Pyrolysis oil purification

Abstract

The invention relates to a method for purifying crude pyrolysis oil, which is at least partially derived from the pyrolysis of plastic waste, in order to obtain purified pyrolysis oil. The invention also relates to a method for producing a cleavage feedstock comprising said purified pyrolysis oil.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for purifying a crude pyrolysis oil at least partially derived from the pyrolysis of plastic waste to obtain a purified pyrolysis oil. The present invention also relates to a method for producing a cracking feedstock, in particular a steam cracking feedstock, which cracking feedstock comprises the purified pyrolysis oil. BACKGROUND ART

[0002] Pyrolysis is an important technology for chemical recycling such as plastic waste. The pyrolysis is generally a thermal degradation of a raw material in an inert atmosphere and produces value-added products such as pyrolysis gas, liquid pyrolysis oil and coke (residue), and the pyrolysis oil containing hydrocarbons is the main product.

[0003] Depending on the type and quality of the raw material used to prepare the pyrolysis oil, various impurities are usually found in the pyrolysis oil. A typical raw material for preparing the pyrolysis oil is plastic waste, but biomass can also be used. The pyrolysis oil produced from plastic waste contains more and different pollutants than fossil raw materials because plastics are used in a wide variety of applications and thus contain various different additives. Such impurities found in the pyrolysis oil are, for example, inorganic compounds such as metal-containing compounds and complexes, and organic compounds containing heteroatoms (such as nitrogen, oxygen, sulfur, silicon and halogens, especially chlorine). The pyrolysis oil usually has a much higher content of unsaturated hydrocarbon compounds (such as olefins, especially dienes) than fossil raw materials. The low concentration of these impurities (especially chlorine-containing compounds and dienes) is, for example, very important for avoiding problems during storage and processing of the pyrolysis oil, including during the storage and processing of the pyrolysis oil as a (steam) cracking feedstock in the production of basic chemicals (such as ethylene and propylene). Otherwise, the impurities will cause problems in the further processing or use of the pyrolysis oil, such as the formation of precipitation and gum, the deactivation / poisoning of the catalyst, the formation of deposits, and the corrosion of pipelines and reactors. For example, Kusenberg et al. discussed the steam cracking of untreated plastic waste pyrolysis oil in "Assessing the feasibility of chemical recycling via steam cracking of untreated plastic waste pyrolysis oils: Feedstock impurities, product yields and coke formation", Waste Management, Vol. 141, pp. 104-114 (2022), in which the authors concluded that purifying the pyrolysis oil before steam cracking is a prerequisite for avoiding operational problems due to increased coking and fouling.

[0004] According to Kusenberg et al. in "Opportunities and challenges for the application of post-consumer plastic waste pyrolysis oil as steam cracker feedstocks: To decontaminate or not to decontaminate?", Waste Management, Vol. 148, pp. 83-115 (2022), typical steam cracking feedstocks for the production of basic chemicals may contain no more than 3 ppm of chlorine, no more than 100 ppm of nitrogen, and no more than 100 ppm of oxygen.

[0005] In order to meet the high purity standards required for the use of such pyrolysis oils (e.g., as steam cracking feedstocks for the production of basic chemicals), dilution with fossil naphtha and / or purification of the pyrolysis oil is usually required. Purification of the crude pyrolysis oil can be accomplished, for example, by an expensive hydrotreating step or simply by a washing step (i.e., by extracting impurities with a solvent immiscible with the oil). However, although such a washing step can be effective for removing polar impurities, only low removal rates are found for non-polar impurities with high solubility in the oil, such as certain organic chlorides.

[0006] It has been proposed to use hydrogen peroxide for oxidative desulfurization of waste tire pyrolysis fuels with high sulfur content, followed by methanol extraction or silica gel adsorption (Kusenberg et al., "Desulfurization of pyrolysis fuels obtained from waste: Lube oils, tires and plastics", Fuel, 150 (2015) pp. 208-216).

[0007] Typically, pyrolysis oils at least partially derived from the pyrolysis of plastic waste need to be dehalogenated (especially dechlorinated), denitrified, and deoxygenated to reduce the concentration of these impurities and allow their use in cracking feedstocks (e.g., steam cracking feedstocks).

[0008] WO 2021 / 224287 A1 relates to a method for purifying crude pyrolysis oil derived from the pyrolysis of plastic waste. The method comprises the following steps: (i) treating the crude pyrolysis oil with a scavenger selected from elemental metals, metal oxides, metal alkoxides, solid adsorbents or a combination of at least two scavengers, and (ii) separating the obtained product into a purified pyrolysis oil fraction having a reduced nitrogen content, sulfur content and halogen content compared to the crude pyrolysis oil, and a fraction of the scavenger that has incorporated at least a portion of the sulfur, nitrogen and halogen present in the crude pyrolysis oil.

[0009] WO 2020 / 178597 discloses a method for upgrading pyrolysis oil. The method comprises the step of treating the pyrolysis oil with an aqueous solution and optionally a hydrocarbon fluid, wherein the pyrolysis oil is derived from the pyrolysis of plastic or rubber or a combination thereof. Also disclosed is an upgraded pyrolysis oil prepared by the method. Summary of the Invention

[0010] The object of the present invention is to provide a method for purifying crude pyrolysis oil derived from the pyrolysis of a raw material, in particular for purifying crude pyrolysis oil having various impurities.

[0011] Another object of the present invention is to provide a method for purifying crude pyrolysis oil at least partially derived from the pyrolysis of plastic waste, the method reducing the content of polar and non-polar impurities in the crude pyrolysis oil.

[0012] Another object of the present invention is to provide a method for purifying crude pyrolysis oil at least partially derived from the pyrolysis of plastic waste, the method having an improved removal efficiency for impurities present in the crude pyrolysis oil.

[0013] Another object of the present invention is to provide a purified pyrolysis oil that meets the standards for use as a cracking feedstock (either alone or diluted with fossil naphtha) in the production of basic chemicals. As used herein, "cracking feedstock" refers to a feedstock suitable for steam cracking, hydrocracking or catalytic cracking. More specifically, the object of the present invention is to obtain a cracking feedstock that meets the requirements for use as a feedstock (either alone or diluted with fossil naphtha) in steam cracking.

[0014] To solve all of the above objects, the present invention provides, in a first aspect, a method for purifying crude pyrolysis oil according to claim 1, and in a second aspect, a method for purifying crude pyrolysis oil according to claim 2.

[0015] In the first aspect, a method for purifying crude pyrolysis oil is provided, the method comprising the following steps:

[0016] A1) Provide a crude pyrolysis oil, the crude pyrolysis oil containing hydrocarbons and impurities, the crude pyrolysis oil being at least partially derived from the pyrolysis of plastic waste,

[0017] A2) In a first reactor, the first reactor preferably being a stirred tank reactor, oxidize the crude pyrolysis oil (preferably a pretreated crude pyrolysis oil) in the presence of an oxidant to obtain an oxidized crude pyrolysis oil containing oxidized impurities,

[0018] A2a) Optionally separate the reacted oxidant obtained in step A2) from the oxidized crude pyrolysis oil, where step A2a) occurs after step A2) and before step A3);

[0019] A3) In the first reactor or a second reactor, mix the oxidized crude pyrolysis oil (preferably the pretreated oxidized crude pyrolysis oil) with a polar washing solvent to obtain a purified pyrolysis oil phase and a polar washing solvent phase, the polar washing solvent phase containing at least a portion of the oxidized impurities,

[0020] A4) Separate the polar washing solvent phase from the purified pyrolysis oil phase to obtain a purified pyrolysis oil,

[0021] wherein the oxidant contains hydrogen peroxide and a metal salt, the metal salt preferably containing an iron salt, the iron salt preferably containing iron(III) nitrate, and

[0022] wherein the polar washing solvent contains water, an alkanol or a mixture thereof, and also contains an acid or a base, preferably the polar washing solvent contains sodium hydroxide in water or sodium methoxide in methanol.

[0023] Optionally, in step A4), also separate the reacted oxidant obtained in step A2) from the purified pyrolysis oil phase.

[0024] In a second aspect, a method for purifying a crude pyrolysis oil is provided, the method comprising the following steps:

[0025] B1) Provide a crude pyrolysis oil, the crude pyrolysis oil containing hydrocarbons and impurities, the crude pyrolysis oil being at least partially derived from the pyrolysis of plastic waste,

[0026] B2) In a first reactor, the first reactor preferably being a stirred tank reactor, mix the crude pyrolysis oil (preferably a pretreated crude pyrolysis oil) with a polar washing solvent to obtain a washed crude pyrolysis oil phase and a polar washing solvent phase, the polar washing solvent phase containing at least a portion of the impurities,

[0027] B3) Separate the polar washing solvent phase from the washed crude pyrolysis oil phase,

[0028] B4) In the presence of an oxidizing agent, oxidize the washed crude pyrolysis oil phase in the first reactor or the second reactor to obtain an oxidized and purified pyrolysis oil containing oxidized impurities.

[0029] B5) Separate the oxidized impurities from the oxidized and purified pyrolysis oil to obtain a purified pyrolysis oil.

[0030] Wherein, the oxidizing agent comprises hydrogen peroxide and a metal salt, the metal salt preferably comprises an iron salt, and the iron salt preferably comprises iron(III) nitrate, and

[0031] Wherein the polar washing solvent comprises water, an alkanol or a mixture thereof, and further comprises an acid or a base. Preferably, the polar washing solvent comprises sodium hydroxide in water or sodium methoxide in methanol.

[0032] Optionally, in step B5), the reacted oxidizing agent obtained in step B4) is also separated from the oxidized and purified pyrolysis oil. In particular, the present invention provides a method for purifying a crude pyrolysis oil by dehalogenation (especially dechlorination) and denitrification of the crude pyrolysis oil, thereby reducing the concentrations of halogen and nitrogen in the crude pyrolysis oil.

[0033] More specifically, the present invention provides a method for purifying a crude pyrolysis oil by dehalogenation (especially dechlorination), denitrification and desulfurization of the crude pyrolysis oil, thereby reducing the concentrations of halogen, nitrogen and sulfur in the crude pyrolysis oil.

[0034] The present invention provides a purified pyrolysis oil having a reduced nitrogen content and halogen content relative to the crude pyrolysis oil, especially a purified pyrolysis oil having a reduced nitrogen content, halogen content and sulfur content relative to the crude pyrolysis oil. Another advantage of the present invention is that the provided purified pyrolysis oil may have a reduced olefin content relative to the crude pyrolysis oil.

[0035] In a specific embodiment, the present invention provides a method for purifying at least a part of a crude pyrolysis oil derived from plastic waste pyrolysis to obtain a purified pyrolysis oil, which generally has a chlorine content of 10 ppm or less by weight, and / or generally has a nitrogen content of 100 ppm or less by weight. In addition, the purified pyrolysis oil generally has an olefin content of 30 wt.% or less.

[0036] As used herein, the term "olefin" refers to unsaturated open-chain (straight-chain) hydrocarbons.

[0037] As used herein, the term "hydrocarbon" refers to an organic compound composed of carbon and hydrogen.

[0038] In step A1) of the method according to the first aspect and in step B1) of the method according to the second aspect, a crude pyrolysis oil is provided. The crude pyrolysis oil contains hydrocarbons and impurities, and the crude pyrolysis oil is at least partially derived from the pyrolysis of plastic waste. Preferably, the crude pyrolysis oil is a crude plastic waste pyrolysis oil.

[0039] In the present invention, the term "pyrolysis" relates to the thermal decomposition or degradation of a feedstock (such as end-of-life plastics (plastic waste) or plastic waste combined with biomass) under inert conditions, and produces gas, liquid and solid coke components. During the pyrolysis of plastic waste, the plastics are converted into various chemical substances, including gases such as H2, C1-C4 alkanes, C2-C4 alkenes, acetylene, propyne, 1-butyne, etc., pyrolysis oil having a boiling point temperature of 25 °C to 500 °C, and coke.

[0040] The term "pyrolysis" includes slow pyrolysis, fast pyrolysis, flash catalysis and catalytic pyrolysis. These types of pyrolysis differ in process temperature, heating rate, residence time, feed particle size, etc., which results in different product qualities. Sharuddin et al. described the typical process conditions for pyrolysis of plastic waste in "A review of pyrolysis of plastic waste", Energy Conversion and Management, Volume 115, pages 308-326 (May 2016).

[0041] In the context of the present invention, the term "pyrolysis oil" should be understood to mean any oil that is at least partially derived from the pyrolysis of plastic waste, including (i) any crude pyrolysis oil that is completely derived from the pyrolysis of plastic waste (herein referred to as "crude plastic waste pyrolysis oil"), (ii) any crude pyrolysis oil that is derived from the pyrolysis of a mixture of plastic waste and biomass, or (iii) any crude pyrolysis oil that contains a mixture of crude plastic waste pyrolysis oil and crude biomass pyrolysis oil.

[0042] As used herein, "crude plastic waste pyrolysis oil" refers to pyrolysis oil derived from pyrolyzing a feedstock composed of plastic waste.

[0043] As used herein, "crude biomass pyrolysis oil" means pyrolysis oil derived from pyrolyzing a feedstock composed of biomass.

[0044] The crude pyrolysis oil is usually liquid at 15 °C. The term "liquid at 15 °C" means that, as determined by ASTM D7042 (for example, using an SVM3000 viscometer), the crude pyrolysis oil has a dynamic viscosity in the range of 0.1 mPa·s to 100 mPa·s.

[0045] Depending on the plastic waste subjected to pyrolysis, the crude pyrolysis oil may have different contents of sulfur, nitrogen, halogens, oxygen, and heavy metals (if present). The crude pyrolysis oils derived from plastic wastes of different compositions vary greatly in quality, which means that the content and type of impurities may vary significantly.

[0046] The crude pyrolysis oil generally contains saturated hydrocarbon compounds, unsaturated hydrocarbon compounds (olefins), and organic or inorganic compounds containing at least one heteroatom selected from oxygen, sulfur, nitrogen, and halogens, especially organic or inorganic compounds containing two or more heteroatoms selected from oxygen, sulfur, nitrogen, and halogens. The crude pyrolysis oil generally contains sulfur-containing compounds, nitrogen-containing compounds, oxygen-containing compounds, and halogen-containing compounds.

[0047] In a specific embodiment, the crude pyrolysis oil is a crude pyrolysis oil of nitrogen- and halogen-containing plastic waste, especially a crude pyrolysis oil of nitrogen-, halogen-, and sulfur-containing plastic waste, and more specifically a crude pyrolysis oil of nitrogen-, halogen-, oxygen-, and sulfur-containing plastic waste.

[0048] In one embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has a sulfur content of 10 mg / l or higher, such as 50 mg / l or higher, or 100 mg / l or higher; or 500 mg / l or higher. In another embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has a sulfur content of 100 mg / l to 5000 mg / l, usually 500 mg / l to 4000 mg / l.

[0049] In another embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has a sulfur content of at least 10 mg / l but not exceeding 100 mg / l, such as in the range of 10 mg / l to 50 mg / l, or in the range of 10 mg / l to 30 mg / l.

[0050] In one embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has a nitrogen content of 50 mg / l or higher, such as 100 mg / l or higher; or 500 mg / l or higher; or 2000 mg / l or higher. In another embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has a nitrogen content of 800 mg / l to 4000 mg / l, usually 900 mg / l to 3000 mg / l.

[0051] In one embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has a halogen content of 10 mg / l or higher, such as 20 mg / l or higher; such as 80 mg / l or higher; or 120 mg / l or higher; or 400 mg / l or higher; or 600 mg / l or higher. In another embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has a halogen content of 100 mg / l to 1000 mg / l, typically 120 mg / l to 900 mg / l.

[0052] When the density of the pyrolysis oil is about 1 g / ml (1000 kg / m 3 ), the above concentrations given in mg / l are equal to the same concentrations expressed in ppm, i.e., 1 mg / l is equal to 1 ppm.

[0053] Organic fluorine, organic chlorine, organic bromine, and / or organic iodine compounds are generally the sources of the halogen content in the crude pyrolysis oil. Specifically, the halogen content is such that the bromine and chlorine content reaches 90% or higher, such as 95% or higher, even 100%. More specifically, the halogen content is the chlorine content reaching 90% or higher, such as 95% or higher, even 100%. Thus, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil can have a chlorine content of 10 mg / l or higher, such as 20 mg / l or higher.

[0054] In one embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has an oxygen content of 40 mg / l or higher, such as 80 mg / l or higher; or 120 mg / l or higher; or 400 mg / l or higher; or 600 mg / l or higher. In another embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has an oxygen content of 100 mg / l to 5000 mg / l, typically 120 mg / l to 2000 mg / l.

[0055] If the crude pyrolysis oil also has a heavy metal content, then relative to the total volume of the crude pyrolysis oil, the heavy metal content is at least 1 mg / l. In one embodiment, relative to the total volume of the crude pyrolysis oil, the crude pyrolysis oil has a heavy metal content of 5 mg / l to 15 mg / l, or 5 mg / l to 20 mg / l.

[0056] As used herein, the term "heavy metal" refers to a metal or metalloid having a density > 4.51 g / cm 3 (at 20 °C). Examples of heavy metals include arsenic, antimony, bismuth, selenium, tin, cadmium, chromium, copper, mercury, nickel, and lead.

[0057] In terms of the sulfur content, nitrogen content, halogen content, oxygen content, and heavy metal content in the crude pyrolysis oil, two or more of the above-described embodiments can be combined in any manner. For example, the crude pyrolysis oil preferably has the nitrogen content, halogen content, and sulfur content as described above.

[0058] In one embodiment, the crude pyrolysis oil has a sulfur content of 10 mg / l or higher, a nitrogen content of 50 mg / l or higher (e.g., 200 mg / l or higher), and a chlorine content of 10 mg / l or higher. More specifically, the crude pyrolysis oil has a sulfur content in the range of 10 mg / l to 50 mg / l (e.g., in the range of 10 mg / l to 30 mg / l), a nitrogen content of 200 mg / l or higher, and a chlorine content of 10 mg / l or higher.

[0059] In another embodiment, the crude pyrolysis oil has an oxygen content of 40 mg / l or higher, a sulfur content of 10 mg / l or higher, a nitrogen content of 50 mg / l or higher, and a chlorine content of 10 mg / 1 or higher.

[0060] In another embodiment, the crude pyrolysis oil has an oxygen content of 40 mg / l or higher, a sulfur content of 10 mg / l or higher, a nitrogen content of 50 mg / l or higher, a chlorine content of 10 mg / 1 or higher, and an olefin content of 30 wt.% or higher based on the total weight of the crude pyrolysis oil.

[0061] The method according to the present invention can provide a purified pyrolysis oil, the nitrogen content of which is reduced by 10% to 95% relative to the nitrogen content of the crude pyrolysis oil, such as at least 50%, or at least 60%, or at least 70%.

[0062] The method according to the present invention can provide a purified pyrolysis oil, the chlorine content of which is reduced by 10% to 95% relative to the chlorine content of the crude pyrolysis oil, such as at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%.

[0063] Preferably, the pyrolysis oil contains alkanes (preferably n-alkanes and / or iso-alkanes), olefins, cycloalkanes, and / or aromatics. The further characteristics of the crude pyrolysis oil derived from plastic waste include but are not limited to:

[0064] The boiling point in the range of 30 °C to 600 °C is measured by ASTM D2887, and / or

[0065] The dynamic viscosity in the range of 0.1 mPa·s to 100 mPa·s is measured by ASTM D7042, for example, using a viscometer SVM3000, and / or

[0066] Based on the total weight of the crude pyrolysis oil, the total alkane content in the range of 5 wt.% to 80 wt.%, 15 wt.% to 70 wt.%, or 20 wt.% to 65 wt.% is determined by GC×GC-FID / MS or GC-MS and GC-FID, and / or

[0067] Based on the total weight of the crude pyrolysis oil, the n-alkane content in the range of 20 wt.% to 80 wt.% is determined by GC×GC-FID / MS or GC-MS and GC-FID, and / or

[0068] Based on the total weight of the crude pyrolysis oil, the isoalkane content in the range of 2 wt.% to 80 wt.%, or 5 wt.% to 60 wt.%, or 10 wt.% to 45 wt.% is determined by GC×GC-FID / MS or GC-MS and GC-FID, and / or

[0069] Based on the total weight of the crude pyrolysis oil, the olefin content in the range of 0 wt.% to 70 wt.%, or 10 wt.% to 70 wt.%, or 15 wt.% to 65 wt.%, or 20 wt.% to 60 wt.% is determined by GC×GC-FID / MS or GC-MS and GC-FID, and / or

[0070] Based on the total weight of the crude pyrolysis oil, the naphthene content in the range of 0 wt.% to 50 wt.%, or 5 wt.% to 45 wt.%, or 10 wt.% to 40 wt.% is determined by GC×GC-FID / MS or GC-MS and GC-FID, and / or

[0071] Based on the total weight of the crude pyrolysis oil, the aromatic content in the range of 0 wt.% to 50 wt.%, or in the range of 5 wt.% to 30 wt.%, or in the range of 10 wt.% to 25 wt.% is determined by GC×GC-FID / MS or GC-MS and GC-FID, and / or

[0072] At 15 °C and 1013 mbar, the density in the range of 600 kg / m 3 to 1200 kg / m 3 is determined according to DIN EN ISO 12185.

[0073] The above further characteristics or properties of the crude pyrolysis oil derived from plastic waste can be combined with each other in any way, or they can be combined with other characteristics or properties of the crude pyrolysis oil derived from plastic waste disclosed herein in any way.

[0074] The feedstock for the pyrolysis is usually plastic waste or plastic waste combined with biomass.

[0075] As used herein, the term "plastic waste" refers to any plastic or rubber material discarded after use, i.e., the plastic material has reached the end of its service life. The plastic waste can be pure polymer plastic waste, mixed plastic waste or film waste, including dirt, adhesive materials, fillers, residues, etc. The plastic waste has a nitrogen content, a sulfur content, a halogen content, an oxygen content, a silicon content, and optionally a heavy metal content. The plastic waste can be sourced from any source containing plastic materials. Thus, the term "plastic waste" includes industrial and household plastic waste, including used tires and agricultural and horticultural plastic materials. The term "plastic waste" can also include used petroleum-based hydrocarbon materials such as used motor oil, machine oil, grease, wax, etc. Preferably, the plastic waste consists mainly of plastic and / or rubber materials.

[0076] Typically, plastic waste is a mixture of different plastic materials, including hydrocarbon plastics (such as polyolefins like polyethylene (HDPE, LDPE) and polypropylene, polystyrene and its copolymers, etc.), and polymers composed of carbon, hydrogen and other elements (such as chlorine, fluorine, oxygen, nitrogen, sulfur, silicon, etc.), such as chlorinated plastics (such as polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), etc.), nitrogen-containing plastics (such as polyamide (PA), polyurethane (PU), acrylonitrile-butadiene-styrene (ABS), etc.), oxygen-containing plastics (such as polyesters like polyethylene terephthalate (PET), polycarbonate (PC), etc.), silicone and / or sulfur-bridged rubber. PET plastic waste is usually sorted before pyrolysis because PET has a profitable resale value. Thus, based on the dry weight of the plastic material, the plastic waste to be pyrolyzed typically contains less than about 10 wt.%, preferably less than about 5 wt.%, and most preferably substantially no PET. As used herein, "biomass" refers to any plant- or animal-based material such as wood residues, lignocellulosic biomass, paper, cardboard, energy crops, agricultural residues, and food waste from industry, households and farms.

[0077] Haoxi et al. provided an example of a crude pyrolysis oil derived from the pyrolysis of biomass in "A comprehensive Characterization of Pyrolysis Oil from Softwood Barks", Polymers, Vol. 11, p. 1387, 2019.

[0078] An oxidant is used to oxidize the crude pyrolysis oil in step A2) of the method according to the first aspect, and an oxidant is used to oxidize the washed crude pyrolysis oil in step B4) of the method according to the second aspect.

[0079] The oxidant contains hydrogen peroxide and a metal salt. The oxidant is usually added in the form of an aqueous solution containing hydrogen peroxide and a metal salt. The hydrogen peroxide can be added in the form of pure hydrogen peroxide, an aqueous solution of hydrogen peroxide, and / or sodium percarbonate (Na2CO3·3H2O2). Preferably, the oxidant contains an aqueous solution of a metal salt and hydrogen peroxide, or consists of an aqueous solution of a metal salt and hydrogen peroxide. More preferably, the oxidant contains an aqueous solution of a metal salt and 20 wt.% to 50 wt.% hydrogen peroxide, or consists of an aqueous solution of a metal salt and 20 wt.% to 50 wt.% hydrogen peroxide. In particular, hydrogen peroxide in the range of 30 wt.% to 50 wt.% (based on the total weight of the aqueous solution).

[0080] The advantage of using hydrogen peroxide is that, for example, it can oxidize most impurities without oxidizing the pyrolysis oil itself. In other words, it does not change the pyrolysis oil but only oxidizes the unwanted components.

[0081] The main decomposition products of the oxidant are O2 and water, i.e., volatile compounds that are easily removed. It is known that O2 catalyzes the oligomerization / polymerization of dienes in pyrolysis oil, resulting in the formation of solids or gels during storage / transport of the oil (e.g., when in contact with air). Due to the O2 released by the peroxide, these dienes have been advantageously removed in solid form to a certain extent in the oxidation or washing step according to the present invention.

[0082] Finally, hydrogen peroxide does not contain any other heteroatoms except O. In other words, hydrogen peroxide does not increase the concentration of, for example, sulfur, which is often a highly toxic substance in subsequent processing steps of pyrolysis oil.

[0083] The metal salt preferably contains an iron salt, a copper salt, a cerium salt, a cobalt salt, a chromium salt, and mixtures thereof. More preferably, it contains an iron salt, or consists of an iron salt.

[0084] The iron salt preferably contains iron nitrate (e.g., iron(III) nitrate), iron sulfate, iron phosphate, iron chloride, and mixtures thereof, or consists of iron nitrate (e.g., iron(III) nitrate), iron sulfate, iron phosphate, iron chloride, and mixtures thereof. More preferably, it contains iron(III) nitrate or consists of iron(III) nitrate.

[0085] The copper salt preferably contains copper sulfate or consists of copper sulfate. The cerium salt preferably contains cerium sulfate and / or cerium oxide, or consists of cerium sulfate and / or cerium oxide. The cobalt salt preferably contains cobalt sulfate or consists of cobalt sulfate. The chromium salt preferably contains potassium chromium sulfate or consists of potassium chromium sulfate.

[0086] In addition to hydrogen peroxide and the metal salt, the oxidant may further comprise one or more other components. The oxidant may further comprise potassium monopersulfate (oxone), sodium persulfate, sodium hypochlorite, sodium perchlorate, sodium borate, sodium bismuthate, ammonium cerium nitrate, peracetic acid, sodium peroxide, potassium superoxide, and mixtures thereof. In other embodiments, the oxidant further comprises sodium chlorite.

[0087] Preferably, in step A2) or step B4), the hydrogen peroxide is added in an amount of 0.15 mol / l to 3.5 mol / l relative to the crude pyrolysis oil.

[0088] Preferably, in step A2) or step B4), the metal salt is added in an amount of 0.2 mmol / l to 25 mmol / l relative to the pyrolysis oil.

[0089] Preferably, a polar solvent is present in step A2), and the polar solvent preferably comprises water, and / or the polar solvent in step A2) is used as the polar washing solvent in step A3).

[0090] Preferably, the method further comprises step A2a), i.e., separating the reacted oxidant obtained in step A2) from the oxidized crude pyrolysis oil, wherein step A2a) occurs after step A2) and before step A3). In step A2), a water phase and a non-aqueous phase are preferably formed. The non-aqueous phase comprises the pyrolysis oil, and the water phase comprises the reacted oxidant. Preferably, the reacted oxidant in step A2a) is separated by separating the water phase containing the reacted oxidant from the non-aqueous phase containing the pyrolysis oil.

[0091] Preferably, in step A2) or B4), the temperature in the reactor is 15°C to 100°C, preferably 20°C to 75°C, more preferably 20°C to 50°C, such as 35°C to 50°C. The mixing time in step A2) or B4) is preferably in the range of 1 minute to 3 hours, more preferably in the range of 10 minutes to 1 hour.

[0092] Preferably, in step A3) or B2), the temperature is 10°C to 600°C, preferably 15°C to 400°C, more preferably 20°C to 360°C, and most preferably 250°C to 350°C. The mixing time in step A3) or B2) is preferably in the range of 1 minute to 3 hours, more preferably in the range of 10 minutes to 30 minutes.

[0093] The polar washing solvent used in step A3) or step B2) comprises water, alkanol, or any mixture thereof, and preferably the polar washing solvent comprises water. The water is preferably distilled water.

[0094] Alkanols are defined as alkane alcohols, i.e., R-OH, where R is an alkyl group, preferably an alkyl group having 1 to 12 carbon atoms. Preferably, the alkanol is selected from C1 to C4 alkanols, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and 2-methyl-1-propanol, preferably methanol or ethanol.

[0095] The polar washing solvent further contains an acid or a base, more preferably contains a base.

[0096] Preferably, the acid contains hydrochloric acid, sulfuric acid, or phosphoric acid. Preferably, the base contains hydroxides or alkoxides of metals of Group 1 or Group 2, preferably, the hydroxides or alkoxides of metals of Group 1 or Group 2 contain sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium methoxide, or potassium methoxide.

[0097] Preferably, before adding the polar washing solvent (such as water), the base (such as sodium hydroxide) can be added to the process in an aqueous solution or as a solid. The advantage of adding the base as a solid is that the pressure in the process will not increase significantly.

[0098] In an embodiment, where the base (such as sodium hydroxide) is added as a solid to the optionally pre-treated oxidized crude pyrolysis oil from step A2) or the optionally pre-treated crude pyrolysis oil from step B1) before adding the polar washing solvent in step A3) or step B2), the base and the oil are preferably mixed at a temperature above 100 °C, more preferably in the temperature range of 250 °C to 350 °C, for a period of 1 minute to 3 hours, preferably 10 minutes to 30 minutes, and then cooled to below 100 °C, such as about 20 °C, and then the polar washing solvent of step A3) or step B2) is added to the cooled mixture.

[0099] Preferably, in step A3), the ratio of the weight of the acid or the weight of the base to the volume of the oxidized crude pyrolysis oil is 0.1 mol / l to 1 mol / l, more preferably 0.1 mol / l to 0.5 mol / l, and most preferably 0.1 mol / l to 0.2 mol / l, or, in step B2), the ratio of the weight of the acid or the weight of the base to the volume of the crude pyrolysis oil is 0.1 mol / l to 1 mol / l, more preferably 0.1 mol / l to 0.5 mol / l, and most preferably 0.1 mol / l to 0.2 mol / l.

[0100] In a preferred embodiment, the polar washing solvent contains water and hydroxides of metals of Group 1 or Group 2, or consists of water and hydroxides of metals of Group 1 or Group 2. Preferably, the hydroxides of metals of Group 1 or Group 2 contain sodium hydroxide, potassium hydroxide, or calcium hydroxide, or consist of sodium hydroxide, potassium hydroxide, or calcium hydroxide.

[0101] In a specific embodiment, the polar washing solvent is an aqueous sodium hydroxide solution of 10 wt.% to 30 wt.%, for example, an aqueous sodium hydroxide solution of 20 wt.%.

[0102] In other specific embodiments, the polar washing solvent is a sodium methoxide methanol solution of 10 wt.% to 30 wt.%, for example, a sodium methoxide methanol solution of 30 wt.%.

[0103] It has been found that: adding a base or an acid to the polar washing solvent can convert some non-polar compounds that are easily protonated (when adding an acid) or deprotonated (when adding a base) into polar compounds with high solubility in the polar washing solvent, so that these non-polar compounds can be removed well. For example, amines can be easily protonated by adding an acid, and fatty acids can be easily deprotonated by adding a base.

[0104] Alternatively or additionally, the method may further include adding an acid or a base together with the oxidant in step A2) or step B4).

[0105] Alternatively, the method may include a pretreatment, which includes step B1a), that is, adding an acid or a base to the crude pyrolysis oil before mixing the pretreated crude pyrolysis oil with the polar washing solvent, where step B1a) occurs after step B1) and before step B2).

[0106] Alternatively, the method may further include a pretreatment, which includes step A1a), that is, adding an acid or a base to the crude pyrolysis oil before oxidizing the pretreated crude pyrolysis oil in the presence of the oxidant, where step A1a) occurs after step A1) and before step A2).

[0107] Alternatively, the method may further include a pretreatment, which includes step A2b), that is, adding an acid or a base to the oxidized crude pyrolysis oil before mixing the pretreated oxidized crude pyrolysis oil with the polar washing solvent, where step A2b) occurs after step A2), or if it exists, after step A2a) and before step A3).

[0108] In particular, the corresponding pretreatment steps B1a), A1a) or A2b) may include: adding the acid or the base to the crude pyrolysis oil in an aqueous solution such that a water / oil phase separation occurs, and removing the water phase from the pretreated crude pyrolysis oil phase before the subsequent steps of the method.

[0109] In a specific embodiment, the method includes:

[0110] A1) Provide a crude pyrolysis oil, the crude pyrolysis oil containing hydrocarbons and impurities, the crude pyrolysis oil being at least partially derived from the pyrolysis of plastic waste,

[0111] A1a) In a pre-reactor (or in the first reactor), add an aqueous solution of an acid (such as hydrochloric acid, sulfuric acid or phosphoric acid, especially sulfuric acid) to the crude pyrolysis oil, thereby providing a pretreated crude pyrolysis oil,

[0112] A1b) Optionally effect a water / oil phase separation and remove the water phase from the pretreated crude pyrolysis oil,

[0113] A2) In a first reactor, which is preferably a stirred tank reactor, oxidize the pretreated crude pyrolysis oil in the presence of an oxidizing agent to obtain an oxidized crude pyrolysis oil, wherein the oxidizing agent comprises an aqueous solution of hydrogen peroxide and a metal salt (such as an iron salt, especially iron(III) nitrate),

[0114] A2a) Separate the reacted oxidizing agent obtained in step A2) from the oxidized crude pyrolysis oil by effecting a water / oil phase separation and removing the water phase from the oxidized crude pyrolysis oil;

[0115] A3) In the first reactor or a second reactor, mix the oxidized crude pyrolysis oil with a polar washing solvent to obtain a purified pyrolysis oil phase and a polar washing solvent phase, the polar washing solvent phase containing at least a portion of the oxidized impurities, wherein the polar detergent is water containing a base, such as a hydroxide of a Group 1 or Group 2 metal, especially sodium hydroxide, and

[0116] A4) Separate the polar washing solvent phase from the purified pyrolysis oil phase to obtain a purified pyrolysis oil.

[0117] In another specific embodiment, the method comprises:

[0118] A1) Provide a crude pyrolysis oil, the crude pyrolysis oil containing hydrocarbons and impurities, the crude pyrolysis oil being at least partially derived from the pyrolysis of plastic waste,

[0119] A1a) In a pre-reactor (or in the first reactor), add an aqueous solution of an acid (such as hydrochloric acid, sulfuric acid or phosphoric acid, especially sulfuric acid) to the crude pyrolysis oil, thereby providing a pretreated crude pyrolysis oil,

[0120] A1b) Optionally effect a water / oil phase separation and remove the water phase from the pretreated crude pyrolysis oil,

[0121] A2) In the first reactor, which is preferably a stirred tank reactor, the pretreated crude pyrolysis oil is oxidized in the presence of an oxidant to obtain oxidized crude pyrolysis oil, wherein the oxidant comprises an aqueous solution of hydrogen peroxide and a metal salt (such as an iron salt, especially iron(III) nitrate).

[0122] A2a) Separate the water / oil phases and remove the aqueous phase from the oxidized crude pyrolysis oil to separate the reacted oxidant obtained in step A2) from the oxidized crude pyrolysis oil.

[0123] A2b) In the first reactor or the second reactor, add a base in solid form, such as sodium hydroxide, to the oxidized crude pyrolysis oil.

[0124] A3) In the first reactor or the second reactor or the third reactor, mix the oxidized crude pyrolysis oil with a polar washing solvent to obtain a purified pyrolysis oil phase and a polar washing solvent phase, wherein the polar washing solvent phase contains at least a part of the oxidation impurities, and the polar washing solvent is water.

[0125] A4) Separate the polar washing solvent phase from the purified pyrolysis oil phase to obtain purified pyrolysis oil.

[0126] In step A1a), the mixing of the aqueous acid solution and the crude pyrolysis oil is preferably carried out in the temperature range of 10°C to 95°C, such as 20°C to 50°C, or 30°C to 50°C. Preferably in step A1a), the aqueous acid solution and the crude pyrolysis oil are mixed for a period ranging from 1 minute to 1 hour, more preferably from 1 minute to 30 minutes.

[0127] In step A2b), the mixing of the base (when added in solid form) and the oxidized crude pyrolysis oil is preferably carried out at a temperature higher than 100°C, more preferably 250°C to 350°C. In step A2b), the base (when added in solid form) and the oxidized crude pyrolysis oil are preferably mixed for a period ranging from 10 minutes to 3 hours, more preferably from 10 minutes to 1 hour. When the mixing of the base (added in solid form) and the oxidized crude pyrolysis oil is carried out at a temperature higher than 100°C in step A2b), before step A3), the method preferably further includes step A2c), that is, cooling the mixture to ambient temperature, such as 20°C.

[0128] In step A4) or step B5) of the method, the separation can be carried out by, for example, centrifugation, decanting the aqueous phase from the oil phase after sedimentation, or phase separation filtration.

[0129] As described above, the crude pyrolysis oil contains many types of impurities. Preferably, the impurities include inorganic compounds, which preferably include metals or metal ions, the metals preferably being heavy metals, the metal ions preferably being heavy metal ions, and / or organic compounds containing heteroatoms, the heteroatoms preferably being oxygen, nitrogen, sulfur, silicon, and / or halogens. The concentrations of these impurities are disclosed above.

[0130] The present invention also provides a method for producing a cracking feedstock, comprising the steps of: mixing 1 wt.% to 100 wt.% of purified pyrolysis oil based on the total weight of the cracking feedstock and 99 wt.% to 0 wt.% of fossil naphtha based on the total weight of the cracking feedstock, wherein the purified pyrolysis oil is obtained by the crude pyrolysis oil purification method according to the present invention.

[0131] If applicable, all preferred embodiments of the crude pyrolysis oil purification method according to the present invention are also preferred embodiments of the method for producing a cracking feedstock.

[0132] Preferably, the cracking feedstock is a steam cracking feedstock.

[0133] In one embodiment, based on the total weight of the cracking feedstock, the cracking feedstock (or steam cracking feedstock) contains at least 5 wt.% of purified pyrolysis oil and no more than 95 wt.% of fossil naphtha. Preferably, based on the total weight of the cracking feedstock, the cracking feedstock (or steam cracking feedstock) contains at least 10 wt.% of purified pyrolysis oil and no more than 90 wt.% of fossil naphtha. More preferably, based on the total weight of the cracking feedstock, the cracking feedstock (or steam cracking feedstock) contains at least 30 wt.% of purified pyrolysis oil and no more than 70 wt.% of fossil naphtha. In particular, based on the total weight of the cracking feedstock, the cracking feedstock (or steam cracking feedstock) contains at least 40 wt.% of purified pyrolysis oil and no more than 60 wt.% of fossil naphtha.

[0134] The present invention also provides the use of purified pyrolysis oil as a cracking feedstock.

[0135] Preferably, the cracking feedstock is a steam cracking feedstock.

[0136] The present invention also relates to the use of an oxidizing agent for removing impurities from crude pyrolysis oil.

[0137] Therefore, the present invention further provides the use of an oxidizing agent comprising an aqueous solution of hydrogen peroxide and a metal salt for removing impurities from crude pyrolysis oil, the metal salt preferably comprising an iron salt, the iron salt preferably comprising iron(III) nitrate, and the crude pyrolysis oil comprising pyrolysis oil and impurities.

[0138] All preferred embodiments of the crude pyrolysis oil purification method according to the present invention are also preferred embodiments of the use of the oxidizing agent, if applicable.

[0139] Preferably, the impurities include inorganic compounds, which preferably include metals or metal ions, the metals preferably being heavy metals, and the metal ions preferably being heavy metal ions, and / or organic compounds containing heteroatoms, the heteroatoms preferably being oxygen, nitrogen, sulfur, silicon and / or halogens.

[0140] The present invention will be further described and illustrated below by non-limiting examples. Detailed Embodiments

[0141] Examples

[0142] Materials

[0143] In the following examples, crude pyrolysis oil (recycled carbon fuel) from a commercially available batch from Renasci Oostende Recycling NV was used. The crude pyrolysis oil is characterized by a boiling point of 50 °C to 482.5 °C. The properties of different batches of crude pyrolysis oil used in the examples are given in Table 1 below.

[0144] An aqueous hydrogen peroxide solution of 35 wt.% was obtained from Merck. An aqueous hydrogen peroxide solution of 50 wt.%, iron(III) nitrate nonahydrate (Fe(NO3)3·9H2O), sodium hydroxide, and a 30 wt.% sodium methoxide in methanol solution were obtained from Sigma-Aldrich Handels GmbH.

[0145] Analysis Methods

[0146] Chlorine content in pyrolysis oil

[0147] Instrument: Model Xprep C-IC from TE Instruments (equipped with combustion module type 2019.010 and component collector type 2019.080, with Archie injection and liquid boat), and ECO IC instrument model 19250020 from Metrohm

[0148] Test method: ASTM D7359–18 (Standard Test Method for Determination of Total Fluorine, Chlorine, and Sulfur in Aromatic Hydrocarbons and Their Mixtures by Oxidative Pyrolysis Combustion–Ion Chromatography Detection (Combustion Ion Chromatography, CIC))

[0149] Each pyrolysis oil sample was measured three times.

[0150] Nitrogen content in pyrolysis oil

[0151] Instrument: Xplorer NS from TE Instruments, equipped with Archie injection and liquid boat

[0152] Test method:

[0153] ASTM D5762-18a (Standard Test Method for Nitrogen in Liquid Hydrocarbons, Petroleum and Petroleum Products by Boat Inlet Chemiluminescence)

[0154] ASTM D4629–17 (Standard Test Method for Trace Nitrogen in Liquid Hydrocarbons by Syringe / Inlet Oxidative Combustion-Chemiluminescence Detection)

[0155] ASTM D4629 is used to analyze pyrolysis oil with a nitrogen concentration below 1000 ppm, while ASTM D5762 is used to analyze pyrolysis oil with a nitrogen concentration above 1000 ppm.

[0156] Each sample was measured three times.

[0157] Sulfur content in pyrolysis oil

[0158] Instrument: Xplorer NS from TE Instruments, equipped with Archie injection and liquid boat

[0159] Test method: ASTM D5453-19a (Standard Test Method for Total Sulfur in Light Hydrocarbons, Spark-Ignition Engine Fuels, Diesel Engine Fuels, and Engine Oils by Ultraviolet Fluorescence)

[0160] Each sample was measured three times.

[0161] Examples

[0162] The following Examples 1 to 5, Example 10 and Comparative Example 4 were carried out in a 100 ml glass reactor (EasyMax reactor system from Mettler Toledo) and a 100 ml high-pressure steel autoclave (Parr GmbH, maximum pressure 200 bar), both equipped with electric heating.

[0163] Example 1

[0164] Fenton oxidation:

[0165] In a 100 ml glass reactor equipped with mechanical stirring, 50 ml of pyrolysis oil was heated to 45 °C. Under stirring, 1.0 ml of an aqueous solution of 10 wt.% Fe(NO3)3·9H2O was added to the pyrolysis oil, followed by 5 ml of an aqueous solution of 50 wt.% hydrogen peroxide. After mixing at 45 °C for 1 hour, the reaction mixture was centrifuged at 4000 rpm for 5 minutes, and the aqueous phase was separated from the pyrolysis oil by decantation.

[0166] High-temperature alkali washing:

[0167] Transfer 40 ml of the pyrolysis oil from the Fenton oxidation step to a 100-ml steel autoclave equipped with an electric heater and a magnetic stir bar. Then, at room temperature, add 1.0 g of a 20 wt.% aqueous sodium hydroxide solution to the stirred pyrolysis oil. Subsequently, heat the autoclave to 350 °C and continue to mix the reaction mixture at this temperature for 1 hour. After cooling the reaction mixture to room temperature, add 10 ml of water and continue to stir for 1 minute at this temperature. Finally, after centrifuging the reaction mixture at 4000 rpm for 10 minutes, separate the aqueous phase from the pyrolysis oil by decantation.

[0168] Example 2

[0169] High-temperature alkali washing:

[0170] Add 40 ml of the pyrolysis oil to a 100-ml steel autoclave equipped with an electric heater and a magnetic stir bar. Then, at room temperature, add 1.0 g of a 20 wt.% aqueous sodium hydroxide solution to the stirred pyrolysis oil. Subsequently, heat the autoclave to 350 °C and continue to mix the reaction mixture at this temperature for 1 hour. After cooling the reaction mixture to room temperature, add 10 ml of water and continue to stir for 1 minute at this temperature. After centrifuging the reaction mixture at 4000 rpm for 10 minutes, then separate the aqueous phase from the pyrolysis oil by decantation.

[0171] Fenton oxidation:

[0172] In a 100-ml glass reactor equipped with an electric heater and mechanical stirring, heat the pyrolysis oil from the high-temperature alkali washing step to 45 °C. With stirring, add 0.8 ml of a 10 wt.% aqueous Fe(NO3)3·9H2O solution to the pyrolysis oil, and then add 4 ml of a 50 wt.% aqueous hydrogen peroxide solution. After mixing at 45 °C for 1 hour, centrifuge the reaction mixture at 4000 rpm for 5 minutes and then separate the aqueous phase from the pyrolysis oil by decantation.

[0173] Example 3

[0174] In a 100 ml glass reactor equipped with an electric heater and a mechanical stirrer, 50 ml of pyrolysis oil was heated to 45 °C. Then, 1 ml of a 10 wt.% aqueous solution of Fe(NO3)3·9H2O was added to the pyrolysis oil under stirring, and then 5 ml of a 50 wt.% aqueous hydrogen peroxide solution was added. After mixing at 45 °C for 1 hour, the temperature was lowered to room temperature, and the reactor contents were transferred to a 100 ml steel autoclave equipped with an electric heater and a magnetic stir bar. Subsequently, 1.0 g of a 20 wt.% aqueous sodium hydroxide solution was added to the stirred pyrolysis oil at room temperature. Then the autoclave was heated to 350 °C, and the reaction mixture was continuously mixed at this temperature for 1 hour. After the reaction mixture was cooled to room temperature, 10 ml of water was added, and stirring was continued at this temperature for 1 minute. Finally, the reaction mixture was centrifuged at 4000 rpm for 10 minutes, and then the aqueous phase was separated from the pyrolysis oil by decantation.

[0175] Example 4

[0176] As in Example 2, except that: in the high-temperature alkali washing, 1.0 g of a 30 wt.% sodium methoxide methanol solution was used instead of 1.0 g of a 20 wt.% aqueous sodium hydroxide solution.

[0177] Example 5

[0178] As in Example 2, except that: in the high-temperature alkali washing, 1.0 g of a 30 wt.% sodium methoxide methanol solution was used instead of 1.0 g of a 20 wt.% aqueous sodium hydroxide solution, and the temperature was 120 °C instead of 350 °C.

[0179] Example 6

[0180] Fenton oxidation:

[0181] In a 1000 ml glass bottle equipped with a mechanical stirrer, 800 ml of pyrolysis oil was heated to 45 °C. Under stirring, 8.0 ml of a 10 wt.% aqueous solution of Fe(NO3)3·9H2O was added to the pyrolysis oil, and then 120 ml of a 35 wt.% aqueous hydrogen peroxide solution was added. After mixing at 45 °C for 30 minutes, the aqueous phase was separated from the pyrolysis oil by decantation and filtration (phase separation paper filter, size 185 mm, grade 108H).

[0182] High-temperature alkali washing:

[0183] Transfer 40 ml of the pyrolysis oil from the Fenton oxidation step to a 100 ml steel autoclave equipped with an electric heater and a magnetic stir bar. Then add 0.29 g of solid sodium hydroxide to the stirred pyrolysis oil at room temperature. Heat the autoclave to 350 °C and continue to mix the reaction mixture at this temperature for 10 minutes. After cooling the reaction mixture to room temperature, add 10 ml of water and continue to stir for 1 minute. Finally, centrifuge the reaction mixture at 4000 rpm for 10 minutes and then separate the aqueous phase from the pyrolysis oil by decantation.

[0184] Example 7

[0185] Fenton oxidation:

[0186] In a 1000 ml glass bottle equipped with mechanical stirring, heat 800 ml of the pyrolysis oil to 45 °C. With stirring, add 8.0 ml of a 10 wt.% aqueous solution of Fe(NO3)3·9H2O, 24 ml of 1 wt.% sulfuric acid, and 12 ml of water to the pyrolysis oil, and then slowly add 120 ml of a 35 wt.% aqueous hydrogen peroxide solution. After mixing at 45 °C for 30 minutes, separate the aqueous phase from the pyrolysis oil by decantation and filtration (phase separation paper filter, size 185 mm, grade 108H).

[0187] High-temperature alkali washing:

[0188] Transfer 40 ml of the pyrolysis oil from the Fenton oxidation step to a 100 ml steel autoclave equipped with an electric heater and a magnetic stir bar. Then add 0.29 g of solid sodium hydroxide to the stirred pyrolysis oil at room temperature. Heat the autoclave to 350 °C and continue to mix the reaction mixture at this temperature for 10 minutes. After cooling the reaction mixture to room temperature, add 10 ml of water and continue to stir for 1 minute. Finally, centrifuge the reaction mixture at 4000 rpm for 10 minutes and then separate the aqueous phase from the pyrolysis oil by decantation.

[0189] Example 8

[0190] Sulfuric acid washing:

[0191] At room temperature, add 500 ml of 0.2% sulfuric acid to 500 ml of the pyrolysis oil in a 1500 ml separating funnel. After shaking vigorously for one minute, allow the two phases to separate and remove the aqueous phase from the pyrolysis oil.

[0192] Fenton oxidation:

[0193] In a 1000 ml glass bottle equipped with mechanical stirring, 700 ml of pyrolysis oil washed with sulfuric acid was heated to 45 °C. With stirring, 7.0 ml of an aqueous solution of 10 wt.% Fe(NO3)3·9H2O was added to the pyrolysis oil, and then 105 ml of an aqueous solution of 35 wt.% hydrogen peroxide was slowly added. After mixing at 45 °C for 30 minutes, the aqueous phase was separated from the pyrolysis oil by decantation and filtration (phase separation paper filter, size 185 mm, grade 108H).

[0194] High-temperature alkaline washing:

[0195] 40 ml of the pyrolysis oil from the Fenton oxidation step was transferred to a 100 ml steel autoclave equipped with electric heating and a magnetic stir bar. Then, 0.29 g of solid sodium hydroxide was added to the stirred pyrolysis oil at room temperature. The autoclave was heated to 350 °C, and the reaction mixture was continuously mixed at this temperature for 10 minutes. After the reaction mixture was cooled to room temperature, 10 ml of water was added and stirring was continued for 1 minute. Finally, after the reaction mixture was centrifuged at 4000 rpm for 10 minutes, the aqueous phase was separated from the pyrolysis oil by decantation.

[0196] Example 9

[0197] Sulfuric acid washing:

[0198] At room temperature, in a 1500 ml separatory funnel, 500 ml of 0.2% sulfuric acid was added to 500 ml of pyrolysis oil. After shaking vigorously for 1 minute, the two phases were separated, and the aqueous phase was removed from the pyrolysis oil.

[0199] Fenton oxidation:

[0200] In a 1000 ml glass bottle equipped with mechanical stirring, 60 ml of pyrolysis oil from the sulfuric acid washing was heated to 45 °C. With stirring, 0.6 ml of an aqueous solution of 10 wt.% Fe(NO3)3·9H2O was added to the pyrolysis oil, and then 0.9 ml of an aqueous solution of 35 wt.% hydrogen peroxide was slowly added. After mixing at 45 °C for 30 minutes, the aqueous phase was separated from the pyrolysis oil by decantation and filtration (phase separation paper filter, size 185 mm, grade 108H).

[0201] High-temperature alkaline washing:

[0202] Transfer 40 ml of the pyrolysis oil from the Fenton oxidation step to a 100 ml steel autoclave equipped with an electric heater and a magnetic stir bar. Then add 0.29 g of solid sodium hydroxide to the stirred pyrolysis oil at room temperature. Heat the autoclave to 350 °C and continue to mix the reaction mixture at this temperature for 10 minutes. After cooling the reaction mixture to room temperature, add 10 ml of water and continue to stir for 1 minute. Finally, centrifuge the reaction mixture at 4000 rpm for 10 minutes and then separate the aqueous phase from the pyrolysis oil by decantation.

[0203] Example 10

[0204] As in Example 8, except that: in the high-temperature alkali washing step, 1 ml of a 29 wt% aqueous sodium hydroxide solution is added instead of 0.29 g of solid NaOH, and the mixing time at 350 °C is 3 hours instead of 10 minutes.

[0205] Example 11

[0206] Fenton oxidation:

[0207] In a 100 ml glass reactor equipped with mechanical stirring, heat 10 ml of the pyrolysis oil to 45 °C. Then, with stirring, add 1.0 ml of a 35 wt.% aqueous hydrogen peroxide solution and 0.01 g of Fe(NO3)3·9H2O, and continue to mix the reaction mixture at this temperature for 3 hours. After centrifuging the reaction mixture at 4000 rpm for 5 minutes, separate the aqueous phase from the pyrolysis oil by decantation.

[0208] At room temperature, add 1.0 ml of water to the oil and then mix for 1 minute. Then centrifuge the reaction mixture at 4000 rpm for 5 minutes and then separate the aqueous phase from the pyrolysis oil by decantation.

[0209] Comparative Example CE1

[0210] High-temperature alkali washing:

[0211] Add 40 ml of the pyrolysis oil to a 100 ml steel autoclave equipped with an electric heater and a magnetic stir bar. Then add 1.0 g of a 20 wt.% aqueous sodium hydroxide solution to the stirred pyrolysis oil at room temperature. Subsequently, heat the autoclave to 150 °C and continue to mix the reaction mixture at this temperature for 1 hour. After cooling the reaction mixture to room temperature, add 10 ml of water and continue to stir at this temperature for 1 minute. Then, centrifuge the reaction mixture at 4000 rpm for 10 minutes and then separate the aqueous phase from the pyrolysis oil by decantation.

[0212] Comparative Example CE2

[0213] High-temperature water washing:

[0214] 40 ml of pyrolysis oil was added to a 100 ml steel autoclave equipped with an electric heater and a magnetic stir bar. Then, 1.0 g of water was added to the stirred pyrolysis oil at room temperature. Subsequently, the autoclave was heated to 150 °C and the reaction mixture was continuously mixed at this temperature for 1 hour. After the reaction mixture was cooled to room temperature, 10 ml of water was added and the mixture was continuously stirred at this temperature for 1 minute. Then, after the reaction mixture was centrifuged at 4000 rpm for 10 minutes, the aqueous phase was separated from the pyrolysis oil by decantation.

[0215] Comparative Example CE3

[0216] As in Comparative Example CE2, except that: in the high-temperature water washing, the temperature used was 350 °C instead of 150 °C.

[0217] Comparative Example CE4

[0218] As in Example CE6, except that: Fe(NO3)3·9H2O was not used.

[0219] Table 1 Chlorine concentration, nitrogen concentration, and sulfur concentration of crude pyrolysis oil and purified pyrolysis oil

[0220]

[0221] N.D. = Not determined

[0222] The reduction amounts in Table 1 were calculated as follows:

[0223]

[0224] c(crude oil) = concentration of each impurity in the pyrolysis oil before purification (ppm)

[0225] c(purified oil) = concentration of each impurity in the pyrolysis oil after purification (ppm).

Claims

1. A method for purifying crude pyrolysis oil, the method comprising the following steps: A1) providing crude pyrolysis oil, which contains hydrocarbons and impurities and is at least partially derived from the pyrolysis of plastic waste, A2) in a first reactor, preferably a stirred tank reactor, oxidizing the crude pyrolysis oil in the presence of an oxidant to obtain oxidized crude pyrolysis oil, which contains oxidized impurities, A3) in the first reactor or a second reactor, mixing the oxidized crude pyrolysis oil with a polar washing solvent to obtain a purified pyrolysis oil phase and a polar washing solvent phase, the polar washing solvent phase containing at least a part of the oxidized impurities, A4) separating the polar washing solvent phase from the purified pyrolysis oil phase to obtain purified pyrolysis oil, wherein the oxidant contains hydrogen peroxide and a metal salt, and wherein the polar washing solvent contains water, an alkanol or a mixture thereof, and also contains an acid or a base, preferably the polar washing solvent contains sodium hydroxide in water or sodium methoxide in methanol.

2. A method for purifying crude pyrolysis oil, the method comprising the following steps: B1) providing crude pyrolysis oil, which contains hydrocarbons and impurities and is at least partially derived from the pyrolysis of plastic waste, B2) in a first reactor, preferably a stirred tank reactor, mixing the crude pyrolysis oil with a polar washing solvent to obtain a washed crude pyrolysis oil phase and a polar washing solvent phase, the polar washing solvent phase containing at least a part of the impurities, B3) separating the polar washing solvent phase from the washed crude pyrolysis oil phase, B4) in the first reactor or a second reactor, oxidizing the washed crude pyrolysis oil phase in the presence of an oxidant to obtain oxidized purified pyrolysis oil, which contains oxidized impurities, B5) separating the oxidized impurities from the oxidized purified pyrolysis oil to obtain purified pyrolysis oil, wherein the oxidant contains hydrogen peroxide and a metal salt, and wherein the polar washing solvent contains water, an alkanol or a mixture thereof, and also contains an acid or a base, preferably the polar washing solvent contains sodium hydroxide in water or sodium methoxide in methanol.

3. The method according to claim 1, wherein the method further comprises the step of: A2a) separating the reacted oxidant obtained in step A2) from the oxidized crude pyrolysis oil, where step A2a) occurs after step A2) and before step A3).

4. The method according to any one of the preceding claims, wherein in step A2) or B4), the temperature in the reactor is 15°C to 100°C.

5. The method according to any one of the preceding claims, wherein in step A2) or step B4), hydrogen peroxide is added in an amount of 0.15 mol / l to 3.5 mol / l relative to the crude pyrolysis oil, and in step A2) or step B4), the metal salt is added in an amount of 0.2 mmol / l to 25 mmol / l relative to the pyrolysis oil.

6. The method according to any one of the preceding claims, wherein the alkanol is methanol or ethanol.

7. The method according to any one of the preceding claims, wherein the acid comprises hydrochloric acid, sulfuric acid or phosphoric acid, or wherein the base comprises a hydroxide or alkoxide of a metal of Group 1 or Group 2.

8. The method according to any one of the preceding claims, wherein the polar washing solvent comprises sodium hydroxide in water or sodium methoxide in methanol.

9. The method according to any one of claims 1 to 8, wherein the method comprises a pretreatment step: B1a) adding an acid or a base to the pretreated crude pyrolysis oil before mixing the pretreated crude pyrolysis oil with the polar washing solvent, wherein step B1a) occurs after step B1) and before step B2); or A1a) adding an acid or a base to the pretreated crude pyrolysis oil before oxidizing the pretreated crude pyrolysis oil in the presence of the oxidant, wherein step A1a) occurs after step A1) and before step A2); or A2b) adding an acid or a base to the pretreated oxidized crude pyrolysis oil before mixing the pretreated oxidized crude pyrolysis oil with the polar washing solvent, wherein step A2b) occurs after step A2), or if present, after step A2a) and before step A3).

10. The method according to any one of claims 1 and 3 to 9, wherein a polar solvent is present in step A2), the polar solvent preferably comprising water, and / or wherein the polar solvent in step A2) is used as the polar washing solvent in step A3).

11. The method according to any one of the preceding claims, wherein in step A3) or B2), the temperature is from 10 °C to 600 °C.

12. The method according to any one of the preceding claims, wherein the impurities comprise inorganic compounds and / or organic compounds containing heteroatoms.

13. The method according to any one of the preceding claims, wherein the metal salt is an iron salt, preferably selected from iron(III) nitrate, iron sulfate, iron phosphate, iron chloride and mixtures thereof, more preferably the metal salt is iron(III) nitrate.

14. A method for producing a cracking feedstock, comprising the following steps: Mixing 1 wt.% to 100 wt.% of the purified pyrolysis oil based on the total weight of the cracking feedstock and 0 wt.% to 99 wt.% of fossil naphtha based on the total weight of the cracking feedstock, wherein the purified pyrolysis oil is obtained by the method according to any one of claims 1 to 13.

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