ES3001908T3 - Process for treating plastic pyrolysis oil including hydrocracking in two steps - Google Patents

Abstract

The present invention relates to a method for treating a plastic pyrolysis oil, comprising: (a) selectively hydrogenating said feedstock to obtain a hydrogenated effluent; (b) hydrotreating said hydrogenated effluent to obtain a hydrotreated effluent; (c) performing a first hydrocracking step on said hydrotreated effluent to obtain a first hydrocracked effluent; (d) separating the hydrocracked effluent in the presence of an aqueous stream, to obtain a gaseous effluent, a liquid aqueous effluent and a liquid hydrocarbon effluent; (e) fractionating the liquid hydrocarbon effluent to obtain at least one gaseous stream, at least one naphtha cut and a heavier cut; (f) performing a second hydrocracking step on the heavier cut to obtain a second hydrocracked effluent; (g) recycling at least a portion of said second hydrocracked effluent in said separation step (d). (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Process for the treatment of plastic pyrolysis oils that includes two-stage hydrocracking

TECHNICAL FIELD

The present invention relates to a process for treating a plastics pyrolysis oil in order to obtain a hydrocarbon effluent that can be recovered, for example, by being integrated at least in part directly into naphtha or diesel fuel or as a feed to a steam cracking unit. More particularly, the present invention relates to a process for treating a feed resulting from the pyrolysis of plastic waste, in order to eliminate at least in part impurities, in particular olefins (mono-, diolefins), metals, in particular silicon, and halogens, in particular chlorine, that said feed may contain in relatively large quantities, and so as to hydrogenate the feed so as to be able to recover it.

The process according to the invention therefore makes it possible to treat plastic pyrolysis oils to obtain an effluent that can be injected, in whole or in part, into a steam cracking unit. The process according to the invention thus makes it possible to recover plastic pyrolysis oils, while reducing coke formation and, therefore, the risk of clogging and/or premature loss of activity of the catalyst(s) used in the steam treatment unit, and thus reducing the risk of corrosion.

PREVIOUS TECHNIQUE

Plastics resulting from collection and sorting channels can undergo a pyrolysis stage to obtain, among other things, pyrolysis oils. These plastic pyrolysis oils are typically burned to generate electricity and/or used as fuel in industrial or district heating boilers.

Another way to valorize plastic pyrolysis oils is to use them as feedstock for a steam cracking unit to (re)create olefins, the latter being constituent monomers of certain polymers. However, plastic waste is generally mixtures of several polymers, for example, blends of polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, and polystyrene. Furthermore, depending on their uses, plastics may contain, in addition to polymers, other compounds, such as plasticizers, pigments, dyes, or even polymerization catalyst residues. Plastic waste may also contain, to a minor extent, biomass from, for example, household waste. This results in the oils resulting from the pyrolysis of plastic waste containing numerous impurities, particularly diolefins, metals, particularly silicon, or halogenated compounds, particularly chlorine-based compounds, heteroelements such as sulfur, oxygen, and nitrogen, and insoluble compounds, often at high levels and incompatible with steam cracking units or with units located downstream of steam cracking units, particularly polymerization processes and selective hydrogenation processes. These impurities can cause operational problems, particularly corrosion, coking, or catalytic deactivation problems, or even incompatibility problems in the uses of the target polymers. The presence of diolefins can also lead to pyrolysis oil instability problems characterized by the formation of gums. Gums and insolubles eventually present in the pyrolysis oil can cause clogging problems in the processes.

Furthermore, during the steam cracking stage, the yields of light olefins sought for petrochemical products, particularly ethylene and propylene, depend largely on the quality of the feedstocks sent to steam cracking. The BMCI (Bureau of Mines Correlation Index) is often used to characterize hydrocarbon cuts. Overall, light olefin yields increase with increasing paraffin content and/or decreasing BMCI. Conversely, the yields of unwanted heavy compounds and/or coke increase with increasing BMCI.

Document WO 2018/055555 proposes a comprehensive, very general, and relatively complex recycling process for plastic waste, ranging from the pyrolysis step of the plastic waste to the steam cracking step. The process of application WO 2018/055555 comprises, among other things, a hydrotreatment step of the liquid phase resulting directly from the pyrolysis, preferably under fairly advanced conditions, particularly in terms of temperature, for example at a temperature between 260 and 300 °C, a step of separating the hydrotreatment effluent, and then a hydrodealkylation step of the separated heavy effluent at a preferably high temperature, for example between 260 and 400 °C.

Unpublished patent application FR20/01.758 describes a process for treating a plastics pyrolysis oil, comprising:

a) the selective hydrogenation of said charge in the presence of hydrogen and a selective hydrogenation catalyst to obtain a hydrogenated effluent;

b) hydrotreating said hydrogenated effluent in the presence of hydrogen and a hydrotreating catalyst, to obtain a hydrotreating effluent;

c) a separation of the hydrotreatment effluent in the presence of an aqueous flow, at a temperature between 50 and 370 °C, to obtain a gaseous effluent, an aqueous liquid effluent and a hydrocarbon liquid effluent;

d) possibly a fractionation stage of all or part of the hydrocarbon effluent resulting from stage c), to obtain a gaseous flow and at least two hydrocarbon flows which may be a naphtha cut and a heavier cut;

e) a recycling stage comprising a recovery phase of a fraction of the hydrocarbon effluent resulting from the separation stage c) or a fraction of and/or at least one of the hydrocarbon flows resulting from the fractionation stage d), towards the selective hydrogenation stage a) and/or the hydrotreatment stage b).

According to application FR20/01.758, the naphtha cut resulting from the fractionation stage may be sent, in whole or in part, either to a steam cracking unit, to a naphtha pool resulting from conventional oil loadings, or to be recycled according to stage e).

The heavier cut resulting from the fractionation stage may be sent, in whole or in part, either to a steam cracking unit, or to a gas oil or kerosene pool resulting from conventional oil loadings, or recycled according to stage e).

Although the heavier cut can be sent to a steam cracker, few refiners prefer this option. In fact, the heavier cut has a high BMCI and contains more naphthenic, naphthenoaromatic, and aromatic compounds than naphtha cut, leading to a higher C/H ratio. This high ratio is a cause of coking in steam cracking, so dedicated steam crackers are required.

Furthermore, steam cracking of such heavy cut produces fewer products of interest, namely ethylene and propylene, but more pyrolysis gasoline.

It would therefore be advantageous to minimize the yield of heavy cut and maximize the yield of naphtha cut by transforming the heavy cut, at least in part, into naphtha cut by two-stage cracking. This makes it possible to obtain more naphtha, which is preferably sent to steam cracking to produce more olefins, particularly reducing the risks of clogging during the treatment stages of plastic pyrolysis oils, such as those described in the prior art, and of coke formation in significant quantities and/or the risks of corrosion encountered during the subsequent stage(s), for example during the steam cracking stage of plastic pyrolysis oils. The heavy cut that has not been transformed in the first hydrocracking stage is sent, after separation, to a second hydrocracking stage that preferably operates at a moderate conversion in order to maximize the selectivity in compounds of the naphtha cut (which has a boiling point less than or equal to 175 °C, in particular between 80 and 175 °C). Furthermore, the C2 to C4 compounds produced during steam cracking can also be sent to steam cracking, allowing for improved yields of light olefins (ethylene and propylene). Overall, olefin yields are at least maintained, if not improved, while eliminating the need for a dedicated steam cracking furnace for heavy shear.

WO 2014/001632 discloses a process for treating biomass that may contain polymers comprising a two-stage prehydrogenation, a hydroprocessing stage, a separation stage, and a fractionation stage. US 3,492,220 describes a process for treating a fossil feedstock comprising a selective hydrogenation stage, a hydrotreatment stage, a separation stage, a fractionation stage, and a recycling stage. US 5,969,201 describes a process for treating plastics comprising chlorinated compounds comprising a hydrotreatment stage, a hydrocracking stage, a step of separating the effluent into a gaseous fraction and a liquid fraction, a step of separating the gaseous fraction supplied by an aqueous solution, and a recycling stage.

SUMMARY OF THE INVENTION

The invention relates to a process for treating a load comprising a plastics pyrolysis oil comprising chlorinated compounds, comprising:

a) a selective hydrogenation stage implemented in a reaction section fed at least by said charge and a gaseous flow comprising hydrogen, in the presence of at least one selective hydrogenation catalyst, at a temperature between 100 and 280 °C, a partial pressure of hydrogen between 1.0 and 10.0 MPa abs. and an hourly volumetric rate between 0.3 and 10.0 h-1, to obtain a hydrogenated effluent;

b) a hydrotreatment step implemented in a hydrotreatment reaction section, implementing at least one fixed bed reactor having n catalytic beds, n being an integer greater than or equal to 1, each comprising at least one hydrotreatment catalyst, said hydrotreatment reaction section being fed by at least said hydrogenated effluent resulting from step a) and a gaseous flow comprising hydrogen, said hydrotreatment reaction section being carried out at a temperature between 250 and 430 °C, a hydrogen partial pressure between 1.0 and 10.0 MPa abs. and an hourly volumetric rate between 0.1 and 10.0 h-1, to obtain a hydrotreatment effluent;

c) a first hydrocracking stage implemented in a hydrocracking reaction section, implementing at least one fixed bed reactor having n catalyst beds, n being an integer greater than or equal to 1, each comprising at least one hydrocracking catalyst, said hydrocracking reaction section being fed by at least said hydrotreated effluent resulting from step b) and a gaseous flow comprising hydrogen, said hydrocracking reaction section being carried out at a temperature between 250 and 480 ° C, a hydrogen partial pressure between 1.5 and 25.0 MPa abs. and an hourly volumetric rate between 0.1 and 10.0 h-1, to obtain a first hydrotreated effluent;

d) a separation stage, fed by the hydrocracked effluent resulting from c) and an aqueous solution, said stage being carried out at a temperature between 50 and 370 °C, to obtain at least a gaseous effluent, an aqueous effluent and a hydrocarbon effluent;

e) a stage of fractionation of all or part of the hydrocarbon effluent resulting from stage d), to obtain at least one gaseous flow and at least two liquid hydrocarbon flows, said two hydrocarbon flows being at least one naphtha cut comprising compounds having a boiling point less than or equal to 175 °C, and a hydrocarbon cut comprising compounds having a boiling point greater than 175 °C,

(f) a second hydrocracking stage implemented in a hydrocracking reaction section, implementing at least one fixed bed reactor having n catalyst beds, n being an integer greater than or equal to 1, each comprising at least one hydrocracking catalyst, said hydrocracking reaction section being fed by at least part of said hydrocarbon cut comprising compounds having a boiling point greater than 175 °C resulting from step e) and a gaseous flow comprising hydrogen, said hydrocracking reaction section being carried out at a temperature between 250 and 480 °C, a hydrogen partial pressure between 1.5 and 25.0 MPa abs. and an hourly volumetric rate between 0.1 and 10.0 h-1, to obtain a second hydrocracked effluent;

g) a step of recycling at least a portion of said second hydrocracked effluent resulting from step f) into separation step d).

An advantage of the process according to the invention is to purify an oil resulting from the pyrolysis of plastic waste from at least part of its impurities, which allows it to be hydrogenated and thus to be able to recover it, in particular by incorporating it directly into a fuel pool or making it compatible with treatment in a steam cracking unit in order to be able to obtain in particular light olefins with increased yields that can be used as monomers in the manufacture of polymers.

Another advantage of the invention is to prevent risks of clogging and/or corrosion of the treatment unit in which the process of the invention is implemented, the risks being exacerbated by the presence, often in significant quantities, of diolefins, metals and halogenated compounds in the plastics pyrolysis oil.

The process of the invention thus makes it possible to obtain a hydrocarbon effluent resulting from a plastics pyrolysis oil that is free, at least in part, of impurities from the initial plastics pyrolysis oil, thereby limiting operational problems, such as corrosion, coking or catalytic deactivation problems that these impurities can cause, particularly in steam cracking units and/or in units located downstream of the steam cracking units, particularly selective polymerization and hydrogenation units. The elimination of at least part of the impurities from the oils resulting from the pyrolysis of plastic waste will also make it possible to increase the variety of applications of the target polymers, reducing incompatibilities of use.

The present invention contributes to the recycling of plastics, proposing a method for treating an oil resulting from the pyrolysis of plastics to purify, hydrotreat and hydrocrack it to obtain a hydrocarbon effluent with a reduced impurity content and therefore recoverable, either directly in the form of naphtha cut and/or diesel cut, or with a composition compatible with a load from a steam cracking unit. Hydrocracking makes it possible to transform at least part of the heavy cut (diesel) into naphtha cut compounds, which makes it possible to obtain better naphtha cut yields and, when this cut is sent for steam cracking, into light olefins, particularly reducing the risks of clogging during the treatment stages of plastic pyrolysis oils, such as those described in the prior art, and of coke formation in significant quantities and/or the risks of corrosion encountered during the subsequent stage(s), for example during the steam cracking stage of plastic pyrolysis oils.

According to a variant, the process further comprises a recycling step h) in which a fraction of the hydrocarbon effluent resulting from the separation step d) or a fraction of the naphtha cut having a boiling point lower than or equal to 175 °C from the fractionation step e) is sent to the selective hydrogenation step a) and/or to the hydrotreatment step b).

According to a variant, the quantity of recycled stream from step h) is adjusted such that the weight ratio between the recycled stream and the feed comprising a plastics pyrolysis oil is less than or equal to 10. According to a variant, the method comprises a step a0) of pretreatment of the feed comprising a plastics pyrolysis oil, said pretreatment step being carried out upstream of the selective hydrogenation step a) and comprises a filtration step and/or a water washing step and/or an adsorption step.

According to one variant, the reaction section of step a) or b) uses at least two reactors operating in interchangeable mode.

According to one variant, before step a) a flow containing an amine is injected.

According to a variant, said selective hydrogenation catalyst comprises a support chosen from alumina, silica, silica-aluminas, magnesia, clays, and mixtures thereof, and a hydro-dehydrogenating function comprising at least one element of group VIII and at least one element of group VIB, or at least one element of group VIII.

According to a variant, said at least one hydrotreatment catalyst comprises a support chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays, and mixtures thereof, and a hydro-dehydrogenating function comprising at least one element of group VIII and/or at least one element of group VIB.

According to one variant, said hydrocracking catalyst comprises a support chosen from halogenated aluminas, combinations of boron and aluminum oxides, amorphous silica-aluminas and zeolites, and a hydrodehydrogenating function comprising at least one metal from group VIB chosen from chromium, molybdenum and tungsten, alone or in a mixture, and/or at least one metal from group VIII chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum. According to this variant, said zeolite is chosen from zeolites Y, alone or in combination, with other zeolites from zeolites beta, ZSM-12, IZM-2, ZSM-22, ZSM-23, SAPO-11, ZSM-48, ZBM-30, alone or in a mixture.

According to a variant, the naphtha cut comprising compounds having a boiling point of less than or equal to 175 °C resulting from step e), in whole or in part, is sent to a steam cracking step i) carried out in at least one pyrolysis furnace at a temperature of between 700 and 900 °C and at a pressure of between 0.05 and 0.3 MPa relative.

According to a variant, the naphtha cut comprising compounds having a boiling point of less than or equal to 175 °C resulting from step e) is fractionated into a heavy naphtha cut comprising compounds having a boiling point between 80 and 175 °C and a light naphtha cut comprising compounds having a boiling point of less than 80 °C, at least part of said heavy cut being sent to an aromatic complex comprising at least one naphtha reforming step.

According to this variant, at least a portion of the light naphtha cut is sent to the steam cracking stage i).

The invention also relates to the product obtainable by the treatment process according to the invention.

According to the present invention, pressures are absolute pressures, also referred to as abs., and are given in MPa absolute (or MPa abs.), unless otherwise indicated.

According to the present invention, the expressions "in the range of... and..." and "between... and..." are equivalent and mean that the limiting values of the range are included within the range of values described. If this is not the case and the limiting values are not included within the range described, such precision will be provided by the present invention.

For the purposes of the present invention, the various parameter ranges for a given stage, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, for the purposes of the present invention, a range of preferred pressure values can be combined with a range of more preferred temperature values.

Particular and/or preferred embodiments of the invention are described below. They may be implemented separately or in combination with each other, with no limitation on the combination where technically feasible.

The following groups of chemical elements are listed according to the CAS classification (CRC Handbook of Chemistry and Physics, CRC Press, Editor-in-Chief D.R. Lide, 81st Edition, 2000–2001). For example, group VIII according to the CAS classification corresponds to the metals in columns 8, 9, and 10 according to the new IUPAC classification.

The metal content is measured by X-ray fluorescence.

DETAILED DESCRIPTION

The load

According to the invention, a "plastics pyrolysis oil" is an oil, advantageously in liquid form at room temperature, resulting from the pyrolysis of plastics, preferably from plastic waste originating in particular from the collection and sorting sectors. It particularly comprises a mixture of hydrocarbon compounds, in particular paraffins, mono- and/or diolefins, naphthenes and aromatics, these hydrocarbon compounds preferably having a boiling point of less than 700°C and preferably less than 550°C. The plastics pyrolysis oil may comprise, and most frequently does also comprise, impurities such as metals, in particular silicon and iron, halogenated compounds, in particular chlorinated compounds. These impurities may be present in the plastic pyrolysis oil at high levels, for example, up to 350 ppm by weight, or even 700 ppm by weight, or even 1000 ppm by weight of halogen elements contributed by halogenated compounds, up to 100 ppm by weight, or even 200 ppm by weight of metallic or semi-metallic elements. Alkali metals, alkaline earth metals, transition metals, poor metals, and metalloids may be classified as contaminants of a metallic nature, called metals or metallic or semi-metallic elements. In particular, the metals or metallic or semi-metallic elements possibly contained in the oils resulting from the pyrolysis of plastic waste include silicon, iron, or both of these elements. The plastic pyrolysis oil may also comprise other impurities such as heteroelements contributed in particular by sulfur compounds, oxygenated compounds and/or nitrogen compounds, with contents generally less than 10,000 ppm by weight of heteroelements and preferably less than 4,000 ppm by weight of heteroelements.

The feedstock for the process according to the invention comprises at least one plastics pyrolysis oil. Said feedstock may consist solely of plastics pyrolysis oil(s). Preferably, said feedstock comprises at least 50% by weight, preferably between 75 and 100% by weight, of plastics pyrolysis oil, i.e. preferably between 50 and 100% by weight, preferably between 70% and 100% by weight of plastics pyrolysis oil. The feedstock for the process according to the invention may comprise, inter alia, one or more plastics pyrolysis oils, a conventional petroleum feedstock, or a feedstock resulting from the conversion of biomass, which is then co-treated with the plastics pyrolysis oil in the feedstock.

Plastic pyrolysis oil can be obtained from thermal or catalytic pyrolysis treatment or even prepared by hydropyrolysis (pyrolysis in the presence of a catalyst and hydrogen).

Pretreatment (optional)

Said feedstock comprising a plastics pyrolysis oil may advantageously be pretreated in an optional pretreatment step a0), before the selective hydrogenation step a), to obtain a pretreated feedstock feeding the step a).

This optional pretreatment step a0) makes it possible to reduce the quantity of contaminants, in particular the quantity of silicon, possibly present in the feed comprising a plastics pyrolysis oil. Thus, an optional step a0) of pretreatment of the feed comprising a plastics pyrolysis oil is advantageously carried out in particular when said feed comprises more than 50 ppm by weight, in particular more than 20 ppm by weight, more particularly more than 10 ppm by weight, or even more than 5 ppm by weight of metallic elements, and in particular when said feed comprises more than 20 ppm by weight of silicon, more particularly more than 10 ppm by weight, or even more than 5 ppm by weight, and even more particularly more than 1.0 ppm by weight of silicon.

Said optional pretreatment step a0) can be implemented by any method known to those skilled in the art that allows reducing the amount of contaminants. In particular, it may comprise a filtration step and/or a water washing step and/or an adsorption step.

According to a variant, said optional pretreatment step a0) is implemented in an adsorption section operating in the presence of at least one adsorbent. Said optional pretreatment step a0) is implemented at a temperature between 0 and 150 °C, preferably between 5 and 100 °C, and at a pressure between 0.15 and 10.0 MPa abs, preferably between 0.2 and 1.0 MPa abs. The adsorption section is advantageously operated in the presence of at least one adsorbent, preferably of the alumina type, having a specific surface area greater than or equal to 100 m2/g, preferably greater than or equal to 200 m2/g. The specific surface area of said at least adsorbent is advantageously less than or equal to 600 m2/g, in particular less than or equal to 400 m2/g. The specific surface of the adsorbent is a surface measured by the BET procedure, that is, the specific surface determined by nitrogen adsorption according to the ASTM D 3663-78 standard established by the BRUNAUER-EMMETT-TELLER method described in the journal 'The Journal of the American Chemical Society', 6Q, 309 (1938).

Advantageously, said adsorbent comprises less than 1% by weight of metallic elements, preferably free of metallic elements. The metallic elements of the adsorbent are understood to mean the elements of groups 6 to 10 of the periodic table of elements (new IUPAC classification).

Said adsorption section of the optional step a0) comprises at least one adsorption column, preferably at least two adsorption columns, preferably between two and four adsorption columns, containing said adsorbent. When the adsorption section comprises two adsorption columns, one operating mode may be a so-called "swing" operation, according to the established Anglo-Saxon term, in which one of the columns is online, i.e., in operation, while the other column is in standby. When the absorbent of the online column is used, this column is isolated while the standby column is brought online, i.e., into operation. The used absorbent may then be regenerated in situ and/or replaced by fresh absorbent so that the column containing it may be brought back online once the other column has been isolated.

Another operating mode is to have at least two columns operating in series. When the absorbent in the column placed on top is used, this first column is isolated and the used absorbent is regenerated in situ or replaced with a fresh absorbent. The column is then brought back online in the last position, and so on. This operation is called permutable mode, or "PRS" for Permutable Reactor System, or "lead and lag" according to the established English term. The combination of at least two adsorption columns makes it possible to overcome poisoning and/or the possible and possibly rapid clogging of the adsorbent under the combined action of metallic contaminants, diolefins, gums resulting from diolefins, and insolubles possibly present in the pyrolysis oil of the plastics to be treated. The presence of at least two adsorption columns facilitates the replacement and/or regeneration of the adsorbent, advantageously without stopping the pretreatment unit or even the process, thus reducing the risks of clogging and therefore avoiding unit shutdown due to clogging, controlling costs and limiting adsorbent consumption.

Said optional pretreatment step a0) may also be supplied, if appropriate, with at least a fraction of a recycling stream, advantageously resulting from step h) of the process, in a mixture or separately from the feed comprising a plastics pyrolysis oil.

This optional pretreatment stage a0) thus allows obtaining a pretreated feed which then feeds the selective hydrogenation stage a).

Stage a) of selective hydrogenation

According to the invention, the process comprises a step a) of selective hydrogenation of the feedstock comprising a plastics pyrolysis oil produced in the presence of hydrogen, under pressure conditions in hydrogen and temperature allowing said feedstock to be maintained in the liquid phase, and with a quantity of soluble hydrogen just necessary for selective hydrogenation of the diolefins present in the plastics pyrolysis oil. The selective hydrogenation of diolefins in the liquid phase thus makes it possible to avoid, or at least limit, the formation of "gums", i.e. the polymerization of diolefins and therefore the formation of oligomers and polymers, which can clog the reaction section of b) hydrotreatment. Said step a) of selective hydrogenation makes it possible to obtain a hydrogenated effluent, i.e. an effluent with a reduced olefin content, in particular diolefins, preferably free of diolefins.

According to the invention, said selective hydrogenation step a) is implemented in a reaction section fed at least by said feedstock comprising a plastics pyrolysis oil, or by the pretreated feedstock resulting from a possible pretreatment step a0), and a gaseous flow comprising hydrogen (H<2>). Optionally, the reaction section of said step a) may also be further fed with at least a fraction of a recycle flow, advantageously resulting from step d) or from the optional step h), either in a mixture with said feedstock, optionally pretreated, or separately from the feedstock, optionally pretreated, advantageously directly at the inlet of at least one of the reactors of the reaction section of step a). The introduction of at least a fraction of said recycle flow into the reaction section of the selective hydrogenation step a) advantageously makes it possible to dilute the impurities of the feedstock, optionally pretreated, and to control the temperature in particular in said reaction section.

Said reaction section implements a selective hydrogenation, preferably in a fixed bed, in the presence of at least one selective hydrogenation catalyst, advantageously at a temperature between 100 and 280 °C, preferably between 120 and 260 °C, preferably between 130 and 250 °C, a hydrogen partial pressure between 1.0 and 10.0 MPa abs., preferably between 1.5 and 8.0 MPa abs., and at an hourly volumetric rate (VVH) between 0.3 and 10.0 h-1, preferably between 0.5 and 5.0 h-1. The hourly volumetric rate (VVH) is defined here as the ratio between the hourly volumetric flow rate of the feed comprising the plastics pyrolysis oil, optionally pretreated, and the volume of catalyst or catalysts. The quantity of the gaseous flow comprising hydrogen (H<2>), which feeds said reaction section of step a), is advantageously such that the hydrogen coverage is between 1 and 200 Nm3 of hydrogen per m3 of charge (Nm3/m3), preferably between 1 and 50 Nm3 of hydrogen per m3 of charge (Nm3/m3), preferably between 5 and 20 Nm3 of hydrogen per m3 of charge (Nm3/m3). The hydrogen coverage is defined as the ratio of the volumetric flow rate of hydrogen taken under normal temperature and pressure conditions to the volumetric flow rate of "fresh" charge, i.e. the charge to be treated, if applicable pretreated, without taking into account any recycled fraction, at 15°C (in normal m3, noted Nm3, of H<2> per m3 of charge). The gaseous flow containing hydrogen, which feeds the reaction section of step a), may be constituted by additional hydrogen and/or recycled hydrogen, resulting in particular from separation d).

Advantageously, the reaction section of said step a) comprises between 1 and 5 reactors. According to a particular embodiment of the invention, the reaction section comprises between 2 and 5 reactors, operating in permutable mode, referred to as "PRS" for Permutable Reactor System or even "lead and lag". The combination of at least two reactors in PRS mode makes it possible to isolate a reactor, discharge the spent catalyst, recharge the reactor with fresh catalyst, and put said reactor back into service without stopping the process. PRS technology is described, in particular, in patent FR2681871.

Advantageously, reactor internals, such as filter trays, can be used to prevent clogging of the reactor(s). An example of a filter tray is described in patent FR3051375.

Advantageously, said at least one selective hydrogenation catalyst comprises a support, preferably mineral, and a hydro-dehydrogenating function.

According to one variant, the hydro-dehydrogenating function comprises in particular at least one element of group VIII, preferably chosen from nickel and cobalt, and at least one element of group VIB, preferably chosen from molybdenum and tungsten. According to this variant, the total content of oxides of the metallic elements of groups VIB and VIII is preferably between 1% and 40% by weight, preferably between 5% and 30% by weight relative to the total weight of the catalyst. The weight ratio, expressed as metallic oxide, of the metal(s) of group VIB to the metal(s) of group VIII is preferably between 1 and 20, and preferably between 2 and 10.

According to this variant, the reaction section of said step a) comprises for example a selective hydrogenation catalyst comprising between 0.5% and 12% by weight of nickel, preferably between 1% and 10% by weight of nickel (expressed as nickel oxide NiO relative to the weight of said catalyst), and between 1% and 30% by weight of molybdenum, preferably between 3% and 20% by weight of molybdenum (expressed as molybdenum oxide MoOs relative to the weight of said catalyst) on a preferably mineral support, preferably on an alumina support.

According to another variant, the hydro-dehydrogenating function comprises, and preferably consists of, at least one element from Group VIII, preferably nickel. According to this variant, the nickel oxide content is preferably between 1 and 50% by weight, preferably between 10 and 30% by weight relative to the weight of said catalyst. This type of catalyst is preferably used in its reduced form, on a preferably mineral support, preferably on an alumina support.

The support of said at least one selective hydrogenation catalyst is preferably chosen from alumina, silica, silica-aluminas, magnesia, clays, and mixtures thereof. Said support may contain doping compounds, in particular oxides chosen from boron oxide, in particular boron trioxide, zirconia, ceria, titanium oxide, phosphoric anhydride, and a mixture of these oxides. Preferably, said at least one selective hydrogenation catalyst comprises an alumina support, optionally doped with phosphorus and optionally boron. When phosphoric anhydride P<2>O<5> is present, its concentration is less than 10% by weight relative to the weight of the alumina and advantageously at least 0.001% by weight relative to the total weight of the alumina. When boron trioxide B<2>O<5> is present, its concentration is less than 10% by weight relative to the weight of the alumina and advantageously at least 0.001% relative to the total weight of the alumina. The alumina used may be, for example, a<y> (gamma) or n (eta) alumina.

Such a selective hydrogenation catalyst is, for example, in the form of extrudates.

Very preferably, in order to hydrogenate the diolefins as selectively as possible, in step a) there may be used, in addition to the selective hydrogenation catalysts described above, also at least one selective hydrogenation catalyst used in step a) comprising less than 1% by weight of nickel and at least 0.1% by weight of nickel, preferably 0.5% by weight of nickel, expressed as nickel oxide NiO relative to the weight of said catalyst, and less than 5% by weight of molybdenum and at least 0.1% by weight of molybdenum, preferably 0.5% by weight of molybdenum, expressed as molybdenum oxide MoOs relative to the weight of said catalyst, on an alumina support. This catalyst with a low metal load is preferably arranged upstream of the selective hydrogenation catalysts described above.

Optionally, the feed comprising a plastics pyrolysis oil, optionally pretreated, and/or optionally premixed with at least a fraction of a recycle stream, advantageously resulting from step d) or from optional step h), may be mixed with the gaseous stream comprising hydrogen before its introduction into the reaction section.

Said feed, optionally pretreated, and/or optionally mixed with at least a fraction of the recycle flow, advantageously resulting from step d) or from the optional step h), and/or optionally mixed with the gaseous flow, can also be heated before its introduction into the reaction section of step a), for example by heat exchange, in particular with the hydrotreatment effluent of step b), to reach a temperature close to the temperature used in the reaction section that it feeds.

The impurity content, particularly diolefins, of the hydrogenated effluent obtained at the end of step a) is reduced compared to that of the same impurities, particularly diolefins, included in the process feedstock. Step a) of selective hydrogenation generally makes it possible to convert at least 90% and preferably at least 99% of the diolefins contained in the initial feedstock. Step a) also makes it possible to eliminate, at least in part, other contaminants, such as silicon. The hydrogenated effluent obtained at the end of step a) of selective hydrogenation is preferably sent directly to step b) of hydrotreatment. When at least a fraction of the recycle stream resulting from step h) is introduced, the hydrogenated effluent obtained at the end of step a) of selective hydrogenation therefore comprises, in addition to the converted feedstock, said fraction(s) of the recycle stream.

Stage b) of hydrotreatment

According to the invention, the treatment process comprises a step b) of hydrotreatment, advantageously in a fixed bed, of said hydrogenated effluent resulting from step a), optionally in a mixture with at least a fraction of a recycle flow, advantageously resulting from step d) or from the optional step h), in the presence of hydrogen and at least one hydrotreatment catalyst, to obtain a hydrotreatment effluent.

Advantageously, step b) implements hydrotreatment reactions well known to those skilled in the art, and more particularly reactions of hydrogenation of olefins, aromatics, hydrodemetalation, hydrodesulfurization, hydrodenitrogenation, etc.

Advantageously, said step b) is implemented in a hydrotreating reaction section comprising at least one, preferably between one and five, fixed bed reactors having n catalyst beds, n being an integer greater than or equal to one, preferably between one and ten, preferably between two and five, each of said bed(s) comprising at least one, and preferably no more than ten, hydrotreating catalysts. When a reactor comprises several catalyst beds, i.e. at least two, preferably between two and ten, preferably between two and five catalyst beds, said catalyst beds are arranged in series in said reactor.

Said hydrotreatment reaction section is fed at least by said hydrogenated effluent resulting from step a) and a gaseous flow comprising hydrogen, advantageously at the level of the first catalytic bed of the first reactor in operation.

Said hydrotreating reaction section of b) may also be supplied with at least a fraction of the recycle stream, advantageously resulting from step d) or from the optional step h). Said fraction(s) of said recycle stream or the entire recycle stream may be introduced into said hydrotreating reaction section mixed with the hydrogenated effluent resulting from step a) or separately. Said fraction(s) of said recycle stream or the entire recycle stream may be introduced into said hydrotreating reaction section at the level of one or more catalyst beds of said hydrotreating reaction section of b). The introduction of at least a fraction of said recycle stream advantageously makes it possible to dilute the impurities still present in the hydrogenated effluent and to control the temperature, in particular to limit the temperature rise, in the catalyst bed(s) of the hydrotreating reaction section implementing highly exothermic reactions.

Advantageously, said hydrotreatment reaction section is carried out at a pressure equivalent to that used in the reaction section of selective hydrogenation step a), but at a temperature higher than that of the reaction section of selective hydrogenation step a). Thus, said hydrotreatment reaction section is advantageously carried out at a hydrotreatment temperature between 250 and 430 °C, preferably between 280 and 380 °C, at a hydrogen partial pressure between 1.0 and 10.0 MPa abs., and at an hourly volumetric rate (VVH) between 0.1 and 10.0 h-1, preferably between 0.1 and 5.0 h-1, preferably between 0.2 and 2.0 h-1, preferably between 0.2 and 0.8 h-1. According to the invention, the "hydrotreating temperature" corresponds to an average temperature in the hydrotreating reaction section of step b). In particular, it corresponds to the Weight Average Bed Temperature (WABT) according to the established English expression, well known to those skilled in the art. The hydrotreating temperature is advantageously determined according to the catalytic systems, the equipment and their configuration used. For example, the hydrotreating temperature (or WABT) is calculated as follows: WABT = (Tin 2x Tout)/3

with Tin: the temperature of the hydrogenated effluent at the inlet of the hydrotreating reaction section, Tout: the temperature of the effluent at the outlet of the hydrotreating reaction section.

The hourly volumetric rate (VVH) is defined here as the ratio of the hourly volumetric flow rate of the hydrogenated effluent resulting from step a) per volume of catalyst or catalysts. The hydrogen coverage in step b) is advantageously between 50 and 1000 Nm3 of hydrogen per m3 of fresh feedstock feeding step a), and preferably between 50 and 500 Nm3 of hydrogen per m3 of fresh feedstock feeding step a), preferably between 100 and 300 Nm3 of hydrogen per m3 of fresh feedstock feeding step a). The hydrogen coverage is defined here as the ratio of the volumetric flow rate of hydrogen taken under standard temperature and pressure conditions to the volumetric flow rate of fresh feedstock feeding step a), i.e. feedstock comprising a plastics pyrolysis oil, or by the possibly pretreated feedstock feeding step a) (in normal m3, noted Nm3, of H<2> per m3 of fresh feedstock). The hydrogen may consist of make-up and/or recycled hydrogen, resulting in particular from separation step d).

Preferably, an additional gaseous flow comprising hydrogen is advantageously introduced into the inlet of each reactor, particularly one operating in series, and/or into the inlet of each catalyst bed from the second catalyst bed of the hydrotreating reaction section. These additional gaseous flows are also referred to as quench flows. They make it possible to control the temperature in the hydrotreating reactor, where the reactions carried out are generally highly exothermic.

Advantageously, said hydrotreating catalyst used in said step b) may be chosen from the known catalysts for hydrodemetallation, hydrotreating, silicon capture, used in particular for the treatment of oil cuttings, and combinations thereof. Known hydrodemetallation catalysts are, for example, those described in patents EP 0113297, EP 0113284, US 5221656, US 5827421, US 7119045, US 5622616 and US 5089463. Known hydrotreating catalysts are, for example, those described in patents EP 0113297, EP 0113284, US 6589908, US 4818743 or US 6332976. Known silicon capture catalysts are, for example, those described in patent applications CN 102051202 and US 2007/080099.

In particular, said hydrotreatment catalyst comprises a support, preferably mineral, and at least one metallic element having a hydro-dehydrogenating function. Said metallic element having a hydrodehydrogenating function advantageously comprises at least one element of group VIII, preferably chosen from the group consisting of nickel and cobalt, and/or at least one element of group VIB, preferably chosen from the group consisting of molybdenum and tungsten. The total content of oxides of the metallic elements of groups VIB and VIII is preferably between 0.1% and 40% by weight, preferably between 5% and 35% by weight relative to the total weight of the catalyst. The weight ratio expressed as metal oxide between the metal(s) of group VIB and the metal(s) of group VIII is preferably between 1.0 and 20, preferably between 2.0 and 10. For example, the hydrotreating reaction section of step b) of the process comprises a hydrotreating catalyst comprising between 0.5% and 10% by weight of nickel, preferably between 1% and 8% by weight of nickel, expressed as nickel oxide and NiO relative to the total weight of the hydrotreating catalyst, and between 1.0% and 30% by weight of molybdenum, preferably between 3.0% and 29% by weight of molybdenum, expressed as molybdenum oxide MoOs relative to the total weight of the hydrotreating catalyst, on a mineral support.

The support of said hydrotreating catalyst is advantageously chosen from alumina, silica, silica-aluminas, magnesia, clays, and mixtures thereof. Said support may also contain doping compounds, in particular oxides chosen from boron oxide, in particular boron trioxide, zirconia, ceria, titanium oxide, phosphoric anhydride, and a mixture of these oxides. Preferably, said hydrotreating catalyst comprises an alumina support, preferably an alumina support doped with phosphorus and optionally boron. When phosphoric anhydride P<2>O<5> is present, its concentration is less than 10% by weight relative to the weight of the alumina and advantageously at least 0.001% by weight relative to the total weight of the alumina. When boron trioxide B<2>O<5> is present, its concentration is less than 10% by weight relative to the weight of the alumina and advantageously at least 0.001% relative to the total weight of the alumina. The alumina used may be, for example, a y (gamma) or n (eta) alumina.

Such hydrotreating catalyst is, for example, in the form of extrudates.

Advantageously, said hydrotreating catalyst used in step b) of the process has a specific surface area greater than or equal to 250 m2/g, preferably greater than or equal to 300 m2/g. The specific surface area of said hydrotreating catalyst is advantageously less than or equal to 800 m2/g, preferably less than or equal to 600 m2/g, in particular less than or equal to 400 m2/g. The specific surface area of the hydrotreating catalyst is measured by the BET method, i.e. the specific surface area determined by nitrogen adsorption in accordance with ASTM D 3663-78, established by the BRUNAUER-EMMETT-TELLER method described in 'The Journal of the American Chemical Society', 6Q, 309 (1938). Such a specific surface area makes it possible to further improve the removal of contaminants, in particular of metals such as silicon.

According to another aspect of the invention, the hydrotreating catalyst described above further comprises one or more organic compounds containing oxygen and/or nitrogen and/or sulfur. Such a catalyst is frequently referred to by the term "additive catalyst." Generally, the organic compound is chosen from a compound comprising one or more chemical functions chosen from a carboxylic, alcohol, thiol, thioether, sulfone, sulfoxide, ether, aldehyde, ketone, ester, carbonate, amine, nitrile, imide, oxime, urea, and amide function, or even compounds including a furan ring or even sugars.

Hydrotreatment step b) advantageously allows for optimized treatment of the hydrogenated effluent resulting from step a). It allows, in particular, to maximize the hydrogenation of the unsaturated bonds of the olefinic compounds present in the hydrogenated effluent resulting from step a), the hydrodemetallation of said hydrogenated effluent and the capture of metals, in particular silicon, still present in the hydrogenated effluent. Hydrotreatment step b) also allows for hydrodenitrogenation (HDN) of the hydrogenated effluent, i.e. the conversion of the nitrogen species still present in the hydrogenated effluent. Preferably, the nitrogen content of the hydrotreatment effluent at the end of step b) is less than or equal to 10 ppm by weight.

In a preferred embodiment of the invention, said hydrotreatment reaction section comprises several fixed-bed reactors, preferably between two and five, very preferably between two and four, each having n catalyst beds, n being an integer greater than or equal to one, preferably between one and ten, preferably between two and five, and advantageously operating in series and/or in parallel and/or in switchable (or PRS) mode and/or in "swing" mode. The various possible operating modes, PRS (or lead and lag) mode and swing mode, are well known to those skilled in the art and are advantageously defined above. The advantage of a hydrotreatment reaction section comprising several reactors lies in optimized treatment of the hydrogenated effluent, while making it possible to reduce the risks of clogging of the catalyst bed(s) and therefore prevent the unit from stopping due to clogging.

According to a very preferred embodiment of the invention, said hydrotreating reaction section comprises, preferably consists of:

• (b1) two fixed bed reactors operating in oscillating or switching mode, preferably in PRS mode, each of the two reactors preferably having a catalytic bed advantageously comprising a hydrotreating catalyst preferably selected from among known hydrodemetallation catalysts, silicon capture catalysts and combinations thereof, and

• (b2) at least one fixed bed reactor, preferably one reactor, located downstream of the two reactors (b1), and advantageously operating in series with the two reactors (b1), said fixed bed reactor (b2) having between 1 and 5 catalytic beds arranged in series and each comprising between one and ten hydrotreating catalysts, of which at least one of said hydrotreating catalysts advantageously comprises a support and at least one metallic element preferably comprising at least one element of group VIII, preferably selected from nickel and cobalt, and/or at least one element of group VIB, preferably selected from molybdenum and tungsten.

Optionally, step b) may implement a heating section located upstream of the hydrotreatment reaction section and in which the hydrogenated effluent from step a) is heated until reaching a temperature suitable for hydrotreatment, i.e. a temperature between 250 and 430 °C. Said optional heating section may thus comprise one or more exchangers, preferably allowing heat exchange between the hydrogenated effluent and the hydrotreatment effluent, and/or a preheating furnace.

Advantageously, hydrotreatment step b) allows for the complete hydrogenation of the olefins present in the initial feedstock and any olefins obtained following selective hydrogenation step a), but also for the conversion, at least in part, of other impurities present in the feedstock, such as aromatic compounds, metal compounds, sulfur compounds, nitrogen compounds, halogenated compounds (particularly chlorinated compounds), and oxygenated compounds. Step b) can also make it possible to further reduce the content of contaminants, such as metals, particularly silicon.

Stage c) of hydrocracking (first stage of hydrocracking)

According to the invention, the treatment process comprises a first step c) of hydrocracking, advantageously in a fixed bed, of said hydrotreated effluent resulting from step b), in the presence of hydrogen and at least one hydrocracking catalyst, to obtain a hydrocracked effluent.

Advantageously, step c) implements steam cracking reactions well known to those skilled in the art, and more particularly makes it possible to convert heavy compounds, for example compounds having a boiling point greater than 175 °C, into compounds having a boiling point less than or equal to 175 °C contained in the hydrotreated effluent resulting from step b). Other reactions, such as hydrogenation of olefins, aromatics, hydrodemetallation, hydrodesulfurization, hydrodenitrogenation, etc. can continue.

Advantageously, said step c) is implemented in a hydrocracking reaction section comprising at least one, preferably between one and five, fixed bed reactors having n catalyst beds, n being an integer greater than or equal to one, preferably between one and ten, preferably between two and five, each of said bed(s) comprising at least one, and preferably no more than ten, hydrocracking catalysts. When a reactor comprises several catalyst beds, i.e. at least two, preferably between two and ten, preferably between two and five catalyst beds, said catalyst beds are arranged in series in said reactor.

Hydrotreating step b) and steam cracking step c) can advantageously be carried out in the same reactor or in different reactors. If they are carried out in the same reactor, the reactor comprises several catalyst beds, the first catalyst beds comprising the hydrotreating catalyst(s) and the subsequent catalyst beds comprising the steam cracking catalyst(s).

Said hydrocracking reaction section is fed at least by said hydrotreated effluent resulting from step b) and a gaseous flow comprising hydrogen, advantageously at the level of the first catalytic bed of the first reactor in operation.

Advantageously, said hydrocracking reaction section is implemented at a pressure equivalent to that used in the reaction section of the selective hydrogenation stage a) or of the hydrotreatment stage b).

Thus, said steam cracking reaction section is advantageously carried out at a hydrotreating temperature between 250 and 480 °C, preferably between 320 and 450 °C, at a hydrogen partial pressure between 1.5 and 25.0 MPa abs., preferably between 2 and 20 MPa abs., and at an hourly volumetric rate (VVH) between 0.1 and 10.0 h-1, preferably between 0.1 and 5.0 h-1, preferably between 0.2 and 4 h-1. According to the invention, the "steam cracking temperature" corresponds to an average temperature in the steam cracking reaction section of step c) and of step f) respectively. In particular, it corresponds to the Weight Average Bed Temperature (WABT) according to the established English expression, well known to those skilled in the art. Steam cracking temperature is advantageously determined based on the catalytic systems, equipment, and their configuration. For example, the hydrocracking temperature (or WABT) is calculated as follows:

WABT = (Tinput 2x Toutput)/3

with Tin: the temperature of the hydrogenated effluent at the inlet of the hydrocracking reaction section, Tout: the temperature of the effluent at the outlet of the hydrocracking reaction section.

The hourly volumetric rate (VVH) is defined here as the ratio of the hourly volumetric flow rate of the hydrogenated effluent resulting from step a) per volume of catalyst or catalysts. The hydrogen coverage in c) is advantageously between 80 and 2000 Nm3 of hydrogen per m3 of fresh feedstock feeding step a), and preferably between 200 and 1800 Nm3 of hydrogen per m3 of fresh feedstock feeding step a). The hydrogen coverage is defined here as the ratio of the volumetric flow rate of hydrogen taken under standard temperature and pressure conditions to the volumetric flow rate of fresh feedstock feeding step a), i.e. feedstock comprising a plastics pyrolysis oil, or by the possibly pretreated feedstock feeding step a) (in normal m3, noted Nm3, of H<2> per m3 of fresh feedstock). The hydrogen may consist of make-up and/or recycled hydrogen, resulting in particular from the separation step d).

Preferably, an additional gaseous flow comprising hydrogen is advantageously introduced into the inlet of each reactor, particularly one operating in series, and/or into the inlet of each catalyst bed from the second catalyst bed of the hydrocracking reaction section. These additional gaseous flows are also called quench flows. They make it possible to control the temperature in the hydrocracking reactor, where the reactions carried out are generally highly exothermic.

In an embodiment that allows to maximize the production of a naphtha cut comprising compounds having a boiling point less than or equal to 175 °C, the operating conditions used in step c) of hydrocracking generally allow to reach conversions per pass, in products that have at least 80% by volume of products having boiling points less than 175 °C, preferably less than 160 °C and preferably less than 150 °C, greater than 15% by weight and even more preferably between 20 and 95% by weight.

Hydrocracking stage c) does not therefore allow all compounds with a boiling point above 175 °C to be transformed into compounds with a boiling point of 175 °C or less. After fractionation stage e), a more or less significant proportion of compounds with a boiling point above 175 °C remains, which is sent to the second hydrocracking stage f).

According to the invention, hydrocracking step c) operates in the presence of at least one steam cracking catalyst.

The hydrocracking catalyst(s) used in steam cracking step c') are conventional hydrocracking catalysts known to those skilled in the art, of the bifunctional type combining an acid function with a hydro-dehydrogenating function and optionally at least one ligand matrix. The acid function is provided by large surface area supports (generally 150 to 800 m2/g) having a surface acidity, such as halogenated aluminas (chlorinated or fluorinated in particular), combinations of boron and aluminium oxides, amorphous silica-aluminas and zeolites. The hydro-dehydrogenating function is provided by at least one metal from group VIB of the periodic table and/or at least one metal from group VIII.

Preferably, the hydrocracking catalyst(s) used in step c') comprise a hydrodehydrogenating function comprising at least one metal from group VIII chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum, and preferably from cobalt and nickel. Preferably, said catalyst(s) also comprise at least one metal from group VIB chosen from chromium, molybdenum and tungsten, alone or in a mixture, and preferably from molybdenum and tungsten. Hydrodehydrogenating functions of the NiMo, NiMoW, and NiW type are preferred.

Preferably, the content of group VIII metal in the hydrocracking catalyst(s) is advantageously between 0.5 and 15% by weight and preferably between 1 and 10% by weight, the percentages being expressed as a percentage by weight of oxides relative to the total weight of the catalyst.

Preferably, the content of metal of the VIB group in the hydrocracking catalyst(s) is advantageously between 5 and 35% by weight and preferably between 10 and 30% by weight, the percentages being expressed as a percentage by weight of oxides with respect to the total weight of the catalyst.

The steam cracking catalyst(s) used in step c) may also optionally comprise at least one promoting element deposited on the catalyst and chosen from the group consisting of phosphorus, boron and silicon, optionally at least one element of group VIIA (preferably chlorine, fluorine), optionally at least one element of group VIIB (preferably manganese), and optionally at least one element of group VB (preferably niobium).

Preferably, the hydrocracking catalyst(s) used in step c) comprise at least one amorphous or slightly crystallized porous mineral matrix of the oxide type chosen from aluminas, silicas, silica-aluminas, aluminates, alumina-boron oxide, magnesia, silica-magnesia, zirconia, titanium oxide, clay, alone or in mixtures, and preferably aluminas or silica-aluminas, alone or in mixtures.

Preferably, the silica-alumina contains more than 50% by weight of alumina, preferably more than 60% by weight of alumina.

Preferably, the steam cracking catalyst(s) used in step c) optionally also comprise a zeolite chosen from Y zeolites, preferably USY zeolites, alone or in combination, with other zeolites from among zeolites beta, ZSM-12, IZM-2, ZSM-22, ZSM-23, SAPO-11, ZSM-48, ZBM-30, alone or in a mixture. Preferably, the zeolite is USY zeolite alone.

In the case where said catalyst comprises a zeolite, the zeolite content in the steam cracking catalyst(s) is advantageously between 0.1 and 80% by weight, preferably between 3 and 70% by weight, the percentages being expressed as a percentage of zeolite with respect to the total weight of the catalyst.

A preferred catalyst comprises, and preferably consists of, at least one metal of group VIB and optionally at least one non-noble metal of group VIII, at least one promoting element, and preferably phosphorus, at least one zeolite Y, and at least one alumina ligand.

An even more preferred catalyst comprises, and preferably consists of, nickel, molybdenum, phosphorus, USY zeolite, and eventually also a beta zeolite, and alumina.

Another preferred catalyst comprises, and preferably consists of, nickel, tungsten, alumina and silica-alumina.

Another preferred catalyst comprises, and preferably consists of, nickel, tungsten, USY zeolite, alumina and silica-alumina.

Such hydrocracking catalyst is, for example, in the form of extrudates.

According to another aspect of the invention, the hydrocracking catalyst described above further comprises one or more organic compounds containing oxygen and/or nitrogen and/or sulfur. Such a catalyst is frequently referred to by the expression "additive catalyst." Generally, the organic compound is chosen from a compound comprising one or more chemical functions chosen from a carboxylic, alcohol, thiol, thioether, sulfone, sulfoxide, ether, aldehyde, ketone, ester, carbonate, amine, nitrile, imide, oxime, urea, and amide function, or even compounds including a furan ring or even sugars.

The preparation of the catalysts of steps a), b) or c) is known and generally comprises a step of impregnating the support with metals of group VIII and group VIB, where present, and optionally phosphorus and/or boron, followed by drying and then, if necessary, calcination. In the case of the catalyst with additives, the preparation is generally carried out by simple drying without calcination after the introduction of the organic compound. Calcination is understood here to mean a heat treatment under a gas containing air or oxygen at a temperature greater than or equal to 200°C. Before being used in a step of the process, the catalysts are generally subjected to sulfidation in order to form the active species. The catalyst of step a) may also be a catalyst used in its reduced form, thus involving a reduction step in its preparation.

Optionally, c) may implement a heating section located upstream of the hydrocracking reaction section and in which the hydrotreated effluent from step b) is heated until reaching a temperature suitable for hydrocracking, i.e. a temperature between 250 and 480 °C. Said optional heating section may thus comprise one or more exchangers, preferably allowing heat exchange between the hydrotreated effluent and the hydrocracked effluent, and/or a preheating furnace.

Stage d) of separation

According to the invention, the treatment process comprises a separation step d), advantageously implemented in at least one washing/separation section, fed at least by the hydrocracked effluent from step c) and an aqueous solution, to obtain at least one of a gaseous effluent, an aqueous effluent, and a hydrocarbon effluent.

The gaseous effluent obtained at the end of d) advantageously comprises hydrogen, preferably at least 90% by volume, preferably at least 95% by volume, of hydrogen. Advantageously, said gaseous effluent can be recycled at least in part in steps a) of selective hydrogenation and/or b) of hydrotreatment and/or c) and f) of hydrocracking, the recycling system being able to comprise a purification section.

The aqueous effluent obtained at the end of step d) advantageously comprises ammonium salts and/or hydrochloric acid.

The hydrocarbon effluent resulting from step d) comprises hydrocarbon compounds and advantageously corresponds to the plastics pyrolysis oil of the feedstock, or to the plastics pyrolysis oil and the feedstock fraction of conventional petroleum or biomass co-treated with pyrolysis oil, in which at least part of the heavy compounds have been converted into lighter compounds in order to maximize the naphtha cut. The hydrocarbon effluent is also freed at least in part from its impurities, in particular from its olefinic (di- and monoolefins), metallic and halogenated impurities.

This separation step d) makes it possible in particular to eliminate the ammonium chloride salts, which are formed by reaction between the chloride ions, released by the hydrogenation of the chlorinated compounds in the form of HCl, particularly during step b) and then dissolution in water, and the ammonium ions, generated by the hydrogenation of the nitrogen compounds in the form of NH<3>, particularly during step b), and/or supplied by injection of an amine and then dissolution in water, and thus to limit the risks of clogging, particularly in the transfer lines and/or in the sections of the process of the invention and/or the transfer lines towards the steam cracking device, due to the precipitation of ammonium chloride salts. It also makes it possible to eliminate the hydrochloric acid formed by the reaction of hydrogen ions and chloride ions.

Depending on the content of chlorinated compounds in the initial feed to be treated, a flow containing an amine such as for example monoethanolamine, diethanolamine and/or monodiethanolamine can be injected upstream of the selective hydrogenation stage a), between the selective hydrogenation stage a) and the hydrotreatment stage b) and/or between the hydrocracking stage c) and the separation stage d), preferably upstream of the selective hydrogenation stage a), in order to ensure a sufficient quantity of ammonium ions to combine with the chloride ions formed during the hydrotreatment stage, thus making it possible to limit the formation of hydrochloric acid and thus limit corrosion downstream of the separation section.

Advantageously, separation step d) comprises an injection of an aqueous solution, preferably an injection of water, into the hydrocracked effluent resulting from step c), upstream of the washing/separation section, so as to at least partially dissolve ammonium chloride salts and/or hydrochloric acid, and thus improve the removal of chlorinated impurities and reduce the risks of blockages due to the accumulation of ammonium chloride salts.

The separation step d) is advantageously carried out at a temperature between 50 and 370 °C, preferably between 100 and 340 °C, preferably between 200 and 300 °C. Advantageously, the separation step d) is carried out at a pressure close to that implemented in steps a) and/or b) and/or c), preferably between 1.0 and 10.0 MPa, so as to facilitate hydrogen recycling.

The washing/separation section of step d) can be carried out at least in part in common or different washing and separation equipment, this equipment being well known (separator flasks that can operate at different pressures and temperatures, pumps, heat exchangers, washing columns, etc.).

In a possible embodiment of the invention, taken additionally or in isolation from other embodiments of the invention described, separation step d) comprises injecting an aqueous solution into the hydrocracked effluent resulting from step c), followed by the washing/separation section advantageously comprising a separation phase making it possible to obtain at least one aqueous effluent laden with ammonium salts, a washed liquid hydrocarbon effluent and a partially washed gaseous effluent. The aqueous effluent laden with ammonium salts and the washed liquid hydrocarbon effluent may then be separated in a decanting flask so as to obtain said hydrocarbon effluent and said aqueous effluent. Said partially washed gaseous effluent may be introduced in parallel into a washing column in which it circulates countercurrent to an aqueous flow, preferably of the same nature as the aqueous solution injected into the hydrocracked effluent, which makes it possible to eliminate at least in part, preferably in its entirety, the hydrochloric acid contained in the partially washed gaseous effluent and thus obtain said gaseous effluent, preferably comprising essentially hydrogen, and an acidic aqueous flow. Said aqueous effluent resulting from the decanting flask may optionally be mixed with said acidic aqueous flow and used, optionally in a mixture with said acidic aqueous flow, in a water recycling circuit for feeding the separation step d) with said aqueous solution upstream of the washing/separation section and/or in said aqueous flow in the washing column. Said water recycling circuit may comprise an addition of water and/or a basic solution and/or a purge making it possible to eliminate the dissolved salts.

In another possible embodiment of the invention, taken separately or in combination with other embodiments of the invention described, the separation step d) may advantageously comprise a "high pressure" washing/separation section operating at a pressure close to the pressure of the selective hydrogenation step a) and/or of the hydrotreatment step b) and/or of the hydrocracking step c), in order to facilitate the recycling of hydrogen. This possible "high pressure" section of step d) may be complemented by a "low pressure" section, in order to obtain a hydrocarbon liquid fraction devoid of a part of the dissolved gases at high pressure and intended to be treated directly in a steam cracking process or optionally sent to the fractionation step e).

The gas fraction(s) resulting from the separation step d) may be subjected to further purification and separation with a view to recovering at least one hydrogen-rich gas which may be recycled upstream of steps a) and/or b) and/or c) and/or light hydrocarbons, in particular ethane, propane and butane, which may advantageously be sent separately or as a mixture to one or more furnaces of the steam-cracking step h) so as to increase the overall olefin yield.

The hydrocarbon effluent resulting from separation stage d) is sent, in part or in whole, preferably in whole, to fractionation stage e).

Stage e) of fractionation

The process according to the invention comprises a step of fractionating all or part, preferably all, of the hydrocarbon effluent resulting from step d), to obtain at least one gaseous flow and at least two liquid hydrocarbon flows, said two hydrocarbon flows being at least one naphtha cut comprising compounds having a boiling point less than or equal to 175 °C, in particular between 80 and 175 °C, and a hydrocarbon cut comprising compounds having a boiling point greater than 175 °C,

e) allows in particular to eliminate gases dissolved in the hydrocarbon liquid effluent, such as ammonia, hydrogen sulfide and light hydrocarbons having 1 to 4 carbon atoms.

The fractionation e) is advantageously carried out at a pressure of less than or equal to 1.0 MPa abs., preferably between 0.1 and 1.0 MPa abs.

According to one embodiment, step e) can be implemented in a section advantageously comprising at least one separation column equipped with a reflux circuit comprising a reflux flask. Said separation column is fed by the liquid hydrocarbon effluent resulting from step d) and by a flow of water vapor. The liquid hydrocarbon effluent resulting from d) can optionally be heated before entering the separation column. Thus, the lighter compounds are entrained to the top of the column and into the reflux circuit comprising a reflux flask in which a gas/liquid separation takes place. The gaseous phase, including the light hydrocarbons, is withdrawn from the reflux flask in a gaseous flow. The naphtha cut comprising compounds having a boiling point less than or equal to 175 °C is advantageously withdrawn from the reflux flask. The hydrocarbon cut comprising compounds having a boiling point greater than 175 °C is advantageously extracted from the bottom of the separation column.

According to other embodiments, the fractionation step e) may implement a separation column followed by a distillation column or only a distillation column.

The naphtha cut, which contains compounds with a boiling point of 175 °C or less, can be sent, in whole or in part, to a steam cracking unit, at the end of which the olefins can be (re)formed to participate in the formation of polymers. It can also be sent to a fuel pool, for example a naphtha pool, or even sent, in part, to step h) of recycling.

The hydrocarbon cut comprising compounds having a boiling point greater than 175 °C is sent at least partially to the second hydrocracking stage f).

According to a preferred embodiment, the naphtha cut comprising compounds having a boiling point of less than or equal to 175 °C, in whole or in part, is sent to a steam cracking unit, while the cut comprising compounds having a boiling point greater than 175 °C is sent to the hydrocracking step f).

In another particular embodiment, the fractionation step e) may make it possible to obtain, in addition to a gaseous flow, a naphtha cut comprising compounds having a boiling point of less than or equal to 175 ° C, preferably between 80 and 175 ° C, and a kerosene cut comprising compounds having a boiling point greater than 175 ° C and less than or equal to 280 ° C, optionally a diesel cut comprising compounds having a boiling point greater than 280 ° C and less than 385 ° C and a hydrocarbon cut comprising compounds having a boiling point greater than or equal to 385 ° C, called heavy hydrocarbon cut. The naphtha cut may be sent, totally or partially, to a steam cracking unit and/or to the naphtha pool resulting from conventional oil loads, it may also be sent to the recycling step h); The kerosene cut and/or diesel cut may also be sent, in whole or in part, to a steam cracking unit, or respectively to a kerosene or diesel pool resulting from conventional oil loadings, or recycled in the process in the same manner as the naphtha cut; the heavy cut is sent, at least in part, to the second hydrocracking stage f).

In another particular embodiment, the naphtha cut comprising compounds having a boiling point less than or equal to 175 °C resulting from step e) is fractionated into a heavy naphtha cut comprising compounds having a boiling point between 80 and 175 °C and a light naphtha cut comprising compounds having a boiling point less than 80 °C, at least part of said heavy naphtha cut being able to be sent to an aromatic complex comprising at least one naphtha reforming step in order to produce aromatic compounds. According to this embodiment, at least part of the light naphtha cut is sent to the steam cracking step i) described below.

The gas fraction(s) resulting from the fractionation step e) may be subjected to further purification and separation with a view to recovering at least light hydrocarbons, in particular ethane, propane and butane, which may advantageously be sent separately or as a mixture to one or more furnaces of the steam cracking step i) so as to increase the overall olefin yield.

Stage f) of hydrocracking (second stage of hydrocracking)

According to the invention, the treatment process comprises a second step f) of hydrocracking, advantageously in a fixed bed, of at least part of said hydrocarbon cut comprising compounds having a boiling point greater than 175 °C resulting from step e), in the presence of hydrogen and at least one hydrocracking catalyst, to obtain a second hydrocracked effluent.

Advantageously, step f) implements hydrocracking reactions well known to those skilled in the art, and more particularly makes it possible to convert at least a portion of the cut comprising compounds having a boiling point greater than 175 °C into compounds having a boiling point lower than or equal to 175 °C. Other reactions, such as hydrogenation of olefins, aromatics, hydrodemetallation, hydrodesulfurization, hydrodenitrogenation, etc. can continue.

Advantageously, said step f) is implemented in a hydrocracking reaction section comprising at least one, preferably between one and five, fixed bed reactors having n catalyst beds, n being an integer greater than or equal to one, preferably between one and ten, preferably between two and five, each of said bed(s) comprising at least one, and preferably no more than ten, hydrocracking catalysts. When a reactor comprises several catalyst beds, i.e. at least two, preferably between two and ten, preferably between two and five catalyst beds, said catalyst beds are arranged in series in said reactor.

Said hydrocracking reaction section is fed by at least part of the cut comprising compounds having a boiling point greater than 175 °C and a gaseous flow comprising hydrogen, advantageously at the level of the first catalytic bed of the first reactor in operation.

Advantageously, said second hydrocracking reaction section is implemented at a pressure equivalent to that used in the reaction section of the selective hydrogenation stage a) or of the hydrotreatment stage b) or of the first hydrocracking stage c).

Thus, said steam cracking reaction section is advantageously carried out at a hydrotreating temperature between 250 and 480 °C, preferably between 320 and 450 °C, at a hydrogen partial pressure between 1.5 and 25.0 MPa abs., preferably between 3 and 20 MPa abs., and at an hourly volumetric rate (HVR) between 0.1 and 10.0 h-1, preferably between 0.1 and 5.0 h-1, preferably between 0.2 and 4 h-1. The hourly volumetric rate (HVR) is defined here as the ratio of the hourly volumetric flow rate of the hydrogenated effluent resulting from step a) to the volume of catalyst or catalysts. The hydrogen coverage in step f) is advantageously between 80 and 2000 Nm3 of hydrogen per m3 of fresh feedstock feeding step a), and preferably between 200 and 1800 Nm3 of hydrogen per m3 of fresh feedstock feeding step a). The hydrogen coverage is defined here as the ratio of the volumetric flow rate of hydrogen taken under standard temperature and pressure conditions to the volumetric flow rate of fresh feedstock feeding step a), i.e. feedstock comprising a plastics pyrolysis oil, or of any pre-treated feedstock feeding step a) (in standard m3, denoted Nm3, of H<2> per m3 of fresh feedstock). The hydrogen may consist of make-up and/or recycled hydrogen, resulting in particular from the separation step d).

Preferably, an additional gaseous flow comprising hydrogen is advantageously introduced into the inlet of each reactor, particularly one operating in series, and/or into the inlet of each catalyst bed from the second catalyst bed of the hydrocracking reaction section. These additional gaseous flows are also called quench flows. They make it possible to control the temperature in the hydrocracking reactor, where the reactions carried out are generally highly exothermic.

These operating conditions used in step f) of the process according to the invention generally make it possible to achieve conversions per pass in products comprising at least 80% by volume of compounds having boiling points less than or equal to 175°C, preferably less than 160°C, and preferably less than 150°C, greater than 15% by weight and even more preferably between 20 and 80% by weight. However, the conversion per pass in step f) is kept moderate in order to maximize the selectivity towards compounds from the naphtha cut (having a boiling point less than or equal to 175°C, in particular between 80 and less than or equal to 175°C). The conversion per pass is limited by the use of a high recycle rate in the loop of the second steam cracking stage. This rate is defined as the ratio between the feed flow rate of stage f) and the load flow rate of stage a), preferably this ratio is between 0.2 and 4, preferably between 0.5 and 2.5.

According to the invention, the hydrocracking step f) operates in the presence of at least one hydrocracking catalyst. Preferably, the hydrocracking catalyst of the second step is selected from among the conventional hydrocracking catalysts known to those skilled in the art, such as those described above in the hydrocracking step c). The hydrocracking catalyst used in said step f) may be identical or different from that used in step c), and preferably different.

Alternatively, the hydrocracking catalyst used in step f) comprises a hydro-dehydrogenating function comprising at least one noble metal of group VIII selected from palladium and platinum, alone or in a mixture. The noble metal content of group VIII is advantageously between 0.01 and 5% by weight and preferably between 0.05 and 3% by weight, the percentages being expressed as a percentage by weight of oxides relative to the total weight of the catalyst.

Optionally, step f) may implement a heating section located upstream of the hydrocracking reaction section and in which said hydrocarbon cut comprising compounds having a boiling point greater than 175 °C resulting from step e) is heated to reach a temperature suitable for hydrocracking, i.e. a temperature between 250 and 480 °C. Thus, said possible heating section may comprise one or more exchangers and/or a preheating furnace.

Stage g) of recycling of the second hydrocracked effluent

According to the invention, the process comprises a step g) of recycling at least a part, and preferably all, of said second hydrocracked effluent resulting from step f) in the separation step d).

A purge may be installed in the recycling of said second hydrocracked effluent from step f). Depending on the operating conditions of the process, said purge may be between 0 and 10% by weight of said hydrocracked effluent resulting from step f) with respect to the incoming feed, and preferably between 0.5% and 5% by weight.

Stage h) (optional) of recycling the hydrocarbon effluent resulting from stage d) and/or from the naphtha cut having a boiling point less than or equal to 175 °C resulting from stage e)

The process according to the invention may comprise the recycling step h), in which a fraction of the hydrocarbon effluent resulting from the separation step d) or a fraction of the naphtha cut having a boiling point of less than or equal to 175 ° C resulting from the fractionation step e) is recovered to constitute a recycle flow that is sent upstream or directly towards at least one of the reaction steps of the process according to the invention, in particular towards the selective hydrogenation step a) and/or the hydrotreatment step b). Optionally, a fraction of the recycle flow may be sent to the optional pretreatment step a0). Preferably, the process according to the invention comprises the recycling step h).

Preferably, at least a fraction of the hydrocarbon effluent resulting from the separation step d) or from the naphtha cut having a boiling point less than or equal to 175 °C from the fractionation step e) feeds the hydrotreatment step b).

Advantageously, the quantity of the recycle stream is adjusted such that the weight ratio between the recycle stream and the feed comprising a plastics pyrolysis oil, i.e. the feed to be treated which feeds the overall process, is less than or equal to 10, preferably less than or equal to 5, and preferably greater than or equal to 0.001, preferably greater than or equal to 0.01, and preferably greater than or equal to 0.1. Very preferably, the quantity of the recycle stream is adjusted such that the weight ratio between the recycle stream and the feed comprising a plastics pyrolysis oil is between 0.2 and 5.

Advantageously, for the initial phases of the process, a hydrocarbon cut external to the process can be used as a recycle stream. A person skilled in the art will then be able to select said hydrocarbon cut.

Recycling a portion of the product obtained towards or before at least one of the reaction steps of the process according to the invention advantageously allows, on the one hand, to dilute the impurities, and on the other hand to control the temperature in the reaction step(s), in which the reactions involved can be strongly exothermic.

According to a preferred embodiment of the invention, the process for treating a feedstock comprising a plastics pyrolysis oil comprises, preferably consists of, the sequence of steps, and preferably in the given order, a) of selective hydrogenation, b) of hydrotreatment, c) of hydrocracking, d) of separation, e) of fractionation, f) of hydrocracking and g) of recycling the hydrocarbon effluent in step d), to produce an effluent of which at least a part is compatible for treatment in a steam cracking unit.

According to another preferred embodiment of the invention, the process for treating a feedstock comprising a plastics pyrolysis oil comprises, preferably consists of, the sequence of steps, and preferably in the given order, a0) of pretreatment, a) of selective hydrogenation, b) of hydrotreatment, c) of hydrocracking, d) of separation, e) of fractionation, f) of hydrocracking and g) of recycling of the hydrocarbon effluent in step d), to produce an effluent of which at least a part is compatible for treatment in a steam cracking unit.

According to a third preferred embodiment of the invention, the process for treating a feedstock comprising a plastics pyrolysis oil comprises, preferably consists of, the sequence of steps, and preferably in the given order, a) of selective hydrogenation, b) of hydrotreatment, c) of hydrocracking, d) of separation, e) of fractionation, f) of hydrocracking and g) of recycling the hydrocarbon effluent in step d), h) of recycling a portion of the cut comprising compounds having a boiling point lower than or equal to 175 °C in steps a) and/or b), to produce an effluent of which at least a portion is compatible for treatment in a steam cracking unit.

According to a fourth preferred embodiment of the invention, the process for treating a feedstock comprising a plastics pyrolysis oil comprises, preferably consists of, the sequence of steps, and preferably in the given order, a0) of pretreatment, a) of selective hydrogenation, b) of hydrotreatment, c) of hydrocracking, d) of separation, e) of fractionation, f) of hydrocracking and g) of recycling the hydrocarbon effluent in step d), h) of recycling a portion of the cut comprising compounds having a boiling point of less than or equal to 175 ° C in steps a) and/or b), to produce an effluent of which at least a portion is compatible for treatment in a steam cracking unit.

Said hydrocarbon effluent or said hydrocarbon stream(s) thus obtained by treatment according to the process of the invention of a plastics pyrolysis oil have a composition compatible with the specifications of an inlet feed to a steam cracking unit. In particular, the composition of the hydrocarbon effluent or of said hydrocarbon stream(s) is preferably such that:

• the total content of metallic elements is less than or equal to 5.0 ppm by weight, preferably less than or equal to 2.0 ppm by weight, preferably less than or equal to 1.0 ppm by weight, and preferably less than or equal to 0.5 ppm by weight, with

A silicon element (Si) content of less than or equal to 1.0 ppm by weight, preferably less than or equal to 0.6 ppm by weight, and

including an iron element (Fe) content of less than or equal to 100 ppb by weight,

• the sulfur content is less than or equal to 500 ppm by weight, preferably less than or equal to 200 ppm by weight,

• the nitrogen content is less than or equal to 100 ppm by weight, preferably less than or equal to 50 ppm by weight, and preferably less than or equal to 5 ppm by weight

• the asphaltene content is less than or equal to 5.0 ppm by weight,

• the total content of the element chlorine is less than or equal to 10 ppm by weight, preferably less than 1.0 ppm by weight,

• the content of olefinic compounds (mono- and diolefins) is less than or equal to 5.0% by weight, preferably less than or equal to 2.0% by weight, preferably less than or equal to 0.1% by weight.

Contents are given in relative concentrations by weight, percentage (%) by weight, parts per million (ppm) by weight, or parts per billion (ppb) by weight, with respect to the total weight of the flow considered.

The process according to the invention therefore makes it possible to treat plastic pyrolysis oils to obtain an effluent which can be injected, totally or partially, into a steam cracking unit.

Stage i) steam cracking (optional)

The naphtha cut comprising compounds having a boiling point of less than or equal to 175 °C resulting from step e), in whole or in part, may be sent to a steam cracking step i).

Advantageously, the gas fraction(s) resulting from the separation stage d) and/or fractionation stage e) and containing ethane, propane and butane can also be sent in whole or in part to the steam cracking stage i).

Said steam cracking step i) is advantageously carried out in at least one pyrolysis furnace at a temperature between 700 and 900 °C, preferably between 750 and 850 °C, and at a pressure between 0.05 and 0.3 MPa relative. The residence time of the hydrocarbon compounds is generally less than or equal to 1.0 seconds (noted s), preferably between 0.1 and 0.5 s. Advantageously, steam is introduced before the optional steam cracking step i) and after separation (or fractionation). The quantity of water introduced, advantageously in the form of steam, is advantageously between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds at the inlet of step i). Preferably, the optional step i) is carried out in several pyrolysis furnaces in parallel, so as to adapt the operating conditions to the different flows feeding step i), in particular those resulting from step e), and also to manage the decoking times of the tubes. A furnace comprises one or more tubes arranged in parallel. A furnace may also refer to a group of furnaces operating in parallel. For example, one furnace may be dedicated to cracking naphtha cut, which comprises compounds having a boiling point less than or equal to 175°C.

The effluents from the various steam-cracking furnaces are generally recombined before separation to form an effluent. Step i) of steam-cracking is understood to comprise the steam-cracking furnaces but also the sub-stages associated with steam-cracking well known to those skilled in the art. These sub-stages may include, in particular, heat exchangers, catalytic columns and reactors, and recycles to the furnaces. A column generally makes it possible to fractionate the effluent in order to recover at least a light fraction comprising hydrogen and compounds having 2 to 5 carbon atoms, a fraction comprising pyrolysis gasoline, and optionally a fraction comprising pyrolysis oil. The columns make it possible to separate the different constituents of the light fractionation fraction in order to recover at least a cut rich in ethylene (cut C2) and a cut rich in propylene (cut C3), and optionally a cut rich in butenes (cut C4). Catalytic reactors allow, in particular, selective hydrogenation of C2, C3, or even C4 cuts and pyrolysis gasoline. Saturates, particularly those containing 2 to 4 carbon atoms, are advantageously recycled to steam cracking furnaces, thereby increasing overall olefin yields.

This steam cracking step i) makes it possible to obtain at least one effluent containing olefins comprising 2, 3 and/or 4 carbon atoms (i.e. C2, C3 and/or C4 olefins), in satisfactory contents, in particular greater than or equal to 30% by weight, in particular greater than or equal to 40% by weight, or even greater than or equal to 50% by weight of the total of olefins comprising 2, 3 and 4 carbon atoms relative to the weight of the steam cracking effluent considered. Said C2, C3 and C4 olefins can then be advantageously used as polyolefin monomers.

According to one or more preferred embodiments of the invention, taken separately or in combination, the process for treating a feedstock comprising a plastics pyrolysis oil comprises, preferably consists of, a sequence of steps described above, and preferably in the order given, i.e.: a) selective hydrogenation, b) hydrotreatment, c) hydrocracking, d) separation, e) fractionation, f) hydrocracking, g) recycling of the second hydrocracked effluent in step d), and step i) steam cracking.

According to a preferred embodiment, the process for treating a feedstock comprising a plastics pyrolysis oil comprises, preferably consists of, the sequence of steps described above, and preferably in the order given, i.e. a0) pretreatment, a) selective hydrogenation, b) hydrotreatment, c) hydrocracking, d) separation, e) fractionation, f) hydrocracking, g) recycling of the second hydrocracked effluent in step d), g) recycling of at least part of the naphtha cut comprising compounds having a boiling point of less than or equal to 175°C in steps a) and/or b), and step i) steamcracking.

The process according to the invention, when it comprises this step i) of steam cracking, thus makes it possible to obtain, from plastic pyrolysis oils, for example plastic waste, olefins that can be used as monomers for the synthesis of new polymers contained in the plastics, with relatively satisfactory yields, without obstructions or corrosion of the units.

Analysis methods used

The analytical methods and/or standards used to determine the characteristics of the various flows, particularly the load to be treated and the effluents, are known to those skilled in the art. They are listed in particular below:

Table 1

LIST OF FIGURES

The mention of the elements referenced in Figure 1 allows a better understanding of the invention, without limiting it to the particular embodiments illustrated in Figure 1. The different embodiments presented can be used alone or combined with each other, without limitation of combination.

Figure 1 represents the scheme of a particular embodiment of the method of the present invention, comprising:

• a step a) of optional selective hydrogenation of a hydrocarbon feed resulting from the pyrolysis of plastics 1, in the presence of a hydrogen-rich gas 2 and possibly an amine supplied by flow 3, carried out in at least one fixed bed reactor comprising at least one selective hydrogenation catalyst, to obtain an effluent 4;

• a step b) of hydrotreating the effluent 4 resulting from step a) in the presence of hydrogen 5, carried out in at least one fixed bed reactor comprising at least one hydrotreating catalyst, to obtain a hydrotreated effluent 6;

• a first step c) of hydrocracking the effluent 6 resulting from step c) in the presence of hydrogen 7, carried out in at least one fixed bed reactor comprising at least one hydrocracking catalyst, to obtain a hydrocracked effluent 8;

•a step d) of separating the effluent 8, carried out in the presence of an aqueous washing solution 9 and which allows obtaining at least a fraction 10 comprising hydrogen, an aqueous fraction 11 containing dissolved salts, and a liquid hydrocarbon fraction 12;

• a step e) of fractionation of the hydrocarbon liquid fraction 12 which allows obtaining at least a gaseous fraction 13, a naphtha cut 14 comprising compounds having a boiling point less than or equal to 175 °C and a cut 15 comprising compounds having a boiling point greater than 175 °C;

• a second step f) of hydrocracking at least part of the cut 15a comprising compounds having a boiling point greater than 175 °C resulting from step e), in the presence of hydrogen 16, carried out in at least one fixed bed reactor comprising at least one hydrocracking catalyst, to obtain a second hydrocracking effluent 17; the other part of the cut 15 constitutes the purge 15b;

• a recycling stage of the second hydrocracked effluent 17 in stage d) of separation.

Instead of injecting the amine flow 3 at the inlet of the selective hydrogenation stage a), it is possible to inject it at the inlet of the hydrotreatment stage b), at the inlet of the hydrocracking stage c), at the inlet of the separation stage d) or even not to inject it, depending on the characteristics of the feed.

At the end of step e), at least part of the naphtha cut 14 comprising compounds having a boiling point less than or equal to 175 °C is sent to a steam cracking process (not shown).

Optionally, part of the naphtha cut 14 comprising compounds having a boiling point less than or equal to 175 °C resulting from step e) constitutes a recycle stream that feeds step a) of selective hydrogenation (fraction 14a), and step b) of hydrotreatment (fraction 14b).

In Figure 1, only the main stages are represented, with the main flows, in order to allow a better understanding of the invention. Of course, it is understood that all the equipment necessary for operation (flasks, pumps, exchangers, furnaces, columns, etc.) is present, although not represented. It is also understood that hydrogen-rich gas flows (addition or recycle), as described above, can be injected into the inlet of each reactor or catalytic bed or between two reactors or two catalytic beds. Means well known to those skilled in the art can also be implemented to purify and recycle hydrogen.

EXAMPLES

Example 1 (according to the invention)

Charge 1 treated in the process is a plastics pyrolysis oil (i.e. comprising 100% by weight of said plastics pyrolysis oil) having the characteristics indicated in Table 2.

Table 2: characteristics of the face

Charge 1 undergoes selective hydrogenation step a) carried out in a fixed-bed reactor in the presence of hydrogen 2 and a NiMo-on-alumina selective hydrogenation catalyst under the conditions indicated in Table 3.

Table 3: Conditions of the selective hydroenation stage a

At the end of stage a) of selective hydrogenation, all of the diolefins initially present in the feedstock have been converted.

The effluent 4 resulting from the selective hydrogenation stage a) is directly subjected, without separation, to a hydrotreatment stage b) carried out in a fixed bed and in the presence of hydrogen 5, and a NiMo-type hydrotreatment catalyst on alumina under the conditions presented in Table 4.

Table 4: Conditions of hydrotreatment stage b

The effluent 6 from hydrotreatment stage b) is subjected directly, without separation, to a first hydrocracking stage c) carried out in a fixed bed and in the presence of hydrogen 7 and a zeolite hydrocracking catalyst comprising NiMo under the conditions presented in Table 5.

Tabl: n i i n l rim r hi r r

The effluent 8 resulting from hydrocracking step c) is subjected to a separation step d) according to the invention, in which a flow of water is injected into the effluent from hydrocracking step c); the mixture is then sent to separation step d) and treated in an acid gas scrubbing column. A gaseous fraction 10 is obtained at the top of the acid gas scrubbing column, while at the bottom, a two-phase separator flask allows the separation of an aqueous phase and a liquid phase. The gas scrubbing column and the two-phase separator operate at high pressure. The liquid phase is then sent to a low-pressure flask to recover a second gaseous fraction, which is purged, and a liquid effluent. The liquid effluent 12 obtained at the end of the separation step d) is sent to a fractionation step e) comprising an extraction column and a distillation column to obtain a fraction having a boiling point less than or equal to 175 °C (fraction PI-175 °C) and a fraction having a boiling point greater than 175 °C (fraction 175 °C+).

The 175 °C+ fraction resulting from fractionation stage e) is sent to the second hydrocracking stage f) to increase the conversion of compounds having a boiling point above 175 °C. A small part of the 175 °C+ fraction is not sent to the second hydrocracking stage f) in order to avoid the accumulation of polyaromatic compounds that could be coke precursors (purge 15b).

The volumetric flow rate of the 175 °C+ fraction resulting from the fractionation stage e) and sent to the second hydrocracking stage f) is equal to 80% of the volumetric flow rate of the liquid effluent resulting from the hydrotreatment stage b) and which feeds the first hydrocracking stage c).

The second stage f) of hydrocracking is carried out in a fixed bed and in the presence of hydrogen 16 and a zeolite hydrocracking catalyst comprising NiMo under the conditions presented in Table 6.

Table 6: Conditions of the second stage f of hydrocracking

The effluent 17 resulting from the second hydrocracking stage (f) is mixed with effluent 8 from the first hydrocracking stage (c). The two effluents undergo a separation stage (d) and then a fractionation stage (e). These two stages are common to both effluents and are carried out as described above.

Table 7 gives the overall yields of the different fractions obtained at the exit of stages c) and f) of hydrocracking at the end of stages d) of separation and e) of fractionation (which includes an extraction column and a distillation column).

Table 7: Yields of the different product fractions obtained at the exit of stages c) and f) of hydrocracking

The compounds H<2>S and NH<3> are eliminated mainly as salts in the aqueous phase removed in separation step d).

The treatment of the feedstock according to the stages of the invention, and in particular by means of hydrocracking stages c) and f), allows obtaining a very high yield of the naphtha-type PI-175 °C fraction.

The characteristics of the PI-175 °C and 175 °C+ liquid fractions obtained after step d) of separation and a step e) of fractionation are shown in Table<8>:

Table<8>: Characteristics of PI-175 °C, 175 °C+ fractions

The PI-175°C and 175°C+ liquid fractions both have compositions compatible with a steam cracking unit because:

• do not contain olefins (mono- and diolefins);

• have very low chlorine element contents (respectively, a non-detectable content and a content of 25 ppb by weight) and lower than the limit required for a steam cracking charge;

• the metal contents, in particular iron (Fe), are also very low (no metal contents detected for the PI-175 °C fraction and < 1 ppm wt for the 175 °C+ fraction; no Fe metal contents detected for the PI-175 °C fraction and 50 ppb wt for the 175 °C+ fraction) and below the limits required for a steam cracking charge (< 5.0 ppm wt, more preferably < 1 ppm wt for metals; < 100 ppb wt for Fe);

• finally, they contain sulfur (< 2 ppm by weight for the PI-175 fraction and < 2 ppm by weight for the 175 °C+ fraction), and nitrogen (< 0.5 ppm by weight for the PI-175 °C fraction and < 3 ppm by weight for the 175 °C+ fraction) at contents well below the limits required for a steam cracking charge (< 500 ppm by weight, preferably < 200 ppm by weight for S and N).

The obtained PI-175 °C liquid fraction is then sent to a steam cracking stage i) (see Table 9).

Table 9: Steam cracking stage conditions

The effluents from the various steam cracking furnaces undergo a separation stage that allows the saturated compounds to be recycled to the steam cracking furnaces and obtain the yields presented in Table 10 (yield = % of product mass relative to the mass of the PI-175 °C fraction upstream of the steam cracking stage, recorded as % m/m).

Table 10: Steam cracking stage yields

Considering the 93% yield obtained for the 175°C+ liquid fraction during the pyrolysis oil treatment process at the outlet of the hydrocracking stages (see Table 7), it is possible to determine the overall yields of the products resulting from stage i) of steam cracking with respect to the initial feed of plastics pyrolysis oil introduced in stage a):

Table 11: Overall process yields in products from the steam cracking stage of the PI-175 °C fraction

When the PI-175°C fraction is sent to the steam cracking unit, the process according to the invention achieves overall mass yields of ethylene and propylene of 31.9% and 17.4%, respectively, relative to the initial mass amount of plastic pyrolysis oil feedstock.

Furthermore, the specific sequence of stages upstream of the steam cracking stage limits coke formation and prevents the corrosion problems that would have arisen if chlorine had not been removed.

Example 2 (not according to the invention)

In this example, the load to be treated is identical to that described in Example 1 (see Table 2).

It is subjected to the steps a) of selective hydrogenation, b) of hydrotreatment and d) of separation, carried out under the same conditions as those described in Example 1. In this example not in accordance with the invention, the effluent resulting from the hydrotreatment step is not subjected to the steps c) and f) of hydrocracking. The liquid effluent obtained at the end of the separation step d) constitutes the PI+ fraction.

The yields of the different products and of the different fractions obtained at the exit of stage b) of the hydrotreatment are indicated in Table 12 (the yields being corresponding to the ratios of the mass quantities of the different products obtained with respect to the mass of the load upstream of stage a), expressed as a percentage and denoted as % m/m).

Table 12: Yields of the different product fractions obtained at the exit of stage b) of hydrotreatment

The characteristics of the PI+ fraction (corresponding to the liquid effluent) obtained after separation step d) are given in Table 13:

Table 13: characteristics of the PI+ fraction

The PI+ fraction obtained by the sequence of steps a), b), and d) consists of approximately 35% naphtha-type compounds with a boiling point less than or equal to 175 °C. This low yield of naphtha-type compounds with a boiling point less than or equal to 175 °C is due to the absence of hydrocracking steps in this non-compliant example.

The liquid effluent of the PI+ fraction is sent directly to a steam cracking stage i) according to the conditions mentioned in Table 14.

Table 14: Steam cracking stage conditions

The steam cracking furnace effluent undergoes a separation stage that allows the saturated compounds to be recycled back to the steam cracking furnace and obtains the yields presented in Table 15 (yield = % of product mass relative to the mass of the PI+ fraction upstream of the steam cracking stage, recorded as % m/m).

Table 15: Steam cracking stage yields of the PI+ fraction

Considering the 99.5% yield obtained for the PI+ fraction during the pyrolysis oil treatment process at the outlet of hydrotreatment stage b) (see Table 12), it is possible to determine the overall yields of the products resulting from steam cracking stage i) with respect to the initial plastics pyrolysis oil feed introduced in stage a):

Table 16: Overall process yields in products from the steam cracking stage of the PI+ fraction

When the liquid PI+ fraction is subjected to a steam cracking step, the process according to the invention achieves overall mass yields of ethylene and propylene of 34.6% and 18.9%, respectively, relative to the initial mass amount of plastic pyrolysis oil feedstock.

Claims (13)

1. Process for treating a load comprising a plastics pyrolysis oil comprising chlorinated compounds, comprising: a) a selective hydrogenation stage implemented in a reaction section fed at least by said charge and a gaseous flow comprising hydrogen, in the presence of at least one selective hydrogenation catalyst, at a temperature between 100 and 280 °C, a partial pressure of hydrogen between 1.0 and 10.0 MPa abs. and an hourly volumetric rate between 0.3 and 10.0 h-1, to obtain a hydrogenated effluent; b) a hydrotreatment step implemented in a hydrotreatment reaction section, implementing at least one fixed bed reactor having n catalytic beds, n being an integer greater than or equal to 1, each comprising at least one hydrotreatment catalyst, said hydrotreatment reaction section being fed by at least said hydrogenated effluent resulting from step a) and a gaseous flow comprising hydrogen, said hydrotreatment reaction section being carried out at a temperature between 250 and 430 °C, a hydrogen partial pressure between 1.0 and 10.0 MPa abs. and an hourly volumetric rate between 0.1 and 10.0 h-1, to obtain a hydrotreatment effluent; c) a first hydrocracking stage implemented in a hydrocracking reaction section, implementing at least one fixed bed reactor having n catalyst beds, n being an integer greater than or equal to 1, each comprising at least one hydrocracking catalyst, said hydrocracking reaction section being fed by at least said hydrotreated effluent resulting from step b) and a gaseous flow comprising hydrogen, said hydrocracking reaction section being carried out at a temperature between 250 and 480 ° C, a hydrogen partial pressure between 1.5 and 25.0 MPa abs. and an hourly volumetric rate between 0.1 and 10.0 h-1, to obtain a first hydrotreated effluent; d) a separation stage, fed by the hydrocracked effluent resulting from c) and an aqueous solution, said stage being carried out at a temperature between 50 and 370 °C, to obtain at least a gaseous effluent, an aqueous effluent and a hydrocarbon effluent; e) a step of fractionating all or part of the hydrocarbon effluent resulting from step d), to obtain at least one gaseous flow and at least two liquid hydrocarbon flows, said two hydrocarbon flows being at least one naphtha cut comprising compounds having a boiling point less than or equal to 175 °C, and a hydrocarbon cut comprising compounds having a boiling point greater than 175 °C, f) a second hydrocracking stage implemented in a hydrocracking reaction section, implementing at least one fixed bed reactor having n catalytic beds, n being an integer greater than or equal to 1, each comprising at least one hydrocracking catalyst, said hydrocracking reaction section being fed by at least part of said hydrocarbon cut comprising compounds having a boiling point greater than 175 °C resulting from step e) and a gaseous flow comprising hydrogen, said section being carried out hydrocracking reaction at a temperature between 250 and 480 °C, a partial pressure of hydrogen between 1.5 and 25.0 MPa abs. and an hourly volumetric rate between 0.1 and 10.0 h-1, to obtain a second hydrocracked effluent; g) a step of recycling at least a portion of said second hydrocracked effluent resulting from step f) into separation step d). 2. Method according to the preceding claim, further comprising a recycling step h) in which a fraction of the hydrocarbon effluent resulting from the separation step d) or a fraction of the naphtha cut having a boiling point lower than or equal to 175 °C from the fractionation step e) is sent to the selective hydrogenation step a) and/or to the hydrotreatment step b). 3. Method according to the preceding claims, wherein the quantity of recycled flow from step h) is adjusted so that the weight ratio between the recycled flow and the load comprising a plastics pyrolysis oil is less than or equal to 10. 4. Method according to one of the preceding claims, comprising a step a0) of pretreatment of the load comprising a plastics pyrolysis oil, said pretreatment step being carried out upstream of the selective hydrogenation step a) and comprising a filtration step and/or a water washing step and/or an adsorption step. 5. Method according to one of the preceding claims, wherein the reaction section of step a) or b) uses at least two reactors operating in interchangeable mode. 6. Method according to one of the preceding claims, wherein before step a) a flow containing an amine is injected. 7. Method according to one of the preceding claims, wherein said selective hydrogenation catalyst comprises a support chosen from alumina, silica, silica-aluminas, magnesia, clays, and mixtures thereof, and a hydro-dehydrogenating function comprising at least one element of group VIII and at least one element of group VIB, or at least one element of group VIII. 8. Method according to one of the preceding claims, wherein a hydrotreatment catalyst comprises a support chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays, and mixtures thereof, and a hydro-dehydrogenating function comprising at least one element of group VIII and/or at least one element of group VIB. 9. Process according to one of the preceding claims, wherein said steam cracking catalyst of step c) or step f) comprises a support chosen from halogenated aluminas, combinations of boron and aluminium oxides, amorphous silica-aluminas and zeolites, and a hydro-dehydrogenating function comprising at least one metal from group VIB chosen from chromium, molybdenum and tungsten, alone or in a mixture, and/or at least one metal from group VIII chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum. 10. Method according to the preceding claim, wherein said zeolite is chosen from the Y zeolites, alone or in combination, with other zeolites among the beta zeolites, Zs M-12, IZM-2, ZSM-22, ZSM-23, SAPO-11, Zs M-48, ZBM-30, alone or in mixture. 11. Method according to one of the preceding claims, wherein the naphtha cut comprising compounds having a boiling point of less than or equal to 175 °C resulting from step e), in whole or in part, is sent to a steam cracking step i) carried out in at least one pyrolysis furnace at a temperature of between 700 and 900 °C and at a pressure of between 0.05 and 0.3 MPa relative. 12. Method according to one of the preceding claims, wherein the naphtha cut comprising compounds having a boiling point of less than or equal to 175 °C resulting from step e) is fractionated into a heavy naphtha cut comprising compounds having a boiling point between 80 and 175 °C and a light naphtha cut comprising compounds having a boiling point of less than 80 °C, at least part of said heavy cut being sent to an aromatic complex comprising at least one naphtha reforming step. 13. Method according to claim 12, wherein at least part of the light naphtha cut is sent to the steam cracking stage i).