Chemical reactor with internal and external filtration systems and process thereof

Abstract

The present invention relates to a catalytic chemical reactor system (1) for hydrogen- assisted catalytic depolymerisation of plastic waste comprising a chemical reactor (2) and a recycling circuit (3), wherein the chemical reactor (2) comprises a reactant port (21), a product removal port (25) and an exit port located at the bottom of the chemical reactor (2), wherein the recycling circuit (3) comprises an entry port communicating with the exit port of the chemical reactor (2), and a recycle injection port (22), and wherein the chemical reactor (2) comprises a first filtration system (4) filtrating the effluent to the exit port to retain catalysts within the chemical reactor (2), while the recycling circuit (3) comprises a second solid / liquid separation system (5) to remove ashes from the flux of the recycling circuit (3).

Description

[0001] CHEMICAL REACTOR WITH INTERNAL AND EXTERNAL FILTRATION SYSTEMS AND PROCESS THEREOF

[0002] Technical Field

[0003] The present invention relates to a chemical reactor system for treatments of plastic waste.

[0004] Background

[0005] Plastics are regarded as an essential component of modern life because of their wide range of uses in both homes and businesses. Because of their widespread use, a significant amount of plastic waste is produced annually, which seriously pollutes the environment. However, when considering energy efficiency and resource utilization, traditional methods of treating plastic waste, such as combustion, mechanical recycling, and refuse-derived fuel, are frequently limited or insufficient. Extensive research is being done to provide environmentally sound solutions for plastic waste. Controlling the pollutants produced when plastic waste is converted into chemicals or energy sources is crucial when looking for such solutions.

[0006] Incineration of plastic waste to produce energy results in the emission of particulate matter and harmful gases that are improper from the environment. Incineration is thus not the preferred method for plastic waste management.

[0007] Thermal cracking, catalytic cracking or catalytic hydrocracking are more environmentally friendly processes for recycling plastic than incineration and are recognized as promising methods among the various waste plastic management methods.

[0008] Cracking is a process in which polymeric materials are broken down into smaller much lighter molecules of gaseous and liquid range. Cracking is carried out in the presence or absence of hydrogen and with or without the use of a catalyst.Thermal cracking or pyrolysis is carried out at elevated temperatures and in the presence of an inert atmosphere.

[0009] Catalytic cracking requires a catalyst to carry out the process of breaking down macromolecules into petrochemicals and fuels at a lower temperature than pyrolysis, while catalytic hydrocracking improves the yield as well as the quality of the resulting product.

[0010] Polymer macromolecules conversion by hydrocracking into naphtha occurs in the presence of hydrogen through carbon-carbon bond cleavage, together with simultaneous or successive hydrogenation of unsaturated molecules formed during the process.

[0011] However, plastic waste contains a relatively high amount, around 1 to 15 percent, of materials that will remain solid after complete conversion of plastic waste.

[0012] These undesirable solid materials, commonly called ashes, hinder the management of the catalyst, as well as the quality of the resulting products during the process of valorisation of plastic waste.

[0013] These ashes thus require to be removed from the resulting products and separated from the catalyst.

[0014] Indeed, as the catalyst and the ashes are in particulate form, treatment of these two types of particles within the process of catalytic hydrocracking without reducing catalytic activity and obtaining high and clean quality product, remains a challenge.

[0015] To remove these ashes and solids, one can wash the sample before entering the process to remove the dust and dirt but in plastic materials, some solids are entangled within the polymer matrix and hence cannot be removed for instance filler materials. Another method would be to filter the polymer once melted and it is commonly done in recycling but works well for low ash content and non-abrasive materials since the viscosity of the molten polymer requires very high pressures to pass through the filters, while toohigh solid content can rapidly damage the filters. Finally, even by using a combination of these methods, some ashes remain in the melt and finer filtration can be required.

[0016] WO2023279016 discloses the catalytic pyrolysis of plastic feeds by an apparatus comprising a reactor and a recycling circuit equipped with two separators within the recycling circuit, one for separating a catalyst rich phase with an ash rich phase, and the other for separating the ash form the resulting hydrocarbon products.

[0017] US 2023 / 139587 describes a pyrolysis facility including a pyrolysis film reactor comprising a reaction section disposed between a top feeding section and bottom pooling section, along with a solid separator arranged in the product recovery line. The reaction section comprises open ended vertical tubes located between openings of the top and bottom foraminous plates. The liquefied feed accumulates on the top foraminous plate before entering the film-generating tubes and flowing down towards the pooling section, while the generated pyrolysis vapours rise to the top of the reactor through the centre of the film-generating tubes. The liquefied plastic fraction not converted to pyrolysis vapours, and the non-plastic solids will accumulate in the pooling section, from where they can be removed from the reactor, or recycled to the reactor without additional filtration.

[0018] There is thus a need to propose a reactor system that permits to obtain high yield and high purity products, that handles the removal of the ashes from the products without reducing the catalyst activity within the reactor.

[0019] Summary

[0020] The present invention is directed to a catalytic chemical reactor system for hydrogen-assisted catalytic depolymerisation of plastic waste comprising a chemical reactor and a recycling circuit, wherein the chemical reactor comprises a reactant port, a product removal port and an exit port located at the bottom of the chemical reactor, wherein the recycling circuit comprises an entry port communicating with the exit port of the chemical reactor, and a recycle injection port, and wherein the chemical reactor comprises a first filtration system filtrating the effluent before the exit port to retaincatalysts within the chemical reactor, while the recycling circuit comprises a second solid / liquid separation system to remove ashes from the flux of the recycling circuit.

[0021] The size of the aperture of the first filtration system is superior to the size of the aperture of the second solid / liquid separation system.

[0022] The size of the aperture of the first filtration system is preferably at least 2 times superior to those of the second filtration system, preferably 10 times superior preferably 20 times superior, more preferably 30 times superior.

[0023] The size of the apertures of the first filtration system is preferably comprised between 200 micrometres and 3 millimetres, preferably between 500 micrometres and 2.5 millimetres, more preferably between 1 to 2 millimetres.

[0024] The first filtration system is located within the chemical reactor, above the exit port of the chemical reactor connected to the recycling circuit.

[0025] According to one characteristic, the chemical reactor comprises an impact plate, while the first filtration system is located below the impact plate.

[0026] According to the previous characteristic, the chemical reactor is a jet-loop type reactor wherein the chemical reactor comprises a draft tube to guide the jet towards the impact plate.

[0027] The first filtration system comprises preferably a metallic mesh filter or perforated plate.

[0028] According to one embodiment, the first filtration system comprises an impact plate on top of a sintered filtered mesh connected to the outlet of the chemical reactor.

[0029] The size of the apertures of the second solid / liquid separation system is preferably comprised between 5 micrometres and 500 micrometres, preferably between 10 and 80 micrometres, more preferably between 20 and 60 micrometres.

[0030] The second solid / liquid separation system comprises preferably a metallic mesh filter.According to another embodiment, the recycling circuit comprises at least two second solid / liquid separation systems (5) arranged in parallel.

[0031] According to a further characteristic, the second solid / liquid separation system is a scraping self-cleaning filter, a duplex filter or a backflush filter.

[0032] According to one embodiment, the second solid / liquid separation system comprises a cyclone.

[0033] The invention also concerns a process for hydrogen-assisted catalytic depolymerisation of plastic waste within the chemical reactor system of the invention, wherein the process comprises the steps of providing catalyst with particle size superior to the aperture of the first filtration system, providing melted plastic waste, and hydrogen gas, operating at temperature comprised between 200 and 500°C, and hydrogen partial pressure between 10 and 200 bar, providing an agitation means to disperse the catalyst in the reaction medium, operating the recycling circuit, wherein the catalyst is held within the chemical reactor by the first filtration system, while the ashes are removed from the reaction medium by the second filtration system.

[0034] According to an embodiment, the process comprises the step of reacting the reaction medium within the chemical reactor for an appropriate reaction time before operating the recycling circuit by using at least one pump.

[0035] According to another characteristic, the chemical reactor system comprises at least one separator which reinjects partially reacted reagent back to the chemical reactor to reduce the reaction medium viscosity and to increase its conversion.

[0036] Brief description of the drawings

[0037] Further particular advantages and features of the invention will become more apparent from the following non-limitative description of at least one embodiment of the invention which will refer to the accompanying drawings, wherein

[0038] Figure 1 is a schematic drawing of chemical reactor system according to a first embodiment.Figure 2 is a schematic drawing of chemical reactor system according to a second embodiment.

[0039] Figure 3 is a schematic drawing of chemical reactor system according to a third embodiment.

[0040] Figure 4 is a schematic drawing of an implementation of the chemical reactor according to the chemical reactor system of figures 1 to 3.

[0041] Detailed description

[0042] The chemical reactor system (1) according to the invention, is designed to retain the catalyst within the reaction chamber of the chemical reactor (2) and remove the ashes from the flow of reagents and products within the recycling circuit (3).

[0043] The present invention does not focus per se on the treatment of plastic waste, but mainly on the handling of solids within the chemical reactor system (1). As a main example the present invention will mainly focus on the treatment of plastic waste by hydrocracking but is not limited to hydrocracking and can be applied to hydrogenolysis, hydrogenation, hydrodenitrogenation, hydrodeoxygenation, hydrodehalogenation, hydrodesulphurisation, hydrodemetallation, hydrodewaxing, hydroisomerisation, catalytic cracking, catalytic solvolysis, catalytic depolymerisation, hydrolysis, or via tandem dehydrogenation-olefin-metathesis-hydrogenation cleavage and combinations thereof.

[0044] Hence, the catalyst is retained within the chemical reactor (2) by a first filtration system (4) located within the chemical reactor (2), while the ashes are removed from the flux of the recycling circuit (3) by a second solid / liquid separation system (5), as explained in more detail later in the description.

[0045] It is understood by filtration system a separation method between a solid and a liquid.

[0046] The first filtration system (4) filtrates the effluent to the exit port to retain catalysts within the chemical reactor (2). More precisely, all the effluent coming out of the exit port of the chemical reactor (2) passes through the first filtration system (4). The first filtrationsystem (4) is thus arranged in such a way that all the effluent coming out of the chemical reactor passes through the first filtration system (4).

[0047] The second solid / liquid separation system (5) comprises a second filtration system and / or a separation system by centrifugation as a cyclone as explained in more detail later in the description.

[0048] According to one implementation, the second solid / liquid separation system (5) comprises at least one second filtration system.

[0049] According to another implementation, the second solid / liquid separation system (5) comprises a solid / liquid separation system as a cyclone.

[0050] According to a supplementary implementation, the second solid / liquid separation system (5) comprises at least one second filtration system and a solid / liquid separation system as a cyclone arranged in series.

[0051] The chemical reactor system (1) is preferably designed for the catalytic hydrocracking of plastic waste, and per se comprises gas handling units, reagent entry ports, product removal ports, recycling entry port communicating with the exit port of the chemical reactor and recycling exit port communicating with the entry port of the chemical reactor, as well as pumps at least in the recycling circuit, allowing the advantageous handling of solids particles.

[0052] It is understood that plastic waste comprises one or more polymers selected from the group comprising polyethylene (PE), polypropylene (PP), polystyrene (PS), polyamide (PA), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polydimethylsiloxane (PDMS), polycarbonates, cellulose, and polyvinylidene chloride (PVDC), preferably selected polyethylene (PE), polypropylene (PP), polystyrene (PS), and or mixture thereof. Other traces polymer and / or biopolymer can be present such as but not limited to polycarbonate, rubber, polyacrylate, glue, paper, cardboard.It is also understood that resulting main products of hydrocracking of plastic waste are mixture of hydrocarbons advantageously selected from a group consisting of saturated linear C1-C40 hydrocarbons, saturated branched C4-C40 hydrocarbons or saturated cyclic C5-C10 hydrocarbons. It is also understood that a smaller portion of this product can be aromatic, comprising benzene, toluene, xylene and ethylbenzene for instance.

[0053] Hence, the chemical reactor system (1) comprises a chemical reactor (2) and a recycling circuit (3).

[0054] The chemical reactor (2) comprises a recycle injection port (22) communicating with the exit port of the recycling circuit (3), and an exit port communicating with the entry port of the recycling circuit (3).

[0055] The recycle injection port (22) and the exit port are preferably at the top and bottom end respectively of the chemical reactor (2).

[0056] The recycle injection port (22) is intended to add the filtered reaction mixture back into the chemical reactor (2).

[0057] It is intended by filtered reaction mixture, the reaction mixture comprising unreacted, partially reacted reagent and resulting hydrocracking products. The ash content of the filtered reaction mixture is substantially decreased by the second solid / liquid separation system (5).

[0058] The recycling circuit (3) thus comprises a riser (31 ) delimited by the entry and the exit ports of the recycling circuit (3).

[0059] The recycling circuit (3) comprises a pump (32) along the riser (31) as well as advantageously a heat exchanger (33).

[0060] According to the first embodiment illustrated in figure 1, the pump (32) is positioned upstream of the second solid / liquid separation system (5).The positioning of the pump (32) upstream of the second solid / liquid separation system (5) allows to overcome the pressure drop of the second solid / liquid separation system (5).

[0061] According to the previous embodiment, the pump (32) is preferentially a slurry pump, a lobe pump, a centrifugal pump, or a membrane pump.

[0062] According to the second embodiment illustrated in figure 3, the pump (32) is located downstream of the second solid / liquid separation system (5) to avoid having too much solid material in contact with the pump (32). In that case, the second solid / liquid separation system (5) is mainly operated by static pressure and different height between the filter and the chemical reactor (2), with contribution of the pump suction.

[0063] According to the previous embodiment, the downstream location of the pump (32) allows to use a pump (32) not specifically designed for high solid content for instance a gear pump.

[0064] The top of the chemical reactor (2) advantageously comprises a headspace gas port (26) to recycle the headspace gas, preferably connected to the recycle injection port (22).

[0065] The chemical reactor (2) also comprises a product removal port (25).

[0066] The product removal port (25) is located at the top of chemical reactor (2), as at the reaction temperature and pressure, the products are in the form of volatile compounds.

[0067] Products resulting from the treatment of plastic waste are hence collected from the chemical reactor (2) by evaporation.

[0068] Subsequent reaction on the product stream can be done in a second reactor for instance using a second or a series of suitable reactors or a combination of the suitable reactors.A suitable reactor can be but not limited to a jet-loop reactor, a fixed-bed reactor, a fluidised bed reactor, a trickle bed reactor, an ebullated bed reactor, a circulating bed reactor, a back mixed reactor, a tubular reactor.

[0069] A second reactor could be installed in the recycling circuit (3) for instance a fixed-bed reactor or a tubular reactor equipped with a catalytic static mixer.

[0070] Suitable methods and equipment for recovering hydrocarbons from the reaction mixture is well known in the field.

[0071] The resulting evaporated product exiting the chemical reactor (2) from the product removal port (25) as hydrocarbons can be recovered for example as follows.

[0072] The hydrocarbons typically escape from the product removal port (25) of the chemical reactor (2) continuously in gas phase. Then the hydrocarbons are cooled down to a temperature between 120°C and 300°C to liquefy a portion of the hydrocarbons (typically the temperature has to be above the liquefaction of water at the used pressure), which are then transferred to high-pressure high-temperature separator as a first separator, not shown here.

[0073] The first separator is preferably operated with a temperature ranging from 120 to 310°C, and under a pressure ranging from 10 to 200 bar.

[0074] The resulting gas from the first separator is cooled down again to a temperature between 4°C and 40°C and transferred to a high-pressure low-temperature separator, as a second separator, whereas the resulting liquid from the first separator is reinjected into the chemical reactor (2) for further treatment.

[0075] During the second cooling, water is often mixed with the product to dilute any corrosive species and / or augment the pH. In this particular aspect, water addition can also help to purify the hydrocarbons via liquid / liquid extraction in both the second and third separator.Finally, the liquid obtained in the second separator is depressurised and transferred to a low-pressure low-temperature separator, as a third separator, whereas the gas obtained in the second separator can be reinjected into the chemical reactor (2) to convert more of the unreacted hydrogen and the obtained liquid in the second separator is transferred to the third separator.

[0076] In the third separator, the liquid hydrocarbons are separated from the gases and a polar phase at a standard atmospheric pressure of about 1.01325 bar or slightly above in order to maintain inertisation of the vessel and a temperature between 4°C and 40°C.

[0077] The chemical reactor (2) comprises advantageously at least one recycle stream port (27).

[0078] The at least on recycle stream port (27) is connected to previously mentioned separators to reinject products requiring longer reaction times and / or reactant gas within the chemical reactor (2).

[0079] The chemical reactor (2) comprises at least one reactant port (21), and preferentially one reactant port (21) to continuously add reactant within the reaction chamber of the chemical reactor (2).

[0080] According to one implementation, the chemical reactor system (1) is designed to run in a batch process.

[0081] According to a preferred implementation, the chemical reactor system (1) is designed to run in a continuous process.

[0082] The chemical reactor (2) also advantageously comprises a solid addition port (23) as well as a slurry removal port (24).

[0083] According to the illustrated embodiments, the chemical reactor (2) comprises a solid addition port (23) as well as a slurry removal port (24) for addition of fresh catalyst and removal of deactivated catalyst.The solid addition port (23) is made of a chamber where the catalyst can be loaded. The chamber can be inertised and filled with different fluids, like gas or liquids, before injecting the chamber content into the chemical reactor (2) using pressure and / or gravity. Conveniently, after injection, the chamber can be flushed with a liquid or a gas to remove the remaining solids. The chamber content can be pre-heated to avoid temperature differences upon addition to the chemical reactor (2). Alternatively, a hot liquid can be used, for instance the liquid from the high-pressure high temperature separator.

[0084] The slurry removal port (24) like the solid addition port (23), are composed of a vessel able to be flushed and / or pressurised with various media, gas or liquid, so that the reacting mixture can be removed in a controlled manner. The slurry removal port (24) is preferably located near the bottom of the chemical reactor (2), where heavier solids will tend to accumulate more preferentially.

[0085] Indeed, as the chemical reactor system (1) preferably runs in a continuous process and that the catalyst remains in the chemical reactor (2), the catalyst can be prone to deactivation during the reaction. It may be required to remove the deactivated catalyst to regenerate or reactivate it, before being able to add it to the reactor at a later stage. The fresh, regenerated or reactivated catalyst is preferentially added to maintain constant reaction rates.

[0086] According to the illustrated embodiments, the recycle injection port (22) is a nozzle inlet injecting the unreacted or partially unreacted reactant, resulting products, reactant and product gases back into the chemical reactor (2).

[0087] The nozzle also intensely mixes the unreacted or partially unreacted reactant, and the resulting product with the reactant gases and product gases using the venturi effect.

[0088] It is intended by reactant, melted plastic waste, by products, hydrocarbons, and by gases, reactant gas as hydrogen and product gas, for instance methane, ethane, propane, butane.The use of a nozzle inlet allows to avoid a mechanical stirring means as impellers connected to a drive shaft.

[0089] According to the illustrated embodiments, the chemical reactor (2) is thus preferably a jet-loop type chemical reactor.

[0090] The nozzle inlet surprisingly allows the dispersion of the catalyst in form of pellet, spheres or tablets within the reaction medium, limiting clogging of the first filtration system (4) by the catalyst.

[0091] According to another embodiment, not illustrated, the chemical reactor (2) comprises impellers connected to a drive shaft as mechanical stirring means.

[0092] According to the previous embodiment, the chemical reactor (2) comprises a catalyst basket to prevent the blades of the impeller to damage the catalyst structure.

[0093] Hydrogen is supplied with a partial pressure, preferably at a partial pressure comprised between 10 to 200 bar, increasing the concentration of the gas within the reaction mixture and increasing its diffusion and solubility therein.

[0094] According to a further characteristic, the chemical reactor (2) comprises a gas inlet, not illustrated, at the bottom of the reactor (2), injecting gases counter current to the liquid flow helping in the suspension of the catalysts.

[0095] According to implementations, the gas inlet blows hydrogen gas and or a mixture of hydrogen gas and light hydrocarbons such methane and ethane extracted from the separators introduced beforehand.

[0096] The gas inlet can also be introduced by the means of the nozzle via the recycle injection port (22) or the headspace gas port (26).

[0097] It is understood that the chemical reactor system (1) comprises upstream of the reactant port (21) an extruder, a kneader, or a twin-screw extruder or a stirred tankequipped with a gear pump to melt and pressurise the plastic waste before introduction into the chemical reactor (2).

[0098] According to a supplementary characteristic, the chemical reactor (2) comprises an impact plate (28), located above, i.e., upstream, of the first filtration system (4), preferably located right above the first filtration system (4), to improve the mixing in the reactor and suspend the catalyst in the reaction medium (4).

[0099] It is intended by an impact plate (28), a plate, a deflector plate which redirects the force of the jet upwards inducing mixing of the reaction medium. The deflector plate can be flat or curved, if it is curved it is preferentially convex with a hemispherical or conical shape.

[0100] According to a supplementary characteristic, as illustrated in figure 4, the chemical reactor (2) can comprise a draft tube (29) to guide the jet towards the impact plate (28) and diminish the contact between the jet and the catalyst, thus reducing attrition.

[0101] The chemical reactor (2) also comprises a means to heat the reaction mixture to temperatures enabling the hydrocracking reaction. The recommended hydrocracking temperature is preferably comprised between 200 and 500°C.

[0102] According to another characteristic, the first and second filtration systems (4, 5) comprise metallic, more precisely stainless-steel functioning parts, as perforated sheet or woven wire mesh or sintered wire mesh.

[0103] According to the first embodiment illustrated in figure 1 , the first filtration system (4) comprises a plane or sensibly plane metallic perforated plate or metallic mesh filters, disposed at the bottom part of the chemical reactor (2), preferably below one third, more preferably below one quarter, of the height of the chemical reactor (2), preferably as low as possible or even at the exit port of the chemical reactor (2).According to the embodiment illustrated in figure 4, the first filtration system (4) can be composed of the deflector plate on the top and a sintered filtered mesh below, i.e. downstream of, the plate connected to the outlet of the chemical reactor (2).

[0104] According to the second embodiment illustrated in figure 2, the first filtration system (4) comprises a candle strainer, preferably two candle strainers connected to the exit port of the chemical reactor (2).

[0105] According to the second embodiment illustrated in figure 2, one of the candle filters can be backflushed while the other is still in activity.

[0106] According to embodiments, the second solid / liquid separation system (5) is a scraping self-cleaning filter or a backflush filter or a duplex filter or a basket filter or a candle filter or a hydrocyclone or a hydrocarbon cyclone or a series of cyclones or a series of filters or a combination thereof.

[0107] According to one of the previous embodiments, the second solid / liquid separation system (5) uses centrifugal forces to separate the solid from the reaction media such as a cyclone more commonly named hydrocyclone when it separates a solid from a liquid.

[0108] When a hydrocyclone is used, the sedimented solids are purged when the bottom part of the cyclone is full. Or alternatively the reaction mixture with a higher solid content after passing through the hydrocyclone is discarded or filtered before joining the reaction mixture with a lower solid content.

[0109] Separation of solids form liquid stream using a hydrocyclone is preferably conducted by differences in densities for instance by removing solids having density higher than 1500 kg / m3, while densities of liquids are inferior to 1000 kg / m3

[0110] The recycling circuit (3) preferably comprises at least two second solid / liquid separation systems (5) arranged in parallel so that while one is operated, the other is cleaned for example by a back flush process.According to another characteristic, the recycling circuit (3) comprises at least two second solid / liquid separation systems (5) as two second filtration system with different aperture size arranged in series so that different particles size can be sieved reducing the chance to block the filter.

[0111] It is understood that an aperture is the opening or hole or pore between the wires of a mesh, or hole of perforated sheet.

[0112] According to one characteristic, the size of the aperture of the first filtration system (4) is at least 2 times superior to those of the second filtration system, preferably 10 times superior preferably 20 times superior, more preferably 30 times superior.

[0113] It is intended by catalyst pellets, spheres or tablets any catalyst carrier having different shapes, as spheres, cylinders, rings, extrudates with cloverleafs cross sections as trilobes or quadrilobes, with advantageously enhanced geometrical surface area which increases access to the catalytic sites for the reactants.

[0114] The used catalyst should have at least an atom able to add the hydrogen on the hydrocarbons. Non-limiting examples of active atoms include Fe, Ni, Mo, V, W, Ti, Zr, Co, Cr, Cu, Zn, Pt, Pd, Ru, Ir, Re, Os, In, Ce, Nb, Rh, Sn, La or any combination thereof. For instance, metallic Ni or Cerium oxide.

[0115] For the purpose of the present invention, the catalyst preferably has an acidic site. A non-limiting list of acidic sites includes a zeolite, an alumina, an aluminosilicate, a zirconia, a sulfonated mixed oxide, or any solid acids or super acids, such as niobic acid, tungstic acid or any combination thereof. The acidic site can be mixed intimately with the transition metal site or not.

[0116] The transition metal can be supported on a metal oxide or a mixed metal oxide but can also be an organometallic complex acting as a precursor. The support is usually porous with different pores size distribution such as micropores, nano pores and mesopores or a combination thereof.As introduced beforehand, plastic waste contains generally 1-15 wt.% of inorganic materials, commonly called ashes.

[0117] It is intended by ashes, inorganic materials like inorganic oxides, coke, aluminium materials that will remain solid after complete combustion of plastic waste.

[0118] The chemical reactor system (1) is designed for using catalysts in the form of pellets, spheres or tablets, in the average particle size range of 0.5 to 10 millimetres, intended to be dispersed within the reaction mixture.

[0119] The particle size range of the catalyst are determined by the size of the extrudates produced by injections and cutting, extrusion, compression in known tableting machines in eccentric or rotary presses, or by spheronization with a spheronizer.

[0120] The size of the ashes present in the plastic waste are usually below 500 pm, more generally below 200 pm, even below 50 pm, even below 20 pm.

[0121] The density of the ashes present in the plastic waste are usually above 1’500 kg / m3.

[0122] The second solid / liquid separation system (5) as a cyclone separates by centrifugation, the ashes having a density higher than the liquids, i.e. , liquids densities are less than 1000 kg / m3 and the solids densities are more than 1500 kg / m3.

[0123] According to one characteristic, the second solid / liquid separation system (5) separates solids from liquid stream with a density difference of at least 500 kg / m3and preferably inferior to 10000 kg / m3, preferably comprised between 1500 and 8000 kg / m3, more preferably between 2000 and 6000 kg / m3.

[0124] As the size of the catalyst is at least two times larger than the size of the ashes to be removed from the flow of reagents and products, the size of the aperture of the first filtration system (4) is superior to those of the second filtration system.According to the previous characteristic, the size of the aperture of the first filtration system (4) is at least 2 to 40 times superior to the size of the aperture of the second filtration system.

[0125] The size of the aperture of the first filtration system (4) is advantageously comprised between 200 micrometres and 3 millimetres, preferably between 500 micrometres and 2.5 millimetres, more preferably between 1 and 2 millimetres.

[0126] The first filtration system (4) is thus able to separate solids using their different particle size, i.e., to filter the catalyst within the chemical reactor (2) and to let pass downstream the ashes with the reaction medium to the recycling circuit (3).

[0127] The size of the aperture of the second solid / liquid separation system (5) as a second filtration system is advantageously comprised between 0.5 micrometres and 200 micrometres, preferably between 10 and 80 micrometres, more preferably between 20 and 60 micrometres.

[0128] As specific examples, the size of the aperture of the first filtration system (4) is around 1.3, 1.5, 1.8 or 2 millimetres.

[0129] As specific examples, the size of the aperture of the second solid / liquid separation system (5) as a second filtration system is around 1, 5, 7, 10, 20, 50, 80, 100 or 200 micrometres.

[0130] The present invention also concerns a process for hydrogen-assisted catalytic depolymerisation of plastic waste, as for example catalytic hydrocracking of plastic waste within the chemical reactor system (1).

[0131] The process comprises the step of providing catalyst with particle size superior to the aperture of the first filtration system (4), providing melted plastic waste, and hydrogen gas, operating at temperature comprised between 150 and 500°C, and hydrogen partial pressure between 10 and 200 bar, providing a means to disperse the catalyst into the reaction medium, operating the recycling circuit (3), while the catalyst isheld within the chemical reactor (2) by the first filtration system (4), and the ashes are removed from the reaction medium by the second solid / liquid separation system (5).

[0132] To ease the filtration or separation of the reaction medium, it is preferred that the viscosity of the reaction medium is lower than the polymer melt.

[0133] According to a first alternative, the process comprises the step of reacting the reaction medium within the chemical reactor (2) for an appropriate reaction time before operating the recycling circuit (3) with the at least one pump (32).

[0134] An appropriate reaction time depends on the reaction parameters as the reaction temperature and preferably ranges from 15 minutes to 6 hours.

[0135] According to a second alternative, the process comprises the addition at the beginning of the process of an appropriate solvent in appropriate quantity, that solubilizes the melted plastic waste.

[0136] It is intended by the beginning of the process, when the recycling circuit (3) is not operational.

[0137] Appropriate solvents may be selected from diesel, xylenes, waxes or a combination of high boiling hydrocarbon mixture.

[0138] Appropriate quantity of solvent may range from 5 to 70 mass percent of the introduced quantity of plastic waste within the chemical reactor (2) at the start of the process.

[0139] More specifically, the viscosity of the final mixture should be lower than the molten plastic itself and should be lower than 3 Pas (pascal-second) more preferably less than 2 Pas even more preferably less than 1 Pas.

Claims

CLAIMS1. A catalytic chemical reactor system (1) for hydrogen-assisted catalytic depolymerisation of plastic waste comprising a chemical reactor (2) and a recycling circuit (3),wherein the chemical reactor (2) comprises a reactant port (21), a product removal port (25) and an exit port located at the bottom of the chemical reactor (2),wherein the recycling circuit (3) comprises an entry port communicating with the exit port of the chemical reactor (2), and a recycle injection port (22), andwherein the chemical reactor (2) comprises a first filtration system (4) filtrating the effluent before the exit port to retain catalysts within the chemical reactor (2), while the recycling circuit (3) comprises a second solid / liquid separation system (5) to remove ashes from the flux of the recycling circuit (3).

2. The catalytic chemical reactor system (1 ) of claim 1 , wherein the size of the aperture of the first filtration system (4) is superior to the size of the aperture of the second solid / liquid separation system (5).

3. The catalytic chemical reactor system (1 ) of claim 1 and 2, wherein the size of the aperture of the first filtration system (4) is at least 2 times superior to those of the second filtration system, preferably 10 times superior preferably 20 times superior, more preferably 30 times superior.

4. The catalytic chemical reactor system (1 ) of anyone of the previous claims, wherein the size of the apertures of the first filtration system (4) is comprised between 200 micrometres and 3 millimetres, preferably between 500 micrometres and 2.5 millimetres, more preferably between 1 to 2 millimetres.

5. The catalytic chemical reactor system (1 ) of anyone of the previous claims, wherein the first filtration system (4) is located within the chemical reactor (2), above the exit port of the chemical reactor (2) connected to the recycling circuit (3).

6. The catalytic chemical reactor system (1 ) of anyone of the previous claims, wherein the chemical reactor (2) comprises an impact plate (28), while the first filtration system (4) is located below the impact plate.

7. The catalytic chemical reactor system (1 ) of the previous claim, wherein the chemical reactor (2) is a jet-loop type reactor wherein the chemical reactor (2) comprises a draft tube (29) to guide the jet towards the impact plate (28).

8. The catalytic chemical reactor system (1 ) of anyone of the previous claims, wherein the first filtration system (4) comprises a metallic mesh filter or perforated plate.

9. The catalytic chemical reactor system (1 ) of anyone of the previous claims, the first filtration system (4) comprises an impact plate (28) on top of a sintered filtered mesh connected to the outlet of the chemical reactor (2).

10. The catalytic chemical reactor system (1 ) of anyone of the previous claims, wherein the size of the apertures of the second solid / liquid separation system (5) is comprised between 5 micrometres and 500 micrometres, preferably between 10 and 80 micrometres, more preferably between 20 and 60 micrometres.

11. The catalytic chemical reactor system (1 ) of anyone of the previous claims, wherein the recycling circuit (3) comprises two second filtration systems (5) arranged in parallel.

12. The catalytic chemical reactor system (1 ) of anyone of the previous claims, wherein the second solid / liquid separation system (5) comprises a scraping self-cleaning filter, a duplex filter or a backflush filter.

13. The catalytic chemical reactor system (1) anyone of the previous claims, wherein the second solid / liquid separation system (5) comprises a cyclone.

14. A process for hydrogen-assisted catalytic depolymerisation of plastic waste within the catalytic chemical reactor system (1) of anyone of the preceding claims, wherein the process comprises:- Providing catalyst with particle size superior to the aperture of the first filtration system (4),- Providing melted plastic waste, and hydrogen gas,- Operating at temperature comprised between 200 and 500°C, and hydrogen partial pressure between 10 and 200 bar,- Providing an agitation means to disperse the catalyst in the reaction medium, - Operating the recycling circuit (3), wherein- The catalyst is held within the chemical reactor (2) by the first filtration system (4), while the ashes are removed from the reaction medium by the second solid / liquid separation system (5).

15. The process of the previous claim, wherein the process comprises the step of reacting the reaction medium within the chemical reactor (2) for an appropriate reaction time before operating the recycling circuit (3) by using at least one pump (32).

16. The process of claim 14 or 15, wherein the catalytic chemical reactor system (1 ) comprises at least one separator which reinjects partially reacted reagent back to the chemical reactor (2) to reduce the reaction medium viscosity.

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