FR3141696A1 - Process for purifying hydrocarbon feed by treatment in the presence of a strong concentrated base and use - Google Patents

Abstract

Process for purifying a composition comprising a plastic liquefaction oil comprising treatment with a strong base in the presence of water followed by washing in the presence of an organic solvent. The process is useful for reducing the concentration of heteroelements, and in particular chlorine, silicon, nitrogen, oxygen, alkali and alkaline earth metal cations, in said composition with a view to making it compatible for introduction as a filler in processes conversion such as steam cracking, catalytic cracking in a fluidized bed, catalytic hydrogenation or hydrocracking, in particular without deactivation of catalysts used in these processes.

Description

Process for purifying hydrocarbon feed by treatment in the presence of a strong concentrated base and use Technical field of the invention

The present invention relates to a process for purifying hydrocarbon feedstock and its subsequent use in refining and petrochemical processes. The process according to the invention makes it possible to purify feeds containing plastic pyrolysis oils and/or plastic hydrothermal liquefaction oils, particularly with a view to their use in a steam cracking process.

Technology background

Patent JP3776335 discloses a process for dechlorination and denitrogenation of an oil resulting from the catalytic or thermal cracking of plastic waste which is treated at different temperatures up to 425°C for 30 minutes in the presence of an aqueous solution of a compound alkaline of an alkali or alkaline earth metal at a pH greater than or equal to 7. All naturally occurring, non-radioactive alkali or alkaline earth metal hydroxides are tested. The reaction product is then separated from the alkaline aqueous solution by liquid-liquid separation with ethyl ether. This document teaches that dechlorination and denitrogenation are better at high temperatures. It also teaches that when an aqueous alkali metal solution is used, the higher the concentration of that alkali metal solution, the better the dechlorination and denitrogenation.

Patent application WO2012/069467 claims a process for eliminating siloxanes contained in a plastic pyrolysis oil by heat treatment between 200 and 350°C in the presence of an alkali metal hydroxide in the solid state or in solution. The use of calcium hydroxide at 5% by mass at 225°C does not make it possible to obtain a reduction in the siloxane content (table 5, p.12 and lines 9 to 11, p.13). At the end of the reaction, the pyrolysis oil is separated by distillation under reduced pressure.

Patent application WO2020/020769 claims a sequence of processes for purifying a composition comprising at least 20 ppm of chlorine. Many recyclable liquid wastes can be treated, including plastic pyrolysis oils. The process sequence includes a heat treatment of the charge in the presence of an alkali metal hydroxide in order to obtain a reduction of at least 50% in the chlorine content relative to the charge, followed by a hydrotreatment in order to obtain a new reduction of at least 50% in chlorine content.

Patent application WO2021/105326 claims a process for recovering liquefied plastic waste comprising a step of pre-treating the liquefied plastic waste by bringing it into contact with an aqueous medium having a pH of at least 7 at a temperature of 200°C or more , followed by liquid-liquid separation in which the aqueous phase is separated from the organic phase, to produce pretreated liquefied waste plastic. The proposed solution includes the use of a solution of NaOH in water. The separation of the aqueous and organic phases is carried out by physical methods (centrifugation) or chemical methods (addition of separation aid additives, for example non-aqueous solvents, addition of additional quantity of the aqueous medium used for the in contact with or an aqueous medium having a different alkaline substance concentration), or by gravity.

Patent application US20140303421A1 describes a process for treating synthetic crude oils making it possible to lower the acid content and/or the presence of particles and contaminants containing heteroatoms. The synthetic crude oil is washed with a basic aqueous solution having a pH no higher than 10 to avoid saponification. The synthetic crude oil is then separated from the aqueous solution. In one embodiment illustrated in Figure 3, the synthetic crude oil is washed with a first solution in order to remove particles, contaminants containing metals or metalloids or alkali metals. For this purpose, the first solution is acidic to neutralize alkaline species and absorb acids or metals, metalloids of organic polar molecules or other impurities and/or the first solution contains chelating agents to eliminate metals. The synthetic crude oil thus washed is then separated and then washed with a second basic aqueous solution having a pH not higher than 10 before being separated again. This type of process generates significant quantities of polluted water which can be complex and/or expensive to purify before discharge and/or reuse.

Patent application WO2020239729 describes a process for purifying plastic pyrolysis oils which includes a purification step in which the oil is subjected to hydrothermal treatment at 150-450°C with water or water at pH>7. The oil is then separated from the aqueous phase and then sent without further intermediate treatment to hydrotreatment, alone or in a mixture, in the presence of a catalyst and hydrogen in order to carry out one or more reactions of hydrogenation, hydrodeoxygenation, hydrodesulfurization, hydrodenitrogenation, hydrodechlorination, hydrodearomatization or hydroisomerization.

The processes described in these documents, however, require the use of high temperatures, generally of the order of 240-325°C, during the alkaline treatment to obtain high reduction performance, particularly in chlorine and silicon.

The invention aims to provide a process for purifying plastic liquefaction oil at low temperature while maintaining high abatement performance.

To this end, the invention relates to a method for reducing the heteroatom concentration of a composition comprising a plastic liquefaction oil containing at least 20 ppm by weight of heteroatoms, comprising:

(a) bringing said composition into contact with an aqueous solution of a strong base comprising an alkali or alkaline earth metal cation, for 1 minute to 60 minutes at a temperature of at most 250°C, the aqueous solution containing 10 to 50% by weight of strong base or being a saturated solution of strong base, to obtain an effluent containing the modified composition and the aqueous solution,

(b) subjecting the effluent from step (a) to washing with a solvent other than water immiscible with the modified composition, and obtaining a purified composition having a reduced heteroatom content, and a phase enriched in heteroatoms .

The process according to the invention makes it possible to effectively eliminate, despite a moderate temperature, impurities containing heteroatoms, in particular alkali metals, alkaline earth metals, silicon, chlorine, bromine, iron, aluminum and others, likely to damage the catalyst of a subsequent hydrotreatment step.

Contacting step (a) may include one or more of the following characteristics:

- contact is made for a period of 1 minute to 60 minutes, preferably 1 minute to 30 minutes,

- the contacting is carried out at a temperature of 50 to 250°C, preferably of 90 to 225°C, more preferably of 120 to 200°C, more preferably of 120 to 190°C, even more preferably of 140 to 190°C,

- contact is made at an absolute pressure of 0.1 to 100 bars, preferably 1 to 50 bars,

- the strong base is chosen from LiOH, NaOH, CsOH, Ba(OH) ₂ , Na ₂ O, KOH, K ₂ O, CaO, Ca(OH) ₂ , MgO, Mg(OH) ₂ and their mixtures.

• préalablement à l’étape (a), ladite composition est soumise à (i) une filtration, (ii) un lavage avec de l’eau ou un solvant polaire non miscible avec la composition, (iii) une distillation, (iv) une décantation, ou (v) à la combinaison de deux, trois ou quatre des étapes (i) à (iv),
• entre l’étape (a) et (b), une étape de séparation entre la solution aqueuse d’une base forte et la composition modifiée issue de l’étape (a). L’étape de séparation peut notamment s’effectuer par (i) centrifugation, (ii) décantation, ou (iii) par la combinaison de ces deux étapes. La solution aqueuse d’une base forte séparée au cours de l’étape de séparation peut être renvoyée, partiellement ou en totalité, dans l’étape (a) de mise en contact.
• l’étape de séparation est précédée d’une étape de séparation des solides par (i) filtration, (ii) centrifugation ou (iii) une combinaison des deux étapes,
• la composition purifiée issue de l’étape (b) subit (c) un hydrotraitement catalytique en une ou deux étapes,
• la composition purifiée issue de l’étape (b) ou l’effluent issu de l’étape (c) est (d) purifié par passage sur un adsorbant solide afin de diminuer la teneur en au moins un élément parmi F, Cl, Br, I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg et Hg et/ou la teneur en eau,
• le solvant autre que l’eau utilisé lors de l’étape (b) est récupéré, régénéré et renvoyé à l’étape (b), la régénération étant par exemple réalisée par adsorption, distillation ou autre et permettant de purifier le solvant issu de l’étape (b).

The method according to the invention may further comprise one or more of the following characteristics:

• prior to step (a), said composition is subjected to (i) filtration, (ii) washing with water or a polar solvent immiscible with the composition, (iii) distillation, (iv) decantation, or (v) the combination of two, three or four of steps (i) to (iv),
• between step (a) and (b), a separation step between the aqueous solution of a strong base and the modified composition resulting from step (a). The separation step can in particular be carried out by (i) centrifugation, (ii) decantation, or (iii) by the combination of these two steps. The aqueous solution of a strong base separated during the separation step can be returned, partially or entirely, to the contacting step (a).
• the separation step is preceded by a solids separation step by (i) filtration, (ii) centrifugation or (iii) a combination of the two steps,
• the purified composition resulting from step (b) undergoes (c) a catalytic hydrotreatment in one or two steps,
• the purified composition resulting from step (b) or the effluent resulting from step (c) is (d) purified by passing over a solid adsorbent in order to reduce the content of at least one element among F, Cl, Br , I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or the water content,
• the solvent other than water used during step (b) is recovered, regenerated and returned to step (b), the regeneration being for example carried out by adsorption, distillation or other and making it possible to purify the solvent resulting from step (b).

According to one embodiment, at least part of the purified composition resulting from step (b) or the effluent resulting from step (c) or (d) can be:

(e) used as such or separated into usable streams for the preparation of fuels such as LPG, gasoline, diesel, heavy fuel oil, kerosene and/or for the preparation of lubricants and/or base oils,

and/or can be treated, pure or diluted, optionally separated into usable streams, in:
(f) a steam cracker to produce olefins, and/or
(g) a fluidized bed catalytic cracker, and/or
(h) a hydrocracker, then optionally in a steam cracker, and/or
(i) a hydrotreatment reactor, in particular a catalytic hydrogenation reactor, and/or a gasification reactor.

Step (i) can in particular be carried out under the same conditions as step (c).

Preferably, the purified composition of step (b) or the purified hydrotreated composition of step (c) can be subjected, pure or diluted, optionally after separation into usable streams, to a steam cracking step (f) to produce olefins such as ethylene and propylene, which can then be used to make new polymers through polymerization.

The previously described steps of the method according to the invention can be implemented one after the other without any intermediate step apart from the optional additional steps described.

Definitions

The Hourly Volume Velocity (VVH) is defined as the hourly volume of feed flow per unit of catalytic volume and is expressed here in h ^-1 .

The terms "comprising" and "includes" as used herein are synonymous with "including", "includes" or "contains", "containing", and are inclusive or unlimited and do not exclude additional features, unspecified elements or method steps.

The specification of a number domain without decimal places includes all whole numbers and, where appropriate, fractions thereof (for example, 1 to 5 may include 1, 2, 3, 4 and 5 when reference is made to a number of elements, and may also include 1.5, 2, 2.75 and 3.80, when reference is made to, for example, a measurement.). Specifying a decimal place also includes the decimal place itself (for example, "from 1.0 to 5.0" includes 1.0 and 5.0). Any range of numerical values recited herein also includes any subrange of numerical values mentioned above.

The expressions % by weight (also noted as %pds) and % by mass (also noted as %m) have an equivalent meaning and refer to the proportion of the mass of a product compared to 100g of a composition comprising it.

Unless otherwise stated, measurements given in parts per million (ppm) are expressed as mass.

By “heteroatom”, we mean any elements of an organic compound other than carbon and hydrogen.

The expression "polar solvent" within the meaning of this patent application covers all chemical species, alone or in a mixture comprising at least one carbon-hydrogen, carbon-halogen, carbon-chalcogen or carbon-nitrogen covalent bond and having a moment non-zero dipolar. It is understood that the term “polar solvent” within the meaning of this definition specifically excludes water.

The term “solvent” includes water, the aforementioned “polar solvents” and apolar solvents, which include for example any type of linear, branched, cyclic and/or aromatic saturated or unsaturated hydrocarbon such as pentane, cyclohexane, olefins, toluene or xylene or certain other solvents with zero or almost zero dipole moment such as tetrachloromethane or carbon disulfide.

The term "naphtha" refers to the general definition used in the oil and gas industry. In particular, it is a hydrocarbon coming from the distillation of crude oil and whose boiling point is between 15 and 250°C, according to the ASTM D2887 standard. Naphtha contains almost no olefins because the hydrocarbons come from crude oil. A naphtha is generally considered to have a carbon number between C5 and C11, although the carbon number can in some cases be as high as C15. It is also generally accepted that the density of naphtha is between 0.65 and 0.77 g/mL.

By “liquefaction oil”, we mean an oil resulting from a pyrolysis process and/or a hydrothermal liquefaction process of a hydrocarbon feedstock. This hydrocarbon filler may include plastics, biomass and/or elastomers, alone or in a mixture, particularly in the form of waste. A liquefaction oil can be formed from a mixture of two or more liquefaction oils originating from the liquefaction of different hydrocarbon feedstocks.

The pyrolysis process must be understood as a thermal cracking process, typically carried out at a temperature of 300 to 1000°C or 400 to 700°C, carried out in the presence or absence of a catalyst and/or a gas ( fast pyrolysis, flash pyrolysis, catalytic pyrolysis, hydropyrolysis, steam pyrolysis, etc.).

The hydrothermal liquefaction process (or HTL for “Hydrothermal Liquefaction” in English) is a thermochemical conversion process using water as a solvent, reagent and catalyst for degradation reactions of a hydrocarbon feedstock, water typically being in a subcritical or supercritical state. The hydrothermal liquefaction process is typically carried out at a temperature of 250 to 500 °C and at pressures of 10 to 25-40 MPa in the presence of water.

The term “plastic oil” or “plastic liquefaction oil” or “oil resulting from the liquefaction of plastic” or “plastic waste liquefaction oil” or “liquefaction oil resulting from the liquefaction of waste containing plastics” designates the hydrocarbon liquid products obtained following pyrolysis or hydrothermal liquefaction of thermoplastic and/or thermosetting polymers and/or elastomers, alone or in a mixture, and generally in the form of waste, optionally in a mixture with at least one other filler, in particular in the form of waste, such as biomass, for example chosen from lignocellulosic biomass, paper and cardboard, and/or an elastomer, for example optionally vulcanized latex or tires.

Plastic can be of any type, including any type of new or used plastic, included in household (post-consumer) or industrial waste. By plastics we mean materials made up of polymers and optionally auxiliary components such as plasticizers, fillers, dyes, catalysts, flame retardants, stabilizers, etc. For example, these polymers can be polyethylene, halogenated polyethylene (Cl, F ), polypropylene, polystyrene, polybutadiene, polyisoprene, poly(ethylene terephthalate) (PET), acrylonitrile-butadiene-styrene (ABS), polybutylene, poly(butylene terephthalate) (PBT) , polyvinyl chloride (PVC), polyvinylidene chloride, polyester, polyamide, polycarbonate, polyether, epoxy polymer, polyacetal, polyimide, polyesteramide, silicone etc. In general, any polymer or mixture of polymers capable of producing hydrocarbons by liquefaction can be used.

Biomass can be defined as an organic plant or animal product. Biomass thus includes (i) biomass produced by surplus agricultural land, not used for human or animal food: dedicated crops, called energy crops; (ii) biomass produced by deforestation (forest maintenance) or cleaning of agricultural land; (iii) agricultural residues from cereal crops, vines, orchards, olive trees, fruits and vegetables, agri-food residues, etc.; (iv) forest residues from silviculture and wood processing; (v) agricultural residues from livestock (manure, slurry, litter, droppings, etc.); (vi) organic household waste (paper, cardboard, green waste, etc.); (vii) ordinary industrial organic waste (paper, cardboard, wood, putrescible waste, etc.). The plastic liquefaction oil treated by the invention can come from the liquefaction of waste containing at least 1%m, optionally from 1 to 50%m, from 2 to 30%m or in an interval defined by any two of these limits, of one or more of the aforementioned biomasses, residues and organic waste, and the remainder consisting of plastic waste, optionally mixed with elastomers, in particular in the form of waste.

Elastomers are linear or branched polymers transformed by vulcanization into an infusible and insoluble, weakly crosslinked three-dimensional network. They include natural or synthetic rubbers. They may be part of tire-type waste or any other household or industrial waste containing elastomers, natural and/or synthetic rubber, mixed or not with other components, such as plastics, plasticizers, fillers, vulcanizing agent, vulcanization accelerators, additives, etc. Examples of elastomeric polymers include ethylene-propylene copolymers, ethylene-propylene-diene terpolymer (EPDM), polyisoprene (natural or synthetic), polybutadiene, styrene-butadiene copolymers, isobutene-based polymers, copolymers of isobutylene isoprene, chlorinated or brominated, butadiene acrylonitrile copolymers (NBR), and polychloroprenes (CR), polyurethanes, silicone elastomers, etc. The plastic liquefaction oil treated by the invention can come from the liquefaction of waste containing at least 1%m, optionally from 1 to 50%m, from 2 to 30%m or in an interval defined by any two of these limits, of one or more aforementioned elastomers, in particular in the form of waste, the remainder consisting of plastic waste, optionally mixed with biomass, residues and organic waste.

The term “Bromine Index” is the number of milligrams of bromine that react with 100 g of sample and can be measured according to the ASTM D2710 or ASTM D5776 methods.

Boiling points as mentioned here are measured at atmospheric pressure unless otherwise noted. An initial boiling point is defined as the temperature value at which a first vapor bubble is formed. A final boiling point is the highest temperature achievable during distillation. At this temperature, no more vapor can be transported to a condenser. The determination of the initial and final points uses techniques known in the trade and several methods adapted depending on the range of distillation temperatures are applicable, for example NF EN 15199-1 (version 2020) or ASTM D2887 for measuring the points d boiling of petroleum fractions by gas chromatography, ASTM D7169 for heavy hydrocarbons, ASTM D7500, D86 or D1160 for distillates.

The concentration of metals in hydrocarbon matrices can be determined by any known method. Acceptable methods include X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), and inductively coupled plasma atomic emission spectrometry (ICP-AES). Specialists in analytical sciences know how to identify the most suitable method for measuring each metal and generally each heteroelement depending on the hydrocarbon matrix considered. The oxygen content can be measured according to the standard: ASTM D5622-17 / D2504-88 (2015). The nitrogen content can be measured according to the standard: ASTM D4629-17. The sulfur content can be measured according to the ISO 20846:2011 standard. The halogen content, in particular chlorine, bromine, fluorine, can be measured according to the standard: ASTM D7359-18.

By “hydrotreatment” we mean any process during which hydrocarbons react with dihydrogen, typically under pressure, in the presence of a catalyst or not. The hydrotreatment can thus comprise one or more reactions chosen from hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodeoxygenation (HDO), hydrodemetallation (HCM), hydrocracking, hydroisomerization and hydrogenation (hydrogenation of unsaturated compounds into saturated compounds).

By “hydrotreatment catalyst”, we mean a catalyst promoting the incorporation of hydrogen into products. This type of catalyst is typically a metal catalyst comprising one or more metals from groups 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 and 14 of the periodic table.

The particular features, structures, properties, embodiments of the invention may be freely combined into one or more embodiments not specifically described herein, as may be apparent to those skilled in the processing of plastic liquefaction oils using their general knowledge.

Description of the composition comprising a plastic liquefaction oil

The plastic liquefaction oil may be a plastic pyrolysis oil, a hydrothermal plastic liquefaction oil or a mixture of the two, for example a plastic pyrolysis oil.

The composition provided in step (a) comprises a plastic liquefaction oil.

In a preferred embodiment, the composition may comprise only a plastic liquefaction oil.

Alternatively, the composition may include at least 1% m plastic liquefaction oil. The remainder can then be composed of at most 99% by mass of a diluent or solvent such as a hydrocarbon and/or one or more of the components listed below, preferably a component coming from biomass, biomass waste and/or elastomeric waste.

In one embodiment, the composition may comprise at least 5%m, preferably 10%m, more preferably at least 25%m, even more preferably at least 50%m, more preferably 75%m, even more preferably at least 90%m plastic liquefaction oil. The composition may comprise at most 80%m or 90%m or 95%m or 100%m of plastic liquefaction oil. The percentage by mass of plastic liquefaction oil(s) in the composition can be included in any interval defined by two of the limits previously set.

The composition may further comprise a component originating from biomass, biomass waste or elastomeric waste, such as tall oil, used food oil, animal fat, vegetable oil such as rapeseed oil, canola, castor, palm, soya, an oil extracted from an algae, an oil extracted from a fermentation of oleaginous microorganisms such as oleaginous yeasts, a biomass liquefaction oil, in particular a biomass liquefaction oil such as Panicum virgatum or a lignocellulosic biomass liquefaction oil, for example a wood, paper and/or cardboard liquefaction oil, an oil obtained by liquefaction of crushed used furniture, an elastomer liquefaction oil for example possibly vulcanized latex or tires, as well as their mixtures.

The composition may further include a component that is a diluent miscible with the plastic liquefaction oil. This diluent preferably has a diene number of not more than 0.5 g I2/100 g, measured according to UOP 326-17, a bromine number of not more than 5 g Br ₂ /100 g, measured according to ASTM D1159. The diluent is preferably chosen from a naphtha and/or a paraffinic solvent and/or a diesel or a direct distillation gas oil, containing at most 1% by mass of sulfur, preferably at most 0.1% by mass of sulfur, and/or a hydrocarbon stream having a boiling range between 50°C and 150°C or a boiling range between 150°C and 250°C or a boiling range between 200°C and 350°C , preferably having a bromine number of not more than 5 gBr ₂ /100g, and/or a diene number of not more than 0.5 gI ₂ /100g or any combination thereof.

The composition may have a bromine number of at most 150 g Br ₂ / 100g, preferably at most 100 g Br ₂ / 100g, even more preferably at most 80 g Br ₂ / 100g, the most preferred being not more than 50 g Br ₂ / 100g, as measured according to ASTM D1159.

The composition may have a heteroatom content of at least 20 ppm.

Plastic liquefaction oils contain paraffins, i-paraffins (iso-paraffins), dienes, alkynes, olefins, naphthenes and aromatics. Plastic liquefaction oils also contain impurities containing heteroatoms, such as chlorinated, oxygenated, sulfurous, nitrogenous and/or silylated organic compounds, metals, salts, phosphorus compounds.

The composition of the plastic liquefaction oil depends on the nature of the liquefied plastic, and optionally on any other waste liquefied with the plastic, and is essentially (in particular more than 80%m, most often more than 90% m) consisting of hydrocarbons having 1 to 150 carbon atoms and impurities.

A plastic liquefaction oil typically comprises 5 to 80% m of paraffins (including cyclo-paraffins), 10 to 95% m of unsaturated compounds (including olefins, dienes and acetylenes), 5 to 70 %m aromatics. These contents can be determined by gas chromatography.

In particular, a plastic liquefaction oil may include a Bromine number of 10 to 130 g Br ₂ /100g, as measured according to standard ASTM D1159, and/or a maleic anhydride index (UOP326-82) of 1 to 55 mg of maleic anhydride/1g.

In a preferred embodiment, said plastic liquefaction oil has an initial boiling point of at least 15°C, and a final boiling point of at most 800°C, preferably at most 600°C. °C, even more preferably at most 560°C, more preferably at most 450°C, even more preferably at most 350°C, preferably 250°C (measured according to standard NF EN 15199- 1/2).

A plastic liquefaction oil typically comprises at least 20 ppm of heteroatoms, or even at least 30 ppm of heteroatoms.

A plastic liquefaction oil may in particular comprise one or more of the following heteroatom contents: from 0 to 8% m of oxygen (measured according to the ASTM D5622 standard), from 1 to 13,000 ppm of nitrogen (measured according to the ASTM standard D4629), from 2 to 10000ppm of sulfur (measured according to ISO 20846), from 1 to 10000ppm of metals (measured by ICP), from 50 to 6000ppm of chlorine (measured according to ASTM D7359-18), from 0 to 200ppm bromine (measured according to ASTM D7359-18), 1 to 40ppm fluorine (measured according to ASTM D7359-18), 1 to 2000 ppm silicon (measured by XRF).

Optional preprocessing step

The invention may comprise an optional step prior to step (a) of contacting, in which said composition is subjected, in particular immediately before step (a), to (i) filtration, (ii) washing with water or a polar solvent immiscible with the composition, (iii) distillation, (iv) decantation, or (v) the combination of two, three or four of steps (i) to (iv). This preliminary step can make it possible to remove some of the impurities contained in the composition such as oxygen, nitrogen, chlorine, sulfur or other heteroatoms. In particular, reducing the quantity of oxygen can help avoid the formation of solids and/or gels during step (b).

The washing step (ii) makes it possible to recover a phase containing the washed composition and a phase containing the water or the immiscible solvent used for washing. In other words, at the exit of the washing step (ii), these phases are recovered separately, for example following a liquid/liquid separation (centrifugation and/or decantation and/or other) carried out at the end of the washing step. .

The washing step (ii) can possibly be repeated one or several times.

During the additional prior washing step (ii), the polar solvent/composition or water/composition volume ratio can be from 10/90 to 90/10, from 20/80 to 80/20, from 30/70 to 70/30, from 35/65 to 65/35, from 35/65 to 60/40, from 40/60 to 60/40.

When water is used for washing (ii), it can have an acidic, basic or neutral pH. An acidic pH can be obtained by adding one or more organic or inorganic acids. Examples of usable organic acids include citric acid (C ₆ H ₈ O ₇ ), formic acid (CH₂O₂), acetic acid (CH₃COOH). Examples of inorganic acids are sulfamic acid (H ₃ NSO ₃ ), hydrochloric acid (HCl), nitric acid (HNO ₃ ), sulfuric acid (H ₂ SO ₄ ), phosphoric acid ( H ₃ PO ₄ ). A basic pH can be obtained by the addition of alkali and alkaline earth metal oxides, alkali and alkaline earth metal hydroxides (e.g. NaOH, KOH, Ca(OH) ₂ ), alkali and alkaline metal bicarbonates -earth and amines (e.g. triethylamine, ethylenediamine, ammonia).

The polar solvent used for washing (ii) may have a density greater or less than the density of the composition comprising a plastic oil. In particular, the density of the polar solvent can be 3 to 50% higher or lower than that of the composition.

The polar solvent is an immiscible solvent in the composition comprising a plastic liquefaction oil to be purified.

In the present invention, it can be considered that the polar solvent (or a mixture of polar solvents where appropriate) is immiscible when its recovery rate is greater than or equal to 0.95. This recovery rate is defined as the ratio of the volume of extract to the volume of initial solvent, this extract being a phase containing the solvent, immiscible with the composition containing a plastic liquefaction oil, recovered after stirring then decantation of a mixture of one part by volume of solvent with twenty-five parts by volume of the composition containing a plastic liquefaction oil to be purified, at atmospheric pressure and a temperature of 20°C.

• Introduction de 50 mL de composition contenant une huile de pyrolyse dans un ballon à fond plat d’un volume de 100mL, à l’aide d’une pipette de précision de +/-0,5mL,
• Introduire 2 mL de solvant dans le ballon, à l’aide d’une pipette de précision +/-0,1mL,
• Introduire un barreau aimanté, fermer le ballon avec un bouchon en polypropylène,
• Agiter le mélange sur une plaque d’agitation mécanique à une vitesse 500 tours/min pendant 5min,
• A la fin des 5 minutes, arrêter l’agitation, retirer le barreau aimanté à l’aide d’une tige aimantée,
• Transférer le contenu du ballon dans un tube gradué présentant une précision de +/-0,05 mL pour un volume inférieur ou égal à 2mL et une précision de +/-0,1 mL pour un volume supérieur à 2mL. Attendre la démixtion complète par décantation et mesurer le volume des 2 phases à l’aide des graduations. On considère que la démixtion complète est atteinte lorsque les volumes des deux phases ne varient plus.

In particular, this recovery rate can be determined by following the following procedure:

• Introduction of 50 mL of composition containing a pyrolysis oil into a flat-bottom flask with a volume of 100 mL, using a precision pipette of +/-0.5 mL,
• Introduce 2 mL of solvent into the flask, using a precision pipette +/-0.1 mL,
• Insert a magnetic bar, close the balloon with a polypropylene cap,
• Stir the mixture on a mechanical stirring plate at a speed of 500 rpm for 5 min,
• At the end of 5 minutes, stop stirring, remove the magnetic bar using a magnetic rod,
• Transfer the contents of the flask into a graduated tube with an accuracy of +/-0.05 mL for a volume less than or equal to 2mL and an accuracy of +/-0.1 mL for a volume greater than 2mL. Wait for complete separation by decantation and measure the volume of the 2 phases using the graduations. We consider that complete demixing is reached when the volumes of the two phases no longer vary.

Acceptable polar solvents, immiscible with the composition comprising a plastic liquefaction oil to be purified, include (i) sulfur compounds, for example dimethyl sulfoxide, (ii) nitrogen compounds, for example N,N-dimethylformamide, (iii) ) halogenated compounds, for example dichloromethane or chloroform, (iv) ethylene glycol, or:

- glycol ethers, including in particular polyethylene glycol of chemical formula HO-(CH ₂ -CH ₂ -O) _n -H with a mass average molar mass of 90 to 800g/mol, for example diethylene glycol and tetraethylene glycol , polypropylene glycol of chemical formula H[OCH(CH ₃ )CH ₂ ] _n OH with a mass average molar mass of 130 to 800 g/mol, for example dipropylene glycol and tetrapropylene glycol,

- dialkyl formamides, in which the alkyl group can comprise from 1 to 8 or from 1 to 3 carbon atoms, in particular dimethyl formamide (DMF),

- dialkyl sulfoxides, in which the alkyl group can comprise from 1 to 8 or from 1 to 3 carbon atoms, in particular dimethyl sulfoxide (DMSO) and sulfolane

- compounds comprising a furan ring,

- cyclic carbonate esters, comprising in particular from 3 to 8 or from 3 to 4 carbon atoms, in particular propylene carbonate and ethylene carbonate.

One or more of the aforementioned solvents may be used. However, advantageously, only one of the aforementioned solvents can be used provided that it is immiscible with the composition containing a plastic oil, to be purified.

Preferably, the polar solvent may be ethylene glycol or a glycol ether, in particular polyethylene glycol of chemical formula HO-(CH ₂ -CH ₂ -O) _n -H with a mass average molar mass of 90 to 800g /mol or polypropylene glycol of chemical formula H[OCH(CH ₃ )CH ₂ ] _n OH with a mass average molar mass of 130 to 800g/mol, or a compound comprising a furan ring, or a cyclic carbonate ester, in particularly propylene or ethylene carbonate, alone or in a mixture, preferably alone.

In a preferred embodiment, the polar solvent is chosen from propylene carbonate, ethylene carbonate, ethylene glycol and polyethylene glycol of chemical formula HO-(CH ₂ -CH ₂ -O) _n -H of mass average molar mass of 90 to 800g/mol, alone or in a mixture, preferably alone.

Step (a) of contact

During step (a), the composition is brought into contact with an aqueous solution of a strong base comprising an alkali or alkaline earth metal cation. Advantageously, the strong base added in step (a) is in solution in water. In particular, step (a) can be carried out without adding any solvent other than water or a solvent possibly already present in the composition.

This step makes it possible to modify the impurities contained in the composition allowing their subsequent separation from the composition. In particular, step (a) is carried out under conditions which do not cause conversion of the composition to be treated.

The strong base content of the aqueous solution is 10% to 50%m, preferably 30% to 50%m, more preferably 40 to 50%m, even more preferably the aqueous solution is saturated with strong base, in particular the aqueous solution contains just a sufficient quantity of strong base to obtain a saturated solution.

Those skilled in the art will choose a sufficient quantity of water to dissolve/solubilize the strong base, preferably the lowest possible quantity of water, or just sufficient to saturate the water with the strong base.

During step (a), the composition is typically brought into contact with 0.1 to 50% by mass of a strong base relative to the mass of the treated composition.

Advantageously, during step (a), the composition can be brought into contact with 0.1 to 15% by weight of a strong base, more preferably with 1 to 15% by weight of a strong base, of still preferably with 2 to 10% by weight of a strong base (% relative to the weight of the treated composition).

In step (a), the volume ratio of the aqueous solution/composition, e.g. the volume ratio of the mixture (strong base + water)/composition may be from 0.1/99.9 to 80/20, from 1/99 to 80/20, from 1/99 to 70/30, from 1 /99 to 65/35, from 1/99 to 60/40, from 1/99 to 50/50, or in any interval defined by any two of the aforementioned limits.

The contacting takes place for a period of 1 to 60 minutes, advantageously for a period of 1 to 30 minutes, preferably for a period of 1 minute to 20 minutes, more preferably from 1 minute to 16 minutes. Note that the contact time can be greater than 60 minutes or 1 hour but does not improve the quality of the products obtained.

Whatever the duration of contacting, this is carried out at a temperature of at most 250°C, for example at a temperature of 50 to 250°C, preferably of 90 to 225°C, more than preferably from 120 to 200°C, more preferably from 120 to 190°C, even more preferably from 140 to 190°C or from 140 to 180°C, or in any range defined by any two of the aforementioned values.

Whatever the duration of contacting and the temperature, contacting can be carried out at an absolute pressure of 0.1 to 100 bars, preferably of 1 to 50 bars.

In a particularly preferred embodiment, the contacting is carried out for a period of 1 minute to 60 minutes, preferably 1 minute to 30 minutes, at a temperature of at most 225°C, preferably at more than 200°C, more preferably not more than 190°C, more preferably not more than 180°C. In this particularly preferred embodiment, contacting can be carried out at a temperature of at least 50°C, preferably at least 90°C, more preferably at least 140°C. In this particularly preferred embodiment, the contacting can be carried out at an absolute pressure of 0.1 to 100 bars, preferably of 1 to 50 bars.

In this particularly preferred embodiment, the composition can advantageously be brought into contact with an aqueous solution containing from 10% to 50%m, preferably from 30% to 50%m, more preferably from 40 to 50%m (percentages masses of strong base relative to water), even more preferably with water saturated with strong base.

In this particularly preferred embodiment, during the contacting step, the composition can be brought into contact with 0.1 to 15% by mass of the strong base comprising an alkali or alkaline earth metal cation, of preferably with 1 to 15% by weight of the strong base, more preferably with 2 to 10% by weight of the strong base (weight percentages of strong base relative to the treated composition).

Whatever the embodiment, a preferred strong base can be chosen from LiOH, NaOH, CsOH, Ba(OH) ₂ , Na ₂ O, KOH, K ₂ O, CaO, Ca(OH) ₂ , MgO, Mg( OH) ₂ and their mixtures. A more preferred strong base can be chosen from NaOH, KOH and mixtures thereof, in particular for the implementation of the particularly preferred embodiment.

At the output of step (a), the composition is thus modified because the impurities (the compounds containing heteroatoms) have been modified by the treatment of step (a). The modified composition obtained at the output of step (b) makes it possible to subsequently obtain a purified composition comprising a reduced heteroatom content, as explained below.

Optional separation step

In one embodiment, the method according to the invention comprises, between step (a) and (b), a step of separation between the aqueous solution of a strong base comprising the alkali or alkaline earth metal cation and the modified composition resulting from bringing said composition into contact. The effluent resulting from contacting contains the modified composition and the aqueous solution of a strong base.

This separation can advantageously be carried out by (i) centrifugation, (ii) decantation, or (iii) by the combination of these two steps.

Typically, this separation step makes it possible to separate an organic phase, corresponding to the modified composition resulting from the contacting of step (a), and an aqueous phase containing the strong base comprising the alkali or alkaline earth metal cation. .

This separation can be preceded by a solids separation step by (i) filtration, (ii) centrifugation or (iii) a combination of the two steps. This solids separation step can facilitate the separation of the organic and subsequent aqueous phases by eliminating all or part of the solids present in the product resulting from step (a).

Also, advantageously, the aqueous solution of a strong base separated during this separation step can be returned (recycled), partially or entirely, in step (a).

Step (b) of washing with a solvent immiscible with the modified composition not containing water

Step (b) can be implemented on the effluent directly from step (a) (comprising the aqueous solution of a strong base and the modified composition resulting from bringing the composition into contact), without intermediate step, or on the modified composition resulting from step (a) having undergone the optional separation step.

Step (b) makes it possible to recover a phase corresponding to the purified composition having a reduced heteroatom content, and at least one other phase containing the aqueous solution, the solvent other than immiscible water used for washing, the base strong and impurities. In other words, at the exit of washing step (b), these phases are recovered separately, for example following a liquid/liquid separation (centrifugation and/or decantation and/or other) carried out at the end of the washing step. .

This step (b) makes it possible to eliminate the impurities containing heteroatoms present in the effluent containing the modified composition leaving step (b) by solubilizing them in a solvent (an organic solvent).

The solvent other than immiscible water may be any organic solvent immiscible with the modified composition, in particular in which the impurities containing heteroatoms are soluble. A solvent other than immiscible water that can be used is for example a polar solvent, in particular a polar solvent belonging to those described in the optional pre-treatment step.

Step (b) can be carried out at a temperature of 0°C to 250°C, 0°C to 200°C or 0°C to 80°C, for example 0°C to 60°C, preferably from 0°C to 40°C, more preferably from 0°C to 30°C, in particular without external heating. In particular, washing can be carried out on the effluent directly from step (a) without prior cooling thereof. Step (b) is then carried out at the temperature of the effluent as it leaves step (a). Step (b) is typically carried out at atmospheric pressure but could also be carried out at low pressure.

During step (b), the solvent/effluent volume ratio, or solvent/modified composition, may be from 10/90 to 90/10, from 20/80 to 80/20, from 30/70 to 70/ 30, from 35/65 to 65/35, from 35/65 to 60/40, from 40/60 to 60/40, or in any interval defined by any two of the aforementioned limits.

Step (b) may include, or consist of, bringing the effluent or the modified composition resulting from step (a) into contact with a solvent by any means known in the prior art. This contact may be carried out once or several times. For example, contacting could be carried out once, twice, three, or even more times, preferably one to three times.

For example, the effluent (or the modified composition) from step (a) and the solvent can be introduced into tanks, reactors or mixers commonly used in the profession and the two components can be mixed. Contacting may include vigorous stirring of the two components by a mixing device. For example, the two components can be mixed together by stirring or shaking. Alternatively, contact can be made in an enclosure in which the two components circulate countercurrent. This contact may occur more than once, particularly under the conditions presented above.

Washing step (b), combined with the treatment of step (a), can make it possible to reduce at least 65%, preferably at least 80%, more preferably at least 85%, more preferably at least 85%. least 90%, or even at least 95% of the heteroatoms initially present. In particular, the silicon content of the purified composition may be less than 2ppm.

At the end of step (b) of washing, the immiscible solvent used can advantageously be recovered (separated for example following the liquid/liquid separation mentioned above), regenerated, i.e. purified, for example by distillation, adsorption or other, before being returned to step (b) to be used again. The use of an immiscible solvent other than water can further facilitate the regeneration of the solvent for reuse in the process and thereby reduce process costs.

Optional hydrotreatment step (c)

The invention may also include an additional step in which:

(vs). the purified composition resulting from the washing of step (b) undergoes catalytic hydrotreatment in one or two steps.

In the case where step (c) is carried out in a single step, the purified composition of step (b) can be hydrotreated at a temperature of 200 to 450°C, preferably of 200 to 340°C in presence of hydrogen at an absolute pressure of 20 to 140 bars, preferably 30 to 100 bars and in the presence of a hydrotreatment catalyst. The hydrotreatment catalyst is for example a catalyst of the NiMo (0.1-60% by mass) and/or CoMo (0.1-60% by mass) type generally on a support.

In the case where the catalytic hydrotreatment is carried out in two stages, step (c) can be carried out in a first step (c-1) in which the purified composition of step (b) is hydrotreated at a temperature of 80 to 250°C, preferably of 130 to 250°C in the presence of hydrogen at an absolute pressure of 5 to 60 bars, preferably of 20 to 45 bars and in the presence of a first hydrotreatment catalyst , and in a second step (c-2) in which the effluent from step (c-1) is hydrotreated at a temperature of 200 to 450°C, preferably of 250 to 340°C in the presence of hydrogen at an absolute pressure of 20 to 140 bars, preferably 30 to 100 bars and in the presence of a second hydrotreatment catalyst. The first step can then make it possible to hydrogenate dienes initially present in the composition.

The first hydrotreatment catalyst is preferably a hydrogenation catalyst, for example a hydrogenation catalyst comprising Pd (0.1-10% by mass) and/or Ni (0.1-60% by mass) and/or NiMo (0.1-60% by mass). The second hydrotreatment catalyst is preferably a catalyst of the NiMo (0.1-60% by mass) and/or CoMo (0.1-60% by mass) type.

This step (c) can be carried out in a single reactor with several catalytic beds placed in series with possibly additional hydrogen between the beds or in several reactors in series depending on the desired objective.

This hydrotreatment step can also have a demetallation, cracking and dearomatization function depending on the characteristics of the catalyst and the hydrotreatment conditions.

Preferably, the purified composition obtained after step (b) is sent to the hydrotreatment step without being cooled and/or depressurized at the temperature and pressure at the outlet of step (b). The feed for the hydrotreatment, containing at least a part of the purified composition can be advantageously heated by a heat exchanger which is supplied by the effluent of the hydrotreatment (given that the hydrotreatment is exothermic, the effluent of hydrotreating will have a higher temperature than the feed entering the hydrotreating).

Preferably, the feed for the hydrotreatment, containing at least part of the purified composition, can be diluted with part of the hydrotreatment effluent, still having a temperature higher than the desired temperature at the inlet of the hydrotreatment. hydrotreatment. This at least partial recycling of the hydrotreatment effluent makes it possible to dilute the unsaturates present in the purified composition and to preheat the charge.

Preferably, the part of the hydrotreatment effluent which is not recycled but still at a high temperature, can exchange its sensible heat with the composition comprising a plastic liquefaction oil and thus ensure the preheating of this entering composition. in step (a).

Optional purification step (d)

The product from step (b) or the effluent from step (c) can be (d) purified by passing over a solid adsorbent in order to reduce the content of at least one element among F, Cl, Br , I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or water content.

The adsorbent can be operated in regenerative or non-regenerative mode, at a temperature below 400°C, preferably below 100°C, more preferably below 60°C, chosen from: (i) a silica gel, ( ii) a clay, (iii) a crushed clay, (iv) apatite, (v) hydroxyapatite and their combinations, (vi) an alumina for example an alumina obtained by precipitation of boehmite, a calcined alumina such as Ceralox ® from Sasol, (vii) boehmite, (viii) bayerite, (ix) hydrotalcite, (x) a spinel such as Pural ® or Puralox from Sasol, (xi) a promoted alumina, for example example Selexsorb ® from BASF, an acid-promoted alumina, an alumina promoted by a zeolite and/or by a metal such as Ni, Co, Mo or a combination of at least two of them, (xii) a clay treated with an acid such as Tonsil ® from Clariant, (xiii) a molecular sieve in the form of an aluminosilicate containing an alkaline or alkaline earth cation, for example sieves 3A, 4A, 5A, 13X, for example sold under the brand Siliporite ® of Ceca, (xiv) a zeolite, (xv) an activated carbon, or the combination of at least two adsorbents, the adsorbent or the at least two adsorbents retaining at least 20% by mass, preferably at least 50% by mass of at least one element among F, Cl, Br, I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or water.

According to a preferred embodiment, the adsorbent is regenerable, has a specific surface area of at least 200 m²/g and is operated in a fixed bed reactor at less than 100°C with a VVH of 0.1 to 10 h ^-1 .

Use of the purified composition

The purified composition leaving step (b) or the effluent leaving step (c) of hydrotreatment optionally washed with water and or purified by passing over a solid adsorbent, can be fractionated into usable flows including cutting points are typically chosen based on subsequent processing. This fractionation is carried out according to distillation temperature ranges, for example to separate flows such as LPG, gasoline, diesel, heavy fuel oil, kerosene, which can then be treated in a steam cracker and/or in a catalytic cracker and/or in a hydrocracker (then possibly in a steam cracker) and/or in a hydrotreatment reactor and/or in a gasification reactor and/or used as such for the preparation of fuels, combustibles, lubricants or base oils. Those skilled in the art know how to select the cuts most suited to subsequent processing units depending on the desired objective.

The purified composition of step (b) or the purified and hydrotreated composition of step (c) can also be used diluted, for example mixed with naphtha, diesel or crude oil in order to obtain a concentration of purified plastic liquefaction oil ranging from 0.01%m by mass at most; preferably from 0.1% m to 25% m, even more preferably from 1% m to 20% m at the entrance to the following treatment.

Detailed description of the optional steam cracking step ( f )

Steam cracking step (f) can be carried out on the purified composition of step (b) with or without dilution with a conventional steam cracking feed, or on the purified hydrotreated composition of step (c) with or without dilution. Prior to this step (f), a separation step by distillation can be implemented depending on the technology of the steam cracking furnaces.

This step (f) makes it possible to produce olefins such as ethylene and propylene and aromatics. Ethylene and propylene can then advantageously be converted into polyethylene and polypropylene respectively in a polymerization section.

Steam cracking step (f) consists of thermally cracking in one or more ovens a mixture of the purified composition and/or the purified and hydrotreated composition and water vapor at high temperatures of the order of 650 to 1200° C, preferably from 700 to 900°C, typically from 750 to 850°C, under low pressures (1 to 3 bars). The cracking reaction is carried out in the absence of oxygen. The reaction time is usually very short, of the order of a few hundred milliseconds. These conditions make it possible to break the carbon-carbon bonds and produce unsaturated hydrocarbons with molecules smaller than the charge introduced into the reactor(s). The effluents leaving the reactor(s) are then cooled quickly to temperatures of 400 to 550°C in order to limit secondary reactions such as polymerization of olefins, dienes and acetylenes. The cooled effluents are finally fractionated to recover light C2-C5 olefins, such as ethylene, propylene, butadiene, isobutene, n -butene and isoprene.

The purified composition of step (b) or the purified and hydrotreated composition of step (c) can be sent to the steam cracker without dilution. The purified composition of step (b) or the purified and hydrotreated composition of step (c) can also be mixed with naphtha, diesel or another cut of crude oil in order to obtain an oil concentration of purified plastic liquefaction ranging from 0.01%m to 50%m maximum; preferably from 0.1% m to 25% m, even more preferably from 1% m to 20% m at the entrance to the steam cracker. The purified composition is then converted into olefins, such as ethylene and propylene, as well as aromatics.

In a preferred embodiment, the purified composition, or purified and hydrotreated, can be sent at least partially directly into a steam cracker without any other dilution than the steam used for steam cracking, and preferably as the only flow sent at least partially into the steam cracker , to produce olefins, such as ethylene and propylene, and aromatics.

The steam cracker is known per se in the art. The feedstock of the steam cracker, in addition to the flow obtained by the inventive process, can be ethane, liquefied petroleum gas, naphtha or gas oils. Liquefied petroleum gas (LPG) is essentially made up of propane and butanes. Gas oils have a boiling range of approximately 200 to 350°C, and consist of C10 to C22 hydrocarbons, including predominantly linear and branched paraffins, cyclic paraffins and aromatics (including mono-, naphtho- and poly-aromatics).

In particular, the cracking products obtained at the outlet of the steam cracker may include ethylene, propylene and benzene, and optionally hydrogen, toluene, xylenes and 1,3-butadiene.

In a preferred embodiment, the outlet temperature of the steam cracker can be between 800 and 1200°C, preferably between 820 and 1100°C, more preferably between 830 and 950°C, more preferably between 840 and 920°C. The outlet temperature can influence the content of high-value chemicals in the cracked products obtained by the present process.

In a preferred embodiment, the residence time in the steam cracker, through the radiation section of the reactor where the temperature is between 650 and 1200°C, can be between 0.005 and 0.5 seconds, preferably between 0 .01 and 0.4 seconds.

In a preferred embodiment, steam cracking is carried out in the presence of water vapor in a ratio of 0.1 to 1.0 kg of steam per kg of hydrocarbon feed, preferably 0.25 to 0.7 kg of steam per kg of hydrocarbon feed in the steam cracker, preferably in a ratio of 0.35 kg of steam per kg of feed mixture, to obtain cracking products as defined above.

In a preferred embodiment, the reactor outlet pressure may be between 500 and 1500 mbar, preferably between 700 and 1000 mbar, more preferably around 850 mbar. The residence time of the charge in the reactor and the temperature must be considered together. Lower operating pressure facilitates the formation of light olefins and reduces the formation of coke. The lowest possible pressure is achieved by (i) maintaining the reactor outlet pressure as close as possible to atmospheric pressure at the cracked gas compressor suction (ii) reducing the hydrocarbon pressure by dilution with steam (which has a substantial influence on slowing down coke formation). The steam/raw material ratio can be maintained at a sufficient level to limit coke formation.

To the extent that the purified and/or purified and hydrotreated composition has a wide distribution in terms of carbon number (or boiling points), the vaporization of such a charge may be incomplete at the entrance to the reactors at the temperature where certain hydrocarbon molecules begin to decompose, the purified and/or purified and hydrotreated composition can then be preheated to a temperature at least 10°C below the decomposition temperature, then subjected to separation of the hydrocarbon vapors produced and residual hydrocarbon liquid in a flash container. In this flash container the liquid comes out from the bottom by gravity and the hydrocarbon vapors from the top. Optionally, the hydrocarbon liquid can be returned to the plastics liquefaction unit or to the optional hydrocracking stage.

Detailed description of the step (h) optional hydrocracking

Prior to steam cracking step (f), the purified composition of step (b), or advantageously the hydrotreated effluent from step (c) or the purified effluent, can be subjected to a cracking reaction in order to reduce the length of the carbon chains of the paraffins present in the feed, particularly in the hydrotreated effluent.

Typically, this cracking reaction is a hydrocracking reaction carried out at a temperature of 250 to 480°C, a partial pressure of hydrogen of 1.5 to 25 MPa abs. and an hourly volume velocity of 0.1 to 10h ^-1 .

A usable hydrocracking catalyst comprises for example 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 the group VIB chosen from chromium, molybdenum and tungsten, alone or in a mixture, and/or at least one metal from Group VIII chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum.

In one embodiment, the hydrocracking step can be carried out by adding a hydrocracking catalyst bed downstream of the last hydrotreating catalyst bed of the hydrotreating section.

Description of the invention Examples

The embodiments of the present invention are illustrated by the following non-limiting examples.

Ex e simple 1 : Purification of a plastic pyrolysis oil in the presence of a strong base

An HPP plastic pyrolysis oil was subjected to various washings after treatment in a concentrated soda solution. The soda treatment was carried out by bringing the oil into contact for 30 minutes at 200°C with an aqueous soda solution containing 50% m NaOH, the soda concentration relative to the oil being 3%. mr.

The oil thus treated with soda was separated into several samples subjected to different washings under the following conditions:

a) A triple wash with millipore water (mixture/water mass ratio: 60/40),

b) A triple wash with acidic water, pH=1 (mixture/water mass ratio: 60/40),

c) A simple wash with millipore water (mixture/water mass ratio: 60/40),

d) A simple wash with acidic water, pH=1 (mixture/water mass ratio: 60/40),

e) A triple wash with an organic solvent: ethylene glycol (mixture/solvent mass ratio: 60/40).

Each oil sample, after washing, is analyzed to measure the heteroatom contents (chlorine, silicon, nitrogen and oxygen). Knowing the initial concentration of impurities, the reductions in each of the elements mentioned are then calculated. The results are collected in Table 1. They show the effectiveness of the organic solvent in removing impurities containing chlorine, nitrogen and oxygen.

Essay Oxygen Nitrogen Chlorine Sodium Essay Content (%m) Reduction (%) ppm content Reduction (%) ppm content Reduction (%) ppm content HPP 1.56 1804 457 8.9 has) 0.21 87 166 91 37 92 <2 b) 0.21 87 106 94 3 92 6.2 vs) 0.22 86 195 89 37 92 6.9 d) 0.22 86 193 89 35 92 6.9 e) 0.13 92 109 94 31 93 <2

Ex e simple 2 : Two-step hydrotreatment and steam cracking of the product of Example 1

One of the pyrolysis oils from Example 1 (test e) can be hydrotreated in two stages according to the following procedure:

The purified and washed pyrolysis oil can be introduced into a first hydrotreatment section (HDT1) essentially to hydrogenate the diolefins and is operated in the liquid phase. This step may include a plurality of reactors in series and/or parallel if guard reactors are used upstream or downstream of the first hydrogenation reactor. These guard reactors can reduce the concentration of certain undesirable chemical species and/or elements such as chlorine, silicon and metals. Particularly undesirable metals include Na, Ca, Mg, Fe and Hg.

A second hydrotreatment section (HDT2) is dedicated to the hydrogenation of olefins and demetallation (HDM), desulfurization (HDS), denitrogenation (HDN) and deoxygenation (HDO). These two sections consist of one or more reactors operated in series, or in parallel, or both. Isolated, lead-lag, series and/or parallel guard reactors can be considered depending on the nature and quantity of the contaminant in the flow to be treated.

In the event that the treatment according to the invention does not make it possible to obtain a sufficient reduction in impurities, guard reactors to eliminate chlorine, metals and silicon can be added. Silicon can also be trapped on the upper bed of a reactor in the HDT2 section or separately, upstream.

Chlorine and mercury can be separated by guard reactors in liquid or gas phase.

As the hydrotreating reactions in sections HDT1 and HDT2 are exothermic, quenching with cold hydrogen or dilution with an inert filler can be used to moderate the temperature increase and control the reaction. Dilution with an inert charge can be carried out by recycling the liquid fraction leaving the reactors.

There may be intermediate quenches between the beds or between the HDT1 and HDT2 reactors or no quenching. In the latter case, recycling of part of the flow leaving the HDT1 or HDT2 must be carried out to control the temperature. Strict control of the temperature in HDT1 must be carried out, in order to avoid blockage of the reactor and deterioration of the catalytic hydrogenation conditions.

The operating pressure in each of the HDT1 and HDT2 hydrotreatments is 5-140 bars, preferably 20-45 bars for HDT1 and 20-140 bars, preferably 30-100 bars for HDT2, typically 30-45 bars for HDT2.

Typical temperature range at the HDT1 inlet at the start of the cycle (SOR: start of run): 150-250°C. The catalyst for HDT 1 usually comprises Pd (0.1-10 wt%) and/or Ni (0.1-60 wt%) and/or NiMo (0.1-60 wt%).

Typical temperature range at the HDT2 inlet at the start of the cycle (SOR: start of run): 200-340°C. Typical HDT2 outlet temperature range (SOR): 300-380°C, up to 450°C. The catalyst for HDT 2 usually includes a NiMo (any type of commercial catalyst for refining or petrochemical application), potentially a CoMo in the very last beds at the bottom of the reactor (any type of commercial catalyst for refining or petrochemical application).

The upper bed of HDT2 should preferably be operated with a NiMo having a hydrogenating capacity as well as a silicon trapping capacity. An upper bed of this type can be considered as an adsorbent as well as a metal trap also having HDN activity and hydrogenating capacity.

It is possible to have two separate beds in an HDT2 reactor, with quenching between the two beds or between the two reactors, if the two beds are in two separate reactors, or no quenching at all. Ideally, the intermediate quenching is carried out using cold HDT2 effluent or by adding cold hydrogen, that is to say at a temperature generally ranging from 15 to 30°C, in order to control the exotherm. of HDT2. Depending on the metals present in the liquefaction oil to be hydrotreated, a hydrodemetallation catalyst, for example commercial, can be added to the upper bed of the HDT2 section in order to protect the lower catalytic beds from deactivation.

Depending on the metals present in the pyrolysis oil to be hydrotreated, a hydrodemetallation catalyst, for example commercial, can be added to the upper bed of the HDT2 section in order to protect the lower catalytic beds from deactivation.

The hydrotreated pyrolysis oil leaving the HDT2 section, optionally after washing with water to remove inorganic compounds (hydrosulfide, hydrogen chloride, ammonia), can be used as is or fractionated according to temperature ranges of distillation, to feed a steam cracker, an FCC, a hydrocracker, a catalytic reformer or a pool of fuels such as LPG, gasoline, jet, diesel, fuel oil.

Alternatively, the treated pyrolysis oil leaving the HDT2 section undergoes an additional purification step by passing over a capture mass such as an adsorbent, for example of the type previously described, the adsorbent or the at least two adsorbents retaining at least 20% by mass, preferably at least 50% by mass of at least one element from F, Cl, Br, I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or water. Ideally, the adsorbent is regenerable, has a specific surface area of at least 200 m²/g and is operated in a fixed bed reactor at less than 100°C with a VVH of 0.1 at 10 h ^-1 .

In one embodiment, the hydrotreated oil is sent to a hydrocracker. This hydrocracking comprises, for example, bringing the hydrotreated effluent into contact with a hydrocracking catalyst, in the presence of H ₂ to produce an effluent meeting the specifications of a steam cracker in terms of final boiling point (<370°C ).

Claims (13)

Process for reducing the heteroatom concentration of a composition comprising a plastic liquefaction oil containing at least 20 ppm by weight of heteroatoms, comprising:
(a) bringing said composition into contact with an aqueous solution of a strong base comprising an alkali or alkaline earth metal cation, for 1 minute to 60 minutes at a temperature of at most 250°C, the aqueous solution containing 10 to 50% by mass of strong base or is a saturated solution of strong base, to obtain an effluent containing the modified composition and the aqueous solution,
(b) subjecting the effluent from step (a) to washing the product resulting from step (a) with a solvent other than water immiscible with the modified composition, and obtaining the purified composition having a content reduced in heteroatoms, and a phase enriched in heteroatoms. Process according to claim 1, comprising, between steps (a) and (b), a separation step between the aqueous solution and the modified composition resulting from step (a). Process according to claim 2, in which the separation step is carried out by (i) centrifugation, (ii) decantation, or (iii) by the combination of these two steps. Process according to claim 2 or 3, in which the aqueous solution separated during the separation step is returned, partially or entirely, to the contacting step (a). Method according to one of claims 2 to 4, in which the separation step is preceded by a step of separating the solids by (i) filtration, (ii) centrifugation or (iii) a combination of the two steps. Method according to any one of claims 1 to 5, in which the contacting step (a) comprises one or more of the following characteristics:
- the contacting takes place for a period of 1 minute to 60 minutes, preferably 1 minute to 30 minutes,
- the contacting is carried out at a temperature of 50 to 250°C, preferably of 90 to 225°C, more preferably of 120 to 200°C, more preferably of 120 to 190°C, even more preferably of 140 to 190°C,
- the contacting is carried out at an absolute pressure of 0.1 to 100 bars, preferably of 1 to 50 bars. Process according to any one of claims 1 to 6, in which the strong base is chosen from LiOH, NaOH, CsOH, Ba(OH) ₂ , Na ₂ O, KOH, K ₂ O, CaO, Ca(OH) ₂ , MgO, Mg(OH) ₂ and their mixtures. Process according to any one of claims 1 to 7, in which, prior to step (a), said composition is subjected to (i) filtration, (ii) washing with water or a polar solvent immiscible with the composition, (iii) distillation, (iv) decantation, or (v) the combination of two, three or four of steps (i) to (iv). A method according to any one of claims 1 to 8, wherein the solvent other than water used in step (b) is recovered, regenerated and returned to step (b). Method according to one of claims 1 to 9, in which:
(c) the purified composition resulting from the washing of step (b) undergoes catalytic hydrotreatment in one or two steps. Process according to claim 10, characterized in that the hydrotreatment of step (c):
- is carried out in a single step in which the purified composition of step (b) is hydrotreated at a temperature of 200 to 450°C, preferably from 200 to 340°C in the presence of hydrogen at an absolute pressure of 20 to 140 bars, preferably 30 to 100 bars and in the presence of a hydrotreatment catalyst, or
- is carried out in a first step (c-1) in which the purified composition of step (b) is hydrotreated at a temperature of 80 to 250°C, preferably 130 to 250°C in the presence of hydrogen at an absolute pressure of 5 to 60 bars, preferably 20 to 45 bars and in the presence of a first hydrotreatment catalyst, and in a second step (c-2) in which the effluent from step (c-1) is hydrotreated at a temperature of 200 to 450°C, preferably 250 to 340°C in the presence of hydrogen at an absolute pressure of 20 to 140 bars, preferably 30 to 100 bars and in the presence a second hydrotreatment catalyst. Process according to any one of claims 1 to 11, in which the purified composition resulting from step (b) or the effluent resulting from step (c) is (d) purified by passing over a solid adsorbent in order to reduce the content of at least one element among F, Cl, Br, I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or the water content. Process according to any one of claims 1 to 12, in which at least part of the purified composition resulting from step (b) or the effluent resulting from step (c) or (d) is:
(e) used as is or separated into usable streams for the preparation of fuels such as LPG, gasoline, diesel, heavy fuel oil, kerosene and/or for the preparation of lubricants and/or base oils,
and/or treated, pure or diluted, optionally separated into usable streams, in:
(f) a steam cracker to produce olefins, and/or
(g) a fluidized bed catalytic cracker, and/or
(h) a hydrocracker, then optionally in a steam cracker, and/or
(i) a hydrotreatment reactor, in particular a catalytic hydrogenation reactor, and/or a gasification reactor.