Field of the invention

The present invention relates to the processing of stabilised compositions comprising hydrocarbon stream resulting from the liquefaction of plastic wastes by pyrolysis or hydrothermal treatment. In particular, the present invention pertains to novel compositions for inhibiting polymerization in industrial plant of hydrocarbon streams obtained from liquefaction of plastic waste, which contain reactive hydrocarbons and potentially oxygenates, thereby preventing fouling in processing equipment.

Background of the invention

Common industrial methods for recycling hydrocarbons from plastic include liquefaction by pyrolysis or hydrothermal treatment of waste plastic that otherwise could have ended in landfill or incinerator, followed by purification including hydrotreatment and contaminant removal using a variety of purification processes such as distillation.

Pyrolysis or hydrothermal treatment transforms plastics, and most of their additives and contaminants, into gaseous chemicals while most of the non-volatile contaminants or additives end up in the solid by-product; chars or ashes. In principle, any kind of plastic waste can be converted, although some pre-sorting of non-organic waste is desired and purification of the output material is necessary as several heteroelements (i.e. presently referred to as elements different of carbon, hydrogen or oxygen) may be volatilized.

Plastic waste is a complex and heterogeneous material, due to several factors. First, plastic as material refers to numerous different polymers with different chemical properties that need to be separated from each other prior to recycling. The main polymers found in plastic from municipal solid waste are polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP) and polystyrene (PS). Other polymers essentially include polyurethanes, polyamides (PA), polycarbonates, polyethers and polyesters other than PET. Second, many different additives are introduced during the production phase to adjust or improve the properties of the plastic or to fulfil specific requirements. These include additives such as functional additives (stabilizers, antistatic agents, flame retardants, plasticizers, lubricants, slipping agents, curing agents, foaming agents, biocides, antioxidants etc.), dyes and pigments, fillers (e.g. glass fibers, talcum, carbon fibers, carbon nanotubes), commonly used in plastic packaging as well as additives such as flame retardants, frequently used in plastic for electronics. In addition, several metal compounds are purposely added during plastic production (often as oxides, carbonates, acids, etc.). Beside additives containing hetero elements other than metals are used in making plastics, for instance halogens such as bromine in flame retardants, plasticizers, stabilizers etc. Silicone polymers, which are silicon containing organic materials, are often used in plastic formulations. Thanks to their surface characteristics, applications for silicones range from silicone rubbers, used as sealants for joints, to silicone surfactants for cosmetic products while they are increasingly used in the plastics sector, as process enhancing additives (processing aids), and for the modification of polymers.

On top of these hetero-elements, the used plastic waste can have been contaminated during lifespan by remains of liquids with which they were in contact (beverages, personal-care products, etc.) and of food that can also introduce contamination of the plastic. Last, some plastic waste may be present in the form of partially decomposed waste, such as partly burnt plastic.

Finally, as plastics are contaminated by oxygenates, pyrolysis or hydrothermal liquefaction plastic oils may also contain oxygenates such as aldehydes or ketones.

Pyrolysis or hydrothermal liquefaction of plastic waste allows producing naphtha, ethylene, propylene and aromatics but, as previously mentioned, those products are polluted by many hetero elements originating from the waste plastic itself. In particular, significant concentration of silicon and of organic silicon can be found in pyrolysis or hydrothermal liquefaction plastic oils. Although many prior art processes were focused on the removal of chlorine compounds, other impurities in the pyrolysis or hydrothermal liquefaction plastic oil simply forbid the direct use of pyrolysis or hydrothermal liquefaction plastic oil in other processes such as steam cracking. Indeed, steam crackers are very sensitive to the presence of olefins or dienes in the feed and to the presence of silicon or of organic silicon compounds. Moreover, oxygenates present in pyrolysis or hydrothermal liquefaction plastic oil are capable to be converted to peroxides and so enhance polymer and gums formation. In particular, the presence of olefins and oxygenates may result in undesirable polymerisation during storage, transport from the production place to further treatment place as well as during purification and further processing treatments.

In particular, purification operations are often carried out at elevated temperatures which can increase the rate of undesired polymerization. Polymerization, such as thermal polymerization, during hydrocarbon processing treatments, results not only in product loss, but also in loss of production efficiency caused by the formation of fouling deposits and their deposition on process equipment, particularly on the heat transfer surfaces of the processing equipment. More specifically the processing may include, for example, preheating, hydrogenation, fractionation, extraction, hydrocracking, vapocracking, fluid catalytic cracking, and the like of hydrocarbon streams to remove, concentrate, or have added thereto the unsaturated hydrocarbons prior to storage or use. These deposits decrease the thermal efficiency of the equipment and decrease the separation efficiency of the distillation towers. In addition, operating modifications to reduce the rate of fouling can result in reduced production capacity. The excessive buildup of such deposits can cause plugging in tower plates, transfer tubes, and process lines, which could result in unplanned shutdowns.

Undesirable polymerization may also cause operational problems such as increase in fluid viscosity, temperature, restricted flow in pipelines, and blocking of filters. In heat requiring operations, such deposition adversely affects heat transfer efficiency.

The behaviour of compositions produced from pyrolysis or hydrothermal liquefaction of waste plastic is difficult to forecast due to the complexity of such compositions. For example, analysis by gas chromatography of pyrolysis plastic oil only allows identification of 25 to 45wt% of the compounds containing oxygen and azote. Moreover, such undesirable polymerisation is generally monitored by measuring the gum content.

There is therefore a need for a stabilized composition comprising liquefaction plastic oil obtained by pyrolysis or hydrothermal treatment.

Brief summary of the invention

The present invention is a composition stabilized against premature polymerization comprising: a) a hydrocarbon stream having a diene value of at least 0.5 g I2/IOO g as measured according to UOP 326, a bromine number of at least 5 g Br2/ 100g as measured according to ASTM D1159, and containing at least 1wt%, or at least 2 wt%, of plastic liquefied oil which is containing contaminants, wherein said contaminants comprise constituents which are not boiling below 700°C, preferably not below 600°C, such as gums in the form of plastic oligomers and residues of liquefaction of plastic, optionally metals and optionally solids, the remaining part of said hydrocarbon stream being a diluent, b) at least one additive capable to reduce gums formation or buildup, c) optionally at least one additive which is a dispersant agent.

In one embodiment, the plastic liquefied oil contained in the hydrocarbon stream is a plastic pyrolysis oil.

In a first embodiment of the invention, the stabilized composition comprises: a) a hydrocarbon stream as defined above, b) at least one additive capable to reduce gums formation or buildup selected from hindered phenols including metal salts thereof, and c) at least one additive which is a dispersant agent.

In the first embodiment, said at least one additive capable to reduce gums formation or buildup may be selected from hindered phenols, advantageously including metal salts thereof, and said at least one dispersant agent may be selected from alkylbenzene sulfonates in which the alkyl group contains 8-18 carbons, metal sulfonates and alkenyl succinimides.

In particular, the additive capable to reduce gums formation or buildup may be a hindered phenol and the dispersant agent may be a polyisobutylene succinimide.

More specifically, the additive capable to reduce gums formation or buildup may be selected from 4-tert butylcatechol (TBC); 2,6-di tertbutylphenol; butylated hydroxyltoluene (BHT) and the at least one dispersant agent may be a polyisobutylene succinimide, in particular of CAS n°84605-20-9.

In a second embodiment of the invention, the stabilized composition comprises: a) a hydrocarbon stream as defined above, b) at least one additive capable to reduce gums formation or buildup which is the product of tall oil fatty acids reacted with a polyamine, c) optionally at least one additive which is a dispersant agent.

Preferably, component c) is not present.

In the second embodiment, the additive capable to reduce gums formation or buildup is the product of tall oil fatty acids reacted with a polyalkylene polyamine, such as a polyethylene polyamine. The polyamine may optionally be selected from diethylenetriamine, triethylenetetramine, or tetraethylenepentamine, preferably diethylenetriamine.

In any of the previous embodiments, optionally, the stabilized composition may further comprise: d) at least one other additive which is a metal passivator and/or a metal chelating agent.

In any embodiment, other additives capable to reduce gums formation or buildup and/or dispersant agent may optionally be present in the composition, as the ones disclosed in the present specification.

In one embodiment of the invention, at least one additive capable to reduce gums formation or buildup and at least one dispersant agent are present.

In one embodiment, the additive capable to reduce gums formation or buildup is an antipolymerant such as a stable free radical or a precursor thereof, such as hydroxylamines. The antipolymerant can be a stable nitroxide free radical and/or a hydroxylamine substituted with at least one alkyl, aryl or alkylaryl group.

In one embodiment, the additive capable to reduce gums formation or buildup is selected among the unhindered phenols, the hindered phenols, the aminophenols, the phenylenediamines and mixtures thereof.

In one embodiment, said at least one additive which is a dispersant agent is selected from products of reaction between a phenol substituted with a C9-110 hydrocarbon chain, an aldehyde and an amine or polyamine or ammonia, from alkenyl succinimides or mixtures thereof.

The present invention also concerns a process for preparing a composition stabilized against premature polymerization, comprising:

(a) providing a hydrocarbon stream having a diene value of at least 0.5 g I2/IOO g as measured according to UOP 326, a bromine number of at least 5 g Br2/ 100g as measured according to ASTM D1159, and containing at least 1wt%, or 2 wt%, of plastic liquefied oil which is containing contaminants, wherein said contaminants comprise constituents which are not boiling below 700°C, preferably not below 600°C, such as gums in the form of plastic oligomers and residues of liquefaction of plastic, optionally metals and optionally solids, the remaining part of said hydrocarbon stream being a diluent,

(b) adding to the hydrocarbon stream provided in step (a) at least one additive capable to reduce gums formation or buildup,

(c) optionally adding to the hydrocarbon stream provided in step (a) at least one additive which is a dispersant agent,

(d) optionally adding to the hydrocarbon stream provided in step (a) at least one other additive which is a metal passivator and/or a metal chelating agent.

In one embodiment, the plastic liquefied oil contained in the hydrocarbon stream provided in step (a) is a plastic pyrolysis oil.

In a first embodiment, the process comprises:

(a) providing a hydrocarbon stream as defined above,

(b) adding to the hydrocarbon stream provided in step (a) at least one additive capable to reduce gums formation or buildup selected from hindered phenols including metal salts thereof and (c) adding at least one additive which is a dispersant agent,

In a second embodiment, the process comprises:

(a) providing a hydrocarbon stream as defined above,

(b) adding to the hydrocarbon stream provided in step (a) at least one additive capable to reduce gums formation or buildup which is the product of tall oil fatty acids reacted with a polyamine, and optionally (c) adding to the hydrocarbon stream provided in step (a) at least one additive which is a dispersant agent.

In any of the above embodiments, the process may further comprise:

(d) adding to the hydrocarbon stream provided in step (a) at least one other additive which is a metal passivator and/or a metal chelating agent.

In any of the above embodiments, the additives are advantageously as previously defined for the composition of the invention. The present invention also concerns a process for the processing of a composition stabilized against premature polymerization, comprising:

(a) providing a composition stabilized against premature polymerization as claimed in the present invention,

(b) optionally submitting the composition provided in step (a) to an evaporation step under operating conditions efficient to obtain a composition containing a reduced amount of additives,

(c) the stabilized composition provided in step (a) or the composition containing a reduced amount of additives provided in step (b) is (i) processed in a steamcracker, (ii) processed in a fluid catalytic cracker, (iii) processed in a hydroprocessing unit, (iv) processed in an -isomerisation unit and/or (v) separated into usable streams for the preparation of fuels such as LPG, naphtha, gas oil, heavy fuel oil and/or for the preparation of lubricants.

In an embodiment, prior to step (b) or prior to step (c), the stabilized composition provided in step (a) may be submitted to a purification step to trap silicon and/or metals and/or phosphorous and/or halogenates over at least one trap to obtain a purified stabilized composition.

In an embodiment, the hydroprocessing unit may include at least one guard bed to trap solid particles.

In an embodiment, step (c) may be performed at temperatures of 200°C or more or may include at least one treatment performed at a temperature of 200°C or more.

Step (c) may include one or several of the following features:

(i) the processing in a steamcracker is performed at temperatures from 800°C to 1200°C;

(ii) the processing in a fluid catalytic cracker is performed at temperatures from 500°C to 550°C,

(iii) the processing in a hydroprocessing unit is performed at temperatures from 100°C to 500°C,

(iv) the processing in the isomerization unit is performed at temperatures from 250°C to 400°C,

(v) the separation into usable streams is performed by distillation.

The use of these novel stabilized compositions prevents fouling of equipment and product during handling, processing, purification, and storage.

In particular, the composition is stabilized against premature polymerization without being contacted with, and/or without any use of, a solid removal material that requires a further separation step. In particular, the present invention does not require the use/presence of solid material suitable for removing oxygen, metals, phosphorous, halogens and/or nitrogen contained in pyrolysis plastic oil or in liquefaction hydrothermal plastic oil, whatever the form of oxygen, metals, phosphorous, halogens and/or nitrogen. Such solid removal materials include silica gel, alumina, promoted alumina, inorganic materials such as clay, pillared clay, apatite, hydroxyapatite, alkaline or alkaline earth metal oxide, calcined alumina, boehmite, bayerite, hydrotalcite, spinel, acid-exchanged clay, molecular sieves (which are alkaline or alkaline earth metal containing aluminosilicate sieves 3A, 4A, 5A or 13X).

Definitions

The terms "alkane" or "alkanes" as used herein describe acyclic branched or unbranched hydrocarbons having the general formula C _n H2n+2, and therefore consisting entirely of hydrogen atoms and saturated carbon atoms; see e.g. IIIPAC. Compendium of Chemical Terminology, 2nd ed. (1997). The term "alkanes" accordingly describes unbranched alkanes ("normal-paraffins" or"n-paraffins" or"n-alkanes" or “paraffins”) and branched alkanes ("iso-paraffins" or "iso-alkanes") but excludes naphthenes (cycloalkanes). They are sometimes referred to by the symbol “HC-“.

The terms “olefin”, “olefins”, “alkene” or “alkenes” as used herein relate to an unsaturated hydrocarbon compound containing at least one carbon-carbon double bond. They are sometimes referred to by the symbol “HC=”.

The terms “alkyne” or “alkynes” as used herein relate to an unsaturated hydrocarbon compound containing at least one carbon-carbon triple bond.

The term “hydrocarbon” or “hydrocarbons” refers to the alkanes (saturated hydrocarbons), cycloalkanes, aromatics and unsaturated hydrocarbons alone or in combination.

As used herein, the terms “C# alcohols”, “C# alkenes”, or “C# hydrocarbons”, wherein “#” is a positive integer, is meant to describe respectively all alcohols, alkenes or hydrocarbons having # carbon atoms. Moreover, the term “C#+ alcohols”, “C#+ alkenes”, or “C#+ hydrocarbons”, is meant to describe all alcohol molecules, alkene molecules or hydrocarbons molecules having # or more carbon atoms. Accordingly, the expression “C5+ alcohols” is meant to describe a mixture of alcohols having 5 or more carbon atoms.

As used herein, the terms “silicon”, “metals”, “phosphorous”, “halogens”, “nitrogen” and “oxygen” refer to their respective chemical elements contained in the stream to be purified.

Weight hourly space velocity (WHSV) is defined as the hourly weight of flow per unit weight of catalyst and liquid hourly space velocity (LHSV) is defined as the hourly volume of flow per unit of volume of catalyst.

The terms "comprising", and "comprises" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the recited endpoint values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

The term "conversion" means the mole fraction (i.e., percent) of a reactant converted to a product or products. The term "selectivity" refers to the percent of converted reactant that went to a specified product.

The terms "wt%", "vol%", or "mol%" refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of component within 100 grams of the material is 10 wt% of components.

Unless otherwise specified, “wtppm” or “ppm” each equally refer to “parts per million” and are given based on weight. For instance, “100 ppm” shall mean 100 ppm by weight. Similarly, the term “wtppb” or “ppb” refers to “parts per billion” and are given based on weight.

The term “naphtha” refers to the general definition used in the oil and gas industry. Naphtha refers to a hydrocarbon originating from crude oil distillation having a boiling range from 15 to 250°C as measured by ASTM D2887. Naphtha contains substantially no olefin as the hydrocarbons originates from crude oil. It is generally considered that a naphtha has carbon number between C3 and C11 , although the carbon number can reach in some case C15. It is also generally admitted that the density of naphtha ranges from 0.65 to 0.77 g/mL.

The term “gas oil” refers to the general definition used in the oil and gas industry. It refers to a hydrocarbon originating from crude oil distillation having a boiling range from 210 to 360°C as measured by ASTM D86. Gas oil contains substantially no olefin as the hydrocarbons originates from crude oil. It is generally considered that a gas oil has carbon number between C12 and C20, although the carbon number can reach in some case C25. It is also generally admitted that the density of gas oil ranges from 0.82 to 0.86 g/mL, wherein commercial specification limits density to 0.86 g/mL according to ASTM D1298 (ISO 3675, IP 160).

The term “LPG” refers to the general definition used in the oil and gas industry. It refers to a hydrocarbon essentially comprised of C3 (propane) with some C4 isomers; n- butane and isobutene.

The term “liquefaction plastic oil” or “plastic liquefied oil” or “liquefied waste plastic” refers to the liquid products resulting from the pyrolysis of plastic and/or from the hydrothermal liquefaction of plastic, alone or in mixture and generally in the form of plastic waste, optionally in mixture with at least one other waste such as an elastomer, for example latex optionally vulcanized or tyre, and/or biomass, e.g. selected from lignocellulosic biomass, paper and board.

The biomass may be defined as a vegetal or animal organic product including residues and organic waste. Biomass includes (i) the biomass produced by the surplus of agricultural land, not used for human or animal food: dedicated crops, called energy crops; (ii) the biomass produced by the deforestation (forest maintenance) or the cleaning of agricultural land; (iii) agricultural residues from cereal crops, vineyards, orchards, olive trees, fruits and vegetables, residues from the agri-food industry,... (iv) forestry residues from forestry and wood processing; (v) agricultural residues from livestock farming (manure, slurry, litter, droppings, etc.); (vi) organic waste from households (paper, cardboard, green waste, etc.); (vii) ordinary industrial organic waste (paper, cardboard, wood, putrescible waste, etc.). The liquefaction plastic oil processed by the invention can be derived from the liquefaction of waste containing at least 1 %m/m, optionally 1-50%m/m, 2-30%m/m, or in a range defined by any two of these limits, of one or more of the aforementioned biomasses, residues and organic waste materials, and the remainder being waste plastics, optionally in admixture with elastomers.

Elastomers are linear or branched polymers transformed by vulcanization into an infusible and insoluble three-dimensional weakly cross-linked network. They include natural or synthetic rubbers. They can be part of tire 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 agents, vulcanization gas pedals, 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, isobutylene-isoprene copolymers, chlorinated or brominated, acrylonitrile butadiene copolymers (NBR), and polychloroprenes (CR), polyurethanes, silicone elastomers, etc. The plastic liquefaction oil processed by the invention can be derived from the liquefaction of waste materials containing at least 1%m/m, optionally 1-50%m/m, 2- 30%m/m or in a range defined by any two of these limits, of one or more of the aforementioned elastomers, especially in the form of waste materials, with the remainder being waste plastics, optionally in admixture with biomass, residues, and organic waste materials.

The term “pyrolysis plastic oil”, “plastic pyrolysis oil” or “oil resulting from the pyrolysis of plastic” refers to the liquid products obtained once waste plastic or plastic waste have been thermally pyrolyzed. The pyrolysis process shall be understood as an unselective thermal cracking process. The term “hydrothermal plastic oil” or “oil resulting from the hydrothermal liquefaction of plastic” refers to the liquid products obtained once waste plastic or plastic waste have been hydrothermally liquefied.

The plastic to be pyrolyzed or hydrothermally liquefied can be of any type. For instance, the plastic can be polyethylene, polypropylene, polystyrene, polyester, polyamide, polycarbonate, etc. These liquefaction plastic oils contain paraffins, i- paraffins (iso-paraffins), dienes, alkynes, olefins, naphthenes, and aromatic components. Liquefied plastic oil may also contain impurities such as organic chlorides, oxygenated and/or silylated organic compounds, organic silicon compounds, metals, salts, phosphorous, sulfur and nitrogen compounds. The plastic used for generating liquefaction plastic oil is a waste plastic, irrespective of its origin or nature. The composition of the liquefaction plastic oil is dependent on the type of plastic that is liquefied. Liquefaction plastic oil is mainly (especially over 80wt%, most often over 90wt%) constituted of hydrocarbons having from 1 to 150 carbon atoms and impurities.

The term “Diene Value” (DV) or “Maleic Anhydride Value” (MAV) is a measure of the conjugated double bonds (dienes) in the oil. For the Maleic Anhydride Value (MAV), one mole of Maleic anhydride corresponds to 1 mole of conjugated double bond and the result corresponds to the amount of maleic anhydride in milligrams that will react with 1 gram of oil. One known method to quantify dienes is the UOP 326-17: Diene Value by Maleic Anhydride Addition Reaction. The term “diene value” (DV) refers to a similar analytical method to quantify dienes by titration, which is expressed in g of iodine per 100 g of sample. There is a correlation between the MAV = DV x 3,863 since 1 mole of conjugated double bond is titrated by 1 mole of Maleic Anhydride or 1 mole of Iodine.

The term “bromine number” corresponds to the amount of reacted bromine in grams by 100 grams of sample. The number indicates the quantity of olefins in a sample. It is determined in grams of Br2 per 100 grams of sample (gBr2/100g) and can be measured according to ASTM D1159-07R17 method.

The term “boiling point” refers to boiling point generally used in the oil and gas industry. Boiling point is measured at atmospheric pressure. The initial boiling point is defined as the temperature value when the first bubble of vapor is formed. The final boiling point is the highest temperature that can be reached during a standard distillation. At this temperature, no more vapor can be driven over into the condensing units. The determination of the initial and final boiling points is known in the art. Depending on the boiling range of the mixture, various standardized methods can be used, such as ASTM D2887-19ae2 relating to the boiling range distribution of petroleum fractions by gas chromatography. For compositions containing heavier hydrocarbons ASTM D7169-05 may alternatively be used. Boiling range of distillates is advantageously measured using ASTM D7500, D86 or D1160. The concentration of metals in the matrix of hydrocarbon can be determined by any method known in the art. Relevant characterization methods include XRF or ICP- AES or ICP-MS methods. Those skilled in the art know which method is the most adapted to each metal measurement and to which hydrocarbon matrix. Features, structures, characteristics or embodiments may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments.

« Potential gums » inform on the tendency of a fuel to form gum and deposits under accelerated aging conditions. They give an indication on the stability of a fuel during its storage. Potential gums can be determined by means of method ASTM D873- 12(2018).

« Existing gums » correspond to quantity of residue remaining after evaporation of a fuel under specific conditions. They give an indication on the stability of a fuel when heated. Existing gums can be determined by means of method NF EN ISO 6246 (2018) et ASTM D381-19.

“Induction period” corresponds to an initial low stage of a chemical reaction in the area of chemical kinetics. After the induction period, the reaction accelerates. It may be estimated by oxidation stability tests such as EN 16091 :2022.

Detailed description of the invention

As regards the hydrocarbon stream, it has a diene value of at least 0.5 g I2/IOO g, preferably at least 1 g I2/IOO g, as measured according to UOP 326, a bromine number of at least 5 g Br2/ 100g as measured according to ASTM D1159.

The hydrocarbon stream contains at least 1wt%, or 2 wt%, of plastic liquefied oil. In a preferred embodiment, said hydrocarbon stream contains at least 5wt%, preferably at least 10wt%, more preferably at least 25 wt % of plastic liquefied oil, most preferably at least 50 wt% still more preferably 75 wt %, even more preferably at least 90 wt % of plastic liquefied oil. It is also possible to use pure plastic liquefied oil, and this is the most preferred embodiment. In the latter case, the hydrocarbon stream is only consisting of plastic liquefied oil.

Contaminants contained in plastic liquefied oil may comprise constituents which are not boiling below 700°C, preferably not below 600°C, such as gums in the form of plastic oligomers and residues of liquefactionof plastic, optionally metals and optionally solids.

Plastic liquefied oil typically comprises from 5 to 80 wt% of paraffins (including cyclo-paraffins), from 10 to 95 wt% w/w of unsaturated compounds (comprising olefins, dienes, acetylenes), from 5 to 70wt% of aromatics. These contents can be determined by gas chromatography. In particular, a plastic liquefied oil may comprise a Bromine Number of 20 to 130 g Br/100g and/or a Maleic Anhydride Index (UOP326-82) of 1 to 55 mg Maleic Anhydride/1g.

Advantageously, the plastic liquefied oil is originating from the stream of liquefied waste plastic for which the C1 to C4 hydrocarbons have been removed and/or the components having a boiling point higher than 350°C have been removed and/or preferably further converted i a FCC, or a hydrocracking unit, a coker or a visbreaker or blended in crude oil or crude oil cut to be further refined.

The other component of said hydrocarbon stream may include any diluent or hydrocarbon stream miscible with the plastic liquefied oil. Such diluent preferably has a diene value of at most 0.5 g I2/IOO g as measured according to UOP 326-17, a bromine number of at most 5 g Br2/ 100g as measured according to ASTM D1159.

The diluent or hydrocarbon stream according to the invention is preferably selected from a naphtha and/or a paraffinic solvent and/or a diesel or a straight run gasoil, containing at most 1 wt% of sulfur, preferably at most 0.1 wt% 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, having preferably a bromine number of at most 5 gBr2/100g, and/or a diene value of at most 0.5 gl2/100g or any combination thereof.

In any of the embodiments of the invention, the above-mentioned plastic liquefied oil my preferably be a pyrolysis plastic oil.

As regards the additives capable to reduce gums formation or buildup, one can cite an antipolymerant such as a stable free radical or a precursor thereof, such as a hydroxylamine compound.

Any stable free radical (or precursor thereof under conditions which produce the stable free radical in situ) as defined may be used in the present invention. The stable free radicals suitable for use in this invention may be selected from, but are not limited to, the following groups of chemicals: nitroxides (e.g., di-tert butylnitroxide), hindered phenoxys (e.g., galvinoxyl), hydrazyls (e.g., diphenylpicrylhydrazyl), and stabilized hydrocarbon radicals (e.g., triphenylmethyl), as well as polyradicals, preferably biradicals of these types. In addition, certain precursors that produce stable free radicals in situ may be selected from the following groups: nitrones, nitrosos, thioketones, benzoquinones, amines and hydroxylamines.

These stable free radicals exist over a wide range of temperatures up to about 260°C. A limiting factor in their use is the temperature of the processing wherein they are employed. Specifically, the present method applies to processing carried on at temperatures at which said stable free radical exists. Pressure has not been seen to be significant to the present method, hence, atmospheric, sub or superatmospheric conditions may be employed.

In an advantageous embodiment the stable free radical may be a stable nitroxide and may be substituted with at least one alkyl, aryl or alkylaryl group.

In an advantageous embodiment the hydroxylamine may be substituted with at least one alkyl, aryl or alkylaryl group.

Preferably, the stable nitroxide free radical or the hydroxylamine may be substituted with a straight or branched chain alkyl of 1 to 20 carbon atoms, a straight or branched chain alkyl of 1 to 20 carbon atoms which is substituted by one to three aryl groups, an aryl of 6 to 12 carbon atoms, or an aryl of 6 to 12 carbon atoms which is substituted by one to three alkyl groups of 1 to 6 carbon atoms.

Specific examples of such suitable hydroxylamines substituted with at least one alkyl, aryl or alkylaryl group as detailed above include, but are not necessarily limited to N-ethylhydroxylamine (EHA); N,N'-diethylhydroxylamine (DEHA); N-ethyl N- methylhydroxylamine (EMHA); N-isopropylhydroxylamine (IPHA); N,N' dibutylhydroxylamine (DBHA); N-amylhydroxylamine (AHA); N-phenylhydroxylamine (PHA); and the like and mixtures thereof.

A stable nitroxide free radical that can be used in this invention is a nitroxide having the formula (I) shown below or an amine precursor thereof. wherein R1 , R2, R3 and R4 are alkyl groups or heteroatom substituted alkyl groups and no hydrogen is bound to the remaining valences on the carbon atoms bound to the nitrogen. The alkyl (or heteroatom substituted) groups R1-R4 may be the same or different, and preferably contain 1 to 15 carbon atoms. Preferably R1-R4 are methyl, ethyl, or propyl groups. In addition to hydrogen the heteroatom substituents may include, halogen, oxygen, sulfur, nitrogen and the like.

The remaining valences R5-R6 in the formula above may be satisfied by any atom or group except hydrogen which can bond covalently to carbon, although some groups may reduce the stabilizing power of the nitroxide structure and are undesirable. Preferably R5 and R6 are halogen, cyano, --COOR wherein R is alkyl or aryl, --CONH2, --S--C6H5, --S--COCH3, --OCOC2H5, carbonyl, alkenyl where the double bond is not conjugated with the nitroxide moiety or alkyl of 1 to 15 carbon atoms, R5 and R6 may also form a ring of 4 or 5 carbon atoms and up to two heteroatoms, such as O, N or S by R5 and R6 together. Examples of suitable compounds having the structure above and in which R5 and R6 form part of the ring are pyrrolidin-1-oxys, piperidinyl-1-oxys, the morpholines and piperazines. Particular examples wherein the R5 and R6 above form part of a ring are 4-hydroxy-2,2,6,6-tetramethyl-piperindino-1-oxy, 2,2,6,6-tetramethyl- piperidino-1-oxy, 4-oxo-2,2,6,6-tetramethyl-piperidino-1-oxy and pyrrolin-1-oxyl. Suitable R5 and R6 groups are methyl, ethyl, and propyl groups. A specific example of a suitable compound where R1-R6 are alkyl groups is di-tert-butylnitroxide. The preferred carbonyl containing nitroxides are those wherein the R5 and R6 form a ring structure with the nitrogen, preferably a six number ring, for example, 4-oxo-2, 2,6,6- tetramethylpiperidino-1-oxy. Examples of nitroxides that can be used in the present invention are the 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (also referred as 4 OH Tempo), the 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (also referred as 4 NH Tempo), and 4 butoxy Tempo, or their amine precursors.

As regards the additives capable to reduce gums formation or buildup, one can also cite as antioxidant the unhindered phenols, the hindered phenols and a metal salt of a hindered phenol, the aminophenols, the phenylenediamines, or combinations thereof, preferably the unhindered phenols, the hindered phenols and a metal salt of a hindered phenol, the aminophenols.

The aminophenol may be selected from the compounds given by the following formula (II):

(II)

Where R1 is selected from hydrogen, a C1-C20 alkyl group, C6-C12 aryl group, or OR', with R' being a H, an C1-C20 alkyl or a C6-C12 aryl group. R2 is selected from an C1-C20 alkyl, a phenyl group, or OR', with R' having the same meaning as before.

Non-exclusive examples of such compounds are 2-aminophenol (2 AP), 3- hydroxy-2-aminophenol, 2-amino-naphthalen-1-ol, 3-amino-naphthalen-2-ol, 1-amino- naphthalen-2-ol, 2-amino-tert-butyl-phenol, and 2-amino-4-methyl-phenol.

Suitable hindered or unhindered phenols may include, but are not necessarily limited to, 4-tert butylcatechol (TBC); tert-butyl hydroquinone (TBHQ); 2,6-di-tert-butyl- 4-methoxyphenol (DTBMP); 2,4 di-tert-butylphenol; 2,5-di-tert-butylphenol; 2,6-di tertbutyl phenol; 2,4, tri-tert-butyl phenol; butylated hydroxyltoluene (BHT, also known as 2,6 di-tert-butyl-paracresol and 2,6 di-tert-butyl methylphenol); 2,6 di-tert-butyl-4- nonylphenol; 2,6-di-tert-butyl-4-sec-butylphenol; 2-butyl-4-methylphenol; 2-tert-butyl-4- methoxyphenol (also known as butylated hydroxyanisole or BHA); 3-tert-butyl-4- methoxyphenol ; 2-tert-butyl-4-heptylphenol; 2-tert-butyl-4-octylphenol; 2-tert-butyl-4- dodecylphenol; 2,6-di-tert-butyl-4-heptylphenol; 2,6-di-tert-butyl-4-dodecylphenol; 2- methyl-6-tert-butyl-4-heptylphenol; 2-methyl-6-tert-butyl-4-dodecyl phenol; 2,2'-bis(4- heptyl-6-t-butyl-phenol); 2,2'-bis(4-octyl-6-t-butyl-phenol); 2,2'-bis(4-dodecyl-6-t-butyl- phenol); 4,4'-bis(2,6-di-t-butyl phenol), 4,4'-methylene-bis(2,6-di-t-butyl phenol); 2,6-di- alkyl-phenolic proprionic ester derivatives; propyl gallate; 2-(1 , 1 -dimethylethyl)-1 ,4- benzenediol; 2-di-tert-butyl hydroquinone 15 (DTBHQ); tert-amyl hydroquinone; 2,5-di- amyl hydroquinone; 3, di-tert-butylcatechol; hydroquinone; hydroquinone monomethyl ether; hydroquinone monoethyl ether; hydroquinone monobenzyl ether; or 3, 3,3', 3'- tetramethyl, 1 ,1-spirobis-indane-5,5',6,6' tetrol (Tetrol); topanol® AN (mixture of BHT and 2,4 Dimethyl-6-tert-butylphenol), tocopherols (C29H50O2) including alpha-, beta-, gamma-, delta-tocopherol, 2-[3,3-bis(3-tert-butyl-4-hydroxyphenyl)butanoyloxy]ethyl 3,3-bis(3-tert-butyl-4-hydroxyphenyl)butanoate (CsoHeeOs), and mixtures thereof.

The phenylenediamines of this invention have at least one N-H group and are advantageously of the following formula (III): wherein R1 , R2, and R3 are the same or different and are hydrogen, straight or branched chain alkyl of 1 to 20 carbon atoms, straight or branched chain alkyl of 1 to 20 carbon atoms which is substituted by one to three aryl groups, aryl of 6 to 12 carbon atoms, or aryl of 6 to 12 carbon atoms which is substituted by one to three alkyl groups of 1 to 6 carbon atoms.

Suitable examples of phenylenediamines include N-phenyl-N'-methyl-1 ,4- phenylediamine, N-phenyl-N'-ethyl-1 ,4-phenylediamine, N-phenyl-N'-n-propyl-1 ,4- phenylediamine, N-phenyl-N'-isopropyl-1 ,4-phenylediamine (NIPP PPDA), N-phenyl-N'- n-butyl-1 ,4-phenylediamine, N-phenyl-N'-iso-butyl-1 ,4-phenylediamine, N-phenyl-N'- sec-butyl-1 ,4-phenylediamine, N-phenyl-N'-t-butyl-1 ,4-phenylediamine, N-phenyl-N'-n- pentyl-1 ,4-phenylediamine, N-phenyl-N'-n-hexyl-1 ,4-phenylediamine, N-phenyl-N'-(l- methyl hexyl)- 1 ,4-phenylediamine, N-phenyl-N'-(1 ,3-dimethylbutyl)-1 ,4-phenylediamine, N-phenyl-N'-(1 ,4-dimethylpentyl)-1 ,4-phenylediamine, N-phenyl-N', N'-dimethyl-1 ,4- phenylenediamine, N-phenyl-N', N'-diethyl-1 ,4-phenylenediamine, N-phenyl-N', N'-di-n- butyl-1 ,4-phenylenediamine, N-phenyl-N, N'-di-sec-butyl-1 ,4-phenylenediamine, N- phenyl-N'-methyl-N'-ethyl-1 ,4-phenylenediamine, N,N'-dimethyl-1 ,4-phenylenediamine, N, N'-di ethyl-1 ,4-phenylenediamine, N,N'-di-isopropyl-1 ,4-phenylenediamine, N,N'-di- iso-butyl-1 ,4-phenylenediamine, N,N'-di-sec-butyl-1 ,4-phenylenediamine (DSB PPDA), N,N'-bis(1 ,4-dimethylpentyl)-1 ,4-phenylenediamine, N, N'-bis(1 ,3-dimethylbutyl)-1 ,4- phenylenediamine, N,N'-diphenyl-1 ,4-phenylenediamine, N,N,N'-trimethyl-1 ,4- phenylenediamine, and N,N,N'-triethyl-1 ,4-phenylenediamine and N-phenyl-p- phenylenediamine (NP PPDA), and mixtures thereof.

In a preferred embodiment, the additive capable to reduce gums formation or buildup is selected among the unhindered phenols, the hindered phenols, the aminophenols, the phenylenediamines, and mixtures thereof.

In a most preferred embodiment, the additive capable to reduce gums formation or buildup is selected among the unhindered phenols, the hindered phenols, aminophenols and mixtures thereof. In another most preferred embodiment, the additive capable to reduce gums formation or buildup is selected among phenylenediamines.

In a preferred embodiment, suitable additives include 4-tert butylcatechol (TBC); 2,6-di tertbutylphenol; butylated hydroxyltoluene (BHT), tocopherols including alpha-, beta-, gamma-, delta-tocopherol, phenylenediamines, in particular those of the above list, and mixtures thereof.

As regards the additive which is a dispersant agent, such additive is a dispersant/detergent capable to prevent the agglomeration of insoluble compounds, formed during oxidation reactions. Such additive does not reduce the gum content.

The dispersant/detergent agent used in the present invention may be selected from:

(i) substituted amines such as N-polyisobutene amine RI-NH2, N-polyisobutene- ethylenediamine R1-NH — R2-NH2,

(ii) alkenyl succinimides, for example obtained by reacting an akenyl succinic anhydride or acid with an amine or a polyamine, or their bissuccinimide, succinnamic, succinamide structural equivalents, for example succinimides of formula (IV): where R1 represents a C2-C120 or C2-C100 alkenyl group, for example a polyisobutylene group of weight-average molecular weight between 140 and 5000 and preferably between 500 and 2000 or preferably between 750 and 1250; and where R2 represents at least one of the following segments — CH2 — CH2 — , CH2 — CH2 — CH2 , — CH — CH(CHs) — and x represents an integer between 1 and 6. (iii) the polyethylenamines. They are for example described in detail in the reference “Ethylene Amines,” Encyclopedia of Chemical Technology, Kirk and Othmer, Vol. 5, pp. 898-905, Interscience Publishers, New York (1950).

(iv) the polyetheramines of formula (V): where R is an alkyl or aryl group having from 1 to 30 carbon atoms; R1 and R2 are each independently a hydrogen atom, an alkyl chain with 1 to 6 carbon atoms or — O — CHR1- CHR2-; A is an amine or N-alkylamine with 1 to 20 carbon atoms in the alkyl chain, an N,N-dialkylamine having from 1 to 20 carbon atoms in each alkyl group, or a polyamine with 2 to 12 nitrogen atoms and from 2 to 40 carbon atoms and x is in the range from 5 to 30.

Such polyetheramines are marketed for example by the companies BASF, HUNSTMAN or CHEVRON.

(v) the products of reaction between a phenol substituted with a hydrocarbon chain, an aldehyde and an amine or polyamine or ammonia. The alkyl group of the alkylated phenol can comprise from 9 to 110 carbon atoms. This alkyl group can be obtained by polymerization of olefinic monomer containing from 1 to 10 carbon atoms (ethylene; propylene; 1 -butene, isobutylene and 1 -decene). The polyolefins that are used in particular are polyisobutene and/or polypropylene. The polyolefins generally have a weight-average molecular weight Mw between 140 and 5000 and preferably between 500 and 2000 or preferably between 750 and 1250.

The alkyl phenols can be prepared by an alkylation reaction between a phenol and an olefin or a polyolefin such as polyisobutylene or polypropylene. The aldehyde used can contain from 1 to 10 carbon atoms, generally formaldehyde or paraformaldehyde.

The amine used can be an amine or a polyamine including the alkanolamines having one or more hydroxyl groups. The amines used are generally selected from ethanolamine, diethanolamines, methylamine, dimethylamine, ethylenediamine, dimethylaminopropylamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and/or 2-(2-aminoethylamino)ethanol. This dispersant can be prepared by a Mannich reaction by reacting an alkylphenol, an aldehyde and an amine as described in patent U.S. Pat. No.5, 697, 988. other dispersants, such as:

(vi) carboxylic dispersants such as those described in U.S. Pat. No.3, 219, 666; (vii)the amine dispersants resulting from reaction between halogenated aliphatics of high molecular weight with amines or polyamines, preferably polyalkylene polyamines, described for example in U.S. Pat. No.3, 565, 804;

(viii) polymeric dispersants obtained by polymerization of alkyl acrylates or alkyl methacrylates (C8 to C30 alkyl chains), aminoalkyl acrylates or acrylamides and acrylates substituted with poly(oxyethylene) groups. Examples of polymeric dispersants are described for example in U.S. Pat. No.3, 329, 658 and U.S. Pat. No.3, 702, 300;

(ix) dispersants containing at least one aminotriazole group such as described for example in U.S. Patent Publication No. 2009/0282731 resulting from reaction of a dicarboyxlic acid or anhydride substituted with a hydrocarbyl and an amine compound or salt of the (amino)guanidine type;

(x) oligomers of polyisobutylsuccinic anhydride (PIBSA) and/or of dodecylsuccinic anhydride (DDSA) and of hydrazine monohydrate, such as those described in EP 1 ,887,074;

(xi) oligomers of ethoxylated naphthol and of PIBSA, such as those described in EP 1 ,884,556;

(xii)quaternized ester, amide or imide derivatives of PIBSA, such as those described in WO2010/132259;

(xiii) mixtures of Mannich bases such as substituted phenols/aldehydes/mono- or polyamines, for example dodecylphenol/ethylenediamine/formaldehyde, and of polyisobutylene succinimides (PIBSI), such as those described in WO2010/097624 and WO 2009/040582;

(xiv) quaternized terpolymers of ethylene, of alkenyl ester(s) and of monomer(s) with at least one ethylenic unsaturation and containing an at least partially quaternized tertiary nitrogen, such as those described in WO2011/134923;

(xv) polyisobutylene succinimides (PIBSAD), in particular represented by the formula (VI) where R ¹ is a hydrocarbyl radical having from about 8 to 800 carbon atoms, X is a divalent alkylene or secondary hydroxy substituted alkylene radical having from 2 to 3 carbon atoms, A is hydrogen or a hydroxyacyl radical selected from the group consisting of glycolyl, lactyl, 2-hydroxy-methyl propionyl and ’,2'bishydroxymethyl propionyl radicals and in which at least 30 percent of said radicals represented by A are said hydroxyacyl radicals, x is a number from 1 to 6, and R ² is a radical selected from the group consisting of -NH2-NHA or a hydrocarbyl substituted succinyl radical having the formula (VII) in which R ¹ is as defined above;

(xvi) products of the reaction of alkenyl succinic anhydride, an amine and phosphorus pentasulfide such as those described in US 3 342 735, where the formula (VIII) of the alkenyl succinic anhydride is where R is a polyalkene derived radical of an average molecular weight between about 300 and 5000 an’ R' is a member selected from the group consisting of hydrogen and alkyl of from 1 to 6 carbon atoms, and an amine selected from the group consisting of

(X) where R” is a C1-C20 alkyl group, A is a C1-C4 alkylene radical and x is a whole integer from 0 to 5 ;

(xvii) alkylbenzene sulfonates, such as alkali metal or ammonium salts of alkylbenzenesulfonates, in which the alkyl group contains 8-18 carbons, for example sodium dodecylbenzenesulfonate; (xviii) Metal sulfonates, such as alkali metal sulfonates or alkaline earth metal sulfonates, for example calcium sulfonate, magnesium sulfonates.

In a preferred embodiment, the dispersant/detergent agent used in the present invention may be selected from the above compounds (ii), (xv), (xvii)and (xviii). Such preferred dispersant/detergent agent(s) may be added to the above described additive(s) capable to reduce gums formation or buildup and more particularly to the preferred additive(s), especially to hindered phenols, more preferably to BHT.

As regards the tall oil fatty acids reacted with a polyamine that can be used as additive capable to reduce gums formation or buildup the correspond to the products of a condensation reaction of tall oil fatty acids with a polyamine. Typically, the reaction products include tall oil fatty acid polyamides.

The tall oil fatty acids and polyamine are generally reacted in a molar ratio 1 :1 at temperatures between 250 and 290 °C and usually a mixture of tall oil fatty acid polyamide and the corresponding tall oil fatty acid imidazoline is obtained. The tall oil fatty acids are typically obtained by distillation of a crude tall oil.

In a preferred embodiment, the polyamine is a polyalkylene polyamine, in particular an ethylene polyamine, such as diethylenetriamine (DETA), triethylenetetramine (TETA), or tetraethylenepentamine (TEPA), preferably DETA.

A suitable additive includes the product registered with the CAS n° 1226892-43- 8.

As regards other additives that may be used, metal passivators and metal chelating agents may be added alone or in combination with any of the preceding additives.

Metal passivators can comprise triazoles, alkylated benzotriazoles and alkylated tolutriazoles, derivatives from 2,5-dimercapto-1 ,3,4-thiadiazole, in particular bisulfides derivatives.

Metal chelating agents can comprise dialkyl phosphonates, in which the alkyl group contains 1-18 carbons.

As regards the stabilized composition, it is of use in industrial processes for plastic recycling in which hydrocarbon streams is handled or manipulated other than the intentional polymerization of the double bonds. Such processes include but are not limited to hydrocarbon cracking processes, preheating, distillation, hydrogenation, extraction, etc.

The proportion of b) with reference to a) can be up to 5000wppm, advantageously up to 3000 wppm, in particular from 50 to 5000 wppm, preferably from 50 to 3000 wppm, most preferably from 100 to 1500 wtppm or from 300 to 1500wppm, or within any of these limits. The proportion of c) with reference to a) can be up to 5000wppm, advantageously up to 3000 wppm, in particular from 50 to 5000 wppm, preferably from 50 to 3000 wppm, most preferably from 100 to 1500 wtppm or from 300 to 1500wppm, or within any of these limits.

The proportion of d) with reference to a) can be up to 5000wppm, advantageously up to 3000 wppm, in particular from 50 to 5000 wppm, preferably from 50 to 3000 wppm, most preferably from 100 to 1500 wtppm or from 300 to 1500wppm, or within any of these limits.

The additives of this invention may also be used with other additives known to prevent fouling such as metal deactivators, corrosion inhibitors and the like. The stabilizer combination of this invention may be applied at any point in an industrial plant stream or process where it is effective.

As regards the process for preparing a composition stabilized against premature polymerization

Step (a) for providing a hydrocarbon stream as defined above may comprise :

(i) providing at least one plastic liquefaction oil by liquefaction of plastic waste,

(ii) optionally providing a diluent,

(iii) preparing a hydrocarbon stream having a diene value of at least 0.5 g I2/IOO g, preferably at least 1 g I2/IOO g, as measured according to UOP 326, a bromine number of at least 5 g Br2/ 100g as measured according to ASTM D1159 by mixing said at least one plastic liquefied oil provided in step (i) with the diluent provided in step (ii) when present, said composition comprising at least 1wt%, or 2wt%, of plastic liquefaction oil, the remaining part of said hydrocarbon stream being a diluent.

Step (i) may include a step of liquefying waste containing plastics and obtaining a hydrocarbon product comprising a gaseous phase, a liquid phase and a solid phase followed by a step of separating the liquid phase of said product, said liquid phase forming a plastic liquefaction oil. The separation step removes the gaseous phase, essentially the C1-C4 hydrocarbons and the solid phase (typically char) to recover only the liquid organic phase forming a liquefaction oil.

Liquefaction step may comprise a pyrolysis step, typically carried out at a temperature of 300 to 1000°C or 400 to 700°C, such pyrolysis being for example fast pyrolysis or flash pyrolysis or catalytic pyrolysis or hydropyrolysis. Alternatively, or in combination, liquefaction step may comprise a hydrothermal liquefaction step, typically performed at a temperature of 250-500°C and at pressures of 10-25-40 MPa.

The waste material processed in liquefaction step may be waste plastic optionally mixed with biomass and/or elastomer, as previously described.

In one embodiment, in step (b), said at least one additive capable to reduce gums formation or buildup is added to said at least one plastic liquefaction oil provided by step (i), prior to step (iii). In an embodiment, the additives are added to the liquefaction plastic oil immediately after the liquefaction of the plastic waste.

In one embodiment, in step (c), said at least one additive is added to said at least one plastic liquefaction oil provided by step (i), prior to step (iii), preferably immediately after the liquefaction of the plastic waste.

In one embodiment, in step (d), said at least one other additive is added to said at least one plastic liquefaction oil provided by step (i), prior to step (iii), preferably immediately after the liquefaction of the plastic waste. In one embodiment, steps (b) and (c), and optionally step (d), are performed simultaneously, preferably immediately after the liquefaction of the plastic waste.

Whatever the embodiment, the additives can be introduced as pure or as a dilute solution in a hydrocarbon or equivalent and/or they can be introduced simultaneously or separately. For example, the additives may be diluted in hydrocarbons, for example C6- C20 aromatic hydrocarbons substituted or not, including toluene, benzene, naphthalene, substituted or not, and their mixtures, heavy aromatic naphtha, a middle distillate (boiling range 180-360°C) such as a jet fuel or a diesel, or in polar solvents, in particular alcohols such as glycols, ethanol, or water.

The stabilized composition described in the present invention or obtained by the process of the present invention may be used as such or further processed alone or in combination with another feedstock such as naphtha, gasoil or any crude oil refining product. It may for example be fractionated according to distillation temperature ranges, to feed a steam cracker, a FCC, a hydrocracker, a catalytic hydroprocessing unit or a pool of fuels or combustibles such as naphtha, gas oil, heavy fuel oil and/or for the preparation of lubricants.

As regards the optional purification step to trap silicon and/or metals and/or phosphorous and/or halogenates over at least one trap to obtain a purified stabilized composition. In one embodiment, this purification step is performed before processing the stabilized composition, before or after the evaporation step when present.

With regards to traps for the silicon and/or metals and/or phosphorous and/or halogenates, it consists in silica gel, clays, alkaline or alkaline earth metal oxide, iron oxide, ion exchange resins, active carbon, active aluminium oxide, molecular sieves, and/or porous supports containing lamellar double hydroxide modified or not and silica gel, or any mixture thereof used in the fixed bed techniques known in the art. The trap is able to capture silicon and/or metals and/or phosphorous and/or halogenates, being preferably chosen among Ca, Mg, Hg via absorption and/or adsorption or it can also be constituted of one or more active guard bed with an adapted porosity. It can work with or without hydrogen coverage. The trap can be constituted of an adsorbent mass such as for instance a hydrated alumina. Molecular sieves can also be used to trap silicon. Other adsorbent can also be used such as silica gel for instance. The silicon trap is preferably able to trap organic silicon. Indeed, it is possible that the silicon present in the streams is in the form of organic silicon.

In a preferred embodiment, silicon and/or metals and/or phosphorous and/or halogenates are trapped with activated carbon. Activated carbon possesses preferably a high surface area (600-1600 m2/g) and is preferably porous and hydrophobic in nature. Those properties lead to a superior adsorption of non-polar molecules or little ionized molecules. Therefore, activated carbon can be used to reduce for instance siloxane from the liquid feed at temperature from 20 to 150°C, at pressures from 1 to 100 bar or from vaporized feed from 150 to 400°C at pressure from 1 to 100 bar.

In a preferred embodiment, silicon and/or metals and/or phosphorous and/or halogenates are trapped with silica or silica gel. Silica gel is an amorphous porous material, the molecular formula usually as (SiC^ nFW, and unlike activated carbon, silica gel possesses polarity, which is more conductive to the adsorption of polar molecules. Because of -Si-O- Si- bonds, siloxanes exhibit partial polar character, which can contribute to adsorb on silica gel surface.

In a preferred embodiment, silicon and/or metals and/or phosphorous and/or halogenates are trapped with molecular sieves. Molecular sieves are hydrous aluminosilicate substance, with the chemical formula Na2O AI2O3 nSiO2 xH2O, which possesses a structure of three-dimensional crystalline regular porous and ionic exchange ability. Compared with silica gel, molecular sieves favour adsorption of high polarity. The regeneration of exhausted absorbents can be achieved via heating at high temperature to remove siloxane. Often, the regeneration is less efficient as the siloxanes might react irreversibly with the molecular sieve. In a most preferred embodiment, the molecular sieves are ion-exchanged or impregnated with a basic element such as Na. Na2O impregnation levels range from 3-10% wt typically and the type of sieve are typically of the A or faujasite crystal structure.

In a preferred embodiment, silicon and/or metals and/or phosphorous and/or halogenates are trapped with activated aluminium oxide. Activated aluminium oxide possesses large surface area (100-600 m2/g), which shows high affinity for siloxanes but also for polar oxide, organic acids, alkaline salts, and water. It can be an alkaline or alkaline-earth or rare-earth containing promoted alumina, the total weight content of these doping elements being less than 20%wt, the doping elements being preferably selected from Na, K, Ca, Mg, La, or mixture thereof. It can also be a metal promoted alumina where the metal is selected from group Vl-B metal with hydrogenating activity such as Mo, W and/or from group VIII metal, such as Ni, Fe, Co

In another embodiment, silicon and/or metals and/or phosphorous and/or halogenates are trapped with alkaline oxide. Alkaline oxide for high temperature treatment such as calcium oxide (CaO) has strong activity to breakdown siloxanes and can be used as non-regeneratable adsorbent at temperature between 150 and 400°C.

In another embodiment, silicon and/or metals and/or phosphorous and/or halogenates are trapped with porous supports containing lamellar double hydroxides, being preferably an hydrotalcite. The hydrotalcite can comprise one or more metals with hydrogenating capacity selected from group VI B or Group VIII, preferably Mo. Those metals can be supported on the surface of the hydrotalcite, or can have been added to the actual structure of the lamellar double hydroxide, in complete or partial substitution; as an example, but without limiting the scope of the present invention, the divalent metal, usually Mg, can be exchanged for Ni, or the trivalent metal, substituted by Fe instead of Al.

The above-mentioned solid adsorbents can be used alone or in any combination in order to optimize the removal of silicon and/or metals and/or phosphorous and/or halogenates.

In another embodiment, silicon and/or metals and/or phosphorous and/or halogenates are trapped with a multi layered guard bed comprising at least two layers wherein the layer on the top of the bed is selected from silica gel, clays, alkaline or alkaline earth metal oxide, iron oxide, ion exchange resins, active carbon, active aluminium oxide, molecular sieves and wherein the layer on the bottom of the bed is selected from silica gel, clays, alkaline or alkaline earth metal oxide, iron oxide, ion exchange resins, active carbon, active aluminium oxide, molecular sieves. More preferably said layer on the top of the guard bed comprises silica gel and/or active carbon and said layer on the bottom of the guard bed comprises molecular sieves and/or active aluminium oxide.

In another embodiment, when the plastic liquefaction oil contains high quantities of HCI and/or Halogenated compounds (namely at least 500 ppm wt of HCI based on the total amount of plastic liquefaction oil), particular adsorbents can be used such as silica, clays - such as bentonite, hydrotalcite - alkaline or alkaline earth metal oxide - such as iron oxides, copper oxides, zinc oxide, sodium oxide, calcium oxide, magnesium oxidealumina and alkaline or alkaline-earth promoted alumina-, iron oxide (hematite, magnetite, goethite), ion exchange resins or combination thereof. In a most preferred embodiment, silicon and/or metals and/or phosphorous and/or halogenates containing at least 500 ppm wt of HCI based on the total amount of plastic liquefaction oil are trapped with activated alumina. As HCI is a polar molecule, it interacts with polar sites on the alumina surface such as hydroxyl groups. The removal mechanism relies predominantly on physical adsorption and low temperature and the high alumina surface area is required to maximize the capacity for HCI removal. The HCI molecules remain physically adsorbed as a surface layer on the alumina and can be removed reversibly by hot purging. Promoted aluminas are a hybrid in which a high alumina surface area has been impregnated with a basic metal oxide or similar salts, often of sodium or calcium. The alumina surface removes HCI through the mechanisms previously described, however the promoter chemically reacts with the HCI giving an additional chloride removal mechanism referred to as chemical absorption. Using sodium oxide as an example of the promoter, the HCI is captured by formation of sodium chloride. This chemical reaction is irreversible unlike physical adsorption and its rate is favoured by higher temperature. The promoted alumina chloride guards are very effective for liquid feeds due to the irreversible nature and high rate of the chemical reaction once the HCI reaches the reactive site.

Another class of chemical absorbents combines Na, Zn and Al oxides in which the first two react with HCI to form complex chloride phases, for example Na2ZnCk and the chemical reactions are irreversible. U.S. 4,639,259 and 4,762,537 relate to the use of alumina-based sorbents for removing HCI from gas streams. U.S. 5,505,926 and 5,316,998 disclose a promoted alumina sorbent for removing HCI from liquid streams by incorporating an alkali metal oxide such as sodium in excess of 5% by weight on to an activated alumina base. Other Zn-based products range from the mixed metal oxide type composed of ZnO and Na2O and/or CaO. The rate of reaction is improved with an increase in reactor temperature for those basic (mixed) oxides.

As regards the process for the processing of a composition stabilized against premature polymerization, it uses a stabilized composition as described in the present invention and in particular obtained by the process for preparing a composition stabilized against premature polymerization of the invention. The use of the stabilized composition of the invention allows performing the processing at temperatures of 200°C or higher, typically from 200°C to 1200°C or allows performing at least one treatment of step (c) in this temperature range without fouling.

In some embodiments, some or all of the additives contained in the stabilized composition (additive(s) capable to reduce gums formation or buildup and/or additive(s) which is a dispersant agent, and optionally other additives) may present a too high boiling point to be used in a further processing step and/or may be detrimental to the further processing.

In such a case, it may be preferable to reduce, or completely remove, some or all of the additives by submitting the stabilized composition provided in step (a) to an evaporation step (b) under operating conditions efficient to obtain a composition containing a reduced amount of additives. Such evaporation may be performed at temperatures and pressure efficient to obtain a gaseous hydrocarbon stream having a final boiling point of at most 650°C, preferably of at most 500°C, more preferably of at most 380°C, and optionally a residue. Such evaporation is optionally performed in presence of steam.

In one embodiment, in the evaporation step, the stabilized composition may be heated using steam, at a temperature which is high enough to avoid condensation of steam when direct mixing is envisioned, since steam condensation could lead to hammering issues. Non-vaporized products are removed in a separation section to produce the gaseous hydrocarbon stream. Alternatively, the stabilized composition may be heated using a hot oil, which is collected in admixture with the non-vaporized products and may be recycled.

The evaporation step may be performed using a flash drum, a kettle, a single or double wall thin film evaporator, a falling film evaporator or a combination of at least two of them.

Such evaporation step (b) may be particularly useful before processing the stabilized composition in a steam cracker. It may be omitted for other processing steps such as hydroprocessing (including catalytic hydrogenation, hydrocracking, etc), fluid catalytic cracking and separation by distillation.

The gaseous hydrocarbon stream obtained from evaporation step (b) is then submitted to the further processing step (c).

In the process for the processing of a stabilized composition according to the invention, the stabilized composition provided in step (a) or the composition containing a reduced amount of additives provided in step (b) may, prior to step (c) and/or (d), be mixed with naphtha, gasoil or any crude oil refining product to have a liquefied plastic oil concentration ranging from 0.01 wt% to at most 90 wt%; preferably 0.1 wt% to 75 wt% even more preferably 1 wt% to 50 wt% or within any of these limits.

The stabilized composition, either before or after the optional evaporation step, may be submitted to the optional purification step before the processing.

As regards the steamcracking processing step performed in a steamcracker, this step is typically performed at a temperature higher than 200°C, to produce olefins, such as ethylene and propylene, and aromatics.

In a preferred embodiment, the stabilized composition is sent at least partially directly to a steam cracker without further dilution and preferably as the only stream sent at least partially to 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 stabilized composition can be ethane, liquefied petroleum gas, naphtha or gasoils or crude oil. Liquefied petroleum gas (LPG) consists essentially of propane and butanes. Gasoils have a boiling range from about 200 to 350°C, consisting of C10 to C22 hydrocarbons, including essentially linear and branched paraffins, cyclic paraffins and aromatics (including mono-, naphtho- and poly-aromatic).

In particular, the cracking products obtained at the exit 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 may range from 800 to 1200°C, preferably from 820 to 1100°C, more preferably from 830 to 950°C, more preferably from 840°C to 920°C. The outlet temperature may influence the content of high value chemicals in the cracking products produced 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, may range from 0.005 to 0.5 seconds, preferably from 0.01 to 0.4 seconds.

In a preferred embodiment, steam cracking is done in presence of steam in a ratio of 0.1 to 1.0 kg steam per kg of hydrocarbon feedstock, preferably from 0.25 to 0.7 kg steam per kg of hydrocarbon feedstock in the steam cracker, preferably in a ratio of 0.35 kg steam per kg of feedstock mixture, to obtain cracking products as defined above.

In a preferred embodiment, the reactor outlet pressure may range from 500 to 1500 mbars, preferably from 700 to 1000 mbars, more preferably may be approx. 850 mbars. The residence time of the feed in the reactor and the temperature are to be considered together. A lower operating pressure results in easier light olefins formation and reduced coke formation. The lowest pressure possible is accomplished by (i) maintaining the output pressure of the reactor as close as possible to atmospheric pressure at the suction of the cracked gas compressor (ii) reducing the pressure of the hydrocarbons by dilution with steam (which has a substantial influence on slowing down coke formation). The steam/feedstock ratio may be maintained at a level sufficient to limit coke formation.

Effluent from the steam cracker contains unreacted feedstock, desired olefins (mainly ethylene and propylene), hydrogen, methane, a mixture of C4's (primarily isobutylene and butadiene), pyrolysis gasoline (aromatics in the C6 to C8 range), ethane, propane, di-olefins (acetylene, methyl acetylene, propadiene), and heavier hydrocarbons that boil in the temperature range of fuel oil (pyrolysis fuel oil). This cracked gas is rapidly quenched to 338-510°C to stop the pyrolysis reactions, minimize consecutive reactions and to recover the sensible heat in the gas by generating high-pressure steam in parallel transfer-line heat exchangers (TLE's). In gaseous feedstock-based plants, the TLE- quenched gas stream flows forward to a direct water quench tower, where the gas is cooled further with recirculating cold water. In liquid feedstock-based plants, a prefractionator precedes the water quench tower to condense and separate the fuel oil fraction from the cracked gas. In both types of plants, the major portions of the dilution steam and heavy gasoline in the cracked gas are condensed in the water quench tower at 35-40°C. The water-quench gas is subsequently compressed to about 25-35 Bars in 4 or 5 stages. Between compression stages, the condensed water and light gasoline are removed, and the cracked gas is washed with a caustic solution or with a regenerative amine solution, followed by a caustic solution, to remove acid gases (CO2, H2S and SO2). The compressed cracked gas is dried with a desiccant and cooled with propylene and ethylene refrigerants to cryogenic temperatures for the subsequent product fractionation: front-end demethanization, front-end depropanization or front-end deethanization.

As regards the fluid catalytic cracking processing step performed in a fluid catalytic cracker unit, this step is typically performed at a temperature higher than 200°C, generally at temperatures of 500-550°C, in presence of well-known suitable catalysts to crack the heavy hydrocarbon molecules. The effluent is typically contacted with a high activity zeolite catalyst in a reactor at high temperature with a short contact time of a few minutes or less. The catalyst on which coked produced during reaction is deposited is then regenerated before being reinjected into the reactor at high temperature.

Non-limiting examples of a FCC catalyst include X- type zeolites, Y-type and/or USY-type zeolites, mordenite, faujasite, nano-crystalline zeolites, MCM mesoporous materials, SBA-15, a silico-alumino phosphate, a gallophosphate, a titanophosphate, spent or equilibrated catalyst from FCC units or any combinations thereof. In some aspects, the zeolites can be metal loaded zeolites. The FCC catalyst can be present in an active or inactive matrix with or without metal loading.

This process is widely used in the refining industry for conversion of atmospheric gas oil, vacuum gas oil, atmospheric residues and heavy stocks recovered from other refinery operations into high-octane gasoline, light fuel oil, heavy fuel oil, olefin-rich light gas (LPG) and coke A conventional FCC unit can be used.

As regards the hydroprocessing step performed in a hydroprocessing unit, this step refers to processes or treatments that react a hydrocarbon-based material with hydrogen, typically under pressure and with a catalyst (hydroprocessing can be non- catalytic). Such processes include, but are not limited to, hydrodeoxygenation (of oxygenated species), hydrodesulfurization, hydrodenitrification, hydrodemetallation, hydrogenation, hydrocracking, hydroisomerization, and hydrodewaxing.

A hydroprocessing unit therefore includes one or several units or zones of (i) hydrodeoxygenation, (ii) hydrodesulfurization, (iii) hydrodesulfurization, (iv) hydrodemetallation, (v) hydrogenation, (vi) hydrocracking, (vii) hydroisomerization, (viii) hydrodewaxing.

The terms "hydroprocessing" and "hydrotreating" are used interchangeably herein. Hydroprocessing is typically performed at a temperature higher than 200°C, in presence of hydrogen with well-known suitable catalysts to saturate the double bonds, to convert heteroatoms such as sulfur and nitrogen components into respectively H2S and NH3, to remove oxygen and other heteroatoms, such as metal, an/or to crack the heavier hydrocarbons. At the same time, aromatic compounds are saturated into cyclic compounds and some additional branching may be produced.

Depending on the composition of the stream entering this hydrotreating step, it is either performed in gas phase or the reactor operates in trickle bed mode. This step can have also a metal trap function, a cracking function, a de-aromatization function depending on the characteristic of the catalyst and the used operating condition. This step can be performed in one reactor with different layers of catalysts or several reactors in series depending on the function sought.

In a preferred embodiment, said hydrotreating step is performed in one or more catalyst bed with preferably an overall temperature increase of at most 100°C and/or a temperature increase of at most 50°C over each catalyst bed, with preferably intermediary quench between said catalyst beds, said quench being preferably performed with H2 or with the stabilized composition.

In a preferred embodiment, the inlet temperature of said hydrotreating step is of at least 200°C, preferably 230°C, more preferably 250°C and at most 500°C. Temperatures as low as 100°C or 140°C are possible when limited hydrogenation is sought.

In another preferred embodiment, said hydrotreating step is performed at a LHSV between 1 to 10h ^-1 , preferably 2 to 4 h’ ¹ .

In another preferred embodiment, said hydrotreating step is performed at a pressure ranging from 1 to 200 barg, preferably from 25 to 200 barg, in presence of H2.

In another preferred embodiment, said hydrotreating step is performed with a ratio H2/hydrocarbon ranging from 5 NL/L to 2000 NL/L, preferably in the presence of at least 0.005 wt %, preferably 0.05 wt % even more preferably 0.5 wt% of sulphur, being preferably H2S or organic sulfur compounds, in the feed stream.

In one embodiment, the hydroprocessing unit may include at least one guard bed to strap solid particles, typically located on top of said hydroprocessing, to remove the solid particles remaining in the feed such as coke particles coming from heating tubes, iron scales from corrosion, dissolved impurities such as iron, arsenic, calcium-containing compounds, sodium chloride, silicon contained in upstream additives, etc. The gard bed may include one or several of the materials listed above to capture silicon and/or metals and/or phosphorous and/or halogenates. Grading materials which have high void space to accumulate and store these particulates are frequently used. Effective feed filtration to remove particulates in combination with high void grading provides a longer mitigation of pressure drop buildup. In a preferred embodiment, said guard bed to trap solid particles has a continuously decreasing particle size including a region 25 to 150 centimeters of particles, having a fraction of 0.3 to 2.0 cm diameter range. Since such guard beds to trap solid particles are designed specifically to handle the contaminants, they help to prolong the life of the hydrotreating catalyst and require fewer total catalyst changeouts.

In particular, on the top of the said hydrotreatment a silicon trap may be present working at a temperature of at least 200°C, and/or a LHSV between 1 to 10h ^-1 , and/or a pressure ranging from 10 to 90 barg in presence of H2; optionally with a metal trap working at a temperature of at least 200°C, a LHSV between 1 to 10h' ¹ , a pressure ranging from 10 to 90 barg in presence of H2.

In another preferred embodiment, said hydrotreating step is performed in a reactor preferably over a catalyst that comprises at least one metal of groups 8-10, preferably selected from the group of Pt, Pd, Ni and/or mixture thereof on a support such as alumina, titania, silica, zirconia, magnesia, carbon and/or mixtures thereof.

In another preferred embodiment, said hydrotreating step is performed over a catalyst that comprises at least one metal of group 6 as for example Mo, W in combination or not with a promotor selected from at least one metal of group 8-10 as for example Ni and/or Co, and/or mixture thereof, preferably these metals being used in sulfided form and supported on alumina, titania, zirconia, silica, carbon and/or mixtures thereof.

In another preferred embodiment, said hydrotreating step is performed over at least one catalyst that presents both (i) an hydrotreating function, namely at least one metal of group 6 as for example Mo, W in combination or not with a promotor selected from at least one metal of group 8-10 as for example Ni and/or Co, and/or mixture thereof, preferably these metals being used in sulfided form and (ii) a trap function, namely said catalyst presents a BET surface area ranging from 150 m ² /g to 400 m ² /g.

In another preferred embodiment, the effluent obtained after said hydrotreating step may be further washed with water to remove inorganic compounds such as hydrosulphide, hydrogenchloride, ammonia and ammonium salts, and optionally further treated in another processing unit including a hydrotreatment unit, a hydrocraking unit, an isomerization unit. Alternatively, the hydroprocessing unit may comprise a hydrogenation zone, a hydrodemetallation zone, a hydrotreatment zone, a hydrocracking zone, a hydro isomerisation zone

In another preferred embodiment, the effluent obtained after said hydrotreating step, optionally washed, is preferably further hydrocracked at a temperature of 350- 430°C, a pressure of 30 - 180 barg, a LHSV of 0.5-4 h’ ¹ , and/or under a H2 to hydrocarbons ratio of 800-2000 NL : L to reduce the final boiling point of at least 10% prior to be sent at least partially to a steam cracker.

In a preferred embodiment, a guard bed to trap solid particles is located on the top of said hydrotreating step.

The effluent of the hydrotreating step can be sent, after a potential separation step typically by distillation, to a steamcracker, a FCC unit, a hydrocracking unit, a hydrogenation unit, or blended in crude oil or base oil or crude oil cut to be further refined.

The hydrotreating unit outlet stream can be fed to a distillation column so as to obtain a flue gas stream which is used as a fuel, an ultra-low sulphur naphtha stream in the case of a naphtha hydrotreater, an ultra-low sulphur diesel stream in the case of gasoil hydrotreater and an ultra-low sulphur fuel oil in the case of heavy oil hydrotreater.

As regards the hydrodemetallation processing step generally performed in a hydrodemetallation unit or zone, this step is typically performed at a temperature from 200 to 500°C, at a pressure from 1 to 180 barg in presence of hydrogen. The conditions are selected to perform the desired hydro-demetallization conversion to reduce or eliminate the undesirable characteristics or components of the feed stream. In accordance with the present invention, it is contemplated that the desired hydrodemetallation conversion includes, for example, dehalogenation, desulfurization, denitrification, olefin saturation and oxygenate conversion.

Liquid hourly space velocities are typically in the range from about 0.05 hr ¹ to about 20 hr ¹ and the hydrogen to feed ratio is generally from about 30 to 8500Nm ³ /m ³ ,

Suitable catalysts contain a metallic component having hydro-demetallation activity combined with a suitable refractory inorganic oxide carrier material of either synthetic or natural origin. Examples of carrier materials are alumina, silica, and mixtures thereof. Suitable metallic components having hydro-demetallization activity are those selected from the group comprising the metals of Groups 6 and 8-10. In addition, any catalyst employed commercially for hydrogenating reduced crude oil to remove nitrogen, metals and sulfur may function effectively. It is further contemplated that hydrodemetallization catalytic composites may comprise one or more of the following components: cesium, francium, lithium, potassium, rubidium, sodium, copper, gold, silver, cadmium, mercury and zinc.

As regards the hydrogenation processing step generally performed in a catalytic hydrogenation unit, this step is typically performed at a temperature higher than 100°C, in presence of hydrogen and suitable hydrogenation catalyst to hydrogenate the aromatic and/or olefinic compounds contained in the feedstock to produce a saturated product, without significant cracking or isomerization. This step is thus a selective hydrogenation step of unsaturated compounds performed under hydrogenation conditions. The hydrogenation conditions may be any conditions suitable to cause the hydrogenable component to react with hydrogen.

The hydrocarbon stream may be contacted with hydrogen at an amount of 25 to 500 Nm ³ hydrogen/m ³ hydrocarbons of the feedstock, carried out at a temperature from 100 to 370 °C, preferably at 150°C to 300°C, at a LHSV from 0.2 to 10 l/h, and at 1 to 350 barg, preferably at 20 to 250 barg hydrogen pressure. Among these standard process controls LHSV refers to volumetric liquid hourly space velocity indicating the reactant liquid flow rate/reactor volume.

The hydrogenation step is performed over a hydrogenation catalyst that may be any catalyst that can facilitate hydrogenation. A suitable catalyst typically comprises at least one metal of groups 6 to 10 such as palladium (Pd) and platinum (Pt). The metal(s) is/are preferably used in sulfided form and supported on alumina, titania, zirconia, silica, carbon and/or mixtures thereof.

As regards the hydrocracking processing step performed in a hydrocracking unit, this step is typically performed at a temperature higher than 200°C, generally at a temperature 200-500°C and high pressure (30-200 barg) in a hydrogen-rich atmosphere in the presence of a suitable catalyst to produce lower-boiling hydrocarbon compounds. Typically hydrocracking is performed in a catalytic reactor with a dual function under a high hydrogen partial pressure and elevated temperatures such that large hydrocarbon molecules crack into smaller molecules while double bonds are saturated and sulphur, nitrogen, oxygen and other heteroatoms, such as metals, are removed by the hydrogen from the hydrocarbon chains. At the same time, aromatic compounds are saturated into cyclic compounds and some additional branching may be produced.

Optionally, the liquefied oil cracking operation may comprise a hybrid fluid catalytic cracking of at least part of the heavy liquefied oil fraction. In this way it is possible to improve the diesel yield of the overall process by at least partially reducing the average molecular weight of the heavy liquefied oil fraction.

In one embodiment, the effluent is hydrocracked at a temperature of 350-430°C, a pressure of 30 - 180barg, a LHSV of 0,05-to 20 h-1 or of 0.5-4 h’ ¹ , and/or under a H2 to hydrocarbons ratio of 800-2000 Nm ³ :m ³ to reduce the final boiling point of at least 10%.

The hydrocracking catalyst generally contains at least one metallic component having hydrogenation activity combined with a suitable refractory inorganic oxide carrier material of either synthetic or natural origin. The carrier material may contain amorphous and/or zeolitic components. The preparation of hydrocracking catalysts is well known to those skilled in the art.

As regards the isomerization step, generally performed in an isomerization unit, this step is typically carried out using an isomerization catalyst at a temperature from 250°C to 400°C, typically in the presence of hydrogen. The operating pressure is typically 10 to 140 barg, and more typically 10 barg to 70 barg. Hydrogen flow rate is typically 8 to 900 Nm ³ /m ³ .

Suitable isomerization catalysts can include, but are not limited to Pt or Pd on a support such as, but further not limited to, SAPO-11 , SM-3, SSZ-32, ZSM-23, ZSM-22; and similar such supports. In some or other embodiments, the step of isomerizing comprises use of a Pt or Pd catalyst supported on an acidic support material selected from the group consisting of beta or zeolite Y molecular sieves, SiC>2, AI2O3, SiOZ-AhCh, and combinations thereof.

Detailed description of the figures

Figure 1 shows a simplified overview of a possible process scheme according to the invention. Raw plastic (1) waste is introduced into a liquefaction unit (2) under conditions suitable to produce a plastic liquefied oil (5), gas (3) and char (4). The plastic liquefied oil (5) then enters a mixing unit (6) where the additives are mixed to the plastic liquefied oil (5) to obtain a stabilized composition (7). The stabilized composition (7) then enters hydrotreatment unit (8), optionally presenting a top guard bed to remove solids and impurities. The hydrotreated plastic liquefied oil (9) then enters an evaporation section (10) before being submitted to steamcracking in a steam cracker (11) to produce light olefins e.g. from C2 to C4 olefins and heavier products. Optionally, the stabilized composition (7) or the hydrotreated plastic liquefied oil (9) may be separated into several streams in a separation section (not represented), for example selected according to distillation ranges, for example to separate streams such as GPL, gasoline, diesel, heavy fuel, kerosene, which may be further treated in the steam cracker. It is then possible to treat in the hydrotreatment unit (8) or into the steam cracker (11) one or several of the separated streams selected as a function of the products sought.

Figure 2 shows a simplified overview of another possible process scheme according to the invention. This process scheme is the same as the one of figure 1 up to the hydrotreatment unit (8), and the same references design the same elements. The hydrotreated plastic liquefied oil (9) here enters another (i) hydroprocessing unit 12 such as a hydrocracking unit, a catalytic hydrogenation unit, or any other hydrotreatment unit, and/or (ii) a FCC unit (13), and/or (iii) an isomerization unit (14) and/or (iv) a separation unit (15). Optionally, the stabilized composition (7) or the hydrotreated plastic liquefied oil (9) may be separated into several streams in a separation section (not represented), for example selected according to distillation ranges, for example to separate streams such as GPL, gasoline, diesel, heavy fuel, kerosene, which may be further treated in hydroprocessing unit (12) and/or the FCC unit (13) and/or the isomerization unit (14). It is then possible to treat in one or several of the units (12)-(14), one or several of the separated streams selected as a function of the products sought. Figure 3 is a graph representing the pressure variation across a reactor during the processing of a plastic liquefied oil without stabilization and with stabilization.

Figures 4 to 6 are photos of the test tubes of example 4 for tests 1-3 respectively.

Examples

Example 1

An additive capable to reduce gums formation or buildup, here a phenolic compound, BHT (butylated hydroxyltoluene), has been added to several pyrolysis plastic oils. Existing gums have been determined by means of NF EN ISO 6246 (2018), potential gums by ASTM D873-12(2018).

The characteristics of the pyrolysis plastic oils alone and with the additive are presented in table 1.

Table 1

These results show a reduction of the formation of gums with the addition of BHT, particularly for potential gums.

Example 2

Tests were performed using a pyrolysis oil cut having a boiling point ranging from 36 to 590°C, a nitrogen content of about 1500 wt ppm, a Si content of about 150 wt ppm, a chlorine content of about 500 wt ppm and a sulfur content of about 20 wt ppm. The pyrolysis oil was also characterized by a MAV at the inlet of about 7 gl2/100g and a Bromine Number of about 60 gBr2/100g. A sulfided NiMo on alumina catalyst was used in dilution with silicon carbide at equal volumes.

The tests were performed in the operating conditions presented in table 2.

Table 2 - test conditions 300 wt ppm of BHT has been added to the pyrolysis oil cut before the test. Since the beginning of the pyrolysis oil feeding, a delta P in the reactor appears, as shown in figure 3.

Then, the same pyrolysis oil with the 300 wt ppm of BHT and about 2000 ppm of a detergent containing sulfonate was processed and no delta P appears during minimum 4 days (see figure 3).

Example 3

A pyrolysis oil cut HPP4 having the properties collected in table 3 has been heated with different additives.

The test proceeding is the following. 30ml of pyrolysis oil cut HPP4 has been introduced in a test tube in glass and heated at 200°C during 2 hours in presence of a piece of steel. This test has been made with the HPP4 alone (Test 1), the HPP4 with 1000 wt ppm of BHT (Test 2), and the HPP4 with 1000 wt ppm of a mixture 50/50 of BHT and a dispersant (Test 3). The dispersant used in test 3 is the commercial dispersant Total PIBSI® and contains reaction products between polyisobutylene succinic anhydride and tetraethylene pentaamine (CAS n°84605-20-9). At the end of the tests, the gum quantity in the HPP4 has been measured by the existing gum method NF EN ISO 6246 (2018) with a lower sample quantity of pyrolysis oil cuts, and the quantity of gums deposited on the test tube and on the piece of steel have ween weighted, the gum contents are collected in table 4.

Table 4 - Gum contents

The photos of the tubes at the end of the tests are shown in figures 4-6. We can observe a difference in the colors of the deposits between the photos of the tube with the dispersant/BHT mixture (test 3-fig. 6) and without additive (test 1 -fig.4). On the other hand, the gum values are lower in the oil and on the test tube with the BHT/dispersant mixture (test 3) than with BHT alone (test 2). This additive mixture seems to be more effective than BHT alone when considering the deposits on the test tube only. In tests 2 and 3, no deposits were observed on the piece of steel.

These tests show a synergy of the dispersant + BHT additives for the minimization of deposits on the test tube compared to BHT alone. As the deposit of gums is less important for the BHT/dispersant mixture than with BHT, high temperatures treatments for a longer period can be envisaged.

Example 4

The pyrolysis oil cut HPP4 of example 3 has been tested with a tall oil derivative as additive which is the reaction product of tall oil fatty acid and diethylenetriamine. The CAS number of the tall oil derivative is 1226892-43-8.

Oxidation stability tests, such as induction period measurements, have been performed with and without the tall oil derivative, in presence of steel. The results are collected in table 5. It can be seen a net improvement of the oxidation stability in the presence of the additive.