EP4284896A1

EP4284896A1 - Method for purifying a pyrolysis oil in order to upgrade it by steam-cracking

Info

Publication number: EP4284896A1
Application number: EP22704934.3A
Authority: EP
Inventors: Thomas COUSTHAM; Marfiza Victoria BERRIO NAVARRO; Hélène COULOMBEAU-LEROY; Sébastien Leplat; Quentin LESUEUR; Didrik HAUDEBOURG
Original assignee: TotalEnergies Onetech SAS
Current assignee: TotalEnergies Onetech SAS
Priority date: 2021-01-29
Filing date: 2022-01-24
Publication date: 2023-12-06
Also published as: KR20230135671A; US20240076558A1; WO2022162298A1

Abstract

The invention relates to a method for purifying a pyrolysis oil originating from the pyrolysis of waste including plastics by liquid/liquid extraction. This extraction is performed by means of a polar solvent that is immiscible with pyrolysis oil, for which a recovery rate is obtained greater than or equal to 0.95, this recovery rate being defined as the ratio of the extract volume over the initial volume of solvent, this extract being a phase containing the solvent which is immiscible with pyrolysis oil, recovered after agitation then decantation of a mixture of one part by volume of solvent with twenty-five parts by volume of pyrolysis oil at atmospheric pressure and at a temperature of 20°C.

Description

DESCRIPTION

TITLE: PROCESS FOR PURIFYING A PYROLYSIS OIL WITH A VIEW TO ITS VALORIZATION BY STEAM CRACKING

Field of invention

The invention relates to the recovery of oils from the pyrolysis of waste, in particular as feedstock for a steam cracking process. The process according to the invention makes it possible in particular to purify the pyrolysis oil resulting from plastic waste of all kinds, whatever their origin. This plastic waste may contain other types of waste in varying proportions, such as lignocellulosic biomass and/or elastomers.

Prior art

Pyrolysis is an endothermic decomposition in a reducing atmosphere (atmosphere devoid of oxygen or poor in oxygen or atmosphere of inert gases) under the effect of heat (from 300°C). This process allows the decomposition of solid organic matter into three phases: solid (pyrolysis coke or char), liquid (consisting of heavy condensables, pyrolysis oils or tars or light, H ₂ O) and gaseous (CO, H ₂ , CO ₂ , olefins and short paraffins). This solid organic material can include plastics, biomass, agricultural waste, household waste. With the increase in the volume of waste, pyrolysis makes it possible to consider recovering this waste by converting it into liquid products that can then be treated to produce products with high added value.

Liquid pyrolysis products, also called pyrolysis oils, can however have high levels of undesirable compounds, particularly for use in charge of a steam cracking treatment. These undesirable compounds (or contaminants) include heteroatoms, in particular oxygen, nitrogen, sulfur, but also halogens and transition metals. Other undesirable compounds include unsaturated hydrocarbon compounds, including aromatics and dienes.

Document WO2020/212315 describes a process for recovering aliphatic hydrocarbons from a liquid product of the pyrolysis of plastic waste, in particular a mixture of plastics. This liquid product is subjected to extraction with a solvent making it possible to obtain a raffinate with a reduced content of aromatic hydrocarbons and/or polar compounds by compared to the liquid product. These polar compounds are organic compounds containing heteroatoms (N, S, O) or salts which can comprise a cation, such as the ammonium cation, an alkali metal cation, an alkaline earth element cation, a cation of a transition metal, and an anion, such as a carboxylate, sulfate, phosphate or halide ion. The raffinate resulting from the liquid-liquid extraction then undergoes again an extraction with water in order to eliminate the solvent present in the raffinate, which is costly in terms of resources.

Document WO2020/178599A1 describes a method for recovering a pyrolysis oil from the pyrolysis of plastic or rubber, or a combination thereof. The pyrolysis oil is treated with an extraction solution comprising a polar organic solvent to provide a mixture comprising an extract and a raffinate. The raffinate obtained by this extraction process is a pyrolysis oil with a reduced content of undesirable compounds such as solid residues, olefins and compounds comprising heteroatoms (sulphur, nitrogen and halogen). Oxygenated compounds are considered desirable compounds. The upgrading solution may further comprise a hydrocarbon fluid (alkanes or alkenes, or a mixture of the two) to promote the separation of the raffinate and the extract.

These documents do not describe the treatment of pyrolysis oils from the pyrolysis of plastic waste mixed with other types of waste.

Summary of the invention

The aim of the invention is to propose a method for purifying a pyrolysis oil which makes it possible to significantly reduce the quantity of compounds comprising heteroatoms, and most particularly oxygen, nitrogen, sulfur, metals, in particular transition metals, and the halides initially contained in the pyrolysis oil. The invention can also make it possible to reduce the quantity of unsaturated hydrocarbon compounds initially contained in the pyrolysis oil, in particular aromatic compounds and diolefins.

A first object of the invention relates to a process for purifying a pyrolysis oil resulting from the pyrolysis of waste containing plastics, comprising the following steps:

- the supply of a pyrolysis oil containing saturated and unsaturated hydrocarbon compounds and polar compounds comprising at least one heteroatom selected from oxygen, sulfur, nitrogen, a transition metal, an alkali metal, an alkaline-earth metal, a halogen,

- bringing the pyrolysis oil into contact with a polar extraction solvent immiscible with the pyrolysis oil,

- the recovery of an extract and an immiscible raffinate, the extract containing the extraction solvent and at least a part of the polar compounds, and optionally at least a part of the unsaturated hydrocarbon compounds, initially contained in the oil pyrolysis oil, the raffinate containing a treated pyrolysis oil with a reduced content of polar compounds and optionally of unsaturated hydrocarbon compounds, in which the polar extraction solvent immiscible with the pyrolysis oil is a solvent for which a degree of recovery greater than or equal to 0.95, this recovery rate being defined as the ratio of the volume of an extract to the volume of initial solvent, and this extract is a phase containing the solvent, immiscible with the pyrolysis oil, recovered after stirring and then decantation of a mixture of one part by volume of solvent with twenty-five parts by volume of the pyrolysis oil at atmospheric pressure and at a temperature of 20°C.

The raffinate obtained by the process according to the invention is thus devoid or almost devoid of solvent so that it does not need to undergo another extraction step before use.

The process according to the invention makes it possible to extract at least 20% m/m, at least 30% m/m, or even at least 40% m/m or at least 50% m/m of all the polar compounds initially contained in the pyrolysis oil, in particular several polar compounds, in particular those containing oxygen, sulfur, nitrogen, halogens, in particular chlorine, fluorine and bromine, and metals, in particular transition metals, especially iron. The process according to the invention can also make it possible to extract at least 10% m/m of the unsaturated hydrocarbon compounds.

The invention also relates to a steam cracking process comprising a steam cracking step of a pyrolysis oil raffinate recovered during the implementation of the process according to the invention.

This pyrolysis oil raffinate can be pure or diluted, in particular introduced as a mixture with a typical steam cracking charge.

Detailed description of the invention When describing the invention, the terms used should be interpreted in accordance with the following definitions, unless the context dictates otherwise.

The terms "comprising", "comprises" as used herein are synonymous with "including", "includes" or "containing", "contains", and are whether or not inclusive of and do not exclude members, elements or additional method steps not described. It will be appreciated that the terms "comprising", "comprises" and "comprises of" as used herein include the terms "comprises of", "consists of" and "consists of".

The description of numerical ranges by limit values includes all the whole numbers and, if applicable, the fractions included in this range (for example, 1 to 5 can include 1 , 2, 3, 4, 5 when it comes to , for example, of a number of elements, and may also include 1 .5; 2; 2.75 and 3.80, when it comes, for example, to measures). The description of numerical ranges also includes the limit values themselves (for example, from 1 .0 to 5.0 includes both 1 .0 and 5.0). Any numeric range mentioned herein is intended to include all sub-ranges included therein.

All references cited in this specification are incorporated by reference in their entirety. In particular, the teachings of all references specifically referred to in this specification are incorporated by reference.

The features and embodiments of the present invention are shown below. Each feature and embodiment of the invention thus defined may be combined with any other feature and/or embodiment, unless otherwise stated. In particular, any feature indicated as being preferred or advantageous may be combined with any other characteristic or embodiment indicated as being preferred or advantageous.

Pyrolysis oil

The pyrolysis oil treated in the present invention (and supplied during the first stage) is a pyrolysis oil resulting from the pyrolysis of waste comprising plastics.

Advantageously, the pyrolysis oil supplied can be a liquid organic phase resulting from the pyrolysis of waste chosen from plastics and at least least one other waste such as biomass, for example chosen from lignocellulosic biomass, paper and cardboard, and/or one or more elastomers.

This liquid organic phase can be a mixture of liquid organic phases, each organic phase coming from the pyrolysis of one of the aforementioned wastes, or can be a single liquid organic phase resulting from the pyrolysis of one of the aforementioned wastes or from a mixture of two or more of the aforementioned wastes. In other words, the pyrolysis oil treated in the present invention can be a single pyrolysis oil or a mixture of several pyrolysis oils.

Typically, the liquid organic phase results from the pyrolysis of the aforementioned waste(s) at a temperature of 300 to 1000° C. or 400 to 700° C., this pyrolysis being for example rapid pyrolysis, flash pyrolysis, or catalytic pyrolysis or hydropyrolysis.

Plastics can be any type of new or used plastics, included in household (post-consumer) or industrial waste. By plastics, we mean materials made up of polymers and optionally of auxiliary components such as plasticizers, fillers, dyes, catalysts, flame retardants, stabilizers, etc. These polymers can be chosen from thermosetting polymers and thermoplastic polymers. These are typically polymers or copolymers based on polyolefins, vinyl polymers, styrenic polymers, acrylic polymers, polyamides, polyesters, polyurethanes, polycarbonates, polyethers, epoxy polymers, polyacetals, polyimides, silicones. In particular, the present invention makes it possible to treat a waste pyrolysis oil comprising mixtures of two or more of these polymers or copolymers, or to treat mixtures of two or more pyrolysis oils, each oil being obtained from the pyrolysis of waste comprising one or more of these polymers or copolymers.

Typical polymers found in plastics are polystyrene (PS), poly(ethylene terephthalate) (PET), polypropylene (PP), acrylonitrile-butadiene-styrene (ABS), polybutylene, poly( butylene terephthalate) (PBT), high and low density polyethylene (PE), halogenated (Cl, F) or not, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), etc., or the polymers obtained by polycondensation such as polyamides, polyesters, polyesteramides, etc.

Elastomers are linear or branched polymers transformed by vulcanization into an infusible weakly cross-linked three-dimensional network and insoluble. They include natural or synthetic rubbers. They can 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, polyisoprene of isobutylene isoprene, chlorinated or brominated, copolymers of butadiene acrylonitrile (NBR), and polychloroprenes (CR), polyurethanes, silicone elastomers, etc.

Table 1 below lists the main characteristics of plastic pyrolysis oils.

Table 1

GC: gas chromatography

ICP-MS: inductively coupled plasma mass spectrometry

ICP-AES: atomic emission spectrometry - inductively coupled plasma (*) measurement by standard ASTM D873.

(**) also noted MAV (for “Maleic Anhydride Value” in English)

Biomass can be defined as an organic plant or animal product. Biomass thus includes:

- biomass produced by surplus agricultural land, not used for human or animal food: dedicated crops, called energy crops; - the biomass produced by deforestation (forest maintenance) or the cleaning of agricultural land;

- agricultural residues from cereal crops, vines, orchards, olive trees, fruits and vegetables, food residues, etc.;

- forest residues from forestry and wood processing;

- agricultural residues from livestock (manure, slurry, litter, droppings, etc.);

- organic household waste (paper, cardboard, green waste, etc.);

- ordinary industrial organic waste (paper, cardboard, wood, putrescible waste, etc.).

The pyrolysis oil treated by the invention can come from the pyrolysis of one or more of the aforementioned biomasses, residues and organic waste.

Advantageously, the pyrolysis oil treated by the invention can result from the pyrolysis of a ligno-cellulosic biomass, essentially consisting of cellulose, hemicellulose and lignin, for example of the wood (hardwood, softwood), straw, energy crops (short rotation coppice (SCR), very short rotation coppice (SRCT), miscanthus, switchgrass, sorghum, etc. and forest or agricultural biomass residues such as bark, chips, sawdust, bagasse. Pyrolysis oils from biomass are produced by depolymerization and fragmentation of the constituent elements of biomass (holocelluloses (cellulose, hemicellulose), lignin), typically under the action of a rapid increase (<2 seconds) in temperature at 450°C-550°C and rapid quenching of intermediate degradation products. Pyrolysis oils from biomass consist of water (typically 10 to 35% m/m) and a complex mixture of oxygenated compounds. Their elementary composition is close to the composition of the starting biomass with in particular a high oxygen content (from 40 to 60% m/m).

Table 2 below groups together the main characteristics of lignocellulosic biomass pyrolysis oils.

Table 2

The pyrolysis oil treated by the invention can also result from the pyrolysis of paper and/or cardboard.

Advantageously, the pyrolysis oil treated in the process according to the invention can be a liquid organic phase resulting from the pyrolysis of waste comprising 50% m/m or more of plastics, optionally from 50% m/m to 99% m/ m of plastics, optionally mixed with biomass, elastomer or mixtures thereof. This liquid organic phase can come from the pyrolysis of very different plastics, in other words from a mixture of two or more of the aforementioned polymers or copolymers.

Advantageously, the pyrolysis oil can be a liquid organic phase resulting from the pyrolysis of waste, this waste comprising plastics, in particular in the proportions indicated above, and at least 1% m/m of at least one other waste different from plastic.

This other waste can be chosen from an elastomer and biomass, in particular one or more biomasses chosen from lignocellulosic biomass, paper and cardboard. In other words, the treated waste can comprise at least 1% m/m of one or more of these wastes of the biomass and/or elastomer type, optionally from 1 to 50% m/m, from 2 to 30% m/m or within an interval defined by any two of these limits. Of preferably, the waste(s) added to the plastics is biomass, or the biomass represents at least 50%m/m, 60%m%m or 80%m/m, preferably at least 90%m/m of the waste added.

Alternatively, the pyrolysis oil supplied can be a mixture of at least two liquid organic phases resulting from the pyrolysis of waste. It can then comprise 50% m/m or more, optionally from 50% m/m to 99% m, of at least one liquid organic phase resulting from the pyrolysis of plastics, in particular of all kinds and/or origins. The pyrolyzed plastics can thus be a mixture of two or more of the aforementioned polymers or copolymers.

The pyrolysis oil supplied may also be a mixture of at least two liquid organic phases resulting from the pyrolysis of waste, including at least one organic phase resulting from the pyrolysis of plastics, in particular in the proportions indicated above, and at at least one organic phase resulting from the pyrolysis of at least one other waste other than a plastic. This other waste can be chosen from an elastomer and biomass, in particular one or more biomasses, especially chosen from lignocellulosic biomass, paper and cardboard. The pyrolysis oil supplied may then comprise at least 1% m/m of an organic phase resulting from the pyrolysis of one or more of these other wastes, optionally from 1 to 50% m/m, from 2 to 30% m/m or within an interval defined by any two of these limits. Preferably, the organic phase or phases resulting from the pyrolysis of at least one other waste are organic phases resulting from the pyrolysis of biomass, or comprise at least 50% m/m, 60% m/m or 80% m/ m, preferably at least 90% m/m of one or more organic phases resulting from the pyrolysis of biomass.

In general, a pyrolysis oil can comprise aliphatic hydrocarbons having a boiling point of 30 to 600° C., in particular aliphatic hydrocarbons comprising cyclic, linear or branched carbon chains containing from 4 to 50, or even from 4 to 150 , carbon atoms. These aliphatic hydrocarbons can comprise paraffins and olefins, in particular diolefins, in variable proportions depending on the nature of the pyrolyzed waste and the type of pyrolysis process applied. The pyrolysis oil may also include aromatic hydrocarbons.

A pyrolysis oil may comprise solids, typically solid pyrolysis residues (“char”) entrained during the pyrolysis process and/or gums formed from gum precursors present in the pyrolysis oil. The solids content of a pyrolysis oil can be reduced by one or more solid-liquid separations, for example by filtration or any other suitable technique.

Before treatment by the process according to the invention, the organic phase or phases resulting from the pyrolysis of one or more waste mentioned above may optionally be pretreated, in particular to reduce their solid matter and/or water content. By way of example, the solids content of the pyrolysis oil supplied may be at most 2%m/m.

The pyrolysis oil treated by the process according to the invention comprises polar compounds and optionally unsaturated compounds which are undesirable, in particular for subsequent use of the pyrolysis oil as feedstock for a steam cracker.

The unsaturated compounds can be aromatic compounds and gum precursor diolefins. Their presence can lead to instability of the pyrolysis oil over time with, for example, a variation in viscosity, volatility, potential separation of phases, formation of gums. In addition, the presence of rubber causes clogging problems in the installations.

The polar compounds comprising heteroatoms can be organic salts, inorganic salts, organic compounds comprising heteroatoms.

The salts may comprise a cation selected from ammonium ion, an alkali metal cation, a transition metal cation or an alkaline earth metal cation, and an anion cation selected from a carboxylate ion, a sulphate ion, a phosphate or a halide.

The organic compounds comprising heteroatoms can comprise amines, amides, nitriles, esters, ethers, acids, aldehydes, ketones, alcohols. Organic compounds comprising heteroatoms can be aliphatic or aromatic.

Typically, amines, amides, nitriles, esters, ethers, acids, halogenated compounds and silicones are present when the treated waste is plastics. Examples of monocyclic aromatic compounds are then terephthalic acid or benzoic acid and an example of polycyclic compounds is then an oligomer of poly(ethylene terephthalate).

Typically, acids, aldehydes (including hydroxy-aldehydes), ketones (including hydroxy-ketones), alcohols (phenols, methanol, ethanol, are present when the treated waste is biomass, in particular lignocellulosic biomass.

Extraction solvent

The extraction solvent is a polar solvent, it can have a higher or lower density than the density of the treated pyrolysis oil.

In particular, the density of the extraction solvent can be 3 to 50% higher or lower than that of the pyrolysis oil.

The extraction solvent is also an immiscible solvent in the pyrolysis oil to be purified.

In the present invention, it is considered that the extraction solvent (or a mixture of 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 pyrolysis oil, recovered after agitation then decantation of a mixture of one part by volume of solvent with twenty-five parts by volume of the pyrolysis oil to be purified, at atmospheric pressure and at a temperature of 20°C.

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

■ Introduction of 50 mL of pyrolysis oil into a flat-bottomed 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,

■ Introduce a magnetic bar, close the balloon with a polypropylene stopper,

■ Shake the mixture on a mechanical stirrer plate at a speed of 500 rpm for 5 min,

■ At the end of the 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 the complete demixing by decantation and measure the volume of the 2 phases using the graduations. It is considered that complete demixing is achieved when the volumes of the two phases no longer vary. The polar solvent can contain one or more heteroatoms, in particular chosen from oxygen, sulfur and nitrogen, preferably oxygen.

The polar solvent immiscible with the pyrolysis oil to be purified can be chosen from:

- water with an acidic, basic or neutral pH. An acid pH can be obtained by adding one or more organic or inorganic acids. Examples of organic acids that can be used include citric acid (C6H ₈ O ₇ ), formic acid (CH ₂ O ₂ ), acetic acid (CH ₃ COOH), sulfamic acid (H3NSO3). Examples of inorganic acids are hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), phosphoric acid (H3PO4). A basic pH can be obtained by adding alkali and alkaline-earth metal oxides, alkali and alkaline-earth hydroxides (for example NaOH, KOH, Ca(OH) ₂ ) and amines (for example triethylamine, ethylenediamine, ammonia).

- glycol ethers, including in particular polyethylene glycol with the chemical formula HO-(CH ₂ -CH2-O) _n -H with a mass-average molar mass of 90 to 800 g/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 cycle, for example furfural, 5- (hydroxymethyl)furfural, furfuryl alcohol (2-furanemethanol),

- 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 can be used. However, advantageously, only one of the aforementioned solvents can be used as extraction solvent provided that it is immiscible with the oil to be purified.

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

In a preferred embodiment, the extraction solvent is chosen from propylene carbonate, ethylene carbonate and polyethylene glycol of chemical formula HO-(CH ₂ -CH2-O) _n -H of average molar mass in mass of 90 to 800 g/mol, alone or as a mixture, preferably alone.

In a preferred embodiment, the extraction solvent is water having an acidic, basic or neutral pH.

Liquid-liquid extraction

The pyrolysis oil and the extraction solvent can be brought into contact by any means known in the prior art.

For example, the pyrolysis oil and the extraction 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 agitation of the two components by a mixing device. For example, the two components can be mixed together by agitation or by shaking. Alternatively, the contacting can be carried out in an enclosure in which the pyrolysis oil and the extraction solvent circulate in countercurrent.

Contacting of the two components may occur more than once. For example, after having brought the pyrolysis oil and the extraction solvent into contact for the first time, the two resulting phases can be brought into contact again, possibly several times. The contacting and forming steps of the two phases can be continuous. Thus, the two components can pass through a mixing device before entering a separation chamber in which a first and a second phase, namely a raffinate and an extract, are formed. Bringing the two components into contact can be achieved using a propeller, a counter-current flow circulation device, a stirring device, a Scheibel® column, a KARR® column, a centrifugal extractor or a mixer-settler, in particular with two or three stages. The pyrolysis oil can be brought into contact several times with new batches of extraction solvent, in particular of one and the same extraction solvent.

Thus, in a preferred embodiment, the method may comprise: a second contacting step during which the recovered raffinate is brought into contact with a new batch of the same extraction solvent as that used during the first contacting step mentioned, - followed by a second step of recovering a second extract and a second immiscible raffinate, optionally, these two steps are repeated n times on the raffinate recovered during the recovery step from the previous iteration, where n is a nonzero integer. A purified pyrolysis oil, which can subsequently be subjected to a steam cracking process (alone or in a mixture) is then formed by the raffinate of the last iteration carried out.

Subsequently, the term "raffinate" generally designates the raffinate recovered during the recovery step when the process comprises a single contacting and recovery step, or the raffinate recovered during the second recovery step or the raffinate recovered during the last iteration of the contacting and recovery steps.

For example, the pyrolysis oil can be brought into contact with a first batch of extraction solvent to obtain a first raffinate and a first extract. After separation of the raffinate from the extract, this first raffinate can be brought into contact with a second batch of extraction solvent to obtain a second raffinate and a second extract. This cycle can be repeated several times with new batches of the same extraction solvent or with batches of different extraction solvents, but preferably with batches of one and the same solvent, which facilitates the implementation of the process and recovery of raffinates.

In one embodiment, the cycle of bringing the pyrolysis oil and its raffinate into contact with an extraction solvent can be implemented from 1 to 9 times, in particular from 1 to 4 times. When this cycle is repeated from 2 to 9 times, the same extraction solvent or different extraction solvents can be used for each cycle, but preferably one and the same solvent.

Typically, the pyrolysis oil and the extraction solvent are contacted to such an extent that efficient extraction of the pyrolysis oil by the extraction solvent is possible. Since the pyrolysis oil and the extraction solvent are immiscible, those skilled in the art will understand that these solutions are generally thoroughly mixed until an emulsion forms, which is then allowed to separate into two phases.

The contacting of the pyrolysis oil with the solvent can in particular be carried out, for a period ranging from a few seconds to 1 hour.

This bringing into contact can be carried out at a temperature of 0 to 60° C., preferably of 0° to 40° C., more preferably of 0° to 30° C., in particular without external heating.

Contacting is typically carried out at atmospheric pressure.

The volume ratio of the extraction solvent to the pyrolysis oil can be from 0.05:1 to 5:1, preferably from 0.5:1 to 2:1, for example 1:1 or in a range defined by the combination of the above values.

The recovery of the two immiscible phases, namely the extract and the raffinate, can be carried out in the usual way, by separation, generally by a physical separation process. This separation generally consists of physically isolating the raffinate, or at least part of it. Thus, this separation generally consists of separating at least part of the raffinate from the extract.

Due to their immiscibility, the two phases (raffinate and extract) are generally separated in the contacting enclosure or can be separated in another enclosure. This separation can simply consist of removing (for example by racking or decanting) at least part of the extract or raffinate.

The process according to the invention can in particular make it possible to obtain a reduction rate of the heteroatoms contained in the polar compounds of 30 to 99%, in particular greater than 40%, this reduction rate being defined, for each element, by the equation 1: [Equation 1]

(x _H — x _R ) Abatement rate = 100 . -

^XH

Where: x is the content in mg/kg of the element in the pyrolysis oil before treatment, x _R is the content in mg/kg of the element in the raffinate.

The process according to the invention can thus make it possible to obtain one or more of the following reduction rates:

- from 20 to 99% or from 30 to 99% for oxygen,

- from 40 to 99% or from 50 to 99% for nitrogen, - from 40 to 99% for sulfur, in particular from 50 to 99%,

- from 10 to 95% or from 40 to 95% for the halogens, in particular chlorine, bromine, fluorine,

- from 10 to 99% for metals, in particular transition metals, in particular iron.

The oxygen content can be measured according to the standard: ASTM D5622 / D2504.

The nitrogen content can be measured according to the standard: ASTM D4629.

Sulfur content can be measured according to ISO 20846.

The halogen content can be measured according to the standard: ASTM D7359

The alkali metal content can be measured according to the standard: ASTM D5708 A or IP 501.

The alkaline-earth metal content can be measured according to the standard: ASTM D5708 A or IP 501.

The transition metal content can be measured according to the standard: ASTM D5708 A or IP 501.

The versions of the standards cited in this patent application are, when not specified, those in force on January 29, 2021.

Advantageously, the raffinate according to the invention may have at least one of the following characteristics:

- an oxygen content less than or equal to 100 mg/kg,

- a nitrogen content less than or equal to 75 mg/kg,

- a sulfur content of not more than 700 ppm (by mass),

- a content of alkali metals, in particular K and Na, less than or equal to 4 mg/kg,

- a halogen content less than or equal to 15 mg/kg, in particular a chlorine content less than or equal to 1 ppm (by mass),

- a total metal content of not more than 2 mg/kg.

The raffinate according to the invention can be subjected to a steam cracking treatment, optionally after one or more post-treatments - typically chosen from a hydrogenation treatment, a cracking and a hydrocracking - alone or in a mixture with other steam cracker charges . In other words, the raffinate can be treated in a neat or diluted steam cracker, optionally after the post-treatment mentioned above. Preferably, the post-treatment(s) does not include a separation of the extraction solvent from the raffinate.

In particular, the raffinate according to the invention may have, after one or more of the aforementioned post-treatments and/or dilution with a typical load of steam cracker, at least one of the characteristics typical of a steam cracker charge, in combination with one or more of the characteristics presented above.

A typical steam cracker charge has the following characteristics:

- a content of oxygenated compounds less than or equal to 50 ppm (by mass),

- an olefin content less than or equal to 1% vol,

- a paraffin content greater than or equal to 65% vol,

- the lowest possible aromatic hydrocarbon content in order to limit the formation of coke during subsequent treatment of the raffinate.

The aromatic hydrocarbon content can be determined according to ISO 22854.

For example, the specifications of a steam cracker charge are defined in the following documents:

- AIChE paper number 36d, Feedstock Contaminants in Ethylene Plants - 2017 Update,

- Open spec naphtha (OSN) CFR FAR EAST OPEN SPECIFICATION FORM NAPHTHA AGREEMENT, 2017 EDITION.

The steam cracking treatment can be carried out in the usual way, in particular at temperatures of 650° to 1000° C., typically from 700 to 900° C. or from 750 to 850° C. The heated feed is introduced into a cracking zone in which it undergoes steam cracking under suitable conditions to produce at least olefins and hydrogen. Steam is introduced into the cracking zone to reduce the partial pressure of hydrocarbons and promote the production of olefins. The steam also reduces the formation and deposition of carbonaceous material and in particular of coke in the cracking zone. Cracking occurs in the absence of oxygen. The residence time in the cracking zone is very short, typically a few milliseconds.

Examples

The charge used is a cut (37-406°C) of a plastic pyrolysis oil (HPP) whose main characteristics are listed in Table 3.

Table 3

Example 1: Miscibility tests

Miscibility tests were carried out with three solvents, polyethylene glycol with an average molar mass of 200g/mol (PEG-200), polypropylene carbonate (PC) and N-formyl morpholine (NFM; CAS 4394-85-8) , following the protocol below:

- in a 100 mL flat-bottomed flask, introduce 50.0 mL of charge, using a precision pipette,

- Introduce 2.0 mL of solvent, using a precision pipette

- Introduce a magnetic bar, close the balloon with a polypropylene stopper,

- Shake the mixture on a magnetic stirrer plate at a speed of 500 rpm for 5 min.

- At the end of the 5 minutes, stop stirring, remove the magnetic bar using a magnetic rod,

- Transfer the contents of the flask into a graduated ASTM centrifuge tube. Wait for complete demixing and measure the volume of the 2 phases using the graduations.

The results are collated in Table 4.

Table 4 After contact of the 2 phases, we recover:

- 100% m of PEG 200.

- 120% m of PC, which means that part of the filler has dissolved in the solvent.

- 90%m of N FM. The remaining 10% is mixed into the filler.

Example 2: liquid/liquid extraction tests

Liquid/liquid extraction tests were carried out by bringing plastic pyrolysis oil (HPP) into contact with each of the three solvents (PEG 200, PC, NFM).

The following protocol was used: bringing the plastic pyrolysis oil (HPP) into contact with the solvent at room temperature in a volume ratio HPP / solvent: 50/50; stirring at 500 rpm for 5 minutes to ensure good contact between the two phases; phase separation after 30 minutes of rest.

A raffinate corresponding to the treated HPP and an extract containing the solvent are obtained. The raffinate/HPP and extract/solvent mass yields are all around 100%. No loss of product is observed. The compositions of the raffinates are collated in Table 5.

Table 5 PEG 200 and PC have a solvent recovery rate after liquid/liquid extraction greater than 95%. Liquid/liquid extraction with PEG 200 makes it possible to extract 55% of the sulphur, 70% of the chlorine, 80% of the nitrogen and 60% of the oxygen contained in a plastic pyrolysis oil. Liquid/liquid extraction with PC makes it possible to extract 60% of the sulphur, 75% of the chlorine, 80% of the nitrogen and 45% of the oxygen contained in a plastic pyrolysis oil.

NFM has a solvent recovery rate of less than 95% after liquid/liquid extraction. If the chlorinated and sulfur species are reduced in proportions comparable to what can be observed with PEG 200 and PC, the results show lower oxygen and nitrogen reduction capacities.

Example 3: liquid/liquid extraction test in water

A liquid/liquid extraction test was carried out by bringing an HPPB pyrolysis oil with a density of 799.1 kg/m ³ into contact with water at neutral pH. This HPPB oil is an oil resulting from the pyrolysis of a filler containing 10 to 15% by mass of biomass, the rest of the filler being made up of plastic.

The following protocol was used: bringing pyrolysis oil (HPPB) into contact with water at room temperature in an HPPB/water volume ratio: 50/50; stirring at 500 rpm for 5 minutes to ensure good contact between the two phases; phase separation after 30 minutes of rest.

The compositions of the HPPB and the raffinate are collated in Table 6. The extraction makes it possible to significantly reduce the chlorine, nitrogen and oxygen content.

Table 6

Claims

22

CLAIMS Process for purifying a pyrolysis oil resulting from the pyrolysis of waste containing plastics, comprising:

- the supply of a pyrolysis oil containing saturated and unsaturated hydrocarbon compounds and polar compounds comprising at least one heteroatom chosen from oxygen, sulfur, nitrogen, a transition metal, an alkali metal, an alkaline metal - earth, a halogen, the pyrolysis oil supplied being a liquid organic phase or a mixture of liquid organic phases resulting from the pyrolysis of waste chosen from plastics and at least one other waste chosen from biomass and an elastomer,

- the recovery of an extract and an immiscible raffinate, the extract containing the extraction solvent and at least a part of the polar compounds, and optionally at least a part of the unsaturated hydrocarbon compounds, initially contained in the oil pyrolysis oil, the raffinate containing a treated pyrolysis oil with a reduced content of polar compounds and optionally of unsaturated hydrocarbon compounds, in which the polar extraction solvent immiscible with the pyrolysis oil is chosen from water having an acid pH , basic or neutral, glycol ethers, dialkyl sulfoxides, in which the alkyl group can comprise from 1 to 8 carbon atoms, compounds comprising a furan ring, cyclic carbonate esters, comprising from 3 to 8 carbon atoms , and mixtures thereof, and is a solvent for which a recovery rate greater than or equal to 0.95 is obtained, this recovery rate being defined as the ratio of the volume of an extract to a volume of initial solvent, and this extract is a phase containing the solvent, immiscible with the pyrolysis oil, recovered after stirring then decantation of a mixture of one part by volume of solvent with twenty-five parts by volume of the pyrolysis oil at atmospheric pressure and at a temperature of 20°C. Purification process according to claim 1, characterized in that the pyrolysis oil supplied is a liquid organic phase resulting from the pyrolysis of waste comprising 50%m or more of plastics, optionally from 50%m to 99%m. Purification process according to claim 2, characterized in that the pyrolysis oil supplied is a liquid organic phase resulting from the pyrolysis of waste comprising at least 1% m/m, optionally from 1 to 50% m/m of at least one other waste chosen from an elastomer and a biomass, optionally a biomass chosen from lignocellulosic biomass, paper and cardboard. Purification process according to claim 1, characterized in that the pyrolysis oil supplied is a mixture of at least two liquid organic phases resulting from the pyrolysis of waste and comprises 50% m or more, optionally from 50% m to 99 %m of at least one liquid organic phase resulting from the pyrolysis of plastics. Purification process according to Claim 4, characterized in that the pyrolysis oil supplied is a mixture of at least one organic phase resulting from the pyrolysis of plastics and of at least one organic phase resulting from the pyrolysis of at least another waste chosen from an elastomer and a biomass, optionally a biomass chosen from lignocellulosic biomass, paper and cardboard, and comprises at least 1% m/m, optionally from 1 to 50% m/m, of an organic phase resulting from the pyrolysis of said at least one other waste. Purification process according to any one of Claims 1 to 5, in which the polar extraction solvent is chosen from propylene carbonate, ethylene carbonate, polyethylene glycol of chemical formula HO-(CH ₂ -CH2- O) _n -H with a mass-average molar mass of 90 to 800 g/mol, polypropylene glycol with the chemical formula H[OCH(CH ₃ )CH ₂ ] _n OH with a mass-average molar mass of 130 to 800 g/mol and their mixtures. Purification process according to any one of claims 1 to 6, comprising:

- a second contacting step during which the recovered raffinate is brought into contact with a new batch of the same extraction solvent as that used during the first contacting step mentioned,

- followed by a second step of recovering a second extract and a second immiscible raffinate, optionally, these two steps are repeated n times on the raffinate recovered during the recovery step of the previous iteration, where n is a nonzero integer. Steam cracking process comprising a steam cracking step of a pyrolysis oil raffinate recovered during the implementation of the process according to any one of claims 1 to 7.