in particular promotes the production of gaseous hydrocarbon(s) from the substrate, and in particular methane, both in terms of yield and selectivity.

In alternative embodiments of the invention, the catalyst is ruthenium. Such a catalyst notably promotes the production of liquid hydrocarbon(s), in particular saturated hydrocarbons, from the substrate.

Alternatively, the reactor may be free of catalytic compound, in particular catalytic metal compound, capable of catalyzing the transformation reaction, by hydrogenolysis and/or pyrolysis, of the substrate into hydrocarbon(s). Preferably, no solid or liquid component other than one or more substrate(s) and one or more heating element(s), as defined above, is introduced, and therefore initially present, in the reactor at the time of starting the heating step. Such a characteristic does not exclude that a catalyst compound of the reaction forms spontaneously in the reactor during the heating step, in particular from the one or more ferromagnetic metallic compound(s) forming the heating element.

The absence of catalytic compound in the reactor during the heating stage advantageously induces, in particular when the heating element is steel wool, the formation of gaseous hydrocarbons, to the detriment of the formation of liquid hydrocarbons, and mainly, or even only, methane.

The method according to the invention preferably comprises a final step of recovering the gaseous fraction contained in the reactor, and where appropriate the liquid fraction which may also be contained therein, after a determined time of implementation of the heating step (i.e. a reaction time). These fractions are advantageously rich in high added-value hydrocarbon(s), which can be used in numerous applications. The method may also comprise a step of recovering the solid fraction contained in the reactor at the end of the heating step.

The duration of the heating step is preferably greater than or equal to 2 hours, preferably greater than or equal to 5 hours, for example between 2 and 15 hours, preferably between 5 and 15 hours. It is within the competence of a person skilled in the art to determine this duration according to the specific characteristics of the substrate, the applied magnetic field, the heating element(s) and, where appropriate, the catalytic metal compound(s) used.

Another aspect of the invention relates to the use of an element, called a heating element, micrometric, that is to say in the form of entity(ies) all of whose dimensions are greater than or equal to 1 μm, and at least one dimension is between 1 and 1000 μm, formed of one or more ferromagnetic metal compound(s), to transform into hydrocarbon(s), by heating this heating element by electromagnetic induction, a solid or liquid substrate chosen from substrates formed of plastic material(s) and heavy oils. This use may meet one or more of the characteristics described above with reference to the method according to the invention.

The characteristics and advantages of the invention will appear more clearly in light of the examples of implementation below, provided for simple illustrative purposes and in no way limiting the invention, with the support of figures 1 to 4, in which:

Figure 1 schematically represents an example of a device for implementing a method according to the invention.

Figure 2 shows examples of transformation reactions which can be carried out by a process according to the invention, from polyethylene.

Figure 3 shows graphs representing, as a function of the reaction time, the respective contents of methane, ethane and propane obtained in the gas phase formed at the end of the implementation of a process in accordance with the invention for the transformation of low-density polyethylene, by magnetic induction at 29.3 mT, in the presence of steel wool (100 mg for 500 mg of polymer) and platinum catalyst supported on Siralox, and, in a/ an atmosphere of argon at atmospheric pressure, in b/ an atmosphere of 3 bars of H2, and in c/ an atmosphere of 5 bars of H.

Figure 4 shows a bar graph representing, for different reaction times, the material balance Bmatière (sum of the masses of the gaseous, liquid and solid fractions obtained at the end of the reaction, divided by the initial polymer mass) at the end of the implementation of a process in accordance with the invention for the transformation of low-density polyethylene, by magnetic induction at 29.3 mT, in the presence of steel wool (100 mg for 500 mg of polymer) and platinum catalyst supported on Siralox, and an argon atmosphere at atmospheric pressure, 3 bars of H2 or 5 bars of H2.

An example of a device for implementing a method according to the invention is shown schematically in Figure 1.

It comprises a reactor 10, formed of non-ferromagnetic material, for example glass, silicon, quartz or silicon carbide. It is in the form of a Fischer-Porter (FP) bottle in the exemplary embodiment shown in the figure.

In this reactor 10 are placed the substrate to be transformed, in solid or liquid form (solid fragments 11 in the embodiment shown in the figure), as well as a micrometric heating element 12 formed of a ferromagnetic metal compound. In the embodiment shown in the figure, the heating element 12 is in the form of pressed steel wool in ball. A catalytic compound catalyzing the reaction of transformation of the substrate into hydrocarbon(s) (not shown in the figure) can also be placed in the reactor 10.

An annular connector 13 is fixed, in a fluid-tight manner, to the reactor 10, at the opening 102 of the latter. The fixing is for example carried out by screwing cooperating screw threads 101, 131 carried respectively by the reactor 10 and the connector 13. The sealing of the fixing can be ensured by any means, for example by a sealing washer 14 arranged in the screw thread 131 of the connector 13.

The connector 13 is hydraulically connected to a pipe 22, allowing the desired gas to be introduced into the reactor 10, or a gaseous fraction to be extracted therefrom. This pipe 22 is for example equipped with an opening/closing valve 15, a pressure gauge 16 and a safety bypass 17, closed during normal operation of the reactor.

The reactor 10 is arranged in an electromagnetic induction coil, also called a magnetic field inductor, 18. This is preferably a water-cooled coil capable of generating an alternating magnetic field (AMF), for example of a frequency of 300 kHz.

The electromagnetic induction coil 18 is connected to a generator 20, which is controlled by a control module 21, provided with a user interface 21 1, for controlling and adjusting the operating parameters, and in particular the percentage of the maximum amplitude of the magnetic field. For the electromagnetic induction coil of frequency 300 kHz used for the examples described below, the relationship between percentage of the maximum magnetic field applied, power in kW and amplitude of the magnetic field applied in mT, is indicated in table 1.

Table 1 - Characteristics of the magnetic field that can be applied by the electromagnetic induction coil used in the examples For the implementation of a method according to the invention, the substrate 11 to be transformed (plastic material in liquid or solid form or heavy oil), the heating element 12 and, where appropriate, the catalytic compound catalyzing the reaction, are placed in the reactor 10. After fixing the connector 13, the desired gas, for example dihydrogen or argon, is introduced, from the pipe 22, into the reactor 10, at the desired pressure, so as to constitute in the reactor an atmosphere 23 devoid of oxygen. The electromagnetic induction coil 18 is then activated, for the desired time to achieve the transformation of the substrate into hydrocarbon(s).

At the end of this substrate transformation reaction, the gaseous fraction formed, which depending on the operating conditions applied may be particularly rich in methane, can be recovered via pipe 22.

dans laquelle, pour ces exemples, n est environ égal à 143, et mettant en œuvre, soit du platine en tant que catalyseur, soit aucun catalyseur. Ces réactions de transformation, correspondant aux différents exemples qui seront décrits ci-après, mènent à différents produits en fonction des conditions opératoires appliquées : atmosphère inerte (argon) ou réductrice (hydrogène), et présence ou non de catalyseur (par exemple de platine, « Catalyseur Pt » sur la figure). Comme on peut le voir sur cette figure, pour chaque type de réaction, hydrogénolyse et/ou pyrolyse, on obtient : As examples, shown in Figure 2 are transformation reactions which can be carried out by a process according to the invention from polyethylene, of formula (I):

in which, for these examples, n is approximately equal to 143, and using either platinum as a catalyst or no catalyst. These transformation reactions, corresponding to the different examples that will be described below, lead to different products depending on the operating conditions applied: inert atmosphere (argon) or reducing (hydrogen), and presence or absence of catalyst (for example platinum, "Pt Catalyst" in the figure). As can be seen in this figure, for each type of reaction, hydrogenolysis and/or pyrolysis, we obtain:

- depending on the conditions, a liquid fraction, in the form of a pyrolyzed brown liquid, formed of hydrocarbon compounds of approximately C10-C40;

- a gaseous fraction, composed, depending on the operating conditions used, of methane alone, or of a mixture mainly consisting of methane, ethane and propane;

dans laquelle, selon la réaction, m peut être : - and a solid fraction, formed of coke, where appropriate of iron carbide Fe _x C _y (non-stoichiometric carbide probably composed of FeaC, FesC2 and Fe2.2C), possibly of amorphous carbides of formulation Fex with x between 0 and 1, in particular between 0 and 0.5, and of compound(s) of formula (II):

in which, depending on the reaction, m can be:

- significantly lower than 143 (“m “< 143 >>) (compounds insoluble in dichloromethane (DCM)),

- much lower than 143 (“m “143”) (waxy compounds, soluble in DCM),

- or less than 143 (“m < 143 >>) (compounds insoluble in DCM).

EXAMPLES

A/ General materials and methods

A.1 / Chemicals and materials

Tetrahydrofuran (THF, >99%) and toluene (>99%) were supplied by Carlo Erba and Fisher Scientific, respectively. Solvents were dried in a solvent purifier (by passage over an alumina desiccant) and degassed by bubbling argon (Ar) for 20 min before being transferred and stored in glove box. HPLC grade dichloromethane (DCM) was supplied by Aldrich and used without further purification.

Siralox (5/320) was obtained from Sasol. Tris(dibenzylideneacetone)diplatinum(0) (Pt2(dba)3, >98%) and [Ru(cod)(cot)] (cod = 1,5-cyclooctadiene; cot = 1,3,5-cyclooctatriene) were purchased from NanoMePS.

Iron wool (trade name "FINE iron wool") was obtained from Gerlon and used without further purification. This iron wool is formed of iron micro-wires of 50 to 100 pm in diameter and a few centimeters long. Its SAR at 93 kHz and 47 mT is 68 Wg ¹ . This iron wool was pressed by hand, in order to give it the shape of a small sphere, for all reactions, in order to establish good contact with the other elements of the mixture.

Also obtained from Aldrich:

- low density polyethylene (LDPE), with a low mass average molar mass (Mw) (mass average molar mass Mw of approximately 4000 g. mol ^-1 ; number average molar mass M _n of approximately 1700 g. mol ^-1 ; melting point 92°C; in powder form),

- high mass average molar mass LDPE (melt index 25 g/10 min (190°C/2.16 kg); melting point 1-16°C, in pellet form),

- high density polyethylene HDPE (flow index 12 g/10 min (190°C/2.16kg)),

- polypropylene (PP) (isotactic, Mw of approximately 12000 g. mol ^-1 ; _Mn of approximately 5000 g. mol ^-1 ; melting point 157°C),

- and polystyrene (PS) (Mw of approximately 35000 g. mol ^-1 ; in powder form).

The plastic bottles made of LDPE grade #4 were purchased from VWR.

All experiments were performed with the polymers as received, without further purification.

A.2/ Characterization

Powder X-ray diffraction (XRD) patterns were obtained using a PANAlytical Empyrean diffractometer (with Cobalt source, K _1.79 Å). Elemental analysis to quantify the mass content of Pt in Pt/Siralox and of Ru in Ru/Siralox was obtained by Inductively Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES) on an iCAP 6300 ICP Duo spectrometer.

Scanning electron microscopy (SEM) images were taken on a JEOL JSM-7800F microscope.

Elemental mapping by scanning electron microscopy coupled with an energy dispersive detection system (SEM-EDX), allowing the identification of the distribution of the elements, was obtained using a Bruker XFIash® EDX detector attached to the microscope.

Bright-field transmission electron microscopy (TEM) images were obtained on a JEOL JEM 1400 microscope (tungsten filament, 120 kV operating voltage).

ImageJ software was used to count nanoparticles, with size distribution histograms obtained based on 150 particles.

High-resolution transmission electron microscopy (HR-STEM) images were recorded on a JEM-ARM200F microscope. The image resolution in STEM mode is 0.78 Å (STEM HAADF 200kV). High-angle annular dark field (HAADF) STEM elemental mapping was conducted to determine the elemental distribution at the nanoscale.

STEM-EDX mapping was obtained using a CENTURIO-X wide-angle SDD detector (129 eV resolution) attached to the microscope.

The specific surface area of the samples was obtained by measuring isotherms using the Brunauer-Emmett-Teller (BET) method.

The solid residues obtained in the case of catalytic reactions using Pt/Siralox were characterized by powder XRD, TEM and solid-state cross polarization magic angle spinning ¹³ C nuclear magnetic resonance (CP/MAS ¹³ C ^- NMR). In the case of reactions involving steel wool, the black residues obtained in some experiments were characterized by powder XRD and Fourier transform Raman spectroscopy (FT-Raman).

During the reactions, apparent temperatures on the surface of the FP bottle were measured and recorded after 10 min of reaction using a Testo 885 infrared (IR) camera.

A.3/ Gas chromatography and mass spectrometry

The gas phase products obtained were analyzed and quantified using a PerkinElmer Clarus® 580 gas chromatograph (GC). The instrument is equipped with a thermal conductivity detector (TCD) for product quantification. In addition, the instrument was connected to a Clarus® SQ-8T mass spectrometer, used for product identification. The initial oven temperature of 80°C was increased to 250°C with a ramp of 16°C/min, then held for 30 min at 250°C. The injection temperature was set at 200°C and the carrier gas (helium He) flow rate in the column set at 1.8 mL/min. A Shin Carbon column (ST 80/100) was used (length of 2 m; internal diameter of 0.53 mm). The retention times under these conditions for the different compounds likely to be obtained at the end of the reactions are as follows: methane 1.82 min; ethylene 5.82 min; ethane 6.66 min; propene 12.51 min; propane 13.39 min; butene 30 min; n-butane 33 min.

B/ Synthesis of supported catalysts

B.1/ Synthesis of the supported Pt/Siralox catalyst

The platinum (Pt) catalyst supported on SIRALOX was synthesized via decomposition of an organometallic precursor. For this purpose, 56.8 mg of Pt2(dba)3 were mixed with 2 g of SIRALOX support (silicon aluminum oxide from Sasol) in a Fischer-Porter (FP) bottle, followed by the addition of 20 mL of THF. The deep violet suspension was stirred for 15 h. Then, the FP bottle was charged with 3 bar of H2 and vigorously stirred for 24 h at room temperature. Instantly, the deep violet solution turned dark brown. After 24 h of stirring, the FP bottle was transferred to a glove box, where the residual pressure was released. After 1 h a precipitate formed, the colorless supernatant was separated and the gray solid recovered, to be finally washed with 3x5 mL of toluene. The solid obtained was dried under vacuum for 4 h then transferred and stored in a glove box. The product obtained is named Pt/Siralox.

ICP-AES analysis showed a Pt mass content of 0.78%.

B.2/ Synthesis of the supported Ru/Siralox catalyst

The Siralox-supported ruthenium (Ru) catalyst was synthesized via decomposition of an organometallic precursor, [Ru(cod)(cot)]. The target Ru content in the sample was 5 wt%. 328.5 mg of [Ru(cod)(cot)] was mixed with 2 g of Siralox support in a Fischer-Porter (FP) bottle, followed by the addition of 20 mL of tetrahydrofuran (THF). The deep yellow suspension was stirred for 15 h. Then, the FP bottle was charged at 3 bar with dihydrogen H2 and stirred vigorously for 24 h at room temperature. Instantly, the deep yellow solution turned dark brown. After 24 h of stirring, the FP bottle was transferred to a glove box, where the residual pressure was released. After 1 h, a precipitate formed, the colorless supernatant was separated and the gray solid recovered to be finally washed with 4x10 mL of toluene. The solid obtained, called Ru/Siralox, was dried under vacuum for 4 h then transferred and stored in a glove box. ICP-AES analysis showed a mass content of Ru of 4.49%.

Scanning electron microscopy (SEM) images confirmed the production of small ruthenium nanoparticles (diameter d = 2 +/- 0.42 nm) homogeneously dispersed on the Siralox support.

C/ Example 1 - Transformation of LD PE in the presence of steel wool and Pt/Siralox catalyst

These experiments were performed using low Mw LDPE.

All catalytic reactions were carried out in a device as described above, with FP bottles as reactors.

The following were introduced into each FP bottle in the glove box:

- 200 mg of Pt/Siralox,

- 500 mg of low Mw LDPE,

- as well as, as a heating element 12, 100, 200 or 300 mg of the steel wool “FINE steel wool”. The atmosphere of the FP bottle was evacuated and replaced with either dihydrogen H2, at a pressure of 3, 5 or 10 bars, or argon, at atmospheric pressure. Then, the FP bottle was placed in the center of the magnetic induction coil capable of generating an alternating magnetic field (AMF) with a frequency of 300 kHz, with a maximum field amplitude of 65 mT.

The catalytic reactions were carried out at 9, 18 or 27% of the maximum magnetic field amplitude, and for different reaction times (2 h, 5 h and 15 h).

After starting the magnetic induction coil, the polymer melted within a few minutes, and a white/grayish smoke was observed. The smoke decreased sharply with the reaction time, until it disappeared. The melting of the polymer, the smoke release and its gradual cessation depend on many factors, such as the polymer mass/iron wool mass ratio, the amount of iron wool, the intensity of the applied magnetic field, etc.

The temperature of the external surface of the FP bottle wall was measured by IR camera, at a value of 180 to 280 °C depending on the operating conditions. After completion of the reaction, the FP bottle was allowed to cool and, after reaching room temperature, the FP bottle was connected to an injection device to the gas chromatograph, allowing the standardized injection at 1 bar of the gas phase contained in the FP bottle, for analysis and quantification of the products formed by GC-MS. The residual gas phase was evacuated and the dark brown/black residue at the bottom of the FP bottle was washed with 3x5 mL of DCM. The solid residue was filtered and dried overnight while the liquid residue was collected after evaporation of the DCM.

Each reaction was repeated twice to ensure reproducibility of experimental results.

(Equation 1 ) dans laquelle Bmatière est le bilan de matière (unité arbitraire), Msoiide est la masse de fraction solide obtenue (g), Müquide est la masse de fraction liquide obtenue (g), Mgaz est la masse de fraction gazeuse obtenue (g) et M_poiymère est la masse de polymère initiale (g). The mass balance was calculated by counting the mass of each fraction obtained at the end of the reaction (solid, liquid and gaseous fractions) weighted by the initial polymer mass, according to Equation 1: ® matter

(Equation 1) where Bmatière is the material balance (arbitrary unit), Msoiide is the mass of solid fraction obtained (g), Müquide is the mass of liquid fraction obtained (g), Mgaz is the mass of gaseous fraction obtained (g) and _Mpolymère is the initial polymer mass (g).

(Equation 2) dans laquelle YCH4 est le rendement en méthane de la réaction, molcH4 est le nombre de moles de méthane obtenu en fin de réaction mesuré par GC-MS, PMCH4 est le poids moléculaire du méthane (g/mol) et Mpoiymère est la masse de polymère initiale (g). The yield (%) of methane (denoted YCH4) was calculated taking into account the total quantity of polymer used for each reaction, according to Equation 2: 100

(Equation 2) in which YCH4 is the methane yield of the reaction, molcH4 is the number of moles of methane obtained at the end of the reaction measured by GC-MS, PMCH4 is the molecular weight of methane (g/mol) and Mpoiymère is the initial polymer mass (g).

The optimization of the catalytic transformations of low Mw LDPE in the presence of the Pt/Siralox catalyst was thus carried out by evaluating the effect, as indicated above: of the reaction time (2, 5 and 15 h), of the composition of the initial atmosphere (argon or dihydrogen), of the pressure of the initial gas phase (3, 5 and 10 bars of H2, or argon at atmospheric pressure), of the % of the maximum applied magnetic field amplitude (9, 18 and 27%, which is equivalent to a magnetic field amplitude of 22.2, 29.3 and 35 mT, and a power of 1.4, 2.6 and 3.8 kW, respectively), and of the amount of steel wool used (100, 200 and 300 mg).

The gas phase obtained at the end of each reaction was analyzed by GC-MS, and its respective methane, ethane and propane contents were determined. The results obtained are illustrated in Figure 3, in a/ for the argon atmosphere, in b/ for the 3 bar H2 atmosphere and in c/ for the 5 bar H2 atmosphere. As can be seen in this figure, methane is the predominantly formed product, and its production increases with the reaction time. Under H2 atmosphere, the ethane and propane contents decrease with the reaction time, due to their hydrogenolysis. The amount of The methane produced is all the more important as the H2 pressure in the reactor is high.

The methane yields obtained for the different atmospheres and reaction times, for 100 mg of steel wool and 18% field amplitude (29.3 mT), as well as the temperatures of the external wall surface of the FP bottles recorded after 10 min of reaction, are shown in Table 2.

Table 2 - Methane yields and temperatures recorded, for conditions of 100 mg of steel wool and 18% field amplitude For each of the reactions, the masses of each of the gaseous, liquid and solid fractions formed were measured and the mass balance Bmatière was calculated according to Equation 1. The results obtained are shown in Figure 4. As can be seen, for all the conditions tested, the mass balance is particularly high, between 0.85 and 0.95. The methane yields obtained for the different % field amplitude, under 5 bars of H2, for 100 mg of steel wool and 15 h of reaction, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction are shown in Table 3.

Table 3 - Methane yields and temperatures recorded, for conditions of 5 bars of H2, 100 mg of steel wool and 15 h of reaction

The methane yield is roughly equivalent for field amplitudes of 18% and 27%, and significantly higher than that obtained for 9% field amplitude.

The methane yields obtained for the different initial quantities of steel wool and the different reaction times, for 18% field amplitude and under 5 bars of H2, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction are indicated in Table 4.

Table 4 - Methane yields and temperatures recorded, for conditions of 5 bars of H2 and 18% field amplitude

Increasing the amount of steel wool reduces the reaction time required to produce a substantially equivalent amount of methane. After 2 h of reaction, the methane selectivity is all the greater as the amount of steel wool used is greater. It is also observed that the higher the reactor temperature, the greater the amount of methane produced in the shortest reaction time.

D/ Example 2 - Transformation of LDPE in the presence of steel wool without catalyst

Experiments were conducted with steel wool alone, in the absence of Pt/Siralox catalyst, according to a protocol similar to that described in Example 1, applied for:

- 500 mg or 1 g of low Mw LDPE,

- 100, 200 or 300 mg of steel wool “FINE steel wool” as described above,

- an atmosphere of dihydrogen at 5 bars of H2 or argon at atmospheric pressure,

- a reaction time of 2, 5 or 15 hours,

- 18% of the maximum amplitude of the magnetic field (29.3 mT, 2.6 kW).

The methane yields obtained for the different initial quantities of steel wool and the different reaction times, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction and the quantities of methane and ethane obtained at the end of the reaction (propane is not detected), for the initial condition of 500 mg of LDPE, are indicated in Table 5. In this table, the results obtained in Example 1 above, in the presence of the Pt/Siralox catalyst, for the same operating conditions, are also indicated for comparison.

Table 5 - Methane yields, quantities of methane and ethane produced, and temperatures recorded, for 0.5 g of LDPE

When the amount of iron wool is equal to 100 mg, the selectivity towards methane and the methane production rate are lower in the absence of the Pt/Siralox catalyst. Particularly surprisingly, when the amount of iron wool used is 200 mg or more (iron wool mass ratio iron I initial polymer greater than or equal to 0.4), the yield and selectivity in methane are substantially similar in the presence or absence of the Pt/Siralox catalyst.

The methane yields obtained for the different initial quantities of steel wool and the different reaction times, as well as the temperatures of the external wall surface of the FP bottles recorded after 10 min of reaction and the quantities of methane, ethane/ethylene and propane/propene obtained at the end of the reaction, for the initial condition of 1 g of LDPE, are indicated in Table 6.

Table 6 - Methane yields, quantities of methane, ethane/ethylene and propane/propene produced, and temperatures recorded, for the 1 g LDPE condition

It is observed that, for 100 mg of iron wool (iron wool/LDPE mass ratio of 0.1), the selectivity and methane yield are low. For quantities greater than or equal to 200 mg of iron wool (iron wool/LDPE mass ratio greater than or equal to 0.2), the methane yield is much higher, and comparable to those obtained in the presence of Pt/Siralox catalyst.

For quantities greater than or equal to 300 mg of steel wool (iron wool/LDPE mass ratio greater than or equal to 0.3), the selectivity with respect to the formation of methane in the gas phase is particularly high.

An additional experiment was performed with a different steel wool, thicker, formed of iron micro-wires of about 300 to 500 pm in diameter, and a few centimeters long. The protocol as described above was applied with: 1 g of low Mw LDPE, 300 mg of this iron wool, a dihydrogen atmosphere at 5 bars of H2, a reaction time of 2 h, 18% of the maximum amplitude of the magnetic field (29.3 mT, 2.6 kW). 27.68 mmol of methane were obtained, with a yield YCH4 = 44.4%. This experiment demonstrates that the dimensions of the iron micro-wires do not modify the selectivity of the reaction with respect to methane and the methane yield.

E/ Example 3 - Transformation of LDPE, HPDE and PP alone or in mixture with PS, in the presence of steel wool without catalyst

The operating protocol described in Example 1 was applied to different plastic materials (low Mw LDPE, high Mw LDPE, HDPE, PP) alone, or to an equimass mixture of low Mw LDPE, HDPE, PP and PS, or to fragments of 4 to 40 mm ² of LDPE bottle, using 1 g of polymer, mixture or fragments, and 300 mg of steel wool "FINE steel wool" as described above, without Pt/Siralox. The FP bottle was charged to a pressure of 5 bar in H2, then subjected to 18% of the maximum amplitude of the magnetic field, for 2 h or 5 h.

Tableau 7 - Rendements en méthane, quantités de méthane, éthane et propane obtenues en fin de réaction, et températures relevées, pour 2 h de réaction On observe que des rendements élevés en méthane, ainsi qu’une bonne sélectivité vis-à-vis de la formation de méthane, sont obtenus pour tous les substrats, y compris pour le mélange « LDPE basse Mw + HDPE + PP + PS ». Un résultat similaire est obtenu pour un mélange « LDPE basse Mw + HDPE + PP + PU » (PU = polyuréthane). The results obtained, in terms of quantities of methane, ethane and propane obtained at the end of the reaction, and methane yields obtained, for 2 h of reaction, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction, are indicated in Table 7.

Table 7 - Methane yields, quantities of methane, ethane and propane obtained at the end of the reaction, and temperatures recorded, for 2 h of reaction It is observed that high methane yields, as well as good selectivity with respect to methane formation, are obtained for all substrates, including for the mixture "LDPE low Mw + HDPE + PP + PS". A similar result is obtained for a mixture "LDPE low Mw + HDPE + PP + PU" (PU = polyurethane).

The results obtained, in terms of quantities of methane, ethane and propane obtained at the end of the reaction, methane yields obtained, for 5 h of reaction, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction, are indicated in Table 8.

Table 8 - Methane yields, quantities of methane, ethane and propane obtained at the end of the reaction, and temperatures recorded, for 5 h of reaction

It is observed that the methane yield increases with the reaction time, as does the methane selectivity, a selectivity greater than 99% of methane being observed for all substrates except high Mw LDPE, for which the selectivity of the reaction with respect to methane is still very high, greater than 80%.

F/ Example 4 - Transformation of LPDE or octadecane, in the presence of steel wool without catalyst

The operating protocol described in Example 1 was applied to low- Mw or octadecane (boiling temperature 317 °C), using 1 g of this substrate and 300 mg of steel wool “FINE steel wool” as described above, without Pt/Siralox. The FP bottle was charged to a pressure of 5 bar in H2, then subjected to 18% of the maximum magnetic field amplitude, for 2 h or 5 h.

The results obtained, in terms of quantities of methane, ethane and propane obtained at the end of the reaction, methane yields obtained, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction, are indicated in Table 9.

Table 9 - Methane yields, quantities of methane, ethane and propane obtained at the end of the reaction, and temperatures recorded, for 2 h or 5 h of reaction

The results are particularly satisfactory for the two substrates tested.

G/ Example 5 - Transformation of LD PE in the presence of steel wool without catalyst, for different quantities of steel wool

The operating protocol described in Example 1 was applied to low Mw LDPE using 1 g of this substrate and different amounts of steel wool “FINE Steel Wool” as described above (100, 200, 250, 300 and 350 mg), without Pt/Siralox. The FP bottle was charged to a pressure of 5 bar in H2, then subjected to 18% of the maximum magnetic field amplitude, for 2 h.

The results obtained, in terms of quantities of methane, ethane and propane obtained at the end of the reaction, methane yields obtained, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction, are indicated in Table 10.

Table 10 - Methane yields, quantities of methane, ethane and propane obtained at the end of the reaction, and temperatures recorded, for 2 h of reaction

The results, in terms of selectivity and methane yield, are excellent from 250 mg of steel wool, i.e. from a steel wool/polymer mass ratio of 0.25. The selectivity towards methane is particularly high from 300 mg of steel wool, i.e. for steel wool/polymer mass ratios of 0.3 and above.

H/ Example 6 - Transformation of LDPE in the presence of steel wool without catalyst, for different quantities of LDPE

The operating protocol described in Example 1 was applied to low Mw LDPE using different quantities (500, 1000 and 1500 mg) of this substrate and 300 mg of steel wool “FINE steel wool” as described above, without Pt/Siralox. The FP bottle was charged to a pressure of 5 bars in H2, then subjected to 18% of the maximum amplitude of the magnetic field, for 2 h or 5 h.

The results obtained, in terms of quantities of methane, ethane and propane obtained at the end of the reaction, methane yields obtained, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction, according to the reaction time, are indicated in Table 1 1 .

Table 11 - Methane yields, quantities of methane, ethane and propane obtained at the end of the reaction, and temperatures recorded, for 300 mg of steel wool

Methane yield is excellent for all LDPE quantities (iron wool/polymer mass ratios greater than or equal to 0.2). Methane selectivity is particularly high for 1000 mg LDPE and less, i.e. for iron wool/polymer mass ratios greater than or equal to 0.3.

I/ Example 7 - Transformation of LDPE in the presence of iron in different forms, with Pt/Siralox catalyst

The operating protocol described in Example 1 was applied to low Mw LDPE (500 mg) and 200 mg of iron, either in the form of iron wool "FINE iron wool" as described above, or in the form of nanometric iron powder (average size 0.5 pm, SAR at 93 kHz and 47 mT of 1 -10 Wg ^-1 ), in the presence of 200 mg of Pt/Siralox. The FP bottle was charged at a pressure of 5 bar in H2, then subjected to 18% or 100% of the maximum magnetic field amplitude, for 2 h.

The results obtained, in terms of quantities of methane, ethane and propane obtained at the end of the reaction, methane yields obtained, according to the reaction time, as well as the temperatures of the external surface of the wall of the FP bottles recorded after 10 min of reaction, are indicated in Table 12.

Table 12 - Methane yields, quantities of methane, ethane and propane obtained at the end of the reaction, and temperatures recorded - "neg" means "negligible quantity"

The use of iron in the form of nanometric powder does not give rise to any methane production, unlike micrometric iron wool.

J/ Example 8 - Transformation of LDPE in the presence of steel wool or steel balls

These experiments were carried out using, as heating element, steel wool as described above (example in accordance with the invention) or steel balls with a diameter of 2 mm (example not in accordance with the invention), and low Mw LDPE.

J.1/ In the absence of a catalyst

The operating protocol applied is as described in Example 2 above, with the following parameters:

- 1 g of low Mw LDPE,

- 300 mg of steel wool “FINE steel wool” as described above, or 0.287 g of steel balls (9 balls),

- dihydrogen atmosphere at 5 bars of H2,

- 2 hour reaction time.

For each of the heating elements, the methane yield obtained, as well as the temperature of the external surface of the FP bottle wall recorded after 10 min of reaction, and the quantities of methane, ethane/ethylene and propane/propene obtained at the end of the reaction, are indicated in Table 13.

Table 13 - Methane yields, quantities of methane, ethane/ethylene and propane/propene produced, and temperatures recorded, for each heating element

It is clearly observed that the change in size of the heating element leads to a significant change in the selectivity towards methane: a high methane yield is obtained by implementing the micrometric heating element according to the invention, whereas this yield is very low when the heating element is millimetric in size (2 mm in diameter).

J.2/ In the presence of the Pt/Siralox catalyst

The operating protocol applied is as described in Example 1 above, with the following parameters:

- 0.5 g of low Mw LDPE,

- 100 mg of steel wool “FINE steel wool” as described above, or 96 mg of steel balls (3 balls),

- dihydrogen atmosphere at 10 bars of H2,

- 15 hour response time.

For each of the heating elements, the methane yield obtained, as well as the temperature of the external surface of the FP bottle wall recorded after 10 min of reaction, and the quantities of methane, ethane/ethylene and propane/propene obtained at the end of the reaction, are indicated in Table 14.

Table 14 - Methane yields, quantities of methane, ethane/ethylene and propane/propene produced, and temperatures recorded, for each element heating - Neg. indicates a negligible quantity

Here again, we clearly observe a drastic drop in methane yield when the heating element is millimeter-sized (2 mm diameter balls), compared to the micrometric shape of the heating element, for which methane selectivity is particularly high.

K/ Example 9 - Transformation of LD PE in the presence of iron wool and Ru/Siralox catalyst

This experiment was performed using 500 mg of low Mw LDPE, 40 mg of Ru/Siralox and 100 mg of steel wool. The operating protocol applied was as described in Example 1 above. The experimental parameters applied were more precisely the following: 10 bars of H2, 18% of the maximum amplitude of the magnetic field, 15 h.

The methane yield thus obtained is 82.6%, and the temperature of the external surface of the FP bottle wall recorded after 10 min of reaction is 150-170°C.

Claims

1. Process for transforming a solid or liquid substrate (11) into hydrocarbon(s) selected from substrates formed from plastic material(s) and heavy oils, by a transformation reaction occurring in a given temperature range, said process comprising steps of: - bringing into contact, in a reactor (10), said substrate (11) and a heating element (12) formed from a ferromagnetic metal compound, under an atmosphere (23) devoid of oxygen, - and heating said heating element (12) by electromagnetic induction by means of a magnetic field inductor (18) external to said reactor (10), at a temperature within said temperature range, said method being characterized in that said heating element (12) is a micrometric heating element in the form of entity(ies) all of whose dimensions are greater than or equal to 1 pm, and at least one dimension is between 1 and 1000 pm. 2. Method according to claim 1, according to which said substrate (11) is formed of solid or liquefied plastic material. 3. A method according to claim 1 or 2, wherein said substrate (11) is formed from polyolefin, polyolefin-based copolymer, polystyrene, or any of their mixtures. 4. Method according to any one of claims 1 to 3, according to which said heating element (12) is chosen from powders of particles based on said ferromagnetic metal compound with a size between 1 and 1000 pm, and wires based on said ferromagnetic metal compound having a wire diameter between 1 and 1000 pm. 5. Method according to any one of claims 1 to 4, according to which said ferromagnetic metallic compound is chosen from those having a magnetic anisotropy less than or equal to 8.10 ⁴ J.nr ³ . 6. Method according to any one of claims 1 to 5, according to which said ferromagnetic metallic compound is chosen from iron and its alloys. 7. A method according to any one of claims 1 to 6, wherein the magnetic field generated by said magnetic field inductor (18) has an amplitude between 1 and 80 mT and a frequency between 30 and 500 kHz. 8. A method according to any one of claims 1 to 7, wherein the atmosphere (23) in said reactor (10) is an inert atmosphere. 9. A method according to any one of claims 1 to 7, wherein the atmosphere (23) in said reactor (10) comprises dihydrogen. 10. Method according to any one of claims 1 to 9, according to which the mass ratio of said heating element (12) and said substrate (11), in said reactor (10), is greater than or equal to 0.2. 11. A method according to any one of claims 1 to 10, wherein a catalytic metal compound catalyzing said transformation reaction is brought into contact with said substrate (11) and said heating element (12), in said reactor (10), during said heating step. 12. Method according to claim 11, according to which said catalytic metal compound is chosen from platinum, ruthenium, manganese, cobalt, nickel, copper, zinc, rhodium, palladium, iridium and/or tin, or any alloy of one or more of these metals. 13. The method of claim 12, wherein said catalytic metal compound is platinum, deposited on a solid support. 14. Method according to any one of claims 1 to 13, according to which said reactor (10) is free of catalytic compound. 15. Method according to any one of claims 1 to 14, comprising a final step of recovering the gaseous fraction contained in the reactor (10). 16. Use of a micrometric heating element (12), in the form of entity(ies) all of whose dimensions are greater than or equal to 1 pm, and at least one dimension is between 1 and 1000 pm, formed of a ferromagnetic metallic compound, to transform into hydrocarbon(s), by heating said heating element (12) by electromagnetic induction, a solid or liquid substrate (11) chosen from substrates formed of plastic material(s) and heavy oils.