EP4189038B1 - Process for treating plastic pyrolysis oil including hydrocracking in two steps - Google Patents

Description

TECHNICAL AREA

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

The method 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 method according to the invention thus makes it possible to recover plastic pyrolysis oils, while reducing the formation of coke and thus the risks of clogging and/or premature loss of activity of the catalyst(s) used in the steam cracking unit, and by reducing the risks of corrosion.

PRIOR TECHNIQUE

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

Another way of valorizing plastic pyrolysis oils is to use these plastic pyrolysis oils as a feedstock for a steam cracking unit in order to (re)create olefins, the latter being constituent monomers of certain polymers. However, plastic waste is generally mixtures of several polymers, for example mixtures of polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, polystyrene. In addition, depending on the uses, plastics may contain, in addition to polymers, other compounds, such as plasticizers, pigments, dyes or even residues of polymerization catalysts. Plastic waste may also contain, in a minor way, biomass originating for example from household waste. As a result, the oils resulting from the pyrolysis of plastic waste include many impurities, in particular diolefins, metals, in particular silicon, or halogenated compounds, in particular chlorine-based compounds, heteroelements such as sulfur, oxygen and nitrogen, insolubles, at levels that are often high and incompatible with steam cracking units or units located downstream of steam cracking units, in particular polymerization processes and selective hydrogenation processes. These impurities can generate operability problems and in particular problems of corrosion, coking or catalytic deactivation, or problems of incompatibility in the uses of the target polymers. The presence of diolefins can also lead to problems of instability of the pyrolysis oil characterized by the formation of gums. Gums and insolubles possibly present in the pyrolysis oil can generate clogging problems in the processes.

In addition, during the steam cracking stage, the yields of light olefins sought for petrochemicals, particularly ethylene and propylene, depend heavily 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, the yields of light olefins increase when the paraffin content increases and/or when the BMCI decreases. Conversely, the yields of unsought heavy compounds and/or coke increase when the BMCI increases.

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

1. a) l'hydrogénation sélective de ladite charge en présence d'hydrogène et d'un catalyseur d'hydrogénation sélective pour obtenir un effluent hydrogéné ;
2. b) l'hydrotraitement dudit effluent hydrogéné en présence d'hydrogène et d'un catalyseur d'hydrotraitement, pour obtenir un effluent d'hydrotraitement ;
3. c) une séparation de l'effluent d'hydrotraitement en présence d'un flux aqueux, à une température entre 50 et 370°C, pour obtenir un effluent gazeux, un effluent liquide aqueux et un effluent liquide hydrocarboné ;
4. d) optionnellement une étape de fractionnement de tout ou partie de l'effluent hydrocarboné issu de l'étape c), pour obtenir un flux gazeux et au moins deux flux hydrocarbonés qui peuvent être une coupe naphta et une coupe plus lourde ;
5. e) une étape de recyclage comprenant une phase de récupération d'une fraction de l'effluent hydrocarboné issu de l'étape c) de séparation ou une fraction du et/ou d'au moins un des flux hydrocarboné(s) issu(s) de l'étape d) de fractionnement, vers l'étape a) d'hydrogénation sélective et/ou l'étape b) d'hydrotraitement.

The unpublished patent application FR20/01.758 describes a method of treating a plastic pyrolysis oil, comprising:

1. (a) selective hydrogenation of said feedstock in the presence of hydrogen and a selective hydrogenation catalyst to obtain a hydrogenated effluent;
2. (b) hydrotreating said hydrogenated effluent in the presence of hydrogen and a hydrotreating catalyst, to obtain a hydrotreating effluent;
3. (c) a separation of the hydrotreatment effluent in the presence of an aqueous stream, at a temperature between 50 and 370°C, to obtain a gaseous effluent, an aqueous liquid effluent and a hydrocarbon liquid effluent;
4. d) optionally a step of fractionation of all or part of the hydrocarbon effluent from step c), to obtain a gas stream and at least two hydrocarbon streams which may be a naphtha cut and a heavier cut;
5. e) a recycling step comprising a phase of recovering a fraction of the hydrocarbon effluent from separation step c) or a fraction of the and/or at least one of the hydrocarbon stream(s) from fractionation step d), to selective hydrogenation step a) and/or hydrotreatment step b).

As per request FR20/01.758 , the naphtha cut from the fractionation stage can be sent, in whole or in part, either to a steam cracking unit, or to a naphtha pool from conventional petroleum feedstocks, or be recycled according to stage e).

The heavier cut from the fractionation stage can be sent, in whole or in part, either to a steam cracking unit, or to a diesel or kerosene pool from conventional petroleum feedstocks, or be recycled according to stage e).

Although the heavier cut can be sent to a steam cracker, few refiners favor this option. Indeed, the heavier cut has a high BMCI and contains more naphthenic, naphtheno-aromatic and aromatic compounds than the naphtha cut, leading to a higher C/H ratio. This high ratio is a cause of coking in the steam cracker, thus requiring steam cracking furnaces dedicated to this cut.

In addition, steam cracking of such a heavy cut produces fewer products of interest, notably ethylene and propylene, but more pyrolysis gasoline.

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

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

SUMMARY OF THE INVENTION

1. a) une étape d'hydrogénation sélective mise en oeuvre dans une section réactionnelle alimentée au moins par ladite charge et un flux gazeux comprenant de l'hydrogène, en présence d'au moins un catalyseur d'hydrogénation sélective, à une température entre 100 et 280°C, une pression partielle d'hydrogène entre 1,0 et 10,0 MPa abs. et une vitesse volumique horaire entre 0,3 et 10,0 h^-1, pour obtenir un effluent hydrogéné ;
2. b) une étape d'hydrotraitement mise en oeuvre dans une section réactionnelle d'hydrotraitement, mettant en oeuvre au moins un réacteur à lit fixe ayant n lits catalytiques, n étant un nombre entier supérieur ou égal à 1, comprenant chacun au moins un catalyseur d'hydrotraitement, ladite section réactionnelle d'hydrotraitement étant alimentée au moins par ledit effluent hydrogéné issu de l'étape a) et un flux gazeux comprenant de l'hydrogène, ladite section réactionnelle d'hydrotraitement étant mise en oeuvre à une température entre 250 et 430°C, une pression partielle d'hydrogène entre 1,0 et 10,0 MPa abs. et une vitesse volumique horaire entre 0,1 et 10,0 h^-1, pour obtenir un effluent d'hydrotraitement ;
3. c) une première étape d'hydrocraquage mise en oeuvre dans une section réactionnelle d'hydrocraquage, mettant en oeuvre au moins un réacteur à lit fixe ayant n lits catalytiques, n étant un nombre entier supérieur ou égal à 1, comprenant chacun au moins un catalyseur d'hydrocraquage, ladite section réactionnelle d'hydrocraquage étant alimentée au moins par ledit effluent hydrotraité issu de l'étape b) et un flux gazeux comprenant de l'hydrogène, ladite section réactionnelle d'hydrocraquage étant mise en oeuvre à une température entre 250 et 480°C, une pression partielle d'hydrogène entre 1,5 et 25,0 MPa abs. et une vitesse volumique horaire entre 0,1 et 10,0 h^-1, pour obtenir un premier effluent hydrocraqué ;
4. d) une étape de séparation, alimentée par l'effluent hydrocraqué issu de l'étape c) et une solution aqueuse, ladite étape étant opérée à une température entre 50 et 370°C, pour obtenir au moins un effluent gazeux, un effluent aqueux et un effluent hydrocarboné ;
5. e) une étape de fractionnement de tout ou partie de l'effluent hydrocarboné issu de l'étape d), pour obtenir au moins un flux gazeux et au moins deux flux hydrocarbonés liquides, lesdits deux flux hydrocarbonés liquides étant au moins une coupe naphta comprenant des composés ayant un point d'ébullition inférieur ou égal à 175°C et une coupe hydrocarbonée comprenant des composés ayant un point d'ébullition supérieur à 175°C ;
6. f) une deuxième étape d'hydrocraquage mise en oeuvre dans une section réactionnelle d'hydrocraquage, mettant en oeuvre au moins un réacteur à lit fixe ayant n lits catalytiques, n étant un nombre entier supérieur ou égal à 1, comprenant chacun au moins un catalyseur d'hydrocraquage, ladite section réactionnelle d'hydrocraquage étant alimentée par au moins une partie de ladite coupe hydrocarbonée comprenant des composés ayant un point d'ébullition supérieur à 175°C issue de l'étape e) et un flux gazeux comprenant de l'hydrogène, ladite section réactionnelle d'hydrocraquage étant mise en oeuvre à une température entre 250 et 480°C, une pression partielle d'hydrogène entre 1,5 et 25,0 MPa abs. et une vitesse volumique horaire entre 0,1 et 10,0 h^-1, pour obtenir un deuxième effluent hydrocraqué ;
7. g) une étape de recyclage d'au moins une partie dudit deuxième effluent hydrocraqué issu de l'étape f) dans l'étape d) de séparation.

The invention relates to a method for treating a load comprising a plastic pyrolysis oil comprising chlorinated compounds, comprising:

1. a) a selective hydrogenation step carried out in a reaction section supplied at least with said feedstock and a gas flow comprising hydrogen, in the presence of at least one selective hydrogenation catalyst, at a temperature between 100 and 280°C, a hydrogen partial pressure between 1.0 and 10.0 MPa abs. and an hourly volumetric flow rate between 0.3 and 10.0 h ^-1 , to obtain a hydrogenated effluent;
2. b) a hydrotreatment step carried out in a hydrotreatment reaction section, using 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 supplied at least by said hydrogenated effluent from step a) and a gas stream comprising hydrogen, said hydrotreatment reaction section being carried out at a temperature between 250 and 430°C, a partial pressure of hydrogen between 1.0 and 10.0 MPa abs. and an hourly volumetric flow rate between 0.1 and 10.0 h ^-1 , to obtain a hydrotreatment effluent;
3. c) a first hydrocracking step carried out in a hydrocracking reaction section, using 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 at least by said hydrotreated effluent from step b) and a gas stream 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 flow rate between 0.1 and 10.0 h ^-1 , to obtain a first hydrocracked effluent;
4. d) a separation step, fed with the hydrocracked effluent from step c) and an aqueous solution, said step being carried out at a temperature between 50 and 370°C, to obtain at least one gaseous effluent, one aqueous effluent and one hydrocarbon effluent;
5. e) a step of fractionating all or part of the hydrocarbon effluent from step d), to obtain at least one gas stream and at least two liquid hydrocarbon streams, said two liquid hydrocarbon streams being at least one naphtha cut comprising compounds having a boiling point less than or equal to 175°C and one hydrocarbon cut comprising compounds having a boiling point greater than 175°C;
6. f) a second hydrocracking step carried out in a hydrocracking reaction section, using 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 with at least a portion of said hydrocarbon cut comprising compounds having a boiling point greater than 175°C from step e) and a gas stream 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 flow rate between 0.1 and 10.0 h ^-1 , to obtain a second hydrocracked effluent;
7. g) a step of recycling at least part of said second hydrocracked effluent from step f) in 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 makes it possible to hydrogenate it and thus to be able to recover it, in particular by incorporating it directly into a fuel pool or by making it compatible with treatment in a steam cracking unit in order to to be able to obtain in particular light olefins with increased yields which can be used as monomers in the manufacture of polymers.

Another advantage of the invention is to prevent risks of blockage 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 plastic pyrolysis oil.

The method of the invention thus makes it possible to obtain a hydrocarbon effluent from a plastic pyrolysis oil freed at least in part from the impurities of the starting plastic pyrolysis oil, thus limiting the operability problems, such as the problems of corrosion, coking or catalytic deactivation, which these impurities can cause, in particular in the steam cracking units and/or in the units located downstream of the steam cracking units, in particular the 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 range of applications of the target polymers, the incompatibilities of use being reduced.

The present invention contributes to the recycling of plastics, by proposing a method for treating an oil resulting from the pyrolysis of plastics to purify it, hydrotreat it and hydrocrack it in order to obtain a hydrocarbon effluent with a reduced impurity content and therefore recoverable, either directly in the form of a naphtha cut and/or a diesel cut, or having a composition compatible with a feedstock of 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 improved yields in naphtha cut and, when this cut is sent to steam cracking, in light olefins, while reducing in particular the risks of clogging during stages of treatment of plastic pyrolysis oils, such as those described in the prior art, and the formation of coke in significant quantities and/or the risks of corrosion encountered during subsequent stage(s), for example during the stage of steam cracking of plastic pyrolysis oils.

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

According to a variant, the quantity of the recycle stream of step h) is adjusted so that the weight ratio between the recycle stream and the feed comprising a plastic pyrolysis oil is less than or equal to 10.

According to one variant, the method comprises a step a0) of pretreatment of the load comprising a plastic pyrolysis oil, said pretreatment step being carried out upstream of step a) of selective hydrogenation and comprises a filtration step and/or a step of washing with water and/or an adsorption step.

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

According to one variant, a stream containing an amine is injected upstream of step a).

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

According to one variant, said at least one hydrotreatment catalyst comprises a support chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and their mixtures, and a hydro-dehydrogenating function comprising at least one element from group VIII and/or at least one element from 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 hydro-dehydrogenating function comprising at least one metal from group VIB chosen from chromium, molybdenum and tungsten, alone or as 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 the Y zeolites, alone or in combination, with other zeolites from the beta zeolites, ZSM-12, IZM-2, ZSM-22, ZSM-23, SAPO-11, ZSM-48, ZBM-30, alone or in a mixture.

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

According to one variant, the naphtha cut comprising compounds having a boiling point of less than or equal to 175°C from step e) is split 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 part of the light naphtha cut is sent to stage i) of steam cracking.

The invention also relates to the product capable of being obtained by the treatment method according to the invention.

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

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

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

In the following, particular and/or preferred embodiments of the invention may be described. They may be implemented separately or combined with each other, without limitation of combination when this is technically feasible.

In the following, the groups of chemical elements are given according to the CAS classification ( CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief DR Lide, 81st edition, 2000-2001 ). For example, group VIII according to the CAS classification corresponds to 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 charge

According to the invention, a "plastic 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 collection and sorting channels. It comprises in particular a mixture of hydrocarbon compounds, in particular paraffins, mono- and/or di-olefins, naphthenes and aromatics, these hydrocarbon compounds preferably having a boiling point of less than 700°C and preferably less than 550°C. The plastic pyrolysis oil may comprise, and most often comprises, in addition impurities such as metals, in particular silicon and iron, halogenated compounds, in particular chlorinated compounds. These impurities may be present in plastic pyrolysis oils at high levels, for example up to 350 ppm by weight or 700 ppm by weight or even 1000 ppm by weight of halogen elements provided 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 assimilated to 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 include other impurities such as heteroelements provided in particular by sulfur compounds, oxygenated compounds and/or nitrogen compounds, at contents generally less than 10,000 ppm by weight of heteroelements and preferably less than 4,000 ppm by weight of heteroelements.

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

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

Pre-processing (optional)

Said feedstock comprising a plastic pyrolysis oil may advantageously be pretreated in an optional pretreatment step a0), prior to selective hydrogenation step a), to obtain a pretreated feedstock which feeds 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 plastic pyrolysis oil. Thus, an optional step a0) of pretreatment of the feed comprising a plastic 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) may be implemented by any method known to those skilled in the art for reducing the quantity of contaminants. It may in particular 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 carried out in an adsorption section operated in the presence of at least one adsorbent. Said optional pretreatment step a0) is carried out 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 m ² /g, preferably greater than or equal to 200 m ² /g. The specific surface area of said at least one adsorbent is advantageously less than or equal to 600 m ² /g, in particular less than or equal to 400 m ² /g. The specific surface area of the adsorbent is a surface area measured by the BET method, i.e. the specific surface area determined by nitrogen adsorption in accordance with standard ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical ' The Journal of the American Chemical Society", 6Q, 309 (1938 ).

Advantageously, said adsorbent comprises less than 1% by weight of metallic elements, preferably is free of metallic elements. By metallic elements of the adsorbent, it is meant the elements of groups 6 to 10 of the periodic table of elements (new IUPAC classification).

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

Another mode of operation is to have at least two columns operating in series. When the absorbent of the column placed at the head is worn out, this first column is isolated and the worn absorbent is either regenerated in situ or replaced by fresh absorbent. The column is then put back online in the last position and so on. This operation is called permutable mode, or according to the English term "PRS" for Permutable Reactor System or "lead and lag" according to the dedicated Anglo-Saxon term. The association of at least two adsorption columns makes it possible to overcome the possible and possibly rapid poisoning and/or clogging of the adsorbent under the joint action of metallic contaminants, diolefins, gums from diolefins and insolubles. possibly present in the pyrolysis oil of 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 stopping the unit due to clogging, controlling costs and limiting adsorbent consumption.

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

Said optional pretreatment step a0) thus makes it possible to obtain a pretreated feed which then feeds the selective hydrogenation step a).

Step a) of selective hydrogenation

According to the invention, the method comprises a step a) of selective hydrogenation of the feedstock comprising a plastic pyrolysis oil carried out in the presence of hydrogen, under hydrogen pressure and temperature conditions making it possible to maintain said feedstock in the liquid phase and with an amount of soluble hydrogen just necessary for selective hydrogenation of the diolefins present in the plastic pyrolysis oil. The selective hydrogenation of the diolefins in the liquid phase thus makes it possible to avoid or at least limit the formation of "gums", i.e. the polymerization of the diolefins and therefore the formation of oligomers and polymers, which can block the reaction section of the hydrotreatment step b). Said selective hydrogenation step a) makes it possible to obtain a hydrogenated effluent, i.e. an effluent with a reduced content of olefins, in particular diolefins, preferably free of diolefins.

According to the invention, said selective hydrogenation step a) is carried out in a reaction section supplied at least by said feedstock comprising a plastic pyrolysis oil, or by the pretreated feedstock resulting from the optional pretreatment step a0), and a gas stream comprising hydrogen (H ₂ ). Optionally, the reaction section of said step a) may also be further supplied by at least a fraction of a recycle stream, 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 step a) of selective hydrogenation 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 flow rate (HVV) between 0.3 and 10.0 h ^-1 , preferably between 0.5 and 5.0 h ^-1 . The hourly volumetric flow rate (HVV) is defined here as the ratio between the hourly volumetric flow rate of the feedstock comprising the optionally pretreated plastic pyrolysis oil, by the volume of catalyst(s). The quantity of the gas flow comprising hydrogen (H ₂ ), feeding said reaction section of step a), is advantageously such that the hydrogen coverage is between 1 and 200 Nm ³ of hydrogen per m ³ of feed (Nm ³ /m ³ ), preferably between 1 and 50 Nm ³ of hydrogen per m ³ of feed (Nm ³ /m ³ ), more preferably between 5 and 20 Nm ³ of hydrogen per m ³ of feed (Nm ³ /m ³ ). The hydrogen coverage is defined as the ratio of the volume flow rate of hydrogen taken under normal temperature and pressure conditions relative to the volume flow rate of “fresh” feed, i.e. the feed to be treated, optionally pretreated, without taking into account the possible recycled fraction, at 15°C (in normal m ³ , denoted Nm ³ , of H ₂ per m ³ of feed). The gas stream comprising hydrogen, which feeds the reaction section of step a), may consist of a hydrogen supplement and/or recycled hydrogen originating in particular from separation step 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, which operate in permutable mode, called according to the English term "PRS" for Permutable Reactor System or "lead and lag". The association of at least two reactors in PRS mode makes it possible to isolate a reactor, to unload the spent catalyst, to reload the reactor with fresh catalyst and to put said reactor back into service without stopping the process. The PRS technology is described, in particular, in the patent FR2681871 .

Advantageously, reactor internals, for example of the filter tray type, may be used to prevent clogging of the reactor(s). An example of a filter tray is described in the 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 from group VIII, preferably chosen from nickel and cobalt, and at least one element from group VIB, preferably chosen from molybdenum and tungsten. According to this variant, the total content of oxides of the metal elements from groups VIB and VIII is preferably between 1% and 40% by weight, preferably from 5% to 30% by weight relative to the total weight of the catalyst. The weight ratio expressed as metal oxide between the metal (or metals) from group VIB relative to the metal (or metals) from 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 is preferably constituted by, at least one element from group VIII, preferably nickel. According to this variant, the content of nickel oxides 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 their mixtures. 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 γ (gamma) or η (eta) alumina.

Said selective hydrogenation catalyst is for example in the form of extrudates.

Very preferably, in order to hydrogenate the diolefins as selectively as possible, step a) may use, 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, which is lightly loaded with metals, is preferably placed upstream of the selective hydrogenation catalysts described above.

Optionally, the feedstock which comprises a plastic pyrolysis oil, optionally pretreated, and/or optionally mixed beforehand with at least a fraction of a recycle stream, advantageously from step d) or from the optional step h), can be mixed with the gas stream comprising hydrogen prior to its introduction into the reaction section.

Said feedstock, optionally pretreated, and/or optionally mixed with at least a fraction of the recycle stream, advantageously from step d) or from the optional step h), and/or optionally mixed with the gas stream, 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 from step b), to reach a temperature close to the temperature used in the reaction section which it feeds.

The content of impurities, in particular diolefins, in the hydrogenated effluent obtained at the end of step a) is reduced compared to that of the same impurities, in particular diolefins, included in the feedstock of the process. 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 sent, preferably directly, to step b) of hydrotreatment. When at least a fraction of the recycle stream from the optional 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.

Step b) of hydrotreatment

According to the invention, the treatment method comprises a step b) of hydrotreatment, advantageously in a fixed bed, of said hydrogenated effluent from step a), optionally mixed with at least a fraction of a recycle stream, advantageously 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) uses hydrotreatment reactions well known to those skilled in the art, and more particularly reactions of hydrogenation of olefins, aromatics, hydrodemetallation, hydrodesulfurization, hydrodenitrogenation, etc.

Advantageously, said step b) is carried out in a hydrotreatment reaction section comprising at least one, preferably between one and five, fixed-bed reactor(s) having n catalytic beds, n being an integer greater than or equal to one, preferably between one and ten, preferably between two and five, said bed(s) each comprising at least one, and preferably not more than ten, hydrotreatment catalyst(s). When a reactor comprises several catalytic beds, i.e. at least two, preferably between two and ten, preferably between two and five catalytic beds, said catalytic beds are arranged in series in said reactor.

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

Said hydrotreatment reaction section of step b) may also be fed with at least a fraction of the recycle stream, advantageously 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 hydrotreatment reaction section in a mixture with the hydrogenated effluent from step a) or separately. Said fraction(s) of said recycle stream or the entire recycle stream may be introduced into said hydrotreatment reaction section at one or more catalytic beds of said hydrotreatment reaction section of step b). The introduction of at least a fraction of said recycle flow advantageously makes it possible to dilute the impurities still present in the hydrogenated effluent and to control the temperature, in particular to limit the increase in temperature, in the catalytic bed(s) of the hydrotreatment reaction section which implements highly exothermic reactions.

avec T_entrée : la température de l'effluent hydrogéné en entrée de la section réactionnelle d'hydrotraitement, T_sortie : la température de l'effluent en sortie de section réactionnelle d'hydrotraitement.Advantageously, said hydrotreatment reaction section is carried out at a pressure equivalent to that used in the reaction section of the selective hydrogenation step a), but at a higher temperature than that of the reaction section of the 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 velocity (HVV) between 0.1 and 10.0 h ^-1 , preferably between 0.1 and 5.0 h ^-1 , preferentially between 0.2 and 2.0 h ^-1 , more preferably between 0.2 and 0.8 h ^-1 . According to the invention, the "hydrotreatment temperature" corresponds to an average temperature in the hydrotreatment reaction section of step b). In particular, it corresponds to the Weight Average Bed Temperature (WABT) according to the dedicated Anglo-Saxon term, well known to those skilled in the art. The hydrotreatment temperature is advantageously determined according to the catalytic systems, the equipment, and the configuration thereof, used. For example, the hydrotreatment temperature (or WABT) is calculated as follows: $$\mathrm{WABT}=\left({\mathrm{T}}_{\mathrm{entrance}}+2\times {\mathrm{T}}_{\mathrm{exit}}\right)/3$$

with T _inlet : the temperature of the hydrogenated effluent entering the hydrotreatment reaction section, T _outlet : the temperature of the effluent leaving the hydrotreatment reaction section.

The hourly volumetric velocity (HVV) is defined herein as the ratio between the hourly volumetric flow rate of the hydrogenated effluent from step a) per volume of catalyst(s). The hydrogen coverage in step b) is advantageously between 50 and 1000 Nm ³ of hydrogen per m ³ of fresh feedstock that feeds step a), and preferably between 50 and 500 Nm ³ of hydrogen per m ³ of fresh feedstock that feeds step a), more preferably between 100 and 300 Nm ³ of hydrogen per m ³ of fresh feedstock that feeds step a). The hydrogen coverage is defined here as the ratio of the volume flow rate of hydrogen taken under normal temperature and pressure conditions to the volume flow rate of fresh feedstock feeding step a), i.e. feedstock comprising a plastic pyrolysis oil, or by the optionally pretreated feedstock, feeding step a) (in normal m ³ , denoted Nm ³ , of H ₂ per m ³ of fresh feedstock). The hydrogen may consist of a make-up and/or recycled hydrogen originating in particular from separation step d).

Preferably, an additional gas stream comprising hydrogen is advantageously introduced at the inlet of each reactor, in particular operating in series, and/or at the inlet of each catalytic bed from the second catalytic bed of the hydrotreatment reaction section. These additional gas streams are also called cooling streams. They make it possible to control the temperature in the hydrotreatment reactor in which the reactions carried out are generally very exothermic.

Advantageously, said hydrotreatment catalyst used in said step b) may be chosen from known hydrodemetallization, hydrotreatment, silicon capture catalysts, used in particular for the treatment of petroleum fractions, and combinations thereof. Known hydrodemetallization catalysts are, for example, those described in the patents EP 0113297 , EP 0113284 , US 5221656 , US 5827421 , US 7119045 , US 5622616 And US 5089463 . Known hydrotreatment catalysts are for example those described in the 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 hydro-dehydrogenating function advantageously comprises at least one element from group VIII, preferably chosen from the group consisting of nickel and cobalt, and/or at least one element from group VIB, preferably chosen from the group consisting of molybdenum and tungsten. The total content of oxides of the metallic elements from groups VIB and VIII is preferably between 0.1% and 40% by weight, preferentially from 5% to 35% by weight, relative to the total weight of the catalyst. The weight ratio expressed as metal oxide between the metal (or metals) of group VIB relative to the metal (or metals) of group VIII is preferably between 1.0 and 20, preferably between 2.0 and 10. For example, the hydrotreatment reaction section of step b) of the process comprises a hydrotreatment catalyst comprising between 0.5% and 10% by weight of nickel, preferably between 1% and 8% by weight of nickel, expressed as nickel oxide NiO relative to the total weight of the hydrotreatment 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 hydrotreatment catalyst, on a mineral support.

The support of said hydrotreatment 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 hydrotreatment 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 γ (gamma) or η (eta) alumina.

Said hydrotreatment catalyst is for example in the form of extrudates.

Advantageously, said hydrotreatment catalyst used in step b) of the process has a specific surface area greater than or equal to 250 m ² /g, preferably greater than or equal to 300 m ² /g. The specific surface area of said hydrotreatment catalyst is advantageously less than or equal to 800 m ² /g, preferably less than or equal to 600 m ² /g, in particular less than or equal to 400 m ² /g. The specific surface area of the hydrotreatment 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 from the BRUNAUER-EMMETT-TELLER method described in the periodical ' The Journal of the American Chemical Society", 6Q, 309 (1938 ). Such a specific surface area allows for further improvement in the removal of contaminants, particularly metals such as silicon.

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

Hydrotreatment step b) advantageously allows optimized treatment of the hydrogenated effluent from step a). In particular, it allows maximizing the hydrogenation of the unsaturated bonds of the olefinic compounds present in the hydrogenated effluent 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 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, fixed-bed reactors, each having n catalytic beds, n being an integer greater than or equal to one, preferably between one and ten, more preferably between two and five, and advantageously operating in series and/or in parallel and/or in permutable mode (or PRS) and/or in "swing" mode. The various possible operating modes, PRS mode (or lead and lag) and swing mode, and 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 an optimized treatment of the hydrogenated effluent, while making it possible to reduce the risks of clogging of the catalytic bed(s) and therefore to avoid stopping the unit due to clogging.

• (b1) deux réacteurs à lit fixe fonctionnant en mode swing ou permutable, de préférence en mode PRS, chacun des deux réacteurs ayant de préférence un lit catalytique comprenant avantageusement un catalyseur d'hydrotraitement de préférence choisi parmi des catalyseurs connus d'hydrodémétallation, de captation du silicium et leurs combinaisons, et
• (b2) au moins un réacteur à lit fixe, de préférence un réacteur, situé en aval des deux réacteurs (b1), et avantageusement fonctionnant en série des deux réacteurs (b1), ledit réacteur (b2) à lit fixe ayant entre 1 et 5 lits catalytiques disposés en série et comprenant chacun entre un et dix catalyseur(s) d'hydrotraitement dont au moins un desdits catalyseurs d'hydrotraitement comprend avantageusement un support et au moins un élément métallique comprenant de préférence au moins un élément du groupe VIII, de préférence choisi parmi le nickel et le cobalt, et/ou au moins un élément du groupe VIB, de préférence choisi parmi le molybdène et le tungstène.

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

• (b1) two fixed-bed reactors operating in swing or permutable mode, preferably in PRS mode, each of the two reactors preferably having a catalytic bed advantageously comprising a hydrotreatment catalyst preferably chosen from known hydrodemetallization catalysts, silicon capture catalysts and combinations thereof, and
• (b2) at least one fixed-bed reactor, preferably a 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 hydrotreatment catalyst(s), at least one of said hydrotreatment catalysts advantageously comprising a support and at least one metallic element preferably comprising at least one element from group VIII, preferably chosen from nickel and cobalt, and/or at least one element from group VIB, preferably chosen 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 to reach 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, the hydrotreatment step b) allows the total hydrogenation of the olefins present in the initial feedstock and those possibly obtained after the selective hydrogenation step a), but also 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 (in particular chlorine compounds), oxygenated compounds. Step b) can also make it possible to further reduce the contaminant content, such as that of metals, in particular the silicon content.

Step c) hydrocracking (first hydrocracking step)

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

Advantageously, step c) implements the hydrocracking 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 from step b). Other reactions, such as the hydrogenation of olefins, aromatics, hydrodemetallation, hydrodesulfurization, hydrodenitrogenation, etc. can continue.

Advantageously, said step c) is carried out in a hydrocracking reaction section comprising at least one, preferably between one and five, fixed-bed reactor(s) having n catalytic beds, n being an integer greater than or equal to one, preferably between one and ten, preferably between two and five, said bed(s) each comprising at least one, and preferably not more than ten, hydrocracking catalyst(s). When a reactor comprises several catalytic beds, i.e. at least two, preferably between two and ten, preferably between two and five catalytic beds, said catalytic beds are arranged in series in said reactor.

The hydrotreatment step b) and the hydrocracking step c) may advantageously be carried out in the same reactor or in different reactors. In the case where they are carried out in the same reactor, the reactor comprises several catalytic beds, the first catalytic beds comprising the hydrotreatment catalyst(s) and the following catalytic beds comprising the hydrocracking catalyst(s).

Said hydrocracking reaction section is supplied at least by said hydrotreated effluent from step b) and a gas 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 step a) of selective hydrogenation or step b) of hydrotreatment.

avec T_entrée : la température de l'effluent hydrogéné en entrée de la section réactionnelle d'hydrocraquage, T_sortie : la température de l'effluent en sortie de section réactionnelle d'hydrocraquage.Thus, said hydrocracking reaction section is advantageously carried out at a hydrotreatment 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 velocity (HVV) between 0.1 and 10.0 h ^-1 , preferably between 0.1 and 5.0 h ^-1 , preferentially between 0.2 and 4 h ^-1 . According to the invention, the "hydrocracking temperature" corresponds to an average temperature in the hydrocracking reaction section of step c) and step f) respectively. In particular, it corresponds to the Weight Average Bed Temperature (WABT) according to the established Anglo-Saxon term, well known to those skilled in the art. The hydrocracking temperature is advantageously determined based on the catalytic systems, equipment, and configuration of these used. For example, the hydrocracking temperature (or WABT) is calculated as follows: $$\mathrm{WABT}=\left({\mathrm{T}}_{\mathrm{entrance}}+2\times {\mathrm{T}}_{\mathrm{exit}}\right)/3$$

with T _inlet : the temperature of the hydrogenated effluent entering the hydrocracking reaction section, T _outlet : the temperature of the effluent leaving the hydrocracking reaction section.

The hourly volumetric velocity (HVV) is defined here as the ratio between the hourly volumetric flow rate of the hydrogenated effluent from step a) per volume of catalyst(s). The hydrogen coverage in step c) is advantageously between 80 and 2000 Nm ³ of hydrogen per m ³ of fresh feedstock which feeds step a), and preferably between 200 and 1800 Nm ³ of hydrogen per m ³ of fresh feedstock which feeds step a). The hydrogen coverage is defined here as the ratio of the volumetric flow rate of hydrogen taken under normal temperature and pressure conditions relative to the volumetric flow rate of fresh feedstock which feeds step a), i.e. of feedstock comprising a plastic pyrolysis oil, or by the optionally pretreated feedstock, which feeds step a) (in normal m ³ , denoted Nm ³ , of H ₂ per m ³ of fresh feedstock). The hydrogen may consist of a make-up and/or recycled hydrogen, in particular from separation step d).

Preferably, an additional gas stream comprising hydrogen is advantageously introduced at the inlet of each reactor, in particular operating in series, and/or at the inlet of each catalytic bed from the second catalytic bed of the hydrocracking reaction section. These additional gas streams are also called cooling streams. They make it possible to control the temperature in the hydrocracking reactor in which the reactions carried out are generally very exothermic.

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

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

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

The hydrocracking catalyst(s) used in hydrocracking 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 binding matrix. The acid function is provided by supports with a large surface area (generally 150 to 800 m ² /g) having a surface acidity, such as halogenated aluminas (chlorinated or fluorinated in particular), combinations of boron and aluminum 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 hydro-dehydrogenating 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 as a mixture, and preferably from molybdenum and tungsten. Hydro-dehydrogenating functions of the NiMo, NiMoW, 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 group VIB metal 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 relative to the total weight of the catalyst.

The hydrocracking catalyst(s) used in step c) may also optionally comprise at least one promoter element deposited on the catalyst and chosen from the group formed by phosphorus, boron and silicon, optionally at least one element from group VIIA (chlorine, fluorine preferred), optionally at least one element from group VIIB (manganese preferred), and optionally at least one element from group VB (niobium preferred).

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

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

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

In the case where said catalyst comprises a zeolite, the zeolite content in the hydrocracking 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 relative to the total weight of the catalyst.

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

An even more preferred catalyst comprises, and preferably consists of, nickel, molybdenum, phosphorus, a USY zeolite, and optionally 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.

Said hydrocracking catalyst is for example in the form of extrudates.

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

The preparation of the catalysts of steps a), b) or c) is known and generally comprises a step of impregnation of the metals of group VIII and group VIB when present, and optionally phosphorus and/or boron on the support, followed by drying, then optionally calcination. In the case of an additive catalyst, the preparation is generally carried out by simple drying without calcination after introduction of the organic compound. Here, calcination means a heat treatment under a gas containing air or oxygen at a temperature greater than or equal to 200°C. Before their use in a step of the process, the catalysts are generally subjected to sulfurization in order to form the active species. The catalyst of step a) can also be a catalyst used in its reduced form, thus involving a reduction step in its preparation.

Optionally, step c) may implement a heating section located upstream of the hydrocracking reaction section and in which the hydrotreated effluent from step b) is heated to reach 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 a heat exchange between the hydrotreated effluent and the hydrocracked effluent, and/or a preheating furnace.

Step d) separation

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

The gaseous effluent obtained at the end of step d) advantageously comprises hydrogen, preferably comprises at least 90% by volume, preferably at least 95% by volume, of hydrogen. Advantageously, said gaseous effluent can at least partly be recycled to 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 from step d) advantageously comprises ammonium salts and/or hydrochloric acid.

The hydrocarbon effluent from step d) comprises hydrocarbon compounds and advantageously corresponds to the plastic pyrolysis oil of the feedstock, or to the plastic pyrolysis oil and the conventional petroleum feedstock fraction or biomass co-treated with the pyrolysis oil, in which at least part of the heavy compounds has been converted into lighter compounds in order to maximize the naphtha cut. The hydrocarbon effluent is furthermore at least partially freed of its impurities, in particular its olefinic (di- and mono-olefin), 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 in particular during step b) then dissolution in water, and the ammonium ions, generated by the hydrogenation of the nitrogen compounds in the form of NH ₃ in particular during step b) and/or provided by injection of an amine then dissolution in water, and thus to limit the risks of blockage, in particular in the transfer lines and/or in the sections of the process of the invention and/or the transfer lines to the steam cracker, 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 feedstock to be treated, a stream containing an amine such as, for example, monoethanolamine, diethanolamine and/or monodiethanolamine may be injected upstream of the selective hydrogenation step a), between the selective hydrogenation step a) and the hydrotreatment step b) and/or between the hydrocracking step c) and the separation step d), preferably upstream of the selective hydrogenation step a), in order to ensure a sufficient quantity of ammonium ions to combine the chloride ions formed during the hydrotreatment step, thereby limiting the formation of hydrochloric acid and thus limiting 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 from step c), upstream of the washing/separation section, so as to dissolve at least in part ammonium chloride salts and/or hydrochloric acid and thus improve the elimination of chlorinated impurities and reduce the risks of blockages due to an accumulation of ammonium chloride salts.

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

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

In a possible embodiment of the invention, taken in addition to or in isolation from other embodiments of the invention described, separation step d) comprises the injection of an aqueous solution into the hydrocracked effluent from step c), followed by the washing/separation section advantageously comprising a separation phase making it possible to obtain at least one aqueous effluent loaded with ammonium salts, a washed liquid hydrocarbon effluent and a partially washed gaseous effluent. The aqueous effluent loaded with ammonium salts and the washed liquid hydrocarbon effluent can then be separated in a settling tank in order to obtain said hydrocarbon effluent and said aqueous effluent. Said partially washed gaseous effluent can in parallel be introduced into a washing column where 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 total, the hydrochloric acid contained in the partially washed gaseous effluent and thus to obtain said gaseous effluent, preferably comprising essentially hydrogen, and an acidic aqueous flow. Said aqueous effluent from the decanter tank may optionally be mixed with said acidic aqueous flow, and may be used, optionally in a mixture with said acidic aqueous flow in a water recycling circuit to supply step d) of separation into said aqueous solution upstream of the washing/separation section and/or into said aqueous flow in the washing column. Said water recycling circuit may include a water and/or basic solution top-up and/or a purge to remove 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 which operates 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 supplemented by a "low pressure" section, in order to obtain a liquid hydrocarbon fraction free of a portion of the gases dissolved at high pressure and intended to be treated directly in a steam cracking process or optionally to be sent to the fractionation step e).

The gas fraction(s) resulting from separation step d) may be subject to additional purification(s) and separation(s) in order to recover at least one hydrogen-rich gas that can 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 steam cracking step h) so as to increase the overall yield of olefins.

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

Step e) of fractionation

The process according to the invention comprises a step of fractionating all or part, preferably all, of the hydrocarbon effluent from step d), to obtain at least one gas stream and at least two liquid hydrocarbon streams, said two liquid hydrocarbon streams 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.

Step e) makes it possible in particular to eliminate gases dissolved in the liquid hydrocarbon effluent, such as for example ammonia, hydrogen sulfide and light hydrocarbons having 1 to 4 carbon atoms.

Fractionation step e) is advantageously carried out at a pressure 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 carried out in a section advantageously comprising at least one stripping column equipped with a reflux circuit comprising a reflux drum. Said stripping column is supplied with the liquid hydrocarbon effluent from step d) and with a stream of water vapor. The liquid hydrocarbon effluent from step d) can optionally be reheated before entering the stripping column. Thus, the lightest compounds are entrained at the top of the column and in the reflux circuit comprising a reflux drum in which a gas/liquid separation takes place. The gas phase which comprises the light hydrocarbons is withdrawn from the reflux drum, in a gas stream. The naphtha cut comprising compounds having a boiling point less than or equal to 175°C is advantageously withdrawn from the reflux drum. The hydrocarbon fraction comprising compounds having a boiling point above 175°C is advantageously withdrawn at the bottom of the stripping column.

According to other embodiments, fractionation step e) may use a stripping column followed by a distillation column or only a distillation column.

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

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

According to a preferred embodiment, the naphtha cut comprising compounds having a boiling point less than or equal to 175°C, all or 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, fractionation step e) can make it possible to obtain, in addition to a gas stream, 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 of greater than 175°C and less than or equal to 280°C, optionally a diesel cut comprising compounds having a boiling point of greater than 280°C and less than 385°C and a hydrocarbon cut comprising compounds having a boiling point of greater than or equal to 385°C, called a heavy hydrocarbon cut. The naphtha cut can be sent, in whole or in part, to a steam cracking unit and/or to the naphtha pool from conventional petroleum feedstocks, it can also be sent to recycling step h); the kerosene cut and/or the diesel cut may also be, in whole or in part, either sent to a steam cracking unit, or respectively to a kerosene or diesel pool from conventional petroleum feedstocks, or be recycled in the process in the same way 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 of less than or equal to 175°C 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 a complex aromatic comprising at least one step of reforming naphtha in order to produce aromatic compounds. According to this embodiment, at least a portion of the light naphtha cut is sent to the steam cracking step i) described below.

The gas fraction(s) resulting from fractionation step e) may be subject to additional purification(s) and separation(s) in order to recover 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 steam cracking step i) so as to increase the overall yield of olefins.

Stage f) hydrocracking (second hydrocracking stage)

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 from step e), in the presence of hydrogen and at least one hydrocracking catalyst, to obtain a second hydrocracked effluent.

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

Advantageously, said step f) is carried out in a hydrocracking reaction section comprising at least one, preferably between one and five, fixed-bed reactor(s) having n catalytic beds, n being an integer greater than or equal to one, preferably between one and ten, preferably between two and five, said bed(s) each comprising at least one, and preferably not more than ten, hydrocracking catalyst(s). When a reactor comprises several catalytic beds, i.e. at least two, preferably between two and ten, preferably between two and five catalytic beds, said catalytic beds are arranged in series in said reactor.

Said hydrocracking reaction section is fed with at least a portion of the cut comprising compounds having a boiling point greater than 175°C and a flow gaseous 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 step a) of selective hydrogenation or step b) of hydrotreatment or step c) of first hydrocracking.

Thus, said hydrocracking reaction section is advantageously carried out at a hydrotreatment 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 flow rate (HVV) between 0.1 and 10.0 h ^-1 , preferably between 0.1 and 5.0 h ^-1 , preferentially between 0.2 and 4 h ^-1 . The hourly volumetric flow rate (HVV) is defined here as the ratio between the hourly volumetric flow rate of the hydrogenated effluent from step a) per volume of catalyst(s). The hydrogen coverage in step f) is advantageously between 80 and 2000 Nm ³ of hydrogen per m ³ of fresh feedstock that feeds step a), and preferably between 200 and 1800 Nm ³ of hydrogen per m ³ of fresh feedstock that feeds step a). The hydrogen coverage is defined here as the ratio of the volume flow rate of hydrogen taken under normal temperature and pressure conditions relative to the volume flow rate of fresh feedstock that feeds step a), i.e. of feedstock comprising a plastic pyrolysis oil, or by the optionally pretreated feedstock, that feeds step a) (in normal m ³ , denoted Nm ³ , of H ₂ per m ³ of fresh feedstock). The hydrogen may consist of a make-up and/or recycled hydrogen originating in particular from separation step d).

Preferably, an additional gas stream comprising hydrogen is advantageously introduced at the inlet of each reactor, in particular operating in series, and/or at the inlet of each catalytic bed from the second catalytic bed of the hydrocracking reaction section. These additional gas streams are also called cooling streams. They make it possible to control the temperature in the hydrocracking reactor in which the reactions carried out are generally very exothermic.

These operating conditions used in step f) of the process according to the invention generally make it possible to achieve conversions per pass, into products having at least 80% by volume of compounds having boiling points less than or equal to 175°C, preferably less than 160°C and more preferably less than 150°C, greater than 15% by weight and even more preferably between 20 and 80% by weight. Nevertheless, the conversion per pass in step f) is kept moderate in order to maximize the selectivity for compounds of 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 on the second hydrocracking stage loop. This rate is defined as the ratio between the feed flow rate of step f) and the flow rate of the feed of step a), preferably this ratio is between 0.2 and 4, preferably between 0.5 and 2.5.

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

In a variant, the hydrocracking catalyst used in step f) comprises a hydro-dehydrogenating function comprising at least one noble metal from group VIII chosen from palladium and platinum, alone or as a mixture. The content of noble metal from 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. Said optional heating section may thus comprise one or more exchangers, and/or a preheating furnace.

Step g) recycling of the second hydrocracked effluent

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

A purge may be installed on the recycle 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 from step f) relative to the incoming feed, and preferably between 0.5% and 5% by weight.

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

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

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

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

Advantageously, for the start-up phases of the process, a hydrocarbon cut external to the process can be used as a recycle stream. The person skilled in the art will then know how to choose said hydrocarbon cut.

The recycling of part of the product obtained to or upstream of at least one of the reaction stages of the process according to the invention advantageously makes it possible on the one hand to dilute the impurities and on the other hand to control the temperature in the reaction stage(s), in which the reactions involved may be highly exothermic.

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

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

According to a third preferred embodiment of the invention, the method for treating a feedstock comprising a plastic pyrolysis oil comprises, preferably consists of, the sequence of steps, and preferably in the given order, a) selective hydrogenation, b) hydrotreatment, c) hydrocracking, d) separation, e) fractionation, f) hydrocracking and g) recycling of the hydrocracked effluent in step d), h) recycling of a portion of the cut comprising compounds having a boiling point 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.

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

• la teneur totale en éléments métalliques est inférieure ou égale à 5,0 ppm poids, de préférence inférieure ou égale à 2,0 ppm poids, préférentiellement inférieure ou égale à 1,0 ppm poids et de manière préférée inférieure ou égale à 0,5 ppm poids, avec :
  • une teneur en élément silicium (Si) inférieure ou égale à 1,0 ppm poids, de préférence inférieure ou égale à 0,6 ppm poids, et
  • une teneur en élément fer (Fe) inférieure ou égale à 100 ppb poids,
• la teneur en soufre est inférieure ou égale à 500 ppm poids, de préférence inférieure ou égale à 200 ppm poids,
• la teneur en azote est inférieure ou égale à 100 ppm poids, de préférence inférieure ou égale à 50 ppm poids et de manière préférée inférieure ou égale à 5 ppm poids
• la teneur en asphaltènes est inférieure ou égale à 5,0 ppm poids,
• la teneur totale en élément chlore est inférieure ou égale à 10 ppm poids, de manière préférée inférieure à 1,0 ppm poids,
• la teneur en composés oléfiniques (mono- et di-oléfines) est inférieure ou égale à 5,0% poids, de préférence inférieure ou égale à 2,0% poids, de manière préférée inférieure ou égale à 0,1% poids.

Said hydrocarbon effluent or said hydrocarbon stream(s) thus obtained by treatment according to the process of the invention of a plastic pyrolysis oil, has(have) a composition compatible with the specifications of an input feedstock of a steam cracking unit. In particular, the composition of the hydrocarbon effluent or 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, preferentially 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 (Si) element content of less than or equal to 1.0 ppm by weight, preferably less than or equal to 0.6 ppm by weight, and
  • an iron (Fe) element 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 more 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 chlorine element content 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 di-olefins) is less than or equal to 5.0% by weight, preferably less than or equal to 2.0% by weight, more preferably less than or equal to 0.1% by weight.

The contents are given in relative weight concentrations, percentage (%) by weight, part(s) per million (ppm) by weight or part(s) per billion (ppb) by weight, relative 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, in whole or in part, into a steam cracking unit.

Step i) of steam cracking (optional)

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

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

Said steam cracking step i) is advantageously carried out in at least one pyrolysis furnace at a temperature of between 700 and 900°C, preferably between 750 and 850°C, and at a pressure of between 0.05 and 0.3 MPa relative. The residence time of the hydrocarbon compounds is generally less than or equal to 1.0 second (denoted s), preferably between 0.1 and 0.5 s. Advantageously, water vapor is introduced upstream of the optional steam cracking step i) and after the separation (or fractionation). The quantity of water introduced, advantageously in the form of water vapor, is advantageously between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds entering 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 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 can also designate a group of furnaces operating in parallel. For example, a furnace can be dedicated to the cracking of the naphtha cut comprising 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 in order to constitute an effluent. It is understood that the steam cracking step i) comprises the steam cracking furnaces but also the sub-steps associated with steam cracking well known to those skilled in the art. These sub-steps may in particular comprise heat exchangers, columns and catalytic reactors and recycling to the furnaces. A column generally makes it possible to fractionate the effluent in order to recover at least one light fraction comprising hydrogen and compounds having 2 to 5 carbon atoms, and a fraction comprising pyrolysis gasoline, and optionally a fraction comprising pyrolysis oil. Columns make it possible to separate the various constituents of the light fractionation fraction in order to recover at least one cut rich in ethylene (C2 cut) and a cut rich in propylene (C3 cut) and possibly a cut rich in butenes (C4 cut). Catalytic reactors allow in particular to carry out selective hydrogenations of C2, C3 or even C4 cuts and pyrolysis gasoline. Saturated compounds, in particular saturated compounds having 2 to 4 carbon atoms are advantageously recycled to steam cracking furnaces so as to increase overall olefin yields.

This step of i) steam cracking 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), at 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 total 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 embodiment(s) of the invention, taken separately or combined with each other, the method for treating a feedstock comprising a plastic pyrolysis oil comprises, preferably consists of, the sequence of the steps described above, and preferably in the order given, that is to say: a) selective hydrogenation, b) hydrotreatment, c) hydrocracking, d) separation, e) fractionation, f) hydrocracking, g) recycling of the second hydrocracked effluent to step d), and step i) steam cracking.

According to a preferred embodiment, the method for treating a feedstock comprising a plastic pyrolysis oil comprises, preferably consists of, the sequence of the 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 to step d), g) recycling of at least a portion of the naphtha cut comprising compounds having a boiling point of less than or equal to 175°C to steps a) and/or b), and step i) steam cracking.

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

Analysis methods used

The analysis methods and/or standards used to determine the characteristics of the various flows, in particular the load to be treated and the effluents, are known to those skilled in the art. They are listed in particular below: Table 1 Features Methods Density @15°C ASTM D4052 Sulfur content ISO 20846 Nitrogen content ASTM D4629 Acid index ASTM D664 Bromine content ASTM D1159 Di-Olefins Content from Maleic Anhydride Index MAV method as described in the article : C. López-Garcia et al., Near Infrared Monitoring of Low Conjugated Diolefins Content in Hydrotreated FCC Gasoline Streams, Oil & Gas Science and Technology - Rev. IFP, Vol.62 (2007), No.1, 57-68 Oxygen content Combustion + Infrared Paraffin Content UOP990-11 Naphthenes content UOP990-11 Olefins Content UOP990-11 Aromatic Content UOP990-11 Halogen Content ASTM-D7359 Asphaltene content IFP9313 Chloride Content ASTM D7536 Metal content: ASTM-D5185 P Fe If N / A B Simulated Distillation ASTM D2887

LIST OF FIGURES

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

• une étape a) d'hydrogénation sélective d'une charge hydrocarbonée issue de la pyrolyse de plastiques 1, en présence d'un gaz riche en hydrogène 2 et éventuellement d'une amine apportée par le flux 3, réalisée dans au moins un réacteur en lit fixe comportant au moins un catalyseur d'hydrogénation sélective, pour obtenir un effluent 4 ;
• une étape b) d'hydrotraitement de l'effluent 4 issu de l'étape a), en présence d'hydrogène 5 réalisée dans au moins un réacteur en lit fixe comportant au moins un catalyseur d'hydrotraitement, pour obtenir un effluent hydrotraité 6 ;
• une première étape c) d'hydrocraquage de l'effluent 6 issu de l'étape c), en présence d'hydrogène 7, réalisée dans au moins un réacteur en lit fixe comportant au moins un catalyseur d'hydrocraquage, pour obtenir un premier effluent hydrocraqué 8 ;
• une étape d) de séparation de l'effluent 8 réalisée en présence d'une solution aqueuse de lavage 9 et permettant d'obtenir au moins une fraction 10 comprenant de l'hydrogène, une fraction aqueuse 11 contenant des sels dissous, et une fraction liquide hydrocarbonée 12 ;
• une étape e) de fractionnement de la fraction liquide hydrocarbonée 12 permettant d'obtenir au moins une fraction gazeuse 13, une coupe naphta 14 comprenant des composés ayant un point d'ébullition inférieur ou égal à 175°C et une coupe 15 comprenant des composés ayant un point d'ébullition supérieur à 175°C ;
• une deuxième étape f) d'hydrocraquage d'au moins une partie de la coupe 15a comprenant des composés ayant un point d'ébullition supérieur à 175°C issu de l'étape e), en présence d'hydrogène 16, réalisée dans au moins un réacteur en lit fixe comportant au moins un catalyseur d'hydrocraquage, pour obtenir un deuxième effluent hydrocraqué 17 ; l'autre partie de la coupe 15 constitue la purge15b ;
• une étape de recycle du deuxième effluent hydrocraqué 17 dans l'étape d) de séparation.

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

• a step a) of selective hydrogenation of a hydrocarbon feedstock resulting from the pyrolysis of plastics 1, in the presence of a hydrogen-rich gas 2 and optionally an amine supplied by the 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 hydrotreatment of the effluent 4 from step a), in the presence of hydrogen 5 carried out in at least one fixed-bed reactor comprising at least one hydrotreatment catalyst, to obtain a hydrotreated effluent 6;
• a first step c) of hydrocracking the effluent 6 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 first hydrocracked effluent 8;
• a step d) of separation of the effluent 8 carried out in the presence of an aqueous washing solution 9 and making it possible to obtain at least one fraction 10 comprising hydrogen, an aqueous fraction 11 containing dissolved salts, and a liquid hydrocarbon fraction 12;
• a step e) of fractionation of the liquid hydrocarbon fraction 12 making it possible to obtain at least one 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 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 hydrocracked effluent 17; the other part of the cut 15 constitutes the purge 15b;
• a step of recycling the second hydrocracked effluent 17 in the separation step d).

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

At the end of step e), at least a portion 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, a portion of the naphtha fraction 14 comprising compounds having a boiling point less than or equal to 175°C from step e) constitutes a recycle stream which feeds step a) of selective hydrogenation (fraction 14a), and step b) of hydrotreatment (fraction 14b).

Only the main stages, with the main flows, are shown on the Figure 1 , in order to allow a better understanding of the invention. It is understood that all the equipment necessary for operation is present (balloons, pumps, exchangers, ovens, columns, etc.), even if not shown. It is also understood that hydrogen-rich gas flows (make-up or recycle), as described above, can be injected at 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 for purifying and recycling hydrogen can also be implemented.

EXAMPLES Example 1 (in accordance with the invention)

Feedstock 1 treated in the process is a plastic pyrolysis oil (i.e. comprising 100% by weight of said plastic pyrolysis oil) having the characteristics indicated in Table 2. Table 2: Load characteristics Description / Methods Unit Pyrolysis oil Density @15°C ASTM D4052 g/cm ³ 0.820 Sulfur content ISO 20846 ppm weight 2500 Nitrogen content ASTM D4629 ppm weight 730 Acid index ASTM D664 mgKOH/g 1.5 Bromine content ASTM D1159 g/100g 80 Di-Olefins Content from Maleic Anhydride Index MAV method ⁽¹⁾ 96 weight 10 Oxygen content Combustion + Infrared % weight 1.0 Paraffin Content UOP990-11 % weight 45 Naphthenes content UOP990-11 % weight 20 Olefins Content UOP990-11 % weight 25 Aromatic Content UOP990-11 % weight 10 Halogen Content ASTM-D7359 ppm weight 350 Asphaltene content FP9313 ppm weight 380 Chloride Content ASTM D7536 ppm weight 320 Metal content: ASTM-D5185 P ppm weight 10 Fe ppm weight 25 If ppm weight 45 N / A ppm weight 2 B ppm weight 2 Simulated Distillation: ASTM D2887 0% °C 40 10% °C 98 30% °C 161 50% °C 232 70% °C 309 90% °C 394 100% °C 432 (1) MAV method described in the article: C. López-García et al., Near Infrared Monitoring of Low Conjugated Diolefins Content in Hydrotreated FCC Gasoline Streams, Oil & Gas Science and Technology - Rev. IFP, Vol. 62 (2007), No. 1, pp. 57-68

Charge 1 is subjected to a selective hydrogenation step a) carried out in a fixed bed reactor and in the presence of hydrogen 2 and a selective hydrogenation catalyst of the NiMo on alumina type under the conditions indicated in Table 3. Table 3: conditions of step a) of selective hydrogenation Temperature °C 180 Partial Pressure of Hydrogen MPa abs 6.4 H ₂ /HC (Hydrogen volume coverage relative to charge volume) Nm ³ /m ³ 50 VVH (volume flow rate of charge/volume of catalysts) h-1 0.5

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

Effluent 4 from selective hydrogenation step a) is subjected directly, without separation, to a hydrotreatment step b) carried out in a fixed bed and in the presence of hydrogen 5, and a NiMo on alumina hydrotreatment catalyst under the conditions presented in table 4. Table 4: conditions of hydrotreatment step b) Hydrotreatment temperature °C 355 Partial Pressure of Hydrogen MPa abs 6.2 H ₂ /HC (Hydrogen volume coverage relative to charge volume) Nm ³ /m ³ 300 VVH (volume flow rate of charge/volume of catalysts) h-1 0.5

The effluent 6 from hydrotreatment step b) is subjected directly, without separation, to a first hydrocracking step c) carried out in a fixed bed and in the presence of hydrogen 7 and a zeolitic hydrocracking catalyst comprising NiMo under the conditions presented in table 5. Table 5: conditions of the first stage c) of hydrocracking Hydrocracking temperature °C 350 Partial Pressure of Hydrogen MPa abs 5.8 H ₂ /HC (Volume coverage of hydrogen relative to the charge volume of step c)) Nm ³ /m ³ 350 VVH (volume flow rate of charge stage c)/volume of catalysts) h ^-1 2

The effluent 8 from the hydrocracking step c) is subjected to a separation step d) according to the invention in which a water stream is injected into the effluent from the hydrocracking step c); the mixture is then sent to the separation step d) and is treated in an acid gas scrubbing column. A gas fraction 10 is obtained at the top of the acid gas scrubbing column while at the bottom, a two-phase separator drum separates an aqueous phase and a liquid phase. The gas scrubbing column and the two-phase separator are operated at high pressure. The liquid phase is then sent to a low-pressure drum so as to recover a second gas fraction which is purged and a liquid effluent. The liquid effluent 12 obtained at the end of separation step d) is sent to a fractionation step e) comprising a stripping column and a distillation column in order 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 from fractionation step e) is sent to the second hydrocracking step f) so as to increase the conversion of compounds having a boiling point higher than 175°C. A small portion of the 175°C+ fraction is not sent to the second hydrocracking step f) so as to avoid the accumulation of polyaromatic compounds which could be a precursor of coke (purge 15b).

The volume flow rate of the 175°C+ fraction from fractionation step e) and sent to the second hydrocracking step f) is equal to 80% of the volume flow rate of the liquid effluent from hydrotreatment step b) and feeding the first hydrocracking step c).

The second hydrocracking step f) is carried out in a fixed bed and in the presence of hydrogen 16 and a zeolitic hydrocracking catalyst comprising NiMo under the conditions presented in Table 6. Table 6: Conditions of the second stage f) of hydrocracking Hydrocracking temperature °C 320 Partial Pressure of Hydrogen MPa abs 5.8 H ₂ /HC (Hydrogen volume coverage relative to the charge volume step f)) Nm ³ /m ³ 350 VVH (volume flow rate of charge stage f)/volume of catalysts) h ^-1 2

Effluent 17 from the second hydrocracking stage f) is mixed with effluent 8 from the first hydrocracking stage c). The two effluents are subjected to a separation stage d) and then a fractionation stage e), these two stages being common to the two effluents and being carried out as described above.

Table 7 gives the overall yields of the different fractions obtained at the outlet of hydrocracking stages c) and f) at the end of separation stages d) and fractionation stages e) (which includes a stripping column and a distillation column). Table 7: yields of the different products and fractions obtained at the outlet of hydrocracking stages c) and f) H ₂ S* % m/m 0.27 NH ₃ * % m/m 0.09 C1 % m/m 0.21 C2 % m/m 0.21 C3 % m/m 1.76 C4 % m/m 6.34 Fraction PI-175°C % m/m 93.00 Fraction 175°C+ % m/m 0.50 Total % m/m 102.37

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

The treatment of the feedstock according to the steps of the invention, and in particular through hydrocracking steps c) and f), makes it possible to obtain a very high yield of naphtha-type PI-175°C fraction.

The characteristics of the liquid fractions PI-175°C and 175°C+ obtained after separation step d) and fractionation step e) are presented in table 8: Table 8: characteristics of the PI-175°C, 175°C+ fractions Fraction PI-175°C Fraction 175°C+ Density @ 15°C (ASTM D4052) g/cm ³ 0.753 0.805 Content in: Sulfur (ASTM D5453) ppm weight <2 <2 Nitrogen (ASTM D4629) ppm weight < 0.5 < 3 Fe (ASTM D5185) ppb weight Not detected 25 Total Metals (ASTM D5185) ppm weight Not detected 1 Chlorine (ASTM D7536) ppb weight Not detected < 25 Paraffins (UOP990-11) % weight 82 83 Naphthenes (UOP990-11) % weight 17.5 15 Olefins (UOP990-11) % weight Not detected Not detected Aromatics (UOP990-11) % weight 0.5 1 Simulated Distillation (ASTM D2887) in % 0 °C 25 175 5 °C 38 185 10 °C 59 206 30 °C 90 235 50 °C 118 265 70 °C 140 285 90 °C 163 320 95 °C 175 344 100 °C 180 350

• elles ne contiennent pas d'oléfines (mono- et di-oléfines) ;
• elles présentent des teneurs en élément chlore très faibles (respectivement une teneur non détectée et une teneur de 25 ppb poids) et inférieures à la limite requise pour une charge de vapocraqueur;
• les teneurs en métaux, en particulier en fer (Fe), sont elles aussi très faibles (teneurs en métaux non détectée pour la fraction PI-175°C et < 1 ppm poids pour la fraction 175°C+ ; teneurs en Fe non détectée pour la fraction PI-175°C et 50 ppb poids pour la fraction 175°C+) et inférieures aux limites requises pour une charge de vapocraqueur (≤ 5,0 ppm poids, de manière très préférée ≤ 1 ppm poids pour les métaux ; ≤ 100 ppb poids pour le Fe) ;
• enfin elles contiennent du soufre (< 2 ppm poids pour la fraction PI-175°C et < 2 ppm poids pour la fraction 175°C+) et de l'azote (< 0,5 ppm poids pour la fraction PI-175°C et < 3 ppm poids pour la fraction 175°C+) à des teneurs très inférieures aux limites requises pour une charge de vapocraqueur (≤ 500 ppm poids, de préférence ≤ 200 ppm poids pour S et N).

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

• they do not contain olefins (mono- and di-olefins);
• they have very low chlorine element contents (respectively an undetected content and a content of 25 ppb by weight) and lower than the limit required for a steam cracker load;
• the metal contents, in particular iron (Fe), are also very low (metal contents not detected for the PI-175°C fraction and < 1 ppm by weight for the 175°C+ fraction; Fe contents not detected for the PI-175°C fraction and 50 ppb by weight for the 175°C+ fraction) and below the limits required for a steam cracker feed (≤ 5.0 ppm by weight, very preferably ≤ 1 ppm by weight for metals; ≤ 100 ppb by weight for Fe);
• finally they contain sulphur (< 2 ppm by weight for the PI-175°C 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 levels well below the limits required for a steam cracker feed (≤ 500 ppm by weight, preferably ≤ 200 ppm by weight for S and N).

The liquid fraction PI-175°C obtained is then sent to a steam cracking stage i) (see table 9). Table 9: Conditions of the steam cracking stage Oven outlet pressure MPa abs 0.2 Fraction oven outlet temperature PI-175°C °C 800 Steam / PI fractions ratio -175°C kg/kg 0.6 Residence time for fractions PI-175°C s 0.3

The effluents from the various steam cracking furnaces are subjected to a separation stage enabling the saturated compounds to be recycled to the steam cracking furnaces and the yields presented in Table 10 to be obtained (yield = % of product mass relative to the mass of the PI-175°C fraction upstream of the steam cracking stage, noted % m/m). Table 10: Yields of the steam cracking stage Fraction Fraction PI-175°C _H2 , CO, C1 % m/m 7.9 Ethylene % m/m 34.3 Propylene % m/m 18.7 C4 Coupe % m/m 14.9 Pyrolysis essence % m/m 19.3 Pyrolysis oil % m/m 4.9

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 from stage i) of steam cracking compared to the initial charge of the plastic pyrolysis oil type introduced in stage a): Table 11: overall process yields in products from the steam cracking stage of the PI-175°C fraction Fraction Fraction PI-175°C _H2 , CO, C1 % m/m 7.4 Ethylene % m/m 31.9 Propylene % m/m 17.4 C4 Coupe % m/m 13.9 Pyrolysis essence % m/m 17.9 Pyrolysis oil % m/m 4.5

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

In addition, the specific sequence of steps upstream of the steam cracking stage makes it possible to limit the formation of coke and avoid corrosion problems which would have arisen if the chlorine had not been eliminated.

Example 2 (not in accordance with the invention)

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

It undergoes 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 from the hydrotreatment step is not subjected to steps c) and f) of hydrocracking. The liquid effluent obtained at the end of separation step d) constitutes the PI+ fraction.

The yields of the different products and the different fractions obtained at the outlet of hydrotreatment stage b) are indicated in table 12 (the yields corresponding to the ratios of the mass quantities of the different products obtained relative to the mass of the feed upstream of stage a), expressed as a percentage and noted % m/m). Table 12: yields of the different products and fractions obtained at the outlet of hydrotreatment stage b) H ₂ S % m/m 0.27 NH ₃ % m/m 0.09 C1 % m/m 0.01 C2 % m/m 0.02 C3 % m/m 0.09 C4 % m/m 0.38 Fraction PI+ 99.55 Total % m/m 100.05

The characteristics of the PI+ fraction (which corresponds to the liquid effluent) obtained after separation step d) are presented in table 13: Table 13: Characteristics of the PI+ fraction Fraction PI+ Density @ 15°C (ASTM D4052) g/cm ³ 0.803 Content in: Sulfur (ASTM D5453) ppm weight < 2 Nitrogen (ASTM D4629) ppm weight < 0.8 Fe (ASTM D5185) ppb weight Not detected Total Metals (ASTM D5185) ppm weight Not detected Chlorine (ASTM D7536) ppb weight Not detected Paraffins (UOP990-11) % weight 66 Naphthenes (UOP990-11) % weight 32 Olefins (UOP990-11) % weight Not detected Aromatics (UOP990-11) % weight 2 Simulated Distillation (ASTM D2887) in % 0 °C 26 5 °C 55 10 °C 93 30 °C 157 50 °C 226 70 °C 304 90 °C 390 95 °C 397 100 °C 431

The PI+ fraction obtained via the sequence of steps a), b) and d) consists of approximately 35% of naphtha-type compounds having a boiling point less than or equal to 175°C. This low yield of naphtha-type compounds having 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 PI+ fraction is sent directly to a steam cracking stage i) according to the conditions mentioned in table 14. Table 14: Conditions of the steam cracking stage Oven outlet pressure MPa abs 0.2 PI+ fraction oven outlet temperature °C 795 Steam / PI+ fraction ratio kg/kg 0.7 Residence time of PI+ fraction oven s 0.3

The effluent from the steam cracking furnace is subjected to a separation step to recycle the saturated compounds to the steam cracking furnace and to obtain the yields presented in Table 15 (yield = % of product mass relative to the mass of PI+ fraction upstream of the steam cracking step, noted % m/m). Table 15: Yields of the steam cracking stage of the PI+ fraction Fraction Fraction PI+ H2, CO, C1 % m/m 8.1 Ethylene % m/m 34.8 Propylene % m/m 19.0 C4 Coupe % m/m 15.1 Pyrolysis essence % m/m 18.8 Pyrolysis oil % m/m 4.2

Considering the yield obtained of 99.5% for the PI+ fraction during the pyrolysis oil treatment process at the outlet of hydrotreatment step b) (see table 12), it is possible to determine the overall yields of the products from step i) of steam cracking compared to the initial charge of plastic pyrolysis oil type introduced in step a): Table 16: overall process yields in products from the steam cracking stage of the PI+ fraction Fraction Fraction PI+ H2, CO, C1 % m/m 8.1 Ethylene % m/m 34.6 Propylene % m/m 18.9 C4 Coupe % m/m 15.0 Pyrolysis essence % m/m 18.7 Pyrolysis oil % m/m 4.2

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

Claims (13)

1. Process for treating a feedstock comprising a plastics pyrolysis oil comprising chlorinated compounds, comprising:

   a) a selective hydrogenation step performed in a reaction section fed at least with said feedstock and a gas stream comprising hydrogen, in the presence of at least one selective hydrogenation catalyst, at a temperature of between 100 and 280°C, a hydrogen partial pressure of between 1.0 and 10.0 MPa abs. and an hourly space velocity of between 0.3 and 10.0 h^-1, to obtain a hydrogenated outflow;

   b) a hydrotreatment step performed in a hydrotreatment reaction section, using 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 at least with said hydrogenated outflow from step a) and a gas stream comprising hydrogen, said hydrotreatment reaction section being operated at a temperature of between 250 and 430°C, a hydrogen partial pressure of between 1.0 and 10.0 MPa abs. and an hourly space velocity of between 0.1 and 10.0 h^-1, to obtain a hydrotreatment outflow;

   c) a first hydrocracking step performed in a hydrocracking reaction section, using 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 at least with said hydrotreated outflow from step b) and a gas stream comprising hydrogen, said hydrocracking reaction section being operated at a temperature of between 250 and 480°C, a hydrogen partial pressure of between 1.5 and 25.0 MPa abs. and an hourly space velocity of between 0.1 and 10.0 h^-1, to obtain a first hydrocracked outflow;

   d) a separation step, fed with the hydrocracked outflow from step c) and an aqueous solution, said step being performed at a temperature of between 50 and 370°C, to obtain at least one gaseous outflow, an aqueous outflow and a hydrocarbon-containing outflow;

   e) a step of fractionating all or a portion of the hydrocarbon-containing outflow from step d), to obtain at least one gas stream and at least two liquid hydrocarbon-containing streams, said two liquid hydrocarbon-containing streams being at least one naphtha cut comprising compounds having a boiling point of less than or equal to 175°C and a hydrocarbon-containing cut comprising compounds having a boiling point of greater than 175°C;

   f) a second hydrocracking step performed in a hydrocracking reaction section, using 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 with at least a portion of said hydrocarbon-containing cut comprising compounds having a boiling point of greater than 175°C from step e) and a gas stream comprising hydrogen, said hydrocracking reaction section being operated at a temperature of between 250 and 480°C, a hydrogen partial pressure of between 1.5 and 25.0 MPa abs. and an hourly space velocity of between 0.1 and 10.0 h^-1, to obtain a second hydrocracked outflow;

   g) a step of recycling at least a portion of said second hydrocracked outflow from step f) to the separation step d).
2. Process according to the preceding claim, which also comprises a recycling step h) wherein a fraction of the hydrocarbon-containing outflow from the separation step d) or a fraction of the naphtha cut having a boiling point of less than or equal to 175°C from the fractionation step e) is sent to the selective hydrogenation step a) and/or the hydrotreatment step b).
3. Process according to the preceding claim, wherein the amount of the recycle stream from step h) is adjusted so that the weight ratio between the recycle stream and the feedstock comprising a plastics pyrolysis oil is less than or equal to 10.
4. Process according to one of the preceding claims, comprising a step a0) of pretreating the feedstock comprising a plastics pyrolysis oil, said pretreatment step being performed upstream of the selective hydrogenation step a) and comprising a filtration step and/or a step of washing with water and/or an adsorption step.
5. Process according to one of the preceding claims, wherein the reaction section in step a) or b) employs at least two reactors operating in an interchangeable manner.
6. Process according to one of the preceding claims, wherein a stream containing an amine is injected upstream of step a).
7. Process according to one of the preceding claims, wherein said selective hydrogenation catalyst comprises a support selected from alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof and a hydrogenating-dehydrogenating function comprising either at least one group VIII element and at least one group VIB element, or at least one group VIII element.
8. Process according to one of the preceding claims, wherein said hydrotreatment catalyst comprises a support selected from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof and a hydrogenating-dehydrogenating function comprising at least one group VIII element and/or at least one group VIB element.
9. Process according to one of the preceding claims, wherein said hydrocracking catalyst in step c) or in step f) comprises a support selected from halogenated aluminas, combinations of boron and aluminium oxides, amorphous silica-aluminas, and zeolites and a hydrogenating-dehydrogenating function comprising at least one group VIB metal selected from chromium, molybdenum and tungsten, alone or as a mixture, and/or at least one group VIII metal selected from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum.
10. Process according to the preceding claim, wherein said zeolite is selected from Y zeolites, alone or in combination, with other zeolites from among beta, ZSM-12, IZM-2, ZSM-22, ZSM-23, SAPC-11, ZSM-48 and ZBM-30 zeolites, alone or as a mixture.
11. Process 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 from step e) is sent in its entirety or in part to a steam cracking step i) performed 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. Process 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 from step e) is fractionated into a heavy naphtha cut comprising compounds having a boiling point of between 80 and 175°C and a light naphtha cut comprising compounds having a boiling point of less than 80°C, at least a portion of said heavy cut being sent to an aromatic complex including at least one naphtha reforming step.
13. Process according to Claim 12, wherein at least a portion of the light naphtha cut is sent to the steam cracking step i) .

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