Method for treating pyrolysis oil for use in a steam cracking unit

Abstract

A method for treating a feedstock comprising pyrolysis oil of plastics and / or tires and / or recovered solid fuels containing halogenated compounds is disclosed, comprising: a) a hydrotreating step to obtain a partially hydrotreated effluent having a reduced halogenated compound content; b) a separation step feeding the hydrotreated effluent from step a) and an aqueous solution to obtain a gaseous effluent, an aqueous effluent, and a partially hydrotreated hydrocarbon effluent; and c) a petroleum feed steam cracking step in which at least a portion of the partially hydrotreated hydrocarbon effluent is introduced as a co-feed without previously being subjected to another hydrotreating step at a higher temperature and / or pressure, wherein the mixture of the petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) has a halogenated compound content of 3 ppm or less by weight.

Description

[Technical Field]

[0001] The present invention relates to a method for treating pyrolysis oil of plastics and / or tires and / or solid recovered fuels (SRF), resulting in partially hydrotreated pyrolysis oil, which can be upgraded as a co-feed with petroleum feedstock in a steam cracking unit. More particularly, the present invention relates to a method for treating pyrolysis oil with a view to eliminating halogenated compounds therein, which can be easily upgraded in a steam cracking unit. [Background technology]

[0002] Plastic waste is generally a mixture of several polymers, such as polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, or polystyrene. Furthermore, depending on the application, plastics may contain other compounds in addition to polymers, such as plasticizers, pigments, dyes, or residues of polymerization catalysts. Plastic waste may also contain small amounts of biomass, for example, originating from household waste. Waste treatment, especially storage, mechanical treatment, sorting, and pyrolysis on the one hand, and storage and transportation of pyrolysis oil on the other hand, can also cause corrosion.

[0003] As for tires, they are mainly composed of rubber (a mixture of elastomers of crosslinked synthetic and natural rubber type with the addition of adjuvants of silica, resin, sulfur, zinc oxide, carbon black, etc.) for their elastic properties, and textile and metal fibers for their reinforcing properties.

[0004] Solid recovered fuel (SRF), also known as refuse-derived fuel (RDF), is solid, non-hazardous waste prepared with a view to energy upgrading, whether derived from household and similar waste, waste from economic activity, or waste from construction and demolition. SRF is generally a mixture of any combustible waste, such as used tires, food by-products (fats, animal meal, etc.), viscose and wood waste, light fractions from shredders (e.g., from used cars, electrical and electronic equipment (WEEE)), household and commercial waste, certain municipal waste, plastic waste, textiles, or residues from recycling various types of waste, including wood, among others. SRF commonly contains plastic waste.

[0005] The plastics or recycled tires or other SRFs coming out of the collection and sorting channels can be subjected to a pyrolysis process to obtain, among other things, pyrolysis oils, which generally contain many impurities, in particular halogenated compounds, especially chlorine-based compounds, but also diolefins, olefins, metals, in particular iron, silicon, or other heteroelements, such as sulfur, oxygen and nitrogen, as well as insoluble substances.

[0006] These plastic and / or tire and / or SRF pyrolysis oils are generally incinerated to generate electricity and / or used as fuel in industrial or district heating boilers.

[0007] Another route for upgrading pyrolysis oils is to use them as feedstock for steam cracking units to (re)produce olefins, which are the constituent monomers of certain polymers. However, plastic and / or tire pyrolysis oils often have high impurity contents and are not compatible with steam cracking units or units located downstream of the steam cracking unit, especially polymerization and selective hydrogenation processes.

[0008] One way to remove these impurities contained in the pyrolysis oil is by hydrotreating in the presence of a catalyst. The steam cracking unit requires very high feedstock purity, especially low contents of chlorine, diolefins, olefins, metals, and sulfur. The specification for the chlorine content at the inlet of the steam cracking unit is typically a maximum of 3 ppm by weight, preferably a maximum of 1 ppm by weight.

[0009] Hydrotreating upstream of steam cracking is then often carried out in some steps under very stringent conditions, especially with respect to temperature and pressure, to achieve the required specifications. Such processes are described, for example, in US Pat. Nos. 5,629,291, 5,629,292, 5,629,293, 5,629,294, 5,629,295, 5,629,296, 5,629,297, 5,629,298, 5,629,29 ...

[0010] The present invention proposes a method for the mild hydrotreatment of pyrolysis oil of plastics and / or tires and / or SRF that makes it possible in particular to reduce the content of halogenated compounds, in particular chlorine, obtaining a pyrolysis oil from which the majority of halogenated compounds have been stripped and which can then be sent as co-feed together with the petroleum feedstock to a steam cracking unit.

[0011] Unlike the hydrotreating processes described in the prior art, the process according to the invention is directed towards mild hydrotreating, in particular hydrotreating at low pressure and moderate temperature. The mild operating conditions in hydrotreating, combined with the separation step involving washing, make it possible to remove a large proportion of the halogenated compounds.

[0012] The method according to the present invention mainly focuses on the removal of halogenated compounds to make the pyrolysis oil suitable as a feedstock for the steam cracking unit. The method according to the present invention is not necessarily directed to complete hydrotreating of the oil. Other impurities (metals, silicon, nitrogen, etc.) contained in the pyrolysis oil are not necessarily completely removed during the method according to the present invention, but the operating conditions make it possible to remove at least a portion of them. These impurities will, in some cases, be converted or removed in downstream units, and the remaining content of impurities contained in the oil will meet the specifications for the steam cracking unit by diluting the oil with petroleum feedstock.

[0013] The "mild" hydrotreatment of the present invention is a hydrotreatment carried out under carefully selected conditions of pressure, temperature and hourly space velocity, which is generally milder than conventional hydrotreatments known from the prior art, which aim to remove all impurities. The hydrotreatment of the present invention makes it possible, inter alia, to remove the majority of halogenated compounds.

[0014] The object of the present invention is therefore to propose a method for treating plastic and / or tire pyrolysis oils that is cheap, easy to implement and can be easily integrated into existing steam cracking units. The fact that mild operating conditions are used makes it possible to minimize the hydrogen consumption and therefore the costs of this purification, as well as the operating and investment costs, while removing as much of the chlorine content as possible.

[0015] Furthermore, the process according to the invention can be carried out in a unit dedicated to pyrolysis oil and therefore in a low-volume unit, which makes it possible to obtain a partially hydrotreated pyrolysis oil, the content of halogenated compounds of which is sufficiently low to be sent directly to co-processing in a steam cracking unit. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] International Publication No. 2016 / 142808 [Patent Document 2] International Publication No. 2016 / 142809 [Patent Document 3] International Publication No. 2018 / 055555 [Patent Document 4] International Publication No. 2021 / 110395 [Patent Document 5] International Publication No. 2021 / 165178 Summary of the Invention [Means for solving the problem]

[0017] (Summary of the Invention) More particularly, the present invention relates to a method for treating a "pyrolysis" feedstock, the feedstock comprising pyrolysis oils of plastics and / or tires and / or solid recovered fuels containing halogenated compounds, said method comprising the steps of: a) Hydrotreating step, which is carried out in a hydrotreating reaction section containing at least one hydrotreating catalyst; the hydrotreating reaction section is fed with at least a pyrolysis feedstock and a gas stream containing hydrogen, and the average temperature during the hydrotreating reaction section is 100°C to 220°C, the hydrogen partial pressure is 1.0 to 3.0 MPa (absolute), and the hourly space velocity is 0.05 to 5 h -1 and the hydrogen coverage is the volume of pyrolysis feedstock (m 3 ) 5-50Nm of hydrogen per 3 obtaining a partially hydrotreated effluent having hydrocarbon compounds with a reduced halogen content; b) a separation step, which receives the partially hydrotreated effluent from step a) and the aqueous solution, to obtain at least a gaseous effluent, an aqueous effluent and a partially hydrotreated hydrocarbon effluent; c) a step of steam cracking a petroleum feedstock; wherein at least a portion of the partially hydrotreated hydrocarbon effluent from step b) is introduced as a co-feed; said partially hydrotreated hydrocarbon effluent from step b) is introduced without first undergoing a separate hydrotreatment step carried out at a temperature and / or pressure higher than the temperature and / or pressure of step a); said mixture of said petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) has a halogen content of not more than 3 ppm by weight.

[0018] According to one variant, the weight ratio of the stream of partially hydrotreated hydrocarbon effluent from step b) to the stream of petroleum feedstock introduced in step c) is less than 1.

[0019] According to one variant, the pyrolysis feedstock consists of pyrolysis oils of plastics and / or tires and / or solid recovered fuels.

[0020] According to one variant, the content of halogenated compounds in the pyrolysis feedstock is between 1 and 5000 ppm by weight.

[0021] According to one variant, a stream containing nitrogen and / or sulfur compounds is injected upstream of step a).

[0022] According to one variant, the hydrotreating catalyst of step a) comprises a support chosen from alumina, silica, silica-alumina, magnesia, clay and mixtures thereof, and a hydrodehydrogenation functional element comprising at least one element from group VIII and either at least one element from group VIB or at least one element from group VIII.

[0023] According to one variant, the method comprises at least one step a0) of pre-treating the pyrolysis feedstock containing pyrolysis oil of plastics and / or tires and / or SRF, said pre-treatment step being carried out upstream of step a) and comprising an adsorption step and / or a filtration step and / or a centrifugation step and / or a sedimentation step and / or an electrostatic separation step and / or a step of washing with an aqueous solution and / or a gas stripping step.

[0024] According to one variant, the petroleum feedstock introduced in the steam cracking step c) is chosen from naphtha, kerosene, gas oil, or a mixture of such feedstocks.

[0025] According to one variant, the reaction section of step a) uses at least two reactors operating in a configurable mode.

[0026] According to one variant, the steam cracking step c) is carried out in at least one pyrolysis furnace at a temperature of 700-900° C. and a pressure of 0.05-0.3 MPa (relative) in the presence of steam.

[0027] According to one variant, in the steam cracking step c), the residence time of the hydrocarbon compounds is less than or equal to 1.0 second and the amount of water introduced in the form of steam is between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds by weight at the inlet of step c).

[0028] In the remainder of the text, the term "pyrolysis oil" is understood to mean oil resulting from the pyrolysis of plastics and / or tires and / or SRF, unless otherwise stated.

[0029] According to the invention, pressures are absolute pressures, also denoted abs., and are given in MPa absolute (or MPa(absolute)) unless otherwise stated.

[0030] According to the present invention, the expressions "of between A and B" and "between A and B" are equivalent and mean that the upper and lower limits of the interval are included in the range of values ​​stated. If this is not the case and if the upper and lower limits are not included in the range stated, such clarification is introduced by the present invention.

[0031] For purposes of the present invention, various parameter ranges for a given process, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, for purposes of the present invention, a range of preferred pressure values ​​can be combined with a range of more preferred temperature values.

[0032] In the following text, specific and / or preferred embodiments of the present invention are described, which can be implemented separately or combined together without any combination restrictions, if the combination is technically feasible.

[0033] Subsequently, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIII (or group VIIIB) according to the CAS classification corresponds to the metals in columns 8, 9, and 10 according to the new IUPAC classification.

[0034] The metal content is measured by X-ray fluorescence. DETAILED DESCRIPTION OF THE INVENTION

[0035] (Detailed explanation) (pyrolysis feedstock) According to the present invention, "plastic pyrolysis oil or tire pyrolysis oil or SRF pyrolysis oil" is an oil, advantageously in liquid form at ambient temperature, resulting from the pyrolysis of plastics, preferably from the pyrolysis of plastic waste, especially from collection and sorting channels, or from the pyrolysis of used tires, or from the pyrolysis of SRF. It contains, in particular, a mixture of hydrocarbon compounds, in particular paraffins, olefins (mono- and / or diolefins), naphthenes, and aromatic compounds. At least 80% by weight of these hydrocarbon compounds preferably have a boiling point below 700°C, preferably below 550°C. In particular, depending on the origin of the pyrolysis oil, it can contain up to 70% by weight of paraffins, up to 90% by weight of naphthenes, up to 90% by weight of olefins, and up to 90% by weight of aromatic compounds, the sum of which is understood to be equal to 100% by weight of hydrocarbon compounds.

[0036] Pyrolysis oils may contain diolefins. The diolefin content is generally determined indirectly as the maleic anhydride value (MAV). This method is based on the Diels-Alder addition reaction between conjugated diolefins and maleic anhydride. The method for determining MAV is described in C. Lopez-Garcia et al., Near Infrared Monitoring of Low Conjugated Diolefins Content in Hydrotreated FCC Gasoline Streams, Oil & Gas Science and Technology - Rev. IFP, Vol. 62 (2007), No. 1, pp. 57-68. MAV is expressed as the weight (mg) of maleic anhydride reacted with 1 g of sample (mg / g). MAV varies between 5 and 100 mg / g in pyrolysis oils.

[0037] The density of pyrolysis oil is typically 0.75 g / cm, measured at 15°C according to ASTM D4052 method. 3 ~0.99g / cm 3 , preferably 0.75 g / cm3 ~0.95g / cm 3 is.

[0038] Pyrolysis oils may contain, and usually do contain, impurities such as metals, especially iron and silicon, or halogenated compounds, especially chlorinated compounds. These impurities may be present in high concentrations in pyrolysis oils, and may be contributed by halogenated compounds, for example, up to 500 ppm by weight, up to 700 ppm by weight, or up to 1000 ppm by weight, or even up to 5000 ppm by weight of halogen elements (especially chlorine, but also bromine, fluorine, iodine, or astatine), typically 1 to 1000 ppm by weight, or 1 to 700 ppm by weight, or 1 to 500 ppm by weight. Pyrolysis oils may contain up to 500 ppm by weight, up to 700 ppm by weight, or up to 1000 ppm by weight, or even up to 5000 ppm by weight of chlorine, typically 1 to 1000 ppm by weight, or 1 to 700 ppm by weight, or 1 to 500 ppm by weight of chlorine, contributed by chlorinated compounds.

[0039] Oils may contain up to 200 ppm by weight or up to 1500 ppm by weight of metal or metalloid elements, generally 1-200 ppm by weight or 1-1500 ppm by weight. Alkali metals, alkaline earth metals, transition metals, post-transition metals, and metalloids can be grouped in the same category as metallic contaminants, referred to as metal or metalloid elements. In particular, metal or metalloid elements include silicon, iron, or both. Pyrolysis oils may contain, among other things, up to 200 ppm by weight or up to 1000 ppm by weight of silicon, generally 1-200 ppm by weight or 1-1000 ppm by weight or 1-500 ppm by weight of silicon. Pyrolysis oils may contain, among other things, up to 50 ppm by weight or up to 100 ppm by weight of iron, generally 1-50 ppm by weight or 1-100 ppm by weight of iron. Pyrolysis oils may also contain phosphorus, sodium, calcium, potassium, and magnesium.

[0040] The pyrolysis oil may also contain other impurities, such as heteroelements, in particular contributed by sulfur compounds, oxygen compounds and / or nitrogen compounds, generally less than 40,000 ppm by weight of heteroelements, preferably less than 15,500 ppm by weight of heteroelements, generally between 1 and 40,000 ppm by weight or between 1 and 15,500 ppm by weight of heteroelements.

[0041] The sulfur compounds are generally present in a content of sulfur compounds of less than 15,000 ppm by weight, preferably less than 10,000 ppm by weight, generally between 1 and 15,000 ppm by weight or between 1 and 10,000 ppm by weight.

[0042] The oxygen compounds are generally present in a content of less than 15,000 ppm by weight, preferably less than 10,000 ppm by weight, generally between 1 and 15,000 ppm by weight or between 1 and 10,000 ppm by weight of oxygen compounds.

[0043] The nitrogen compounds are generally present in a content of less than 10,000 ppm by weight, preferably less than 5000 ppm by weight, generally between 1 and 10,000 ppm by weight or between 1 and 5000 ppm by weight of nitrogen compounds.

[0044] The content of sulfur, oxygen and / or nitrogen compounds often depends on the origin of the oil. Tire pyrolysis oil therefore generally contains more heteroelements, especially sulfur compounds, than plastic pyrolysis oil.

[0045] The pyrolysis oil may also contain other impurities, for example heavy metals such as mercury, arsenic, zinc and lead, for example up to 100 ppb by weight or up to 200 ppb by weight of mercury or arsenic, typically 1-200 ppb by weight or 1-100 ppb by weight of heavy metals.

[0046] The pyrolysis feedstock for the process according to the invention comprises pyrolysis oil of at least one plastic and / or tire and / or SRF. The feedstock may consist exclusively of one or more pyrolysis oils. Preferably, the feedstock comprises at least 50% by weight, preferably 70% to 100% by weight, of pyrolysis oil, i.e. preferably 50% to 100% by weight, preferably 70% to 100% by weight, of plastic pyrolysis oil, relative to the total weight of the feedstock.

[0047] Particularly preferably, the pyrolysis feedstock for the process according to the invention consists exclusively of pyrolysis oils of one or more plastics and / or tyres and / or SRF.

[0048] In the case of a mixture of plastic pyrolysis oil, tire pyrolysis oil and / or SRF pyrolysis oil, this mixture can be produced in any proportion.

[0049] According to another variant, the pyrolysis feedstock of the process according to the invention introduced in step a) can comprise, in addition to one or more pyrolysis oils, conventional petroleum feedstocks or feedstocks resulting from biomass conversion, which are then co-processed with the pyrolysis oils of the feedstock.

[0050] The conventional petroleum feedstock introduced in step a) can advantageously be a fraction or mixture of fractions of naphtha or gas oil type.

[0051] The feedstock resulting from the conversion of biomass introduced in step a) can advantageously be selected from vegetable oils, oils from algae or algae oils, fish oils, waste cooking oils, and fats of vegetable or animal origin, or mixtures of such feedstocks. The vegetable oils can advantageously be crude or fully or partially refined and can be obtained from plants selected from rapeseed, sunflower, soybean, palm, olive, coconut, copra, castor oil plants, cotton plants, peanut oil, linseed oil, and sea kale oil, as well as all oils obtained from sunflower or rapeseed, for example, by genetic modification or hybridization, although this list is not limiting. The animal fats can advantageously be selected from blubber and fats composed of residues from the food industry or from the catering industry. Frying oils, various animal oils, such as fish oil, tallow, or lard, can also be used. The feedstock resulting from the conversion of biomass may advantageously also be chosen from fatty acid methyl esters of vegetable and / or animal origin, or fatty acid methyl esters from waste edible vegetable oils.

[0052] Feedstocks obtained from biomass conversion can also be selected from feedstocks derived from thermal or catalytic biomass conversion processes, such as oil produced from biomass, particularly lignocellulosic biomass, using various liquefaction methods, such as hydrothermal liquefaction or pyrolysis. The term "biomass" refers to material derived from recently living organisms, including plants, animals, and their by-products. The term "lignocellulosic biomass" refers to biomass derived from plants or their by-products. Lignocellulosic biomass is composed of carbohydrate polymers (cellulose, hemicellulose) and aromatic polymers (lignin).

[0053] The feedstock resulting from biomass conversion may also advantageously be chosen from feedstocks resulting from the paper industry.

[0054] The pyrolysis oils of plastics and / or tires and / or SRF result from thermal or catalytic pyrolysis processes or can also be prepared by hydropyrolysis (pyrolysis in the presence of a catalyst and hydrogen).

[0055] (Preprocessing (optional)) Said pyrolysis feedstock comprising pyrolysis oils of plastics and / or tires and / or SRF can advantageously be pretreated in at least one optional pretreatment step a0) before the hydrotreatment step a), to obtain a pretreated feedstock which is fed to step a).

[0056] According to one variant, this optional pretreatment step a0) makes it possible to reduce the amount of contaminants and solid particles, in particular the amount of iron and / or silicon and / or chlorine, that may be present in the pyrolysis oil-containing feedstock. This optional step a0) makes it possible, inter alia, to remove sediments that may form as a result of the unstable nature of the pyrolysis oil and / or compatibility problems between two different feedstocks. Therefore, the optional step a0) of pretreatment of the pyrolysis oil-containing feedstock is advantageously carried out in particular when the feedstock contains more than 10 ppm by weight, in particular more than 20 ppm by weight, more particularly more than 50 ppm by weight of metal elements and / or solid particles, and in particular when the feedstock contains more than 5 ppm by weight of silicon, more particularly more than 10 ppm by weight, in fact even more than 20 ppm by weight. Likewise, the optional step a0) of pre-treatment of the feedstock comprising pyrolysis oil is advantageously carried out, in particular when said feedstock contains more than 10 ppm by weight of chlorine, in particular more than 20 ppm by weight, more particularly more than 50 ppm by weight.

[0057] Said optional pretreatment step a0) can be carried out by any method known to those skilled in the art making it possible to reduce the amount of contaminants, and it can comprise, inter alia, an adsorption step and / or a filtration step and / or a centrifugation step and / or a sedimentation step and / or an electrostatic separation step and / or a step of washing with an aqueous solution and / or a gas stripping step.

[0058] The optional pretreatment step a0) is advantageously carried out at a temperature of between 20 and 400° C., preferably between 40 and 350° C., and at a pressure of between 0.15 and 10.0 MPa (absolute), preferably between 0.2 and 7.0 MPa (absolute).

[0059] According to one variant, the optional pretreatment step a0) is carried out in an adsorption section operated in the presence of at least one adsorbent. The adsorbent may be chosen from zeolites, activated carbon, clays, silica or alumina. Preferably, the adsorbent has a specific surface area of ​​100 m 2 / g or more, preferably 200m 2 The specific surface area of ​​said at least one adsorbent is advantageously 600 m 2 / g or less, especially 400m 2 The specific surface area of ​​the adsorbent is the surface area measured by the BET method, i.e. the specific surface area determined by nitrogen adsorption according to standard ASTM D 3663-78, which is derived from the Brunauer-Emmett-Teller method described in the periodical The Journal of the American Chemical Society, 6Q, 309 (1938).

[0060] Advantageously, the adsorbent contains less than 1% by weight of metal elements, preferably no metal elements. Metal elements of the adsorbent should be understood to mean elements from groups 6 to 10 of the Periodic Table of Elements (new IUPAC classification). The residence time of the feedstock in the adsorption section is generally between 1 and 180 minutes.

[0061] The adsorption section of optional step a0) comprises at least one adsorption column, preferably at least two adsorption columns, and preferentially two to four adsorption columns, containing the adsorbent. When the adsorption section comprises two adsorption columns, one operating mode can be a "swing" operation, where one of the columns is online, i.e., in operation, while the other column is in reserve. When the adsorbent of the online column is consumed, this column is isolated, while the in-reserve column is placed online, i.e., in operation. The consumed adsorbent can then be regenerated in situ and / or replaced with fresh adsorbent, and the column containing it can be placed back online again, where the other column is isolated.

[0062] Another operating mode is to operate at least two columns in series. When the adsorbent material in the first column is consumed, this first column is isolated and the spent adsorbent is either regenerated in-situ or replaced with fresh adsorbent. The column is then brought back online at the last position, and so on. This operation is called permutable mode, or PRS, or permutable reactor system, or "lead and lag." The combination of at least two adsorption columns makes it possible to overcome the potentially rapid poisoning and / or clogging of the adsorbent material due to the combined action of metal contaminants, diolefins, gums derived from diolefins, and insoluble materials that may be present in the pyrolysis oil being treated. This is because the presence of at least two adsorption columns makes it easy to replace and / or regenerate the adsorbent, advantageously without shutting down the pretreatment unit and indeed even the process, thus reducing the risk of clogging and therefore making it possible to avoid shutting down the unit due to clogging, control costs and limit the consumption of adsorbent.

[0063] According to another variant, the optional pretreatment step a0) is carried out in a section for washing with an aqueous solution, for example water or an acidic or basic solution. This washing section can comprise equipment that allows the feedstock to be brought into contact with the aqueous solution and for the phase separation to obtain, on the one hand, the pretreated feedstock and, on the other hand, the aqueous solution containing the impurities. These equipment can include, for example, stirred reactors, settlers, mixer-settlers and / or cocurrent or countercurrent washing columns.

[0064] According to another variant, the optional pretreatment step a0) is carried out by filtration. The filtration step makes it possible to remove inorganic solids, sediments and / or fine particles contained in the feedstock, especially metals, metal oxides and metal chlorides. The pore size (e.g., diameter or equivalent diameter) of the filters generally used is less than 25 μm, preferably less than 10 μm, and even more preferably less than 5 μm. According to another variant, the pore size of the filters that may be used is less than 25 μm but more than 5 μm. A series of filters with different pore sizes may also be used, especially a series of filters with pore sizes decreasing in the direction of flow of the feedstock. These filtration media are well known for industrial use. For example, cartridge filters or self-cleaning filters are suitable. The solid content can be measured, for example, by the heptane insoluble matter test, ASTM D-3279. The content of insoluble matter in heptane must be reduced to less than 0.5% by weight, preferably less than 0.1% by weight.

[0065] According to a particular embodiment, step a0) of pretreatment by filtration comprises at least one filter whose pore size is less than 10 μm and preferably greater than 5 μm, optionally followed by a filtration system whose pore size is less than 2 μm, preferably less than 1 μm.

[0066] According to another particular embodiment, step a0) of pretreatment by filtration comprises at least one filter whose pore size is less than 10 μm and preferably greater than 5 μm, followed by an electrostatic precipitation system.

[0067] According to another particular embodiment, step a0) of pretreatment by filtration comprises at least one filter whose pore size is less than 10 μm and preferably greater than 5 μm, followed by a system of one or more filters using a filtration adjuvant such as sand or diatomaceous earth.

[0068] According to another variant, said optional pre-treatment step a0) is carried out by centrifugation. According to another variant, the pre-treatment step a0) comprises centrifugation and filtration.

[0069] According to another variant, said optional pretreatment step a0) is carried out by sedimentation. According to another variant, the pretreatment step a0) comprises sedimentation and filtration.

[0070] According to another variant, the optional pretreatment step a0) is carried out by gas stripping, thus reducing the oxygen content in the feedstock. Gas extraction can remove oxygen (O2) that may be dissolved in the feedstock, thus reducing the probability of free radical formation that leads to polymerization in downstream processes. This method generally involves contacting the feedstock with an extraction gas (e.g., H2, N2, or a mixture thereof), thus transferring at least a portion of the dissolved oxygen in the feedstock to the extraction gas, and then separating the extraction gas from the feedstock. The ratio of the volume of the extraction gas to the volume of the feedstock (the two volumes measured under gas extraction conditions) is generally greater than 1, preferably at least 3. In certain embodiments, the extraction gas can contain at least 60% (mole percent) H2. Any dissolved H2 remaining in the feedstock after the gas extraction step is not a problem for downstream hydroprocessing. Preferably, the gas extraction step is completed before any (pre)heating of the feedstock to minimize potential fouling.

[0071] Said optional pretreatment step a0) generally comprises one or more, preferably several, of the above-mentioned treatments. It may comprise, inter alia, a series of aqueous washing and / or adsorption steps followed by a gas stripping step and a filtration and / or centrifugation step. All these steps are preferably carried out before any (pre)heating of the feedstock.

[0072] Said optional pretreatment step a0) therefore makes it possible to obtain a pretreated feedstock which is then fed to the mild hydrotreatment step a).

[0073] (Hydrotreatment step a)) According to the present invention, the method comprises step a) carried out in a hydrotreating reaction section containing at least one hydrotreating catalyst, said hydrotreating reaction section being fed with at least a gas stream containing a pyrolysis feedstock and hydrogen, said hydrotreating reaction section being used at an average temperature of 100°C to 220°C, a hydrogen partial pressure of 1.0 to 3.0 MPa (absolute), and an hourly space velocity of 0.05 to 5 h -1 and the hydrogen coverage is the volume of pyrolysis feedstock (m 3 ) 5-50Nm of hydrogen per 3 to obtain a partially hydrotreated effluent having hydrocarbon compounds with reduced halogen content.

[0074] Step a) is carried out under mild hydrogen pressure and temperature conditions which allow, inter alia, the removal of halogens, especially chlorine, making it suitable as a co-feed in a steam cracking unit.

[0075] Other impurities contained in the pyrolysis oil (metals, silicon, nitrogen, etc.) are not necessarily completely removed during the process according to the invention, but the operating conditions make it possible to remove at least a portion of them. Step a) therefore mainly comprises hydrogenation reactions of halogenated compounds and, to a lesser extent, other hydrotreating reactions well known to those skilled in the art, in particular hydrogenation of aromatic compounds, hydrodesulfurization and hydrodenitrogenation, as well as the hydrogenation of olefins and diolefins.

[0076] Said hydrotreating reaction section is advantageously operated at an average hydrotreating temperature (or WABT as defined below) of between 100°C and 220°C, preferably between 120°C and 200°C, a hydrogen partial pressure of between 1.0 and 3.0 MPa (absolute), preferably between 1.0 and 2.4 MPa (absolute), preferably between 1.2 and 2.2 MPa (absolute), and a hydrotreating time of between 0.1 and 5 h -1 , preferably 0.1 to 2 hours -1 , preferentially 0.1 to 1.0 h -1 The hydrogen coverage in step a) is advantageously determined by the volume (m ) of fresh feedstock. 3 ) 5-50Nm of hydrogen per 3 , preferably the volume of fresh feedstock (m 3 ) 10-40Nm of hydrogen per 3 , preferably the volume of fresh feedstock (m 3 ) 15-30Nm of hydrogen per 3 is.

[0077] According to the present invention, the "average temperature" of the reaction section corresponds to the weight average bed temperature (WABT), which is well known to those skilled in the art. The average temperature is advantageously determined as a function of the catalyst system used, the equipment, and their configuration. The average temperature (or WABT) is calculated in the following way:

[0078]

number

[0079] In the formula, T inlet is the temperature of the stream at the inlet of the reaction section, and Toutlet is the temperature of the effluent at the outlet of the reaction section. Unless otherwise stated, the "average temperature" of the reaction section is given at the start of the cycle conditions.

[0080] Hourly space velocity (HSV) is defined herein as the ratio of the hourly volumetric flow rate of the feedstock, optionally including pretreated pyrolysis oil, to the volume of the catalyst(s).

[0081] The hydrogen coverage is defined as the ratio of the volumetric flow rate of hydrogen taken under standard temperature and pressure conditions relative to the volumetric flow rate of the "fresh" feedstock, i.e., the feedstock to be treated, possibly pretreated, at 15°C without taking into account the recycled fraction (volume (m) of feedstock). 3 ) standard volumetric flow rate of H2 per m 3 (Nm 3 (denoted as).

[0082] The hydrogen-containing gas stream fed to the hydrotreating reaction section can consist of hydrogen feed and / or recycled hydrogen. Preferably, an additional hydrogen-containing gas stream is advantageously introduced at the inlet of each reactor, in particular at the inlet of reactors operating in series, and / or at the inlet of each catalyst bed starting from the second catalyst bed of the reaction section. These additional gas streams are also called cooling streams. They make it possible to control the temperature in the reactors, where the reactions taking place are generally highly exothermic.

[0083] The hydrogen-containing gas stream may be derived from fossil or renewable sources, for example from the gasification of plastic waste, or may be produced by electrolysis.

[0084] Advantageously, the hydrogen-containing gas stream originates from a compressor used in the refinery and feeds another hydrogen-using hydrorefining unit, such as a hydrocracking, hydrotreating or hydroconversion unit, which has the advantage of eliminating the need for a dedicated compressor for recycling hydrogen from step b), thus saving investment costs.

[0085] Optionally, the reaction section of step a) may also be fed with a portion of the partially hydrotreated hydrocarbon (recycle) effluent from step b), as described below.

[0086] Preferably, the process according to the invention comprises a hydrotreating step a) carried out in a hydrotreating reaction section using at least one fixed bed reactor having n catalyst beds, n being an integer greater than or equal to 1, preferably between 1 and 10, preferably between 2 and 5, each containing at least one hydrotreating catalyst.

[0087] The hydrotreating reaction section is advantageously fed with at least the optionally pretreated pyrolysis feedstock and a gas stream containing hydrogen in the first catalyst bed of the first reactor in operation. Injection of at least a portion of the pyrolysis feedstock and / or at least a portion of the hydrogen between the various catalyst beds is also possible.

[0088] The hydrotreating reaction section, which employs at least one fixed bed reactor, can be operated with downflow or upflow of gas and liquid.

[0089] Advantageously, the reaction section of step a) comprises 1 to 5 reactors, preferably 2 to 5 reactors, particularly preferably it comprises 2 reactors. The advantage of a hydrotreating reaction section comprising several reactors is that it optimizes the processing of the feedstock while reducing the risk of clogging one or more catalyst beds and thus making it possible to avoid unit shutdowns due to clogging.

[0090] According to this embodiment, the hydrotreating reaction section of step a) comprises two reactors operated in permutable mode, also known as PRS (permutable reactor system) or "lead and lag". The combination of at least two reactors in PRS mode makes it possible to isolate the reactors, drain the spent catalyst, recharge the reactors with fresh catalyst and return said reactors to operation without shutting down the process. PRS technology is described in particular in FR 2 681 871.

[0091] According to another embodiment, the hydrotreating reaction section comprises a single fixed bed reactor containing n catalyst beds, where n is an integer greater than or equal to 1, preferably between 1 and 10, suitably between 2 and 5.

[0092] Advantageously, reactor internals, for example of the filter plate type, can be used to prevent clogging of one or more reactors. Examples of filter plates are described in patent FR 3 051 375.

[0093] Preferably, step a) can use at least one guard bed upstream of the hydrotreating catalyst(s) containing an adsorbent material of the alumina, silica, silica-alumina, zeolite and / or activated carbon type, optionally containing a metal from group VIB and / or group VIII. Use may also be made of a series of guard beds with particles of different sizes, in particular with sizes decreasing (also called "grading") in the direction of flow of the feedstock.

[0094] Advantageously, said hydrotreating catalyst comprises a support, preferably a mineral support, and a hydrodehydrogenation functional element.

[0095] According to one variant, the hydrogenation-dehydrogenation functional elements comprise, in particular, at least one element from group VIII and at least one element from group VIB. The at least one element from group VIII is preferably chosen from nickel and cobalt, and the at least one element from group VIB is preferably chosen from molybdenum and tungsten. According to this variant, the total content of metal elements from groups VIB and VIII, expressed as oxides, is preferably between 1% and 40% by weight, preferentially between 5% and 30% by weight, relative to the total weight of the catalyst. When the metal is cobalt or nickel, the metal content is expressed as CoO and NiO, respectively. When the metal is molybdenum or tungsten, the metal content is expressed as MoO3 and WO3, respectively.

[0096] The weight ratio of the metal(s) from group VIB to the metal(s) from group VIII, expressed as metal oxides, is preferably 1-20, suitably 2-10.

[0097] According to this variant, the reaction section of step a) comprises a hydrotreating catalyst, for example, comprising 0.5% to 12% by weight of nickel, preferably 0.9% to 10% by weight of nickel (expressed as nickel oxide NiO relative to the weight of the catalyst), and 1% to 30% by weight of molybdenum, preferably 3% to 20% by weight of molybdenum (expressed as molybdenum oxide MoO3 relative to the weight of the catalyst), preferably on a mineral support, preferably an alumina support.

[0098] According to another variant, the hydrogenation-dehydrogenation functional element comprises, and preferably consists of, at least one group VIII element, preferably nickel. According to this variant, the content of nickel oxide is preferably between 1% and 50% by weight, preferably between 10% and 30% by weight, relative to the weight of the catalyst. This type of catalyst is preferably used in its reduced form, preferably on a mineral support, preferably on an alumina support.

[0099] The support for the hydrotreating catalyst is preferably selected from alumina, silica, silica-alumina, magnesia, clay, and mixtures thereof. The support may contain a dopant compound, in particular an oxide selected from boron oxide, especially boron trioxide, zirconia, ceria, titanium oxide, phosphorus pentoxide, and mixtures of these oxides. Preferably, the hydrotreating catalyst comprises an alumina support, optionally doped with phosphorus and optionally boron. If phosphorus pentoxide P2O5 is present, its concentration is less than 10% by weight relative to the weight of the alumina, and advantageously at least 0.001% by weight relative to the total weight of the alumina. If boron trioxide B2O3 is present, its concentration is less than 10% by weight relative to the weight of the alumina, and advantageously at least 0.001% by weight relative to the total weight of the alumina. The alumina used may be, for example, γ (gamma) or η (eta) alumina.

[0100] The hydrotreating catalyst is, for example, in the form of extrudates or in the form of beads.

[0101] Highly preferably, step a) may employ at least one hydrotreating catalyst used in step a) which, in addition to the one or more hydrotreating catalysts described above, contains, on an alumina support, less than 1% by weight of nickel and at least 0.1% by weight of nickel, preferably 0.5% by weight of nickel, expressed as nickel oxide NiO, relative to the weight of the catalyst, and less than 5% by weight of molybdenum and at least 0.1% by weight of molybdenum, preferably 0.5% by weight of molybdenum, expressed as molybdenum oxide MoO3, relative to the weight of the catalyst. This catalyst, which is not highly loaded with metals, may preferably be placed upstream or downstream, preferably upstream, of the one or more hydrotreating catalysts described above.

[0102] The preparation of the catalyst for hydrotreating step a) is known and generally comprises the impregnation of a support with a Group VIII metal and a Group VIB metal, if present, and optionally phosphorus and / or boron, followed by drying and then optionally calcination. The catalyst of step a) can be a catalyst used in its reduced form, and therefore its preparation comprises a reduction step.

[0103] Before being used in the process steps, the catalyst is generally subjected to sulfurization to form active species. Depending on the content of sulfur compounds in the initial feedstock to be treated, a stream containing a sulfurizing agent can be injected upstream of the optional pretreatment step a0) or hydrotreating step a), preferably upstream of hydrotreating step a), to ensure a sufficient amount of sulfur to form the active species (sulfide form) of the catalyst. This activation or sulfurization step is carried out by methods well known to those skilled in the art, advantageously in a sulfo-reducing atmosphere in the presence of hydrogen and hydrogen sulfide. The sulfurizing agent is preferably a hydrocarbon fraction with a boiling point below 400°C containing H2S gas, elemental sulfur, CS2, mercaptans, sulfides and / or polysulfides, sulfur compounds with a view to sulfurizing the catalyst, or any other sulfur-containing compound used to activate the hydrocarbon feedstock. The sulfur-containing compound is advantageously selected from alkyl disulfides, such as dimethyl disulfide (DMDS), alkyl sulfides, such as dimethyl sulfide, thiols, such as n-butyl mercaptan (or 1-butanethiol), and polysulfide compounds of the tert-nonyl polysulfide type. The catalyst can also be sulfided by sulfur contained in the feedstock to be desulfurized. Preferably, the catalyst is sulfided in situ in the presence of a sulfiding agent and a hydrocarbon feedstock. Highly preferably, the catalyst is sulfided in situ in the presence of a feedstock to which dimethyl disulfide has been added. The sulfiding agent can be injected continuously.

[0104] The partially hydrotreated effluent obtained at the end of the hydrogenation step a) is preferably sent directly to the washing / separation step b).

[0105] (Separation step b)) According to the invention, the treatment process comprises a separation step b), which is advantageously carried out in at least one washing / separation section, to which is fed at least the partially hydrotreated effluent from step a) and the aqueous solution, and which obtains at least a gaseous effluent, an aqueous effluent and a partially hydrotreated hydrocarbon effluent.

[0106] This separation step b) makes it possible in particular to remove halogens (chlorine) in the form of hydrogen halides (in particular HCl) formed by reaction of the hydrogen ions released by the hydrogenation of the halogenated compounds in step a) with halide ions, dissolved in aqueous solution.

[0107] Separation step b) is advantageously carried out at a temperature between 20° C. and 200° C., preferentially between 50° C. and 180° C., and preferably between 80° C. and 150° C. Advantageously, separation step b) is carried out at a pressure close to that used in step a), preferably between 1.0 and 2.0 MPa, to facilitate the recycling of hydrogen, if necessary.

[0108] The separation step can advantageously be carried out by any method known to those skilled in the art, such as a combination of one or more separators (drums) and / or one or more stripping columns, to which or these separators (drums) and / or columns a stripping gas, for example a hydrogen-rich gas stream, can optionally be fed. The washing / separation section of step c) can be made up, at least in part, of common or separate washing and separation equipment.

[0109] Advantageously, separation step b) comprises injecting an aqueous solution, preferably water, into the partially hydrotreated effluent from step a) upstream of the washing / separation section, to dissolve some, preferably all, of the hydrogen halide (in particular HCl) and any salts present.

[0110] The aqueous solution may be water. It may also be a basic aqueous solution (for example, by adding NaOH). The use of a basic solution makes it possible to neutralize the hydrogen halide and any dissolved salts.

[0111] In one optional embodiment of the present invention, separation step b) comprises the injection of an aqueous solution into the partially hydrotreated effluent from step a), followed by a scrubbing / separation section, which advantageously comprises separate phases to obtain at least one aqueous effluent loaded with hydrogen halide (especially HCl) and any dissolved salts present, a scrubbed partially hydrotreated effluent, and a partially washed gaseous effluent. The aqueous effluent and the scrubbed partially hydrotreated effluent can then be separated in a knockout drum to obtain the scrubbed partially hydrotreated effluent and the aqueous effluent. The partially washed gaseous effluent can simultaneously be introduced into a scrubbing column, where it flows countercurrently relative to an aqueous stream, preferably an aqueous stream of the same nature as the aqueous solution injected into the partially hydrotreated effluent, thereby removing at least part, preferably all, of the hydrochloric acid contained in the partially washed gaseous effluent and thus obtaining the gaseous effluent, preferably essentially comprising hydrogen, and an acidic aqueous stream. The aqueous effluent from the knock-out drum can optionally be mixed with the acidic aqueous stream and can be used, optionally in admixture with the acidic aqueous stream, to feed the aqueous solution upstream of the washing / separation section and / or the aqueous stream in the wash column to separation step c) in a water recycle circuit, which can include a supply of water and / or a basic solution and / or a discharge allowing impurities to be discharged.

[0112] The hydrotreating step a) mainly involves the hydrogenation of halogenated compounds and, to a lesser extent, also other hydrotreating reactions, such as hydrodenitrogenation, the hydrogenation of nitrogen compounds to produce NH3, and hydrodesulfurization, the hydrogenation of sulfur compounds to produce H2S.

[0113] If NH3 is present in the partially hydrotreated effluent from step a), separation step b) also makes it possible to remove ammonium chloride salts formed in particular by reaction between chloride ions released in the form of HCl by the hydrogenation of chlorinated compounds during step a) and ammonium ions generated in the form of NH3 by the hydrogenation of nitrogen compounds during step a), by dissolving them in aqueous solution.

[0114] If H2S is present in the partially hydrotreated effluent from step a), separation step b) also makes it possible to remove the ammonium sulfide ((NH4)2S) salts formed by the reaction between H2S resulting from the hydrodesulfurization of sulfur compounds and NH3, by dissolving them in aqueous solution.

[0115] According to one embodiment, depending on the content of chlorine compounds in the initial or pretreated feedstock, a stream containing nitrogen compounds, such as ammonia or amines, such as monoethanolamine, diethanolamine and / or monodiethanolamine, can be injected upstream of the hydrotreating step a), ensuring a sufficient amount of ammonium ions to combine with the chloride ions formed during the hydrotreating step in the form of ammonium chloride salts, thus making it possible to limit the formation of hydrochloric acid and therefore corrosion downstream of the separation section.

[0116] The gaseous effluent obtained at the end of step b) advantageously contains hydrogen, preferably at least 80% by volume, preferably at least 85% by volume. The gaseous effluent obtained at the end of step b) contains very small amounts of chlorine, generally with a chlorine content of less than 3 ppm by weight, which makes it possible to send it to a refinery unit requiring hydrogen.

[0117] According to one embodiment, the gaseous effluent can be at least partially recycled to the hydrotreatment step a), the recycling system being capable of comprising a purification section (e.g. for the adsorption of heavy metals such as mercury).

[0118] According to another preferred embodiment, the gaseous effluent can be at least partly recycled upstream of the hydrogen compressor used to feed the hydrorefining units of the hydrogen-using refinery, for example hydrocracking, hydrotreating or hydroconversion units, which has the advantage that a dedicated compressor for recycling hydrogen from step b) is not required, thus saving investment costs.

[0119] With regard to the partially hydrotreated hydrocarbon liquid effluent from step b), according to one variant, part of the partially hydrotreated hydrocarbon effluent from step b) can be recycled upstream of step a). Recycling part of the partially hydrotreated hydrocarbon effluent from step b) to step a) or upstream of step a) advantageously makes it possible, on the one hand, to dilute impurities and, on the other hand, to control the temperature in step a), in which the reactions involved may be highly exothermic. Diluting the impurities makes it possible to limit undesired reactions, such as the polymerization of diolefins (gum formation) and / or coke formation.

[0120] Advantageously, the recycled amount of the partially hydrotreated hydrocarbon effluent from step b), i.e. the recycled proportion of the product obtained, is adjusted so that the weight ratio of the recycle stream from step b) to the feedstock comprising pyrolysis oil, i.e. the feedstock to be treated and fed to the entire process, is at most 10, preferably at most 7, and preferentially at least 0.001, preferably at least 0.01 and suitably at least 0.1. Preferably, the recycled amount of the partially hydrotreated hydrocarbon effluent from step b) is adjusted so that the weight ratio of the recycle stream to the feedstock comprising pyrolysis oil is between 0.01 and 10, preferably between 0.1 and 7, particularly preferably between 0.2 and 5. This recycle ratio makes it possible, inter alia, to control the temperature increase in step a), since a high recycle ratio results in a high dilution of the feedstock and therefore makes it possible to control the temperature increase at the start of the reaction section of step a) by the dilution effect. Injection of the partially hydrotreated hydrocarbon effluent from step b) can take place in the first catalyst bed of the reaction section of step a) or between the various catalyst beds. If the hydrotreating reaction section of step a) comprises two reactors operating in a variable sequence mode, at least a portion of the partially hydrotreated hydrocarbon effluent from step b) can be recycled between the two reactors.

[0121] According to another preferred embodiment, the partially hydrotreated hydrocarbon effluent from step b) is partially, preferably completely, sent directly to the inlet of the steam cracking unit as a co-feed with the petroleum feedstock, which has the advantage that no recycle compressor is required.

[0122] Said partially hydrotreated hydrocarbon effluent from step b) thus obtained by treatment according to steps a) and b) of the process of the present invention has a composition suitable for being introduced into a steam cracking unit as co-feed.

[0123] The partially hydrotreated hydrocarbon effluent from step b) is in particular an effluent with a reduced content of halogenated compounds, in particular chlorine.

[0124] Preferably, at least 50%, more preferably at least 75%, of the halogenated compounds in the initial feedstock is removed during steps a) and b).

[0125] Other impurities (metals, silicon, nitrogen, etc.) contained in the pyrolysis oil are not necessarily completely removed during steps a) and b) of the method according to the invention, but the operating conditions make it possible to remove at least a portion of them. In fact, the pyrolysis oil, which is a partially hydrotreated hydrocarbon effluent, does not need to be completely hydrotreated so that it can be introduced into the steam cracking unit as a co-feed. It does not need to undergo another hydrotreatment, particularly one carried out at a temperature and / or pressure higher than that of step a), before being introduced into the steam cracking unit. The residual content of impurities contained in the oil is adapted to the specifications for the steam cracking unit by diluting the oil with the petroleum feedstock injected in step c).

[0126] Preferably, at least 50%, more preferentially at least 75% of the metal elements in the initial feedstock are removed during steps a) and b).

[0127] Generally, up to 50%, more preferentially up to 25%, of the sulfur compounds in the initial feedstock are removed during steps a) and b).

[0128] Preferably, at least 25%, more preferentially at least 50% of the oxygenates in the initial feedstock are removed during steps a) and b).

[0129] Generally, up to 30%, more preferentially up to 15%, of the nitrogen compounds in the initial feedstock are removed during steps a) and b).

[0130] The content of heavy metals such as mercury, arsenic, zinc and lead remains essentially unchanged.

[0131] The content is given as a relative concentration by weight, percentage (%) by weight, parts per million (ppm) by weight or parts per billion (ppb) by weight relative to the total weight of the stream under consideration.

[0132] (Steam cracking process c) According to the invention, the process comprises a step c) of steam cracking a petroleum feedstock, in which at least a portion of the partially hydrotreated hydrocarbon effluent from step b) is introduced as a co-feed, said partially hydrotreated hydrocarbon effluent from step b) being introduced without first undergoing another hydrotreatment step carried out at a temperature and / or pressure higher than the temperature and / or pressure of step a), and wherein said mixture of said petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) has a halogen content of not more than 3 ppm by weight.

[0133] Thanks to the hydrotreating step a) which makes it possible to release halogenated compounds (such as chlorine) mainly in gaseous form (in particular hydrogen halides of the HCl type), and the subsequent washing / separation step b) which makes it possible to dissolve and remove the hydrogen halides, the halogenated compounds content of the partially hydrotreated hydrocarbon effluent from step b) is sufficiently reduced to make it possible to inject it as co-feed into a unit for steam cracking of petroleum feedstocks.

[0134] The partially hydrotreated hydrocarbon effluent from step b) is introduced into a unit for steam cracking of a petroleum feedstock in an amount such that the chlorine content in the mixture of the petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) is less than or equal to 3 ppm by weight, preferably less than or equal to 1 ppm by weight.

[0135] Generally, in the process according to the invention, the weight ratio of the flow rate of the partially hydrotreated hydrocarbon effluent (pyrolysis oil) from step b) to the flow rate of the petroleum feedstock introduced into the unit of step c) is generally less than 1, preferably between 0.01 and 0.9, preferably between 0.02 and 0.5.

[0136] If the content of halogenated compounds in the partially hydrotreated hydrocarbon effluent from step b) is more than 3 ppm by weight, or even more than 1 ppm by weight, a chlorine content of 3 ppm or even 1 ppm can be achieved by dilution with petroleum feedstock at the inlet of the unit.

[0137] The petroleum feedstock used in the steam cracking unit is preferably selected from naphtha, kerosene, gas oil, or a mixture of such feedstocks.

[0138] The steam cracking step c) is advantageously carried out in at least one pyrolysis furnace in the presence of steam at temperatures between 700 and 900°C, preferably between 750 and 850°C, and at pressures between 0.05 and 0.3 MPa (relative). The residence time of the hydrocarbon compounds is generally less than 1.0 second (expressed as s), preferably between 0.1 and 0.5 s. Steam is advantageously introduced upstream of the steam cracking step c) after separation (or fractional distillation). The amount of water introduced in the form of steam is advantageously between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds by weight at the inlet of step c). Steam cracking step c) can be carried out in several pyrolysis furnaces in parallel in order to adapt the operating conditions to the various streams feeding step c) and to manage the decoking times of the tubes. A furnace may comprise one or several tubes arranged in parallel. The furnace may also refer to a group of furnaces operating in parallel. For example, a furnace may be dedicated to the cracking of middle distillate fractions.

[0139] The effluents from the various steam cracking furnaces are generally recombined before separation to form the effluent. It is understood that steam cracking step c) includes the steam cracking furnace, but also sub-steps related to steam cracking that are well known to those skilled in the art. These sub-steps may include, inter alia, heat exchangers, columns, catalytic reactors, and recycle to the furnace. The columns generally allow fractionation of the effluent with the aim of recovering at least a light fraction containing hydrogen and compounds having 2 to 5 carbon atoms, as well as a fraction containing pyrolysis gasoline, and optionally a heavy fraction. The columns allow separation of the various components of the light fraction to recover at least an ethylene-rich fraction (C2 fraction), a propylene-rich fraction (C3 fraction), and optionally a butene-rich fraction (C4 fraction). The catalytic reactors allow, inter alia, hydrogenation of C2, C3, and even C4 fractions and pyrolysis gasoline. Saturates, especially those having 2 to 4 carbon atoms, are advantageously recycled to the steam cracking furnace to increase the overall yield of olefins.

[0140] This steam cracking step c) makes it possible to obtain at least one effluent containing olefins containing 2, 3 and / or 4 carbon atoms (i.e. C2, C3 and / or C4 olefins) in a satisfactory content, in particular a content of 30% by weight or more of total olefins containing 2, 3 and 4 carbon atoms, relative to the weight of the steam cracking effluent under consideration, which C2, C3 and C4 olefins can then advantageously be used as polyolefin monomers.

[0141] (Analysis methods used) The analytical methods and / or specifications used to determine the characteristics of the various streams, in particular the feedstock and effluent streams to be treated, are known to those skilled in the art and are specifically listed below in Table 1 for information purposes. Other methods that are said to be equivalent, in particular equivalent IP, EN or ISO methods, can also be used.

[0142] [Table 1]

[0143] (1) The MAV method is described in the paper C. Lopez-Garcia et al., Near Infrared Monitoring of Low Conjugated Diolefins Content in Hydrotreated FCC Gasoline Streams, Oil & Gas Science and Technology - Rev. IFP, Vol. 62 (2007), No. 1, pp. 57-68.

[0144] (List of drawings) The information regarding the elements referenced in Figure 1 allows for a better understanding of the invention, but the invention is not limited to the specific embodiments shown in Figure 1. The various embodiments presented can be used alone or in combination with each other, and there are no limitations on the combinations.

[0145] FIG. 1 represents a diagram of a general embodiment of the method of the present invention, comprising the following steps: - step a): hydrotreating the pyrolysis oil (1) in the presence of a hydrogen-rich gas (2) and optionally an amine provided by stream (3) and optionally a sulfiding agent provided by stream (4); - separation / washing step b); the partially hydrotreated effluent (5) from the hydrotreatment step a) is fed in the presence of an aqueous solution (6); at least a gaseous effluent (7), an aqueous effluent (8) and a partially hydrotreated hydrocarbon effluent (9) are obtained; a part (9a) of the hydrocarbon effluent (9) can be recycled to step a); - step c); steam cracking of a petroleum feedstock (10); introducing at least a portion, preferably all, of the partially hydrotreated hydrocarbon effluent (9) from step b) as co-feed, said partially hydrotreated hydrocarbon effluent (9) from step b) being introduced without first undergoing another hydrotreatment step carried out at a higher temperature and / or pressure.

[0146] To allow a better understanding of the invention, only the main steps are shown in the diagram, along with the main flows. It is clearly understood that all equipment necessary for the operation (drums, pumps, exchangers, furnaces, columns, etc.) is present even if not shown. It is also understood that a hydrogen-rich gas stream (feed or recycle stream) can be injected at the inlet of each reactor or catalyst bed, or between two reactors or two catalyst beds, as described above.

[0147] (Example) The pyrolysis feedstock treated in this method is plastic pyrolysis oil (i.e., containing 100 wt. % of said plastic pyrolysis oil) having the characteristics indicated in Table 2.

[0148] [Table 2]

[0149] The pyrolysis feedstock is subjected to a hydrotreating step a), which is carried out in the presence of hydrogen and an alumina-supported NiMo hydrotreating catalyst in a fixed-bed reactor under different operating conditions as indicated in Table 3.

[0150] [Table 3]

[0151] At the end of the hydrogenation step a), the observed conversions (=(initial concentration-final concentration) / initial concentration) for chlorine, diolefins and olefins are given in Table 4.

[0152] [Table 4]

[0153] The effluent from the hydrotreating step a) is subjected to a separation step b): a stream of water is injected into the effluent from the hydrotreating step a); the mixture is then treated in an acid gas washing column and a separation drum.

[0154] The yields of the various fractions obtained after separation are shown in Table 5 (yields correspond to the ratio of the amounts by weight of the various products obtained relative to the weight of the upstream feedstock of step a), expressed as a percentage and indicated in % w / w).

[0155] [Table 5]

[0156] The characteristics of the liquid fraction obtained after separation step b) are shown in Table 6.

[0157] [Table 6]

[0158] The effluent from step b) is then mixed with an oil feedstock (naphtha) for steam cracking having a chlorine content of 0 ppm by weight in a weight ratio of 10% oil / 90% oil feedstock. A mixture is obtained, which contains less than 3 ppm by weight of chlorine (in all examples), and is introduced into a fluidized bed catalytic steam cracking unit.

[0159] According to examples 2 and 3, less energy (temperature in step a) and less hydrogen (H2 consumption) is used.

[0160] Example 3, conducted under very mild conditions of temperature and pressure, shows that it is possible to obtain an oil that is fully stripped of chlorine while using less pressure (and therefore less energy) than Example 2. [Brief explanation of the drawings]

[0161] [Figure 1] 1 shows a diagram of a general embodiment of the method of the present invention;

Claims

1. 1. A method for treating a pyrolysis feedstock, the feedstock comprising pyrolysis oils of plastics and / or tires and / or solid recovered fuels containing halogenated compounds, the method comprising the steps of: a) A hydrotreating step carried out in a hydrotreating reaction section containing at least one hydrotreating catalyst; the hydrotreating reaction section is fed with at least a pyrolysis feedstock and a gas stream containing hydrogen, the average temperature during the hydrotreating reaction section being 100°C to 220°C, the hydrogen partial pressure being 1.0 to 3.0 MPa (absolute), and the hourly space velocity being 0.05 to 5 h －１ and the hydrogen coverage is the volume (m ３ ) 5 to 50 Nm of hydrogen per ３ obtaining a partially hydrotreated effluent having hydrocarbon compounds with a reduced halogen content; b) a separation step of feeding the partially hydrotreated effluent from step a) and the aqueous solution to obtain at least a gaseous effluent, an aqueous effluent and a partially hydrotreated hydrocarbon effluent; c) a step of steam cracking a petroleum feedstock; introducing at least a portion of the partially hydrotreated hydrocarbon effluent from step b) as a co-feed; introducing said partially hydrotreated hydrocarbon effluent from step b) without first passing it through another hydrotreatment step carried out at a temperature and / or pressure higher than the temperature and / or pressure of step a); said mixture of said petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) having a halogen content of not more than 3 ppm by weight.

2. 2. The method of claim 1, wherein the weight ratio of the stream of partially hydrotreated hydrocarbon effluent from step b) to the stream of petroleum feedstock introduced in step c) is less than 1.

3. 3. The method according to claim 1 or 2, wherein the pyrolysis feedstock consists of pyrolysis oil of plastics and / or tires and / or solid recovered fuels.

4. 4. The method according to claim 1, wherein the content of halogenated compounds in the pyrolysis feedstock is 1 to 5000 ppm by weight.

5. 5. The process according to claim 1, wherein a stream containing nitrogen and / or sulfur compounds is injected upstream of step a).

6. 6. The method according to claim 1, wherein the hydrotreating catalyst in step a) comprises a support selected from alumina, silica, silica-alumina, magnesia, clay and mixtures thereof, and a hydrodehydrogenation functional element comprising either at least one Group VIII element and at least one Group VIB element, or at least one Group VIII element.

7. 7. The method according to claim 1, comprising at least one step a0) of pre-treating the pyrolysis feedstock comprising pyrolysis oil of plastics and / or tires and / or SRF, said pre-treatment step being carried out upstream of step a), said pre-treatment step comprising an adsorption step and / or a filtration step and / or a centrifugation step and / or a sedimentation step and / or an electrostatic separation step and / or a step of washing with an aqueous solution and / or a gas stripping step.

8. 8. The process according to any one of claims 1 to 7, wherein the petroleum feedstock introduced in steam cracking step c) is chosen from naphtha, kerosene, gas oil, or a mixture of such feedstocks.

9. 9. The process according to any one of claims 1 to 8, wherein the reaction section of step a) employs at least two reactors operating in a sequence-variable mode.

10. 10. The process according to claim 1, wherein the steam cracking step c) is carried out in at least one pyrolysis furnace in the presence of steam at a temperature of from 700 to 900°C and a pressure of from 0.05 to 0.3 MPa (relative).

11. 11. The method according to claim 1, wherein in the steam cracking step c), the residence time of the hydrocarbon compounds is 1.0 second or less and the amount of water introduced in the form of steam is 0.3 to 3.0 kg of water per kg of hydrocarbon compounds by weight at the inlet of step c).