METHOD FOR THE PURIFICATION OF A PLASTIC LIQUEFACTION OIL COMPOSITION

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for purifying a composition comprising a plastic liquefaction oil and the subsequent use thereof in refining and petrochemical methods. The method according to the invention in particular makes it possible to reduce the heteroatom concentration of the feedstocks coming from plastic waste, particularly in view of the use thereof in a steam cracking method.

TECHNOLOGICAL BACKGROUND

Plastic waste is often directed towards landfill sites or incinerated, and a smaller portion is recycled. However, there is a significant need, encouraged by regulations, to limit plastic waste in landfill sites. On the other hand, the elimination of plastic waste in landfill sites is becoming increasingly difficult. Therefore, it is necessary to recycle plastic waste.

One possible area for recycling plastic is the liquefaction of plastic by pyrolysis or hydrothermal liquefaction. However, the plastic oil obtained generally contains large amounts of dienes and heteroatoms, of which metals. Many heteroatoms, including metals, are contaminants for the catalysts in the hydrotreatment methods usually carried out to recycle plastics. Furthermore, dienes react easily by forming gums. Dienes are also coke precursors in a steam cracker. It is therefore necessary to pre-treat the plastic liquefaction oils in order to be able to recycle them.

Many treatment methods exist for reducing the heteroatom content of plastic liquefaction oils. Patent JP3776335 discloses a method for the dechlorination and denitrogenation of an oil derived from catalytic or thermal cracking of plastic waste that is treated at various temperatures up to 425° C. for 30 minutes in the presence of an aqueous solution of an alkaline compound of an alkali metal or alkaline-earth metal at a pH greater than or equal to 7. The product of the reaction is subsequently separated from the alkaline aqueous solution by liquid-liquid separation with ethyl ether.

Patent application WO2012/069467 claims a method for eliminating siloxanes contained in a plastic pyrolysis oil by heat treatment between 20° and 350° C. in the presence of an alkali metal hydroxide in the solid state or in solution. The use of calcium hydroxide at 5% by weight at 225° C. does not make it possible to obtain reduction of the siloxane content (Table 5, p. 12 and rows 9 to 11, p. 13). At the end of the reaction, the pyrolysis oil is separated by distillation under reduced pressure.

Patent F1128848 describes a method sequence comprising heat treating a plastic pyrolysis oil at at least 200° C. in the presence of an alkaline aqueous solution. At the end of the reaction, the pyrolysis oil is separated from the alkaline aqueous phase. A final hydrotreatment makes it possible to obtain a steam-cracker feedstock that is possibly washed by an acid solution before introduction into the steam cracker.

Patent application WO2020/020769 claims a method sequence for purifying a composition comprising at least 20 ppm of chlorine. A large amount of recyclable liquid waste can be treated, including plastic pyrolysis oils. The method sequence comprises heat treating the feedstock in the presence of an alkali metal hydroxide in order to obtain a reduction of at least 50% of the chlorine content in relation to the feedstock, followed by hydrotreatment in order to obtain a further reduction of at least 50% of the chlorine content.

Patent application WO2021/105326 claims a method for recovering liquefied plastic waste comprising a step of pre-treating the liquefied plastic waste by bringing it into contact with an aqueous medium having a pH of at least 7 at a temperature of 200° C. or more, followed by liquid-liquid separation wherein the aqueous phase is separated from the organic phase, to produce a pre-treated liquefied waste plastic material. The proposed solution comprises using a NaOH solution in water. The separation of aqueous and organic phases is implemented by physical (centrifugation) or chemical (addition separation assistance additives, for example non-aqueous solvents, addition of extra quantities of the aqueous medium used for contact or of an aqueous medium with a different alkaline concentration) methods, or by gravity.

Most existing purification treatments are carried out at relatively high temperatures. Furthermore, these treatments do not have means for reducing the content of silicon or also of alkali/alkaline-earth metals present in the plastic pyrolysis oil after pre-treatment by a base. Yet, it is known that the presence of alkali/alkaline-earth metals may result in deactivating the catalysts used in the catalytic methods for recycling purified plastic liquefaction oil. In addition, known purification methods use high amounts of reagents and/or water.

Therefore, there is a need to improve the existing purification methods.

Document WO2022/079053A1 describes a method for recovering hydrocarbons from a hydrocarbon liquid comprising aliphatic hydrocarbons, organic compounds containing heteroatoms, and optionally aliphatic hydrocarbons. In one embodiment, the feedstock is subjected to a first wash at a temperature of 4 to 300° C. with a solvent that may be basic water. Then, after separation of the solvent, the washed feedstock is sent into an extraction column to be treated there with a solvent which may be water at a pH of 6 to 8. The feedstock (separated from the water) leaving this extraction column is then sent to a second extraction column into which an extraction solvent and possibly water are introduced. At the outlet of this second extraction column, the feedstock is recovered on the one hand and on the other hand the extraction solvent, possibly mixed with water, which is then mixed with a demixing solvent (which may be water) then sent into a decanter and into a distillation column that separates the extraction solvent and the demixing solvent. This can then be reused for the first wash. However, this method is complex and requires purifying the demixing solvent to reuse it.

SUMMARY OF THE INVENTION

The aim of the invention is to propose a method for purifying plastic liquefaction oil for facilitating the purification thereof and reducing the amount of reagents and water used, while maintaining high performance in reducing heteroatoms, particularly silicon, including for reducing the alkali and/or alkaline-earth metal content resulting from treating plastic liquefaction oil by a basic compound containing for example an alkali metal or alkaline-earth metal.

To this end, the invention relates to a method for purifying a composition comprising a plastic liquefaction oil comprising the following steps of:

• • (a) providing a composition comprising a plastic liquefaction oil, said composition containing at least 20 ppm by mass of heteroatoms,
  • (b) washing the composition provided in step (a) with a first aqueous solution to obtain an organic phase containing the washed composition and a first aqueous effluent containing the first aqueous solution and at least a portion of the heteroatoms initially contained in the composition,
  • (c) treating the organic phase of step (b) in the presence of a basic compound at a temperature of at most 450° C. to obtain an organic effluent comprising a treated composition,
  • (d) washing the organic effluent of step (c) with a second aqueous solution and obtaining a purified composition having a reduced heteroatom content, and a second aqueous effluent containing the second aqueous solution, the basic compound, and at least a portion of the heteroatoms initially contained in the treated composition,
  • the method further comprising at least one of the following features:
    • in step (b), the first aqueous effluent is returned in whole or in part to step (d) and added to the second aqueous solution,
    • in step (d), the second aqueous effluent is returned in whole or in part to step (b) and added to the first aqueous solution, or constitutes the first aqueous solution.

The first washing step (b) makes it possible in particular to reduce the content of the composition in oxygenated compounds and also to limit the amount of solids formed during step (c), while the second washing step (d) will make it possible to remove impurities containing heteroatoms, in particular alkaline metals, alkaline-earth metals, silicon, chlorine, bromine, iron, aluminum and the like, as well as the basic compound used in treatment step (c).

Surprisingly, the use of the first aqueous effluent and/or the second aqueous effluent in steps (d) and (b) respectively makes it possible to improve the treatment of the composition while limiting both the amount of water used, but also the amount of basic compound used. In particular, the method according to the invention makes it possible to remove 65 to 98% of one or more heteroatoms present in the composition. In particular, the method according to the invention makes it possible to obtain a purified composition having a silicon content of less than 2 ppm, and/or a metal content, in particular alkaline-earth metals, of less than 2 ppm.

This advantage is more particularly observed when the first aqueous effluent is returned in whole or in part to step (d) and the second aqueous effluent is returned in whole or to part in step (b). The first and second aqueous effluents can then circulate in a circuit connecting the two washing sections carrying out the two washing steps, optionally with the possibility of injecting fresh water into this circuit and/or extracting part of the aqueous phase circulating in the circuit.

Thus, in one embodiment, the first aqueous effluent and the second aqueous effluent circulate in a circuit connecting a first washing section carrying out the washing step (b) to a second washing section carrying out the washing step (d). This circuit thus forms a fluid circulation loop connecting, in particular directly, the first washing section and the second washing section, this loop leading, on the one hand, the first aqueous solution from the first washing section to the second washing section, and, on the other hand, the second aqueous solution from the second washing section to the first washing section. Advantageously, this circuit has no treatment sections except, optionally, for one or more sections for separating the solids by (i) filtration, (ii) centrifugation, (iii) hydrocyclone or (iv) a combination of these techniques, to remove the solids. There are therefore no extraction, distillation or similar columns in the circuit.

In order to maintain a constant water flow in this circuit, water can be added by regularly injecting water inside the circuit, advantageously upstream of the second washing section. It may also be provided to withdraw a portion of the fluid circulating in the circuit, preferably a portion of the first aqueous effluent, upstream of the water injection.

Thus, advantageously, water is injected into the circuit, optionally upstream of the second washing section, and optionally a portion of the fluid circulating in the circuit is withdrawn. Advantageously, before entering step (c), the organic phase of step (b) can be pre-heated in a heat exchanger by the second effluent of step (c).

Step (c) according to the invention may comprise one or more of the following features:

• • step (c) is carried out in the presence of 0.1 to 50% m of basic compound in relation to the total mass of the treated organic phase,
  • prior to step (c) or during step (c), (i) a solid basic compound, (ii) a basic compound solubilized beforehand in an aqueous medium, preferably water, or (iii) a basic compound solubilized beforehand in a solvent, is added to the organic phase of step b),
  • the basic compound comprises an oxide, a hydroxide, a bicarbonate or an alcoholate of an alkali metal cation or of an alkaline-earth metal cation, or a hydroxide or a bicarbonate of a quaternary ammonium cation, alone or in a mixture,
    • the basic compound may be selected from LiOH, NaOH, CsOH, Ba(OH)₂, Na₂O, KOH, K₂O, CaO, Ca(OH)₂, MgO, Mg(OH)₂, NH₄OH, TBuOH, TEAOH, TMAOH, EtONa, MeONa and mixtures thereof,
  • step c) is carried out at a temperature of 50 to 450° C., preferably of 50 to 350° C., more preferably of 50 to 250° C., even more preferably of 50 to 225° C. or of 50 to 200° C., or of 90° C. to 200° C. or of 150 to 200° C. or in any interval defined by any two of these limits,
    • step (c) is performed for a duration of 0.1 seconds to 3 hours, preferably of 0.1 seconds to 2 hours, more preferably of 1 minute to 1 hour, even more preferably of 1 minute to 20 minutes or of 1 minute to 16 minutes.

Step (c) according to the invention can be followed by a separation step during which the basic compound is separated from the effluent and returned in whole or in part upstream of step (c), advantageously at the inlet of step (c), the separation step being performed by (i) filtration (ii) centrifugation, (iii) hydrocyclone, (iv) decantation or (v) a combination of two or more of these steps.

Step (d) according to the invention can be followed by a step of separating solids by (i) filtration, (ii) centrifugation, (iii) hydrocyclone or (iv) a combination of two or more of these steps.

Advantageously, prior to the treatment in step (b), said composition is subjected to (i) filtration, (ii) distillation, (iii) decantation, or (iv) a combination of two or three of steps (i) to (iii).

Advantageously, (e) the purified composition of step (d), pure or diluted, can be subjected to catalytic hydrotreatment, i.e. catalytic treatment under hydrogen, in one or two steps to provide a hydrotreated purified composition.

The hydrotreatment of step (e):

• • can be carried out in a single step wherein the purified composition of step (d) is hydrotreated at a temperature of 200 to 450° C., preferably of 200 to 380° C. in the presence of hydrogen at an absolute pressure of 20 to 140 bar, preferably of 30 to 100 bar and in the presence of a hydrotreatment catalyst, or
  • can be carried out in a first step (e-1) wherein the purified composition of step (d) is hydrotreated, preferably selectively hydrogenated, at a temperature of 80 to 250° C., preferably of 130 to 250° C. in the presence of hydrogen at an absolute pressure between 5 and 150 bar, preferably 20 to 100 bar and in the presence of a first hydrotreatment catalyst, and in a second step (e-2) wherein the effluent from step (e-1) is hydrotreated at a temperature of 200 to 450° C., preferably of 250 to 340° C. in the presence of hydrogen at an absolute pressure of 20 to 150 bar, preferably of 30 to 100 bar and in the presence of a second hydrotreatment catalyst.

Advantageously, the hydrotreated and purified composition exiting step (e) can further be washed in water to eliminate inorganic compounds such as hydrosulfide, hydrogen chloride, ammonia.

Advantageously, the purified composition of step (d) or the hydrotreated purified composition of step (e) can be:

• • (f) used as such or separated into usable streams for preparing fuels and combustibles such as LPG, petrol, diesel, heavy fuel, kerosene and/or for preparing lubricants and/or base oils, and/or treated, pure or diluted, optionally separated into usable streams, in:
  • (g) a steam cracker to produce olefins, and/or
  • (h) a fluidized-bed catalytic cracker, and/or
  • (i) a hydrocracker, then optionally in a steam cracker.

Preferably, the purified composition of step (d) or the hydrotreated purified composition of step (e) may be subjected, pure or diluted, optionally after separating into usable flows, to a step of steam cracking (g) to produce olefins such as ethylene and propylene as well as aromatics such as toluene, xylene and benzene, which may subsequently serve to manufacture new polymers by polymerization.

The previously described steps of the method according to the invention may be carried out one after another without any intermediate steps apart from the optional additional steps described.

In particular, in one particularly preferred embodiment, the method may comprise one or more of the following features:

• • in step (b), the first aqueous effluent is returned in whole or in part to step (d) and added to the second aqueous solution without any intermediate treatment step other than an optional step of separating the solids by (i) filtration (ii) centrifugation (iii) hydrocyclone or (iv) a combination of two or three of these steps,
  • in step (d), the second aqueous effluent is returned in whole or in part to step (b) and added to the first aqueous solution, or constitutes this first aqueous solution, without any intermediate treatment step other than an optional step of separating the solids by (i) filtration (ii) centrifugation (iii) hydrocyclone or (iv) a combination of two or three of these steps.

The invention also relates to an installation comprising an optional pretreatment section (A), a first washing section (B), a treatment section (C), an optional separation section (S), a second washing section (D), an optional hydrotreatment section (E) and/or an optional section (F) for preparing a fuel or lubricant or base oil and/or an optional treatment section in a steam cracker (G) and/or an optional treatment section in a fluidized-bed catalytic cracker (H) and/or an optional treatment section in a hydrocracker (I), wherein the different sections are fluidically connected to carry out the method according to the invention.

Advantageously, the first washing section (B) and the second washing section (D), can be connected directly to each other without passing through another treatment section other than an optional solids separation section.

Definitions

The Hourly Volumic Velocity (HVV) is defined as the hourly feedstock flow volume by the catalytic volume unit and is expressed here as h⁻¹.

The terms “comprising” and “comprises” as used here are synonymous with “including”, “includes” or “contains”, “containing”, and are inclusive or without limits and do not exclude additional features, elements or method steps not specified.

The specification of a numerical domain without decimals includes all whole numbers and, when suitable, fractions of the latter (for example, 1 to 5 may include 1, 2, 3, 4 and 5 when reference is made to a number of elements, and may also include 1.5, 2, 2.75 and 3.80, when reference is made to, for example, a measurement).

The specification of a decimal also comprises the decimal itself (for example, “from 1.0 to 5.0” includes 1.0 and 5.0). Any range of numerical values mentioned again here also comprises any sub-range of numerical values mentioned above.

The expressions % by weight and % by mass have an equivalent meaning and refer to the proportion of the mass in grams of a product relative to 100 g of a composition comprising it. Unless indicated otherwise, the measurements given in parts per million (ppm) are expressed by weight.

“Heteroatom” means any element of an organic compound other than carbon and hydrogen. The term “naphtha” refers to the general definition used in the oil and gas industry. In particular, this concerns a hydrocarbon coming from the distillation of crude oil and of which the boiling point is between 15 and 250° C., according to the standard ASTM D2887. Naphtha contains practically no olefins because the hydrocarbons come from crude oil. It is generally considered that a naphtha has a carbon number between C5 and C11, although the carbon number may in some cases reach C15. It is also generally accepted that the density of naphtha is between 0.65 and 0.77 g/mL.

“Liquefaction oil” means an oil derived from a pyrolysis method and/or from a hydrothermal liquefaction method of hydrocarbon feedstock. This hydrocarbon feedstock may comprise plastics, biomass and/or elastomers, alone or in a mixture, particularly in the form of waste. A liquefaction oil may be formed of a mixture of two or more liquefaction oils coming from the liquefaction of different hydrocarbon feedstocks.

The pyrolysis method must be understood as a thermal cracking method, typically performed at a temperature of 300 to 1,000° C. or of 400 to 700° C., carried out in the presence or not of a catalyst and/or of a gas (rapid pyrolysis, flash pyrolysis, catalytic pyrolysis, hydropyrolysis, steam pyrolysis, etc.).

The Hydrothermal Liquefaction (or HTL) method is a thermochemical conversion method using water as solvent, reagent and catalyst of reactions for degrading a hydrocarbon feedstock, water typically being in a sub-critical or super-critical state. The hydrothermal liquefaction method is typically performed at a temperature of 250 to 500° C. and at pressures of 10 to 25-40 MPa in the presence of water.

The expression “plastic liquefaction oil” or “oil resulting from plastic liquefaction” or “plastic-waste liquefaction oil” or “liquefaction oil resulting from the liquefaction of waste containing plastics materials” refers to the hydrocarbon liquid products obtained at the end of pyrolysis or of hydrothermal liquefaction of thermoplastic and/or thermosetting polymers, alone or in a mixture and generally in the form of waste, optionally in a mixture with at least one other feedstock, in particular in the form of waste, such as biomass, for example selected from lignocellulosic biomass, paper and cardboard, and/or an elastomer, for example latex, optionally vulcanized, or tires.

The plastic may be of any type, particularly any type of new or used plastic, including in household (post-consumption) or industrial waste. Plastics means materials formed of polymers and optionally of auxiliary components such as plasticizers, feedstocks, dyes, catalysts, flame retardants, stabilizers, etc. For example, these polymers may be polyethylene, halogenated polyethylene (Cl, F), polypropylene, polystyrene, polybutadiene, polyisoprene, polyethylene terephthalate (PET), polylactic acid (PLA), acrylonitrile-butadiene-styrene (ABS), polybutylene, polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polyvinylidene chloride, a polyester, a polyamide, a polycarbonate, a polyether, a polymer epoxide, a polyacetal, a polyimide, a polyester amide, silicone, etc. Generally speaking, it is possible to use any polymer or mixture of polymers able to produce hydrocarbons by liquefaction.

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

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

The expression “MAV” (the acronym of “Maleic Anhydride Value”) refers to the UOP326-82 method that is expressed in mg of maleic anhydride that reacts with 1 g of sample to be measured.

The expression “Bromine number” corresponds to the amount of bromine in grams having reacted on 100 g of sample and can be measured according to the ASTM D1159-07 method. The expression “Bromine index” is the number of milligrams of bromine that react with 100 g of sample and can be measured according to the ASTM D2710 or ASTM D5776 methods.

The boiling points as mentioned here are measured at atmospheric pressure, unless specified otherwise. An initial boiling point is defined as the temperature value from which a first vapor bubble is formed. A final boiling point is the highest temperature that can be reached during a distillation. At this temperature, no more vapor can be transported to a condenser. Determining the initial and final points makes use of techniques known in the art and a plurality of methods adapted according to the distillation temperature range are applicable, for example NF EN 15199-1 (2020 version) or ASTM D2887 for measuring the boiling points of petroleum fractions by gas chromatography, ASTM D7169 for heavy hydrocarbons, ASTM D7500, D86 or D1160 for distillates.

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

“Hydrotreatment” means any method during which hydrocarbons react with dihydrogen, typically under pressure, in the presence of a catalyst or not. Hydrotreatment may thus comprise one or more reactions selected from hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodeoxygenation (HDO), hydrodemetallation (HCM), hydrocracking, hydroisomerization and hydrogenation (hydrogenation of unsaturated compounds to saturated compounds).

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

The particular features, structures, properties, embodiments of the invention can be freely combined into one or more embodiments not specifically described here, as this may be apparent to plastic liquefaction oil treatment specialists implementing their general knowledge.

DETAILED DESCRIPTION OF THE INVENTION

Description of the Composition Comprising a Plastic Liquefaction Oil

The composition provided in step (a) comprises a plastic liquefaction oil. This plastic liquefaction oil may be a plastic pyrolysis oil, a plastic hydrothermal liquefaction oil, or a mixture of both.

In one preferred embodiment, the composition may only comprise a plastic liquefaction oil. Alternatively, the composition treated by the method according to the invention can comprise at least 1% by mass, or at least 2% by mass plastic liquefaction oil(s). The remainder may then be composed of at most 99% by mass, respectively at most 98% by mass, of a diluent or solvent such as a hydrocarbon and/or of one or more components listed below.

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

The composition may comprise one or more of the following components: a tall oil, a waste food oil, an animal fat, a vegetable oil such as a colza, canola, castor, palm or soya oil, an oil extracted from algae, an oil extracted by fermentation of oleaginous microorganisms such as oleaginous yeasts, a biomass liquefaction oil, in particular a biomass liquefaction oil such as Panicum virgatum or a lignocellulosic biomass liquefaction oil, for example a wood, paper and/or cardboard liquefaction oil, an oil obtained by liquefying crushed used furniture, an elastomer liquefaction oil, for example latex, which may be vulcanised, or tires, as well as mixtures thereof.

The composition may have a bromine content of at most 150 g Br₂/100 g, preferably of at most 100 g Br₂/100 g, even more preferably at most 80 g Br₂/100 g, the most preferred being at most 50 g Br₂/100 g, as measured according to the standard ASTM D1159.

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

The other component may comprise any diluent miscible with the plastic liquefaction oil. Preferably, this diluent has a diene index of at most 0.5 g l₂/100 g, measured according to UOP 326-17, a bromine index of at most 5 g Br₂/100 g, measured according to ASTM D1159. Preferably, the diluent is selected from a naphtha and/or a paraffinic solvent and/or a diesel or a direct distillation gas oil, containing at most 1% by weight of sulfur, preferably at most 0.1% by weight of sulfur, and/or a hydrocarbon stream having a boiling range between 50° C. and 150° C. or a boiling range between 150° C. and 250° C. or a boiling range between 200° C. and 350° C., preferably having a bromine index of at most 5 g Br₂/100 g, and/or a diene index of at most 0.5 gl₂/100 g or any combination thereof.

Step (a) of providing the composition may comprise:

• • (a1) a step of liquefying waste containing plastics and obtaining a hydrocarbon product comprising a gaseous phase, a liquid phase and a solid phase,
  • (a2) a step of separating the liquid phase from said product, said liquid phase forming a plastic liquefaction oil,
  • (a3) an optional step of mixing the plastic liquefaction oil with a diluent or a solvent.

The liquefaction step (a1) may comprise a pyrolysis step, typically performed at a temperature of 300 to 1,000° C. or of 400 to 700° C., this pyrolysis being for example a rapid pyrolysis or a flash pyrolysis or a catalytic pyrolysis or a hydropyrolysis.

Alternatively or in combination, the liquefaction step (a1) may comprise a hydrothermal liquefaction step, typically performed at a temperature of 250 to 500° C. and at pressures of 10 to 25-40 MPa.

The waste treated in step (a1) can be plastic waste optionally mixed with biomass, as described above.

The separation step (a2) removes the gaseous phase, essentially C1-C4 hydrocarbons and the solid phase (typically char) in order to only recover the liquid organic phase forming a liquefaction oil.

A plastic liquefaction oil typically comprises 30 to 80% m/m of paraffins (including cyclo-paraffins), 10 to 95% m/m of unsaturated compounds (comprising olefins, dienes and acetylenes), 5 to 70% m/m of aromatics. These contents may be determined by gas chromatography.

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

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

A plastic liquefaction oil can in particular comprise one or more of the following heteroatom contents: from 0 to 8% m/m oxygen (measured in accordance with ASTM D5622), from 1 to 13,000 ppm of nitrogen (measured in accordance with ASTM D4629), from 2 to 10,000 ppm of sulfur (measured in accordance with ISO 20846) from 1 to 10,000 ppm of metals (measured by ICP), from 50 to 6,000 ppm of chlorine (measured in accordance with ASTM D7359-18), from 0 to 200 ppm of bromine (measured in accordance with ASTM D7359-18), from 1 to 40 ppm of fluorine (measured in accordance with ASTM D7359-18), 1 to 2,000 ppm of silicon (measured by XRF).

Detailed Description of the Optional Step of Pre-Treating the Composition

Prior to washing step (b), generally between step (a) and (b), the invention may also comprise an optional pre-treatment step, wherein said composition is subjected, in particular immediately prior to step (b) to (i) filtration, (ii) distillation, (iii) a decantation, or (iv) the combination of two or three of the steps (i) to (iii). This additional step may make it possible to reduce a proportion of the impurities contained in the composition such as oxygen, nitrogen, chlorine, sulfur or other heteroatoms. In particular, reducing the amount of oxygen may make it possible to prevent the formation of solids and/or of gels during step (d).

Detailed Description of the First Washing Step (Step (b))

During this first washing step (b), the composition provided in step (a), optionally pre-treated as described above, is washed with a first aqueous solution to obtain an organic phase containing the washed composition and a first aqueous effluent containing the first aqueous solution and at least a portion of the heteroatoms initially contained in the composition. In other words, at the end of this first washing step, the organic phase and the first aqueous effluent are recovered separately, for example following a liquid/liquid separation (centrifugation and/or decantation and/or other such as by hydrocyclone or filtration) carried out at the end of the washing step. The washing step thus integrates a liquid/liquid separation.

This first aqueous solution may have a neutral (pH=7), basic (pH>7) or acidic (pH<7) pH.

This first aqueous solution may comprise water, and optionally some or all of the second aqueous effluent from the second washing step (d). In one particularly preferred embodiment, the second aqueous effluent can be returned in whole or in part to step (b) and added to the first aqueous solution, or constitute this first aqueous solution, without any intermediate treatment step other than an optional step of separating the solids by (i) filtration (ii) centrifugation (iii) hydrocyclone or (iv) a combination of two or three of these steps.

In one embodiment, the first aqueous solution may comprise only the second aqueous effluent. In other words, the first aqueous solution is then composed of the second aqueous effluent.

In one particularly preferred embodiment, the first aqueous solution may consist of water (acid, basic or neutral) and/or the second aqueous effluent. The volume of the second aqueous effluent may be insufficient to carry out the first washing step. In this case, it may be necessary to add water to obtain the desired volume of first aqueous solution. However, most often, the volume of second aqueous effluent is sufficient to obtain the desired volume of first aqueous solution and to fully constitute it.

When the second aqueous effluent of the second washing step (d) is used in whole or in part as the first aqueous solution in this step, the pH of the second aqueous solution will then generally be basic, which promotes the removal of the oxygenated compounds.

The first aqueous solution used may nonetheless have an acidic, basic or neutral pH, preferably a basic pH (pH>7). An acidic pH may be obtained by adding one or more organic or inorganic acids. Examples of usable organic acids comprise citric acid (C₆H₈O₇), formic acid (CH₂O₂), acetic acid (CH₃COOH). Examples of inorganic acids are sulfamic acid (H₃NSO₃), hydrochloric acid (HCl), nitric acid (HNO₃), sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄). A basic pH may be obtained by adding alkali and alkaline-earth metal oxides, alkali and alkaline-earth metal hydroxides (for example NaOH, KOH, Ca(OH)), alkali and alkaline-earth metal bicarbonates and amines (for example triethylamine, ethylenediamine, ammonia).

However, preferably no basic compound other than that present in the second aqueous effluent is added to the first aqueous solution.

This first step typically makes it possible to remove all or part of the oxygenated compounds (carboxylic acids, esters, carbonyls, alcohols) initially contained in the composition.

Part, or even all, of the basic compound from the second aqueous solution and present in the first aqueous solution may be neutralized during this first washing step so that the first aqueous effluent may have a neutral, or even acidic, pH, promoting the separation of the basic compound when the second washing step carried out.

During this washing step (b), the first aqueous solution/composition volume ratio can be from 1/99 to 90/10, from 10/90 to 90/10, from 20/80 to 80/20, from 30/70 to 70/30, from 35/65 to 65/35, from 35/65 to 60/40, or from 40/60 to 60/40.

Step (b) may be performed at a temperature of 10° C. to 120° C., preferably of 15° C. to 95° C., more preferably of 15° C. to 80° C., or also in any interval defined by any two of these limits, advantageously without external heating. Step (b) is typically carried out at atmospheric pressure.

Step (b) may comprise, or consist of, bringing the composition provided by step (a) into contact with water and/or the second aqueous effluent in a washing section by any means known in the prior art.

For example, the composition provided by step (a) and the first aqueous solution may be introduced into tanks, reactors or mixers commonly used in the profession and the two components can be mixed. Contact may comprise vigorously stirring the two components with a mixing device. For example, the two components may be mixed together by stirring or by shaking. Alternatively, contact may be made in an enclosure wherein the two components flow counter-current, for example in contact columns with an adequate lining in order to increase the contact between the treated composition phase and the water or an immiscible solvent. Alternatively, contact may be made in a static mixer in co-current mode or in a cavitation chamber.

Contact may occur more than once, particularly in the conditions set out above.

The washing step (b) may be carried out continuously or in batches.

Detailed Description of Step (c)

Step (c) is a step of treating the organic phase of step (b) in the presence of a basic compound at a temperature of at most 450° C. to obtain an organic effluent comprising a treated composition.

In particular, this treatment makes it possible to modify the compounds containing heteroatoms and to promote their subsequent elimination.

In general, it should be noted that, as part, or even the majority, of oxygenated compounds initially present in the composition were removed during the first washing step, the amount of basic compound required in this treatment step may be reduced compared to a method not comprising this first washing step. The invention thus makes it possible to save up to 40% or more of the amount of basic compound used during step (c), but also to limit the corrosion problems related to the presence of acidic oxygenated compounds and to limit the formation of solids during the washing step (d), facilitating the implementation thereof. The invention can also make it possible to reduce the amount of impurities to be removed remaining in the organic effluent comprising the treated composition exiting step (c), which can make it possible to reduce, the amount of water required during step (d).

Step (c) is carried out in the presence of a basic compound, preferably a nucleophilic basic compound.

Advantageously, the basic compound may have a pKa in water of at least 7.5.

Advantageously, the amount of basic compound used is 0.1 to 50% m, preferably 0.1 to 40% m, more preferably 0.1 to 30% m, more preferably 0.1 to 20% m, even more preferably 0.1 to 15% m relative to the total mass of the treated composition (organic phase provided by step (b)).

Preferably, the amount of basic compound used is at least 0.5% m, more preferably at least 1% m, even more preferably at least 3% m, even more preferably at least 5% m or even at least 10% m, and at most 50% m, 40% m, 30% m, 20% m or 15% m, relative to the total mass of the treated composition (organic phase provided by step (b)).

In one embodiment, during step (c), the organic phase may be brought into contact with 0.1 to 15% by mass of a basic compound, preferably in the presence of water, more preferably with 0.5 to 15% by mass of a basic compound, still more preferably with 1 to 15% by mass of a basic compound, in particular from 3 to 15% by mass, or even from 5 to 15% by mass or from 10 to 15% by mass relative to the total mass of the treated composition, or in any interval defined by two of the preceding limits.

The basic compound may be added to the organic phase provided by step (b) either before step (c) or during step (c). This addition of the basic compound to the organic phase can optionally be followed by a mixing step before carrying out step (b).

The basic compound may be added to the organic phase in solid form or solubilized in an aqueous medium, preferably water. In particular, step (c) may be carried out without the addition of a solvent other than water or a solvent possibly already present in the composition.

Advantageously, the basic compound added in step (c) is in solution in water. Thus, during step (c), the organic phase may be brought into contact with an aqueous solution of a basic compound, preferably a basic compound comprising an alkali or alkaline-earth metal cation. A person skilled in the art will then choose an amount of water sufficient to dissolve/solubilize the basic compound, preferably the smallest amount of water possible, or just enough to saturate the water with the basic compound.

Alternatively, the basic compound may be added to the organic phase solubilized in a solvent, miscible or non-miscible with said organic phase.

When the basic compound is solubilized in a solvent or in water, a person skilled in the art will then select a sufficient amount of solvent/water to dissolve/solubilize it, preferably the smallest possible amount of solvent/water. The volume ratio of the solvent/water containing the basic compound/organic phase, i.e. the volume ratio of the mixture (basic compound+solvent or water)/organic phase, may be 0.1/99.9 to 80/20, 1/99 to 80/20, 1/99 to 70/30, 1/99 to 65/35, 1/99 to 60/40, 1/99 to 50/50, or also in any interval defined by any two of the aforementioned limits.

A solution, particularly an aqueous solution, saturated in basic compound may advantageously be used.

Advantageously, the basic compound added in step (c) is in solution in water or in a solvent, and the basic compound content of the water or of the solvent is from 0.1 to 50% by mass, preferably from 15 to 50% by mass, more preferably from 25% to 50% by mass, preferably from 40 to 50% by mass, even more preferably the water (or the solvent) is saturated with basic compound, in particular the water (or the solvent) contains just enough basic compound to obtain a saturated solution.

A usable miscible solvent may be a polar solvent comprising an alcohol function and/or an ether function, ideally selected from C1 to C4 alcohols, preferably from methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, 2-methylpropan-1-ol, propylene glycol.

A usable non-miscible solvent may be a non-miscible polar solvent.

By way of example, it may be considered that the polar solvent (or that a mixture of polar solvents if applicable) is immiscible when the recovery rate thereof is higher than or equal to 0.95. This recovery rate is defined as the ratio of the volume of extract to the volume of initial solvent, this extract being a phase containing the solvent, not miscible with the composition containing a liquefaction oil, recovered after stirring and then decantation of a mixture of one part per volume of solvent with twenty-five parts per volume of the composition containing a liquefaction oil to be purified, at atmospheric pressure and at a temperature of 20° C.

In particular, it will be possible to determine this recovery rate by following the following procedure:

• • Introduce 50 mL of composition containing a liquefaction oil into a flat-bottomed flask with a volume of 100 mL, with the aid of a precision pipette of +/−0.5 mL,
  • Introduce 2 mL of solvent into the flask, with the aid of a precision pipette of +/−0.1 mL,
  • Introduce a magnetic stirring bar, close the flask with a polypropylene cap,
  • Stir the mixture on a mechanical stirrer plate at a speed of 500 rpm for 5 min.,
  • At the end of the 5 minutes, stop stirring, remove the magnetic stirring bar with the aid of a magnetic rod,
  • Transfer the content of the flask into a graduated tube having a precision of +/−0.05 mL for a volume less than or equal to 2 mL and a precision of +/−0.1 mL for a volume greater than 2 mL. Wait for complete demixing by decantation and measure the volume of the 2 phases with the aid of graduated markings. It is considered that complete demixing is achieved when the volumes of the two phases no longer vary.

Acceptable immiscible polar solvents comprise (i) sulfur compounds, for example dimethyl sulfoxide, (ii) nitrogen compounds, for example N,N-dimethylformamide, (iii) halogen compounds, for example dichloromethane or chloroform, (iv) ethylene glycol, or also:

• • glycol ethers, particularly including polyethylene glycol of chemical formula HO—(CH₂—CH₂—O)_n—H with a weight-average molar mass of 90 to 800 g/mol, for example diethylene glycol and tetraethylene glycol, polypropylene glycol of chemical formula H[OCH(CH₃)CH₂]_nOH with a weight-average molar mass of 130 to 800 g/mol, for example dipropylene glycol and tetrapropylene glycol,
  • dialkyl formamides, wherein the alkyl group may comprise 1 to 8 or 1 to 3 carbon atoms, particularly dimethyl formamide (DMF),
  • dialkyl sulfoxides, wherein the alkyl group may comprise 1 to 8 or 1 to 3 carbon atoms, particularly dimethyl sulfoxide (DMSO) and sulfolane,
  • compounds comprising a furan cycle,
  • cyclic carbonate esters, particularly comprising 3 to 8 or 3 to 4 carbon atoms, particularly propylene carbonate and ethylene carbonate.

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

Preferably, the polar solvent may be ethylene glycol or a glycol ether, in particular polyethylene glycol of chemical formula HO—(CH₂—CH₂—O)_n—H with a weight-average molar mass of 90 to 800 g/mol or polypropylene glycol of chemical formula H[OCH(CH₃)CH₂]_nOH with a weight-average molar mass of 130 to 800 g/mol, or a compound comprising a furan cycle, or a cyclic carbonate ester, in particular ethylene or propylene carbonate, alone or in a mixture, preferably alone.

In one preferred embodiment, the polar solvent is selected from propylene carbonate, ethylene carbonate, ethylene glycol and polyethylene glycol of chemical formula HO—(CH₂—CH₂—O)_n—H with a weight-average molar mass of 90 to 800 g/mol, alone or in a mixture, preferably alone.

In one embodiment, the basic compound may comprise an oxide, a hydroxide, a bicarbonate, or an alcoholate of an alkali metal cation or of an alkaline-earth metal cation, or a hydroxide or a bicarbonate of a quaternary ammonium cation, for example of a tetramethylammonium (TMA+), tetraethylammonium (TEA+), tetrapropylammonium (TPA+), tetrabutylammonium (TBA+) cation. Preferably, the basic compound may comprise an aforementioned oxide or hydroxide, alone or in a mixture.

In one preferred embodiment, the basic compound can be selected from LiOH, NaOH, CsOH, Ba(OH)₂, Na₂O, KOH, K₂O, CaO, Ca(OH)₂, MgO, Mg(OH)₂, NH₄OH, TMAOH, TEAOH, TBuOH, EtONa, MeONa, and mixtures thereof. A preferred basic compound may be selected from NaOH, KOH and mixtures thereof, preferably as solution in water.

The solvent used to solubilize the basic compound may be water, an alcohol, for example methanol or ethanol, or any other organic solvent for solubilizing the selected basic compound, preferably water or alcohol.

Step (c) may be carried out at a temperature of at most 450° C. In one embodiment, step (c) may be carried out at a temperature of 50 to 450° C., preferably 50 to 350° C., more preferably 50 to 250° C., even more preferably 50 to 225° C. or 50 to 200° C., even 90° C. to 200° C. or 150 to 200° C. or in any interval defined by any two of these limits.

The treatment step c) may be carried out at an absolute pressure of 0.1 to 100 bar, preferably from 1 to 50 bar.

In one particularly preferred embodiment, step (c) is performed for a duration of 1 minute to 3 hours, preferably from 1 minute to 1 or 2 hours, more preferably from 1 minute to 20 minutes, preferably from 1 minute to 16 minutes, at a temperature of at most 250° C., more preferably at most 225° C., even more preferably at most 200° C. In this particularly preferred embodiment, step (c) can be performed at a temperature of at least 50° C., preferably at least 90° C., more preferably at least 150° C. In this particularly preferred embodiment, step (c) can be performed at an absolute pressure of 0.1 to 100 bar, preferably from 1 to 50 bar.

In this particularly preferred embodiment, the organic phase may advantageously be brought into contact with:

• • 0.1 to 15% by mass of a basic compound, advantageously comprising an alkali or alkaline-earth metal cation, and preferably in the presence of water or an alcohol, preferably with 0.5 to 15% by mass of a basic compound, more preferably with 1 to 10% by mass of a basic compound (mass percentages of basic compound relative to the organic phase), and/or
  • with water or an alcohol containing from 15 to 50% by mass of basic compound, preferably from 25% to 50% by mass, more preferably from 40 to 50% by mass (mass percentages of basic compound relative to water or alcohol), even more preferably with water saturated in basic compound.

A preferred strong base may be selected from LiOH, NaOH, CsOH, Ba(OH)₂, Na₂O, KOH, K₂O, CaO, Ca(OH)₂, MgO, Mg(OH)₂, TMAOH, TEAOH, TBuOH, EtONa, MeONa and mixtures thereof. A more preferred strong base may be chosen from NaOH, KOH and mixtures thereof, in particular for implementing the particularly preferred embodiment.

Detailed Description of the Optional Additional Separation Step

Step (c) can be followed by a separation step during which the basic compound is separated from the organic effluent and returned in whole or in part upstream of step (c), advantageously at the inlet of step (c), the separation step being performed by (i) filtration (ii) centrifugation, (iii) hydrocyclone, (iv) decantation or (v) a combination of two or more of these steps. This makes it possible in particular to reduce the amount of basic compound used in step (c).

This optional step makes it possible to recover the basic compound in aqueous solution or in a solvent, or in solid form depending on the nature of the basic compound added in step (c). It may therefore be a liquid-liquid or liquid-solid separation, depending on the case.

Detailed Description of the Optional Additional Step of Separating the Solids

Step (d) may be followed by a step of separating the solids from the effluent of step (c) or from the organic effluent of the optional separation step by (i) filtration (ii) centrifugation (iii) hydrocyclone or (iv) a combination of two or three of these steps. This optional step may facilitate the implementation of the subsequent treatment step (steps (e), (f), (g), (h)), in particular when the optional separation step described above is not performed.

Alternatively or in combination, this optional step may be carried out on the first aqueous effluent and/or on the second aqueous effluent.

Detailed Description of the Second Washing Step (d)

In step (d), the organic effluent of step (c) is washed with a second aqueous solution. This step (d) makes it possible to recover an organic phase which forms the purified composition having a reduced heteroatom content, and a second aqueous effluent containing the second aqueous solution, the basic compound, and at least a portion, or all, of the heteroatoms initially contained in the treated composition. In other words, at the end of this second washing step, the organic phase and the second aqueous effluent are recovered separately, for example following a liquid/liquid separation (centrifugation and/or decantation and/or other such as by hydrocyclone or filtration) carried out at the end of the washing step. The washing step thus integrates a liquid/liquid separation.

This washing step (d) makes it possible to eliminate the impurities containing heteroatoms present in the organic effluent containing the treated composition exiting step (c) by solubilizing them in water. This washing step also makes it possible to separate the basic compound from the purified composition.

The second aqueous solution may comprise water, and optionally some or all of the first aqueous effluent from the first washing step (b). In one particularly preferred embodiment, the first aqueous effluent can be returned in whole or in part to step (d) and added to the second aqueous solution without any intermediate treatment step other than an optional step of separating the solids by (i) filtration (ii) centrifugation (iii) hydrocyclone or (iv) a combination of two or three of these steps.

In one embodiment, the second aqueous solution may comprise only the first aqueous effluent.

In one particularly preferred embodiment, the second aqueous solution may consist of water (acid, basic or neutral) and/or the first aqueous effluent. The volume of the first aqueous effluent may be insufficient to carry out the second washing step. In this case, it may be necessary to add water to obtain the desired volume of second aqueous solution.

In one embodiment, the second aqueous solution may comprise the first aqueous effluent to which water has been added, particularly pH neutral or acidic water.

The second aqueous solution used in step (d) may have a basic pH, an acidic pH (PH<7) or a neutral pH (pH=7). In particular, when the first aqueous solution is returned in whole or in part to the second washing step and in particular when the second aqueous solution is itself returned in whole or in part to the first washing step, the second aqueous solution used may contain basic compound used in step (c) and may thus have a basic, generally weakly basic pH. An acidic pH may be obtained by adding one or more organic or inorganic acids. Examples of usable organic acids comprise citric acid (C6H₈O₇), formic acid (CH₂O₂), acetic acid (CH₃COOH)′. Examples of inorganic acids are hydrochloric acid (HCl), sulphamic acid (H₃NSO₃), nitric acid (HNO₃), sulfuric acid (H₂SO₄) and phosphoric acid (H₃PO₄). Preferably, the water may have a pH of 0.1 to 6.9.

In one particularly preferred embodiment, in step (b), the first aqueous effluent is returned in whole or in part to step (d) and added to the second aqueous solution, and in step (d), the second aqueous effluent is returned in whole or in part to step (b) and added to the first aqueous solution. The first aqueous effluent and the second aqueous effluent can then circulate in a circuit forming a loop connecting a first washing section carrying out the washing step (b) to a second washing section carrying out the washing step (d). Such a circuit typically comprises a fluid circulation device (pump or other) and forms a circulation loop for the aqueous washing media used in steps (b) and (d). Advantageously, this circuit may comprise a water injection device for injecting water into the circuit and a tapping device, for extracting a portion of the fluid circulating in the circuit, so as to maintain a substantially constant flow of fluid between the two washing sections and/or for adjusting the volume of liquid entering each washing section. Preferably, tapping and/or injection is/are carried out upstream of the second washing section, which can promote the control of the pH of the second aqueous solution; the injected water may advantageously have a neutral or acidic pH. Preferably, this circuit does not comprise a treatment section other than an optional solids separation section.

Step (d) may be performed at a temperature of 10° C. to 120° C., preferably of 15° C. to 95° C., more preferably of 15° C. to 80° C., or also in any interval defined by any two of these limits, advantageously without external heating. Step (d) is typically carried out at atmospheric pressure or at a pressure close to the pressure at which step (c) is carried out.

Step (d) can be carried out on the effluent directly from step (c), without any intermediate step.

During step (d), the volume ratio of second aqueous solution/effluent containing the treated composition can be from 1/99 to 90/10, from 20/80 to 80/20, from 30/70 to 70/30, from 35/65 to 65/35, from 35/65 to 60/40, from 40/60 to 60/40, or in any interval defined by any two of the aforementioned limits.

Step (d) may comprise, or consist of, bringing the effluent from step (c) into contact with water and/or the first aqueous effluent in a washing section by any means known in the prior art. Devices similar to those described with reference to step (b) may be used.

Contact may occur more than once, particularly in the conditions set out above.

The washing step (d) may be carried out continuously or in batches.

Detailed Description of the Optional Catalytic Hydrotreatment Step (e)

The hydrotreatment of step (e) may be carried out in a single step or in two steps. When it is performed in a single step, the purified composition from step (d) with or without dilution is hydrotreated at a temperature of 200 to 450° C., preferably of 200 to 380° C. in the presence of hydrogen with an absolute pressure of 20 to 140 bar, preferably of 30 to 100 bar and in the presence of a hydrotreatment catalyst, for example a catalyst of the NiMo (0.1-60% by mass) and/or CoMo (0.1-60% by mass) type generally on a support.

Alternatively, the hydrotreatment of step (e) can be carried out in a first step (e-1) wherein the purified composition from step (d) with or without dilution is hydrotreated, preferably selectively hydrogenated, at a temperature of 80 to 250° C., preferably of 130 to 250° C. in the presence of hydrogen at an absolute pressure between 5 and 150 bar, preferably 20 to 100 bar and in the presence of a first hydrotreatment catalyst, preferably a hydrogenation catalyst, for example a hydrogenation catalyst comprising Pd (0.1-10% by weight) and/or Ni (0.1-60% by weight) and/or NiMo (0.1-60% by weight), and in a second step (e-2) wherein the effluent from step (e-1) is hydrotreated at a temperature of 200 to 450° C., preferably of 250 to 340° C. in the presence of hydrogen at an absolute pressure of 20 to 150 bar, preferably of 30 to 100 bar and in the presence of a second hydrotreatment catalyst, for example a catalyst of the NiMo (0.1-60% by weight) and/or CoMo (0.1-60% by weight) type. The first step may then make it possible to hydrogenate dienes initially present in the composition.

The purified composition from step (d) may be hydrotreated pure or diluted, for example with a hydrocarbon of fossil origin, such as naphtha, gas oil or crude oil or another hydrocarbon of fossil origin. For example, a concentration of purified plastic liquefaction oil ranging from 0.01 wt. % to 50 wt. % maximum may be obtained; preferably from 0.1 wt. % to 25 wt. %, even more preferably from 1 wt. % to 20 wt. % at the inlet of the hydrotreatment.

This step (e) can be carried out in a single reactor with a plurality of catalytic beds in series, possibly with hydrogen replenishment between the beds, or in a plurality of reactors in series, depending on the desired objective.

This hydrotreatment step may also have a demetallization, cracking, dearomatization function depending on the features of the catalyst and on the hydrotreatment conditions.

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

Preferably, the feedstock for the hydrotreatment, containing at least one portion of the purified composition, may be diluted with a portion of the hydrotreatment effluent, still having a higher temperature than the desired hydrotreatment inlet temperature. This at least partial recycling of the hydrotreatment effluent dilutes the unsaturates present in the purified composition and preheats the feedstock.

Preferably, the portion of the hydrotreatment effluent that is not recycled but still at a high temperature can exchange its sensible heat with the organic phase entering step (c) and ensure the pre-heating thereof.

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

The adsorbent may be operated in regenerative or non-regenerative mode, at a temperature lower than 400° C., preferably lower than 100° C., more preferably lower than 60° C., selected from: (i) a silica gel, (ii) clay, (iii) crushed clay, (iv) apatite, (v) hydroxyapatite and combinations thereof (vi) an alumina for example an alumina obtained by precipating boehmite, a calcined alumina such as Ceralox® from Sasol, (vii) boehmite, (viii) bayerite, (ix) hydrotalcite, (x) a spinel such as Pural® or Puralox from Sasol, (xi) a promoted alumina, for example Selexsorb® from BASF, an acid-promoted alumina, an alumina promoted by a zeolite and/or by a metal such as Ni, Co, Mo or a combination of at least two of them, (xii) clay treated by acid such as Tonsil® from Clariant, (xiii) a molecular sieve in the form of an aluminosilicate containing an alkali or alkaline-earth cation for example the sieves 3A, 4A, 5A, 13X, for example sold under the trade name Siliporite® from Ceca, (xiv) a zeolite, (xv) an activated carbon, or the combination of at least two adsorbents, the adsorbent or the at least two adsorbents retaining at least 20% by weight, preferably at least 50% by weight of at least one element from F, Cl, Br, I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or water. According to a preferred embodiment, the adsorbent is regeneratable, has a specific surface of at least 200 m²/g and is operated in a fixed bed reactor at less than 100° C. with a VVH of 0.1 at 10 h⁻¹.

The effluent exiting the hydrotreatment step (e), namely the purified and hydrotreated composition, optionally purified by passing over a solid adsorbent, may be washed with water to eliminate inorganic compounds such as hydrosulfide, hydrogen chloride and ammonia before being subjected to subsequent treatments.

The purified composition exiting step (d) or the effluent exiting the hydrotreatment step (e) optionally washed with water, may be fractionated into usable streams, the cutting points of which are typically chosen depending on the subsequent treatment. This fractionation is performed according to distillation temperature ranges, for example to separate streams of the LPG, petrol, diesel, heavy fuel oil, kerosene, which may subsequently be treated in a steam cracker and/or in a catalytic cracker and/or in a hydrocracker (then possibly in a steam cracker) and/or in a hydrotreating reactor and/or used as such as for preparing fuels, combustibles, lubricants or base oils. The person skilled in the art knows how to select the most suitable cuts for the subsequent treatment units depending on the objective sought.

The purified composition of step (d) or the purified and hydrotreated composition of step (e) may also be used diluted, for example mixed with naphtha, gas oil or crude oil in order to obtain, for example, a purified plastic liquefaction oil concentration ranging from 0.01% by weight to 50% by weight at most; preferably from 0.1% by weight to 25% by weight, even more preferably from 1% by weight to 20% by weight at the start of the next treatment.

Detailed Description of the Optional Steam Cracking Step (g)

The steam cracking step (g) may be carried out on the purified composition of step (d) with or without dilution, or on the hydrotreated purified composition of step (e) with or without dilution. Prior to this step (g), a distillation separation step may be carried out depending on the technology of the steam cracking furnaces.

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

The steam cracking step (g) involves thermally cracking in one or more furnaces a mixture of the purified composition and/or the purified and hydrotreated composition and steam at high temperatures in the order of 650 to 1,000° C., preferably of 700 to 900° C., typically of 750 to 850° C., under low pressures (1 to 3 bar). The cracking reaction is performed in the absence of oxygen. The reaction time is usually very short, in the order of a few hundreds of milliseconds. These conditions make it possible to break the carbon-carbon bonds and produce unsaturated hydrocarbons with molecules smaller than the feedstock introduced into the reactor(s). The effluents exiting the reactor(s) are subsequently rapidly cooled at temperatures of 400 to 550° C. in order to limit the secondary reactions of the olefin, diene and acetylene polymerization type. The cooled effluents are finally fractionated to recover C2-C5 light olefins, such as ethylene, propylene, butadiene, isobutene, n-butene and isoprene.

The purified composition of step (d) or the hydrotreated purified composition of step (e) can be sent to the steam cracker without dilution. The purified composition of step (d) or the purified and hydrotreated composition of step (e) may also be mixed with naphtha, gas oil or crude oil in order to obtain a purified plastic liquefaction oil concentration ranging from 0.01% by weight to 50% by weight at most; preferably from 0.1% by weight to 25% by weight, even more preferably from 1% by weight to 20% by weight entering the steam cracker. The purified composition is subsequently converted into olefins, such as ethylene and propylene, as well as aromatics.

In one preferred embodiment, the purified composition, or purified and hydrotreated composition, may be sent at least partially directly to a steam cracker with no dilution other than the steam used for the steam cracking, 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 stream obtained by the inventive method, may be ethane, liquefied petroleum gas, naphtha or gas oils. Liquefied petroleum gas (LPG) consists substantially of propane and butane. The gas oils have a boiling range of around 200 to 350° C., and consist of C10 to C22 hydrocarbons, including substantially linear and branched paraffins, cyclic paraffins and aromatics (including mono-, naphto- and poly-aromatics).

In particular, the cracking products obtained from the steam cracker may comprise ethylene, propylene and benzene, and possibly hydrogen, toluene, xylenes and 1,3-butadiene.

In one preferred embodiment, the output temperature of the steam cracker may be between 800 and 1,200° C., preferably between 820 and 1,100° C., more preferably between 83° and 950° C., more preferably between 84° and 920° C. The output temperature may influence the high value chemical product content in the cracking products obtained by the present method.

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 1,200° C., may be between 0.005 and 0.5 seconds, preferably between 0.01 and 0.4 seconds.

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

In one preferred embodiment, the output pressure of the reactor may be between 500 and 1,500 mbar, preferably between 700 and 1,000 mbar, more preferably may be around 850 mbar. The residence time of the feedstock in the reactor and the temperature must be considered together. A lower operating pressure makes it possible to facilitate the formation of light olefins and to reduce the formation of coke. The lowest possible pressure is obtained (i) by maintaining the output pressure of the reactor as close as possible to atmospheric pressure upon suction of the cracking gas compressor (ii) by reducing the pressure of the hydrocarbons by dilution with steam (which has a substantial influence on slowing the formation of coke). The steam/raw material ratio may be maintained at a sufficient level to limit the formation of coke.

Insofar as the purified composition and/or purified and hydrotreated composition has a wide distribution in terms of carbon number (or boiling points), the vaporization of such a feedstock may be incomplete at the reactor inlet at the temperature where some hydrocarbon molecules start to decompose. The purified and/or purified and hydrotreated composition may then be preheated to a temperature of at least 10° C. below the decomposition temperature, then subjected to a separation of the hydrocarbon vapors produced and of the residual hydrocarbon liquid in a flash container. In this flash container, the liquid exits by gravity from the bottom and the hydrocarbon vapours from the top. Optionally, the hydrocarbon liquid may be sent back to the plastic liquefaction unit or to the optional hydrocracking step.

Detailed Description of the Optional Hydrocracking Step

Prior to the steam cracking step (g), the purified effluent from step (d) or the purified and hydrotreated effluent from step (e) may be subjected to a cracking reaction in order to reduce the length of the carbon chains of the paraffins present in the hydrotreated effluent.

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

A usable hydrocracking catalyst comprises, for example, a support selected from halogenated alumina, combinations of boron and aluminum oxides, amorphous silica-alumina and zeolites and a hydro-dehydrogenated function comprising at least one metal of group VIB selected from chromium, molybdenum and tungsten, alone or in a mixture, and/or at least one metal of group VIII selected from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum.

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

DESCRIPTION OF THE FIGURES

FIG. 1 describes a possible embodiment of the invention.

FIG. 2 describes another possible embodiment of the invention.

In the figures, the same sections bear the same reference numerals.

In the embodiment shown in FIG. 1, the plastic liquefaction oil (1) is first optionally pre-treated in the pre-treatment section (A) to be subjected to pre-treatment (PTT) by (i) filtration, (ii) distillation, (iii) decantation, or (iv) a combination of two or three of steps (i) to (iii). The pre-treated oil (2) is then sent to a first washing section (B) carrying out the first washing step (b) of the method to perform a first wash W1 and obtain a first organic phase (3) and a first aqueous effluent (4). The organic phase (3) is then subjected to a treatment (TT) carrying out step (c) in a treatment section (C) in the presence of a basic compound (5) to produce the effluent (6) containing the treated composition. The effluent (6) of step (c) can then be sent to one or more optional separation sections (S). It may be an optional separation section for the basic compound (7′) contained in the effluent carried out by (i) filtration (ii) centrifugation (iii) hydrocyclone, (iv) decantation or (v) a combination of two or more of these steps, this basic compound (7′) being at least partially recyclable in step (c) or upstream thereof. Alternatively, it may be an optional solids separation section by (i) filtration (ii) centrifugation (iii) hydrocyclone or (iv) a combination of two or three of these steps (in this case the recycle (7′) is omitted). This optional solids separation section could be provided downstream of section (D). The two separation sections can also be provided. The second effluent (6) exiting the section (C) or the effluent (7) exiting the section (S) is then sent to a second washing section (D) carrying out the second washing step (d) of the method to perform a second wash W2 and obtain a second organic phase (8) and a second aqueous effluent (9). In the illustrated embodiment, the first aqueous effluent (4) exiting the first washing section (B) is sent to the second washing section (D) and the second aqueous effluent (9) exiting the second washing section (D) is sent to the first washing section (B). The second organic phase (8) exiting the section (D), optionally after fractionation and/or dilution, may be sent to one or more of the following optional sections: an optional hydrotreatment (HDT) section (E) for carrying out step (e), an optional preparation section (Pool) of a fuel or a lubricant or a base oil (F), an optional treatment section (SC) in a steam cracker (G), an optional treatment section (FCC) in a fluidized-bed catalytic cracker (H), an optional treatment section (HCK) in a hydrocracker (I). The hydrotreating section may comprise one or more hydrotreating and/or selective hydrotreating units. Preferably, the effluent (10) exiting the hydrotreatment section (E) is subsequently steam cracked to obtain olefins that may subsequently be polymerized. Preferably, the effluent (11) exiting the hydrocracking section (I) is subsequently steam cracked to obtain olefins that may subsequently be polymerized. In the example shown, the second organic phase (8) is sent directly to sections F, H, I, wherein it can be treated, typically in mixture with a hydrocarbon feedstock typical of these sections. Alternatively, the effluent (10) exiting the section (E) could be sent directly to the sections F, H, I, wherein it can advantageously be treated without mixing with another feedstock.

In the embodiment shown in FIG. 2, the plastic liquefaction oil (100) is introduced into a first washing section (B) to be subjected there to the first wash W1. A first organic phase (101) and a first aqueous effluent (102) exit the first washing section (B). The first organic phase (101) is sent to the treatment section (C). Upstream of the treatment section (C), a basic compound (103) is added to the first organic phase (101), via a line and one or more valves. The mixture (104) of the organic phase (101) and the basic compound (103) then passes through two heat exchangers (105), (106) to be heated therein before entering the treatment section (C). The effluent (107) exiting the treatment section (C) is used in particular to heat the mixture (104) via the first heat exchanger (105). It may then be cooled in a third heat exchanger (108) before entering the second washing section (D) to be subjected there to the second wash W2. A second organic phase (109) and a second aqueous effluent (110) exit the second washing section (D). The organic phase (109) forms the purified composition which can then be treated, for example, as described with reference to FIG. 1.

In this embodiment, a circuit (111) connects the first and second washing section (B) and (D) via a first line (112) going from the second washing section to the first and a second line (113) going from the first washing section to the second. This circuit (111) comprises a pump (114), a water injection line (115) and a tapping line (116), located here on the second line (113). Valves (117), (118) make it possible to close the tapping line (116) and the water injection line (115). The second aqueous effluent (110) may be sent entirely to the first washing section (B) as a washing solution, as shown. As described with reference to FIG. 1, optional pre-treatment and separation sections could be provided.

In the embodiments shown in FIGS. 1 and 2, the first aqueous effluent and the second aqueous effluent do not undergo an intermediate treatment step between the washing sections. In an embodiment not shown, one and/or the other of the aqueous effluents could optionally be subjected to a solids separation step. Regardless of the embodiment, it is not necessary to subject these aqueous effluents to additional treatment steps of the distillation and/or liquid-liquid extraction type.

EXAMPLES

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

Example 1: Two-Step Hydrotreatment and Steam Cracking a Plastic Liquefaction Oil

A purified plastic liquefaction oil exiting step (d) of the method according to the invention may be hydrotreated in two steps according to the following procedure:

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

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

In the hypothesis where the treatment according to the invention would not make it possible to obtain a sufficient reduction of the impurities, guard reactors for eliminating chlorine, metals and silicon may be added. Silicon may also be trapped on the upper bed of a reactor of the section HDT2 or separately, upstream.

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

As the hydrotreatment reactions in the sections HDT1 and HDT2 are exothermic, quenching by cold hydrogen or diluting with an inert feedstock may be used to moderate the temperature increase and control the reaction. Dilution by an inert feedstock may be performed by recycling the liquid fraction exiting the reactors.

There may be intermediate quenchings between the beds or between the reactors HDT1 and HDT2 or no quenching. In the latter case, recycling part of the stream exiting HDT1 or HDT2 must be performed to control the temperature. A strict control of the temperature in HDT1 must be carried out, in order to avoid blocking the reactor and adversely affecting the catalytic hydrogenation conditions.

The operating pressure in each of the hydrotreatments HDT1 and HDT2 is 5-150 bar, preferably 20-100 bar for HDT1 and 20-150 bar, preferably 30-100 bar for HDT2, typically 30-45 bar for HDT2.

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

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

The upper bed of the HDT2 should preferably be operated with NiMo having a hydrogenating capacity as well as a silicon trapping capacity. An upper bed of this type may be considered as a metal trap also having an HDM activity and a hydrogenating capacity. It is possible to have two separate beds in an HDT2 reactor, with quenching between the two beds or between the two reactors, if the two beds are in two distinct reactors, or no quenching at all. Ideally, intermediate quenching is carried out by means of cold effluent of HDT2 or by adding cold hydrogen, that is to say a temperature generally ranging from 15 to 30° C., in order to control the exotherm of the HDT2.

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

The hydrotreated liquefaction oil leaving the section HDT2, optionally after washing with water to eliminate inorganic compounds (hydrosulfide, hydrogen chloride, ammonia), may be as such or fractionated according to distillation temperature ranges, in order to feed a steam cracker, an FCC, a hydrocracker, a catalytic reformer or a pool of fuels or combustibles such as LPG, petrol, jet oil, diesel, fuel oil or a pool of base oil.

In one embodiment, the hydrotreated liquefaction oil is sent to a hydrocracker. This hydrocracker comprises, for example, bringing the hydrotreated effluent into contact with a hydrocracking catalyst, in the presence of H₂ to produce an effluent respecting the specifications of a steam cracker in terms of final boiling point (<370° C.).

Example 2

Material Used

A 1.5 L AISI-316L grade stainless steel autoclave with mechanical stirring is loaded with pyrolysis oil, a strong base in the form of NaOH and water.

The sum of the volume of pyrolysis oil and the volume of solvent or water introduced is close to 600 mL at room temperature, without taking into account any effects of volume variation during their mixing. The autoclave is closed and the gaseous atmosphere in the autoclave is flushed with nitrogen for 30 minutes. The autoclave is then heated under autogenous pressure with stirring at a speed of 400 to 1,500 rpm at a temperature of 225° C. for 30 minutes, once the target temperature has been reached. The rate of temperature rise is fixed at 30° C./10 minutes. At the end of the reaction, the autoclave is cooled to room temperature and then the mixture is discharged.

Prior to the reaction, the oil can be pre-washed by clean or recycled aqueous effluent with a mass ratio of 1:1.

At the end of the reaction, the cooled mixture exiting the autoclave is washed three times with clean or partially recycled water with, at each wash, a water/feedstock volume ratio=40/60.

Test 1: Basic Treatment without Pre-Wash

A pyrolysis oil HPP1 is subjected to treatment in the presence of sodium hydroxide at 225° C. described above under the conditions set out in Table 1. The pyrolysis oil has not been pre-washed.

	TABLE 1
		Water	NaOH	Feedstock
		mass	mass	mass	Reaction time	Temperature
	Feedstock	g	g	g	min	° C.

Feedstock	HPP1	7.6	7.8	400.5	30	225

On leaving the autoclave, the oil is washed in 3 times as described above. The 3 wash waters are collected and mixed. These wash waters are marked EA1, their pH and COD (Chemical Oxygen Demand) were measured, the values are summarized in Table 5.

The oil recovered after washing in 3 times, marked HPP1-T1 was analyzed (0, N, Cl, Si content before and after treatment, and reduction), the results are summarized in Table 4.

Test 2: Pre-Wash with Dirty Water Followed by Basic Treatment

A sample of HPP1 oil is pre-washed using the wash waters EA1 generated during test 1, the mass ratio HPP1:EA1 is 1:1. The water recovered from the pre-wash, marked EA2, was analyzed (see table 5).

Then the pre-washed HPP1 oil is subjected to the basic treatment described above under the conditions set out in Table 2.

	TABLE 2
		Water	NaOH	Feedstock
		mass	mass	mass	Reaction time	Temperature
	Feedstock	g	g	g	min	° C.

Feedstock	Washed	7.71	7.63	399.96	30	225
	HPP1

On leaving the autoclave, the oil is washed in 3 times with clean water as described above. The water from these 3 washes is recovered and analyzed (EA3 water in Table 5). The oil recovered after this washing, marked HPP1-T2, was analyzed (0, N, Cl, Si content before and after treatment and reduction), the results are summarized in Table 4.

Test 3: Pre-Wash with Clean Water and Basic Treatment, Final Wash with Pre-Wash Water Recovery

A sample of HPP1 oil is pre-washed using clean water, the mass ratio HPP1:clean water is 1:1. The pre-wash waters, marked EA4, are collected and analyzed. The pre-washed oil is then subjected to the basic treatment described above in the conditions set out in Table 3. On leaving the autoclave, the oil is washed in 3 times as described above with a mixture of the pre-wash waters EA4 and clean water (mass ratio 1:1). The water from these 3 washes is recovered and analyzed (water EA5 in Table 5).

The oil recovered after washing, marked HPP1-T3 was analyzed (0, N, Cl, Si content before and after treatment and reduction), the results are summarized in Table 4.

	TABLE 3
		Water	NaOH	Feedstock
		mass	mass	mass	Reaction time	Temperature
	Feedstock	g	g	g	min	° C.

Feedstock	Washed	7.92	7.64	400.02	30	225
	HPP1

Results

The analyses in Table 4 demonstrate the efficacy of pre-washing, whether performed with recycled water or not (tests 2 and 3), in particular to improve silicon reduction compared to test 1 performed without pre-washing. Tests 2 and 3 also demonstrate that it is possible to reuse the wash and pre-wash waters for the method, in either direction, without damaging the efficiency.

The analyses in Table 5 show that the pH of the waters resulting from the pre-wash are acidic, whereas the wash waters after sodium hydroxide treatment are basic. It should be noted that despite an initially high COD (Chemical Oxygen Demand), recycled waters used for pre-washing or for washing after basic treatment see their COD increase, which highlights the capture of impurities.

	TABLE 4
	Oxygen	Nitrogen	Silicon	Chlorine	Sodium

	Content	Reduction	Content	Reduction	Content	Reduction	Content	Reduction	Content
Feedstock	(% m)	(%)	ppm	(%)	ppm	(%)	ppm	(%)	ppm

HPP1	1.53		3086		42		155		<2
HPP1-T1	0.53	65%	1262	59%	5	88%	36	77%	<2
HPP1-T2	0.4	74%	895	71%	2	95%	19	88%	<2
HPP1-T3	0.41	73%	809	74%	2	95%	20	87%	<2

TABLE 5
Analyses (*)	COD	pH
Standard used	ISO 15705	NF T90-008
Unit	mg, L-1 O2	pH at 20° C.
EA1- wash water Test 1	64651	9.9
EA2: pre-washing outlet water Test 2	77181	5.5
EA3: wash water Test 2	44921	10.3
EA4: pre-wash water outlet Test 3	31185	3.9
EA5: wash water outlet Test 3	64120	11.8
(*) analyses were carried out after filtration on pleated paper