Method for purifying a crude pyrolysis product

Abstract

This invention relates to a method for purifying crude pyrolysis products, the method comprising the following steps: A1) providing crude pyrolysis products containing hydrocarbons and impurities, the crude pyrolysis products being obtained at least partially through the pyrolysis of plastic waste; A2) contacting the crude pyrolysis products with an alkali metal hydroxide in a continuous mode at a temperature of 330°C to 400°C, preferably 340°C to 360°C, for a residence time of less than 10 min, to obtain a treated pyrolysis product and a residue containing reaction impurities; A3) washing the treated pyrolysis products with a polar washing solvent to obtain a purified pyrolysis product and a polar washing solvent phase; A4) separating the polar washing solvent phase and the purified pyrolysis product.

Description

Technical Field

[0001] This invention relates to a method for purifying crude pyrolysis products, which preferably can be obtained at least partially from the pyrolysis of plastic waste to obtain purified pyrolysis products. The invention also relates to a method for producing pyrolysis feedstock, particularly steam pyrolysis feedstock, comprising the purified pyrolysis products. Background Technology

[0002] Pyrolysis is an important technology for the chemical recycling of materials such as plastic waste. Pyrolysis typically involves the thermal degradation of raw materials in an inert atmosphere, producing high-value-added products such as pyrolysis gas, liquid pyrolysis oil, and coke (residue), with hydrocarbon-containing pyrolysis oil being the primary product.

[0003] Depending on the type and quality of the feedstock used to prepare pyrolysis oil, various impurities are typically found in it. A typical feedstock is plastic waste, but biomass can also be used. Pyrolysis oil from plastic waste contains more and more diverse contaminants than fossil feedstock because plastics are used in a wide range of applications and therefore contain a variety of additives. These impurities found in pyrolysis oil include, for example, inorganic compounds such as metal-containing compounds and complexes, and organic compounds containing heteroatoms (e.g., nitrogen, oxygen, sulfur, silicon, and halogens, especially chlorine). Pyrolysis oil typically has a much higher content of unsaturated hydrocarbons (such as olefins) than fossil feedstock. Maintaining low concentrations of these impurities (especially chlorinated compounds and dienes) is crucial, for example, to prevent problems during storage and processing, and to ensure its usability as a (steam) cracking feedstock for the production of basic chemicals (e.g., ethylene and propylene). Otherwise, these impurities can cause problems in further processing or use of the pyrolysis oil, such as precipitation and gum formation, catalyst deactivation / poisoning, sediment formation, and corrosion of pipelines and reactors. For example, Kusenberg et al., 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), discussed the steam cracking of untreated plastic waste pyrolysis oils, in which the authors concluded that purifying the pyrolysis oil before steam cracking is a prerequisite for avoiding operational problems caused by increased coking and scaling.

[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 can contain no more than 3 ppm of chlorine, no more than 100 ppm of nitrogen, and no more than 100 ppm of oxygen.

[0005] To ensure that these pyrolysis oils meet the high purity standards required for their intended use (e.g., as steam cracking feedstock for the production of basic chemicals), they typically need to be diluted with naphtha and / or purified. Purification of crude pyrolysis oil can be accomplished, for example, through an expensive hydrogenation process or simply by a washing step (i.e., by extracting impurities with a solvent immiscible with the oil). However, while such washing steps can be effective for removing polar impurities, they are found to achieve only low removal rates for non-polar impurities with high solubility in the oil, such as certain organochlorides.

[0006] Typically, pyrolysis oil, which can be obtained at least partially from the pyrolysis of plastic waste, requires dehalogenation (especially dechlorination), denitrification, and deoxygenation to reduce the concentration of these impurities and allow it to be used as a pyrolysis feedstock, such as a steam cracking feedstock.

[0007] WO2022 / 234225A1 discloses a method for purifying hydrocarbon feedstocks in the presence of a solvent. This document describes a purification process using an alkali treatment with a polar component having alcohol or ether functional groups. The pyrolysis oil can be contacted with the alkali and the polar component having alcohol or ether functional groups, or held in a reactor, for up to 48 hours.

[0008] However, achieving short residence times becomes a challenge when scaling up high-temperature reaction extraction processes to a commercial scale. This is because, as reactor size increases, heat transfer efficiency must be reconsidered, and the ratio of heated surface area to batch volume decreases, slowing down the heating and cooling processes. Furthermore, in commercial plants, all necessary heating and cooling times are considered wasteful, thus hindering the achievement of optimal process efficiency. Summary of the Invention

[0009] The purpose of this invention is to provide a method for purifying crude pyrolysis products obtained by pyrolysis of raw materials, particularly a method for purifying crude pyrolysis products containing various impurities.

[0010] Another object of the present invention is to provide a method for purifying crude pyrolysis products obtained at least partially by pyrolysis of plastic waste, the method being able to improve the removal efficiency of impurities present in the crude pyrolysis products.

[0011] Another object of the present invention is to provide a method for purifying crude pyrolysis products, which has a short residence time and improved removal efficiency for impurities present in the crude pyrolysis products.

[0012] Another object of the present invention is to provide a purified pyrolysis product that meets the criteria for use as a pyrolysis feedstock (alone or diluted with fossil naphtha) in the production of basic chemicals. As used herein, "pyrolysis feedstock" means feedstock suitable for steam cracking, hydrocracking, or catalytic cracking. More specifically, the object of the present invention is to obtain a pyrolysis feedstock that meets the requirements for use as a feedstock (alone or diluted with fossil naphtha) in steam cracking.

[0013] To achieve all the above objectives, the present invention provides a method for purifying crude pyrolysis products, the method comprising the following steps: A1) Provides a crude pyrolysis product comprising hydrocarbons and impurities, the crude pyrolysis product being obtained at least partially from the pyrolysis of plastic waste. A2) The crude pyrolysis product is contacted with an alkali metal hydroxide in a continuous mode at a temperature of 330°C to 400°C, preferably 340°C to 360°C, for a residence time of less than 10 min, to obtain a treated pyrolysis product and a residue containing reaction impurities. A3) Wash the treated pyrolysis product with a polar washing solvent to obtain a purified pyrolysis product and a polar washing solvent phase. A4) Separate the polar washing solvent phase and the purified pyrolysis product obtained in step A3).

[0014] This invention provides a purified pyrolysis product with reduced nitrogen and halogen content compared to crude pyrolysis product. Specifically, it provides a purified pyrolysis product with reduced nitrogen, halogen, and sulfur content compared to crude pyrolysis product. Another advantage of this invention is that the provided purified pyrolysis product can have a reduced olefin content compared to crude pyrolysis oil.

[0015] Another advantage is that the method for purifying crude pyrolysis products according to the present invention can be carried out in a continuous high-temperature mode. This allows for shorter residence times, thereby enabling more efficient implementation of the entire purification process.

[0016] Another advantage of the purification method of this invention is that it minimizes the increase in the final boiling point of the pyrolysis products due to high-temperature treatment. An increase in the final boiling point of purified pyrolysis oil is generally an undesirable effect because it affects the quality of the purified pyrolysis oil. This is because purified pyrolysis oil obtained from plastic waste is often used as feedstock for steam pyrolysis plants. For steam pyrolysis plants, the acceptable final boiling point should be as low as possible, for example, below 400°C.

[0017] Therefore, the present invention synergistically provides the advantages of high-temperature processing in continuous mode, allowing for shorter residence time while minimizing the rise in the final boiling point of the pyrolysis products.

[0018] As used in this article, the term "olefin" refers to unsaturated open-chain (straight-chain) hydrocarbons.

[0019] As used in this article, the term "hydrocarbon" refers to an organic compound composed of carbon and hydrogen.

[0020] In step A1) of the method according to the invention, a crude pyrolysis product is provided. The crude pyrolysis product comprises hydrocarbons and impurities, and is at least partially derived from the pyrolysis of plastic waste. Preferably, the crude pyrolysis product is a crude plastic waste pyrolysis product.

[0021] In this invention, the term "pyrolysis" refers to the thermal decomposition or degradation of raw materials (e.g., waste plastics or plastic waste mixed with biomass) under inert conditions, producing gaseous, liquid, and solid coke components. During the pyrolysis of plastic waste, the plastic is converted into a variety of chemical substances, including gases such as H2, C1-C4 alkanes, C2-C4 olefins, acetylene, propyne, and 1-butyne, pyrolysis oil with boiling points ranging from 25°C to 500°C, and coke.

[0022] The term "pyrolysis" includes slow pyrolysis, fast pyrolysis, flash catalytic pyrolysis, and catalytic pyrolysis. These types of pyrolysis differ in process temperature, heating rate, residence time, and feed particle size, resulting in varying product qualities. Sharuddin et al. described typical process conditions for pyrolysis of plastic waste in "A review of pyrolysis of plastic waste," Energy Conversion and Management, Vol. 115, pp. 308-326 (May 2016).

[0023] In the text of this invention, the term “crude pyrolysis product” should be understood to mean any product obtained at least in part by the pyrolysis of plastic waste, including (i) any crude pyrolysis product that can be obtained entirely by the pyrolysis of plastic waste (referred to herein as “crude plastic waste pyrolysis product”), (ii) any crude pyrolysis product that can be obtained by the pyrolysis of a mixture of plastic waste and biomass, or (iii) any crude pyrolysis product comprising a mixture of crude plastic waste pyrolysis product and crude biomass pyrolysis product.

[0024] As used in this article, "pyrolysis products of crude plastic waste" refers to pyrolysis products obtained from the pyrolysis of raw materials composed of plastic waste.

[0025] As used in this article, "crude biomass pyrolysis products" refers to pyrolysis products obtained from the pyrolysis of raw materials composed of biomass.

[0026] As used herein, the term "pyrolysis products" generally includes pyrolysis gas, pyrolysis oil, and / or char (residue). In other words, pyrolysis products can exist as pyrolysis gas (i.e., in the gas phase), and / or as pyrolysis oil (i.e., in the liquid phase) and / or as char (i.e., in the solid phase).

[0027] The term "pyrolysis gas" is also referred to herein as "pyrolysis products in the gas phase." The terms "liquid pyrolysis oil" and "pyrolysis oil" are also referred to herein as "pyrolysis products in the liquid phase."

[0028] The crude pyrolysis oil, i.e., the crude pyrolysis product in the liquid phase, is typically liquid at 15°C and 1013 mbar. The term "liquid at 15°C" means that the crude pyrolysis oil has a dynamic viscosity in the range of 0.1 mPa•s to 100 mPa•s as determined by ASTM D7042 (e.g., using an SVM3000 viscometer).

[0029] Depending on the plastic waste undergoing pyrolysis, the crude pyrolysis products may contain varying amounts of sulfur, nitrogen, halogens, oxygen, and heavy metals (if present). The quality of crude pyrolysis products from plastic waste of different compositions varies considerably, meaning that the content and type of impurities can differ significantly.

[0030] The crude pyrolysis products typically contain saturated hydrocarbon compounds, unsaturated hydrocarbon compounds (olefins), and organic or inorganic compounds containing at least one heteroatom selected from oxygen, sulfur, nitrogen, and halogens, particularly organic or inorganic compounds containing two or more heteroatoms selected from oxygen, sulfur, nitrogen, and halogens. The crude pyrolysis products typically contain sulfur-containing compounds, nitrogen-containing compounds, oxygen-containing compounds, and halogen-containing compounds. The crude pyrolysis oil may also contain cyclic hydrocarbon molecules such as cycloalkanes and aromatics.

[0031] In one specific embodiment, the crude pyrolysis product is a pyrolysis product of nitrogen- and halogen-containing crude plastic waste, particularly a pyrolysis product of nitrogen-, halogen-, and sulfur-containing crude plastic waste, and more specifically a pyrolysis product of nitrogen-, halogen-, oxygen-, and sulfur-containing crude plastic waste.

[0032] In one embodiment, the crude pyrolysis product has a sulfur content of 10 mg / L or more, for example, 50 mg / L or more, or 100 mg / L or more, or 500 mg / L or more, relative to the total volume of the crude pyrolysis product. In another embodiment, the crude pyrolysis product has a sulfur content of 100 mg / L to 5000 mg / L, typically 500 mg / L to 4000 mg / L, relative to the total volume of the crude pyrolysis product.

[0033] In another embodiment, the crude pyrolysis product has a sulfur content of at least 10 mg / L but not more than 100 mg / L relative to the total volume of the crude pyrolysis product, for example, a sulfur content in the range of 10 mg / L to 50 mg / L, or a sulfur content in the range of 10 mg / L to 30 mg / L.

[0034] In one embodiment, the crude pyrolysis product has a nitrogen content of 50 mg / L or more, for example, 100 mg / L or more; or 500 mg / L or more; or 2000 mg / L or more, relative to the total volume of the crude pyrolysis product. In another embodiment, the crude pyrolysis product has a nitrogen content of 800 mg / L to 4000 mg / L, typically 900 mg / L to 3000 mg / L, relative to the total volume of the crude pyrolysis product.

[0035] In one embodiment, the crude pyrolysis product has a halogen content of 10 mg / L or more, for example, 20 mg / L or more; 80 mg / L or more; 120 mg / L or more; 400 mg / L or more; or 600 mg / L or more, relative to the total volume of the crude pyrolysis product. In another embodiment, the crude pyrolysis product has a halogen content of 100 mg / L to 1000 mg / L, typically 120 mg / L to 900 mg / L, relative to the total volume of the crude pyrolysis product.

[0036] When the density of the pyrolysis oil is about 1 g / ml (1000 kg / m³), 3When the concentration is expressed in mg / l, the concentration expressed in mg / l is equal to the same concentration expressed in ppm, that is, 1 mg / l equals 1 ppm.

[0037] Organofluorine, organochlorine, organobromine, and / or organoiodine compounds are typically sources of halogen content in the crude pyrolysis product. Specifically, the bromine and chlorine content of the halogen product accounts for 90% or more, for example, 95% or more, or even 100%. More specifically, the chlorine content of the halogen product accounts for 90% or more, for example, 95% or more, or even 100%. Therefore, relative to the total volume of the crude pyrolysis product, the crude pyrolysis product may have a chlorine content of 10 mg / L or more, for example, 20 mg / L or more.

[0038] In one embodiment, the crude pyrolysis product has an oxygen content of 40 mg / L or more, for example, 80 mg / L or more; or 120 mg / L or more; or 400 mg / L or more; or 600 mg / L or more, relative to the total volume of the crude pyrolysis product. In another embodiment, the crude pyrolysis product has an oxygen content of 100 mg / L to 5000 mg / L, typically 120 mg / L to 2000 mg / L, relative to the total volume of the crude pyrolysis product.

[0039] If the crude pyrolysis product also contains heavy metals, the heavy metal content is at least 1 mg / L relative to the total volume of the crude pyrolysis product. In one embodiment, the crude pyrolysis product has a heavy metal content of 5 mg / L to 15 mg / L, or 5 mg / L to 20 mg / L, relative to the total volume of the crude pyrolysis product.

[0040] As used in this article, the term "heavy metals" refers to substances with a concentration >4.51 g / cm³. 3 Metals or metalloids with a density of (at 20°C). Examples of heavy metals include arsenic, antimony, bismuth, selenium, tin, cadmium, chromium, copper, mercury, nickel, and lead.

[0041] Regarding the sulfur content, nitrogen content, halogen content, oxygen content, and heavy metal content in the crude pyrolysis product, two or more of the above-described embodiments can be combined in any manner. For example, the crude pyrolysis product may preferably have the nitrogen content, halogen content, and sulfur content described above.

[0042] In one embodiment, the crude pyrolysis product has a sulfur content of 10 mg / L or more, a nitrogen content of 50 mg / L or more (e.g., 200 mg / L or more), and a chlorine content of 10 mg / L or more. More specifically, the crude pyrolysis product 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 more, and a chlorine content of 10 mg / L or more.

[0043] In another embodiment, the crude pyrolysis product has an oxygen content of 40 mg / L or more, a sulfur content of 10 mg / L or more, a nitrogen content of 50 mg / L or more, and a chlorine content of 10 mg / L or more.

[0044] In another embodiment, the crude pyrolysis product has an oxygen content of 40 mg / L or more, a sulfur content of 10 mg / L or more, a nitrogen content of 50 mg / L or more, a chlorine content of 10 mg / L or more, and an olefin content of 30 wt.% or more based on the total weight of the crude pyrolysis product.

[0045] The method according to the invention can provide purified pyrolysis oil, wherein the nitrogen content of the purified pyrolysis oil is reduced by 10% to 95%, for example at least 50%, or at least 60%, or at least 70%, relative to the nitrogen content of the crude pyrolysis product.

[0046] The method according to the invention can provide purified pyrolysis products, wherein the purified pyrolysis products have a chlorine content reduced by 10% to 95%, for example at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, relative to the chlorine content of the crude pyrolysis products.

[0047] Typically, the pyrolysis products comprise alkanes (e.g., n-alkanes and / or isoalkanes), alkenes, cycloalkanes, and / or aromatics. Further characteristics of the crude pyrolysis oil obtained from plasticizable waste include, but are not limited to: Boiling point in the range of 30°C to 600°C, determined by ASTM D2887, and / or Dynamic viscosity in the range of 0.1 mPa•s to 100 mPa•s, determined by means of ASTM D7042, for example using a viscometer SVM3000, and / or The total alkane content, determined by GC×GC-FID / MS or GC-MS and GC-FID, is within the range of 5 wt.% to 80 wt.%, or 15 wt.% to 70 wt.%, or 20 wt.% to 65 wt.%, based on the total weight of the crude pyrolysis products, and / or The content of n-chain alkanes, in the range of 20 wt.% to 80 wt.%, based on the total weight of the crude pyrolysis products, was determined by GC×GC-FID / MS or GC-MS and GC-FID, and / or The isoparaffin content, determined by GC×GC-FID / MS or GC-MS and GC-FID, is within the range of 2 wt.% to 80 wt.%, or 5 wt.% to 60 wt.%, or 10 wt.% to 45 wt.%, based on the total weight of the crude pyrolysis products, and / or The olefin content, determined by GC×GC-FID / MS or GC-MS and GC-FID, is within the range of 0 wt.% to 70 wt.%, or 15 wt.% to 65 wt.%, or 20 wt.% to 60 wt.%, based on the total weight of the crude pyrolysis products, and / or The cycloalkanes content, determined by GC×GC-FID / MS or GC-MS and GC-FID, based on the total weight of the crude pyrolysis products, is in the range of 0 wt.% to 50 wt.%, or 5 wt.% to 45 wt.%, or 10 wt.% to 40 wt.%, and / or The aromatic content, determined by GC×GC-FID / MS or GC-MS and GC-FID, is within the range of 0 wt.% to 50 wt.%, or 5 wt.% to 30 wt.%, or 10 wt.% to 25 wt.%, based on the total weight of the crude pyrolysis products, and / or According to DIN EN ISO 12185, at 15°C and 1013 mbar, at 600 kg / m 3 Up to 1200 kg / m 3 Density within the range.

[0048] The above-mentioned further features or properties of crude pyrolysis oil obtainable from plastic waste may be combined with each other in any way, or they may be combined with other features or properties of crude pyrolysis oil obtainable from plastic waste disclosed herein in any way.

[0049] The raw materials used for the pyrolysis are typically plastic waste or plastic waste mixed with biomass.

[0050] As used herein, the term "plastic waste" refers to any plastic or rubber material that has been 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 filth, adhesives, fillers, residues, etc. The plastic waste has a nitrogen content, sulfur content, halogen content, oxygen content, silicon content, and optionally, heavy metal content. The plastic waste can originate from any source containing plastic materials. Therefore, the term "plastic waste" includes industrial and household plastic waste, including used tires and agricultural and horticultural plastic materials. The term "plastic waste" may also include used petroleum-based hydrocarbon materials, such as used motor oil, engine oil, grease, wax, etc. Preferably, the plastic waste consists primarily of plastic and / or rubber materials.

[0051] Typically, plastic waste is a mixture of different plastic materials, including hydrocarbon plastics (such as polyethylene (HDPE, LDPE), 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 polyethylene terephthalate (PET), polycarbonate (PC), etc.), silicone resins and / or sulfur-bridged crosslinked rubbers. PET plastic waste is usually sorted before pyrolysis because PET has profitable resale value. Therefore, 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 in this article, “biomass” means 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.

[0052] In “A comprehensive Characterization of Pyrolysis Oil from Softwood Barks”, Polymers, Vol. 11, 2019, p. 1387, Haoxi et al. provide an example of crude pyrolysis oil derived from biomass pyrolysis.

[0053] The method according to the invention includes three preferred embodiments. In a first embodiment, the crude pyrolysis product is substantially in the gas phase; in a second embodiment, the crude pyrolysis product is substantially in the liquid phase; and in a third embodiment, a first portion of the crude pyrolysis product is in the gas phase, and a second portion of the crude pyrolysis product is in the liquid phase.

[0054] In the first embodiment of the present invention, the crude pyrolysis product is basically in the gas phase, and step A2) includes: contacting the crude pyrolysis product with molten alkali metal hydroxide in a reactor in a continuous mode at a temperature of 330°C to 400°C for a residence time of 0.5 min to less than 10 min to obtain the treated pyrolysis product.

[0055] As used herein, the term "substantially in the gas phase" means that, based on the total weight of the crude pyrolysis products, at least 95 wt.%, preferably at least 98 wt.%, preferably at least 99 wt.%, more preferably at least 99.9 wt.%, and most preferably 100 wt.% of the crude pyrolysis products are in the gas phase.

[0056] As used herein, the term "continuous mode" refers to a continuous contact between fresh reactants, i.e., freshly fed alkali metal hydroxides and freshly fed crude pyrolysis products. This is the opposite of batch operation, which operates in a discontinuous mode.

[0057] Preferably, the dwell time in step A2) of the first embodiment is 0.5 min to less than 5 min, more preferably 0.5 min to less than 1 min.

[0058] Preferably, the temperature in step A2) of the first embodiment is 340°C to 360°C.

[0059] Preferably, in step A2) of the first embodiment, the weight ratio of the crude pyrolysis product to the solid alkali metal hydroxide is 10:1 to 1000:1, more preferably 50:1 to 50:1.

[0060] Step A2) of the first embodiment preferably further includes cooling the treated pyrolysis product. Preferably, the treated pyrolysis product is cooled in a heat exchanger, and / or the treated pyrolysis product is cooled to a temperature of 25°C to 100°C, more preferably to a temperature of 35°C to 70°C.

[0061] In a second embodiment of the present invention, the crude pyrolysis product is substantially in the liquid phase, and step A2) includes: contacting the crude pyrolysis product with a solid alkali metal hydroxide in a mixing unit, preferably in a continuous mode, heating it to a temperature of 330°C to 400°C using a heating device, and preferably in a continuous mode, the pressure in the heating device is 0.5 bar to 50 bar, and the residence time is 0.5 min to less than 10 min.

[0062] The term "substantially in the liquid phase" means that, based on the total weight of the crude pyrolysis products, at least 95 wt.%, preferably at least 98 wt.%, more preferably at least 99 wt.%, and most preferably at least 99.9 wt.% of the crude pyrolysis products are in the liquid phase.

[0063] Preferably, the dwell time in step A2) of the second embodiment is 0.5 min to less than 5 min, more preferably 0.5 min to less than 1 min.

[0064] Preferably, the temperature in step A2) of the second embodiment is 340°C to 360°C.

[0065] Preferably, in step A2) of the second embodiment, the weight ratio of the crude pyrolysis product to the solid alkali metal hydroxide is 10:1 to 1000:1, more preferably 50:1 to 500:1.

[0066] Step A2) of the second embodiment preferably further includes cooling the treated pyrolysis product. Preferably, the treated pyrolysis product is cooled in a heat exchanger, and / or the treated pyrolysis product is cooled to a temperature of 25°C to 100°C, more preferably to a temperature of 35°C to 70°C.

[0067] In a third embodiment of the invention, the first portion of the crude pyrolysis product is in the gas phase, and the second portion of the crude pyrolysis product is in the liquid phase. Step A2) includes: contacting the first portion of the crude pyrolysis product with molten alkali metal hydroxide in a reactor in a continuous mode at a temperature of 330°C to 400°C, preferably 340°C to 360°C, for a residence time of 0.5 min to less than 10 min, to obtain a first treated pyrolysis product. Furthermore, step A2) further includes: contacting a second portion of the crude pyrolysis product with a solid alkali metal hydroxide in a continuous mode in a mixing unit, and heating it to a temperature of 330°C to 400°C, preferably 340°C to 360°C, with a residence time of 0.5 min to less than 10 min, to obtain a second treated pyrolysis product. The method further includes step A2a): combining the first treated pyrolysis product with the second treated pyrolysis product to obtain a combined treated pyrolysis product, optionally cooling the combined treated pyrolysis product obtained in step A2a) to obtain a cooled combined treated pyrolysis product. Step A3) includes washing the cooled, combined, treated pyrolysis products obtained in step A2a) with a polar washing solvent, or washing the optionally cooled, combined, treated pyrolysis products obtained in step A2a).

[0068] Preferably, the weight ratio of the first portion of the crude pyrolysis product to the molten alkali metal hydroxide is 10:1 to 1000:1, more preferably 50:1 to 500:1.

[0069] Preferably, the weight ratio of the second portion of the crude pyrolysis product to the solid alkali metal hydroxide is 10:1 to 1000:1, more preferably 50:1 to 500:1.

[0070] Preferably, step A2) of the third embodiment of the present invention further includes cooling the first treated pyrolysis product and / or cooling the second treated pyrolysis product.

[0071] Preferably, the first treated pyrolysis product is cooled in a heat exchanger, and / or the first treated pyrolysis product is cooled to a temperature of 25°C to 100°C; and / or the second treated pyrolysis product is cooled in a heat exchanger, and / or the second treated pyrolysis product is cooled to a temperature of 25°C to 100°C.

[0072] Preferred features of the first, second, and third embodiments of the present invention are described below. Unless otherwise stated, the following preferred features are preferred features of the first, second, and third embodiments of the present invention (if applicable).

[0073] In the first and third embodiments of the method according to the present invention, the reactor in step A2) is preferably a bubble column reactor.

[0074] A bubble column reactor is a vertical cylinder into which gas is fed from the bottom through a gas distributor or, for example, a perforated plate distributor to minimize the size of the gas bubbles. The bubble column operates as a multiphase reactor, in which the gas phase is dispersed in a liquid phase. A liquid phase comprising or consisting of molten alkali metal hydroxides can be supplied, for example, countercurrently to the upward-flowing gas stream. The gas comprises or consists of crude pyrolysis products substantially in the gas phase and is fed (preferably continuously) into the bubble column reactor.

[0075] Preferably, the reactor in step A2) further includes a heating device for controlling the heat in the reactor, and the reactor is preferably a bubble column reactor. Preferably, the heating device includes microwave and / or electric heating.

[0076] In the second and third embodiments of the method according to the present invention, the mixing unit in step A2) can be any mixing unit suitable for mixing the pyrolysis product with a solid alkali metal hydroxide, preferably continuously. Preferably, the mixing unit in step A2) is a homogenizing pump.

[0077] In the second and third embodiments of the method according to the present invention, the heating device in step A2) is preferably a heat exchanger, preferably a tubular heat exchanger, preferably an electrothermal or combustion heat exchanger, or an electrothermal or combustion tubular heat exchanger. Preferably, the pressure inside the heating device in step A2) is 0.5 bar to 50 bar. If the heating device is a combustion heat exchanger, the pressure inside the combustion heat exchanger is 1 bar to less than 10 bar.

[0078] Preferably, the alkali metal hydroxide in step A2) comprises sodium hydroxide, potassium hydroxide, or a mixture thereof, or is composed of sodium hydroxide, potassium hydroxide, or a mixture thereof; more preferably, it comprises sodium hydroxide, or is composed of sodium hydroxide.

[0079] In a first embodiment of the invention, the provided crude pyrolysis product is substantially in the gas phase. This is, for example, if the crude pyrolysis product is provided directly by the pyrolysis reactor. However, if the provided crude pyrolysis product is not substantially in the gas phase, preheating is required to convert the remaining liquid phase portion of the crude pyrolysis product into the gas phase as well. Preferably, in the first embodiment of the invention, before step A2), the crude pyrolysis product provided in step A1) is preheated to a temperature in the range of 330°C to 400°C, preferably in the range of 340°C to 360°C.

[0080] In a third embodiment of the invention, the first portion of the provided crude pyrolysis product is substantially in the gas phase, and the second portion of the provided crude pyrolysis oil is in the liquid phase. If it is desired that a larger portion of the provided crude pyrolysis product is in the gas phase, a preheating step is required. Preferably, in the third embodiment of the invention, before step A2), the first portion of the crude pyrolysis product provided in step A1) is preheated to a temperature in the range of 330°C to 400°C, preferably in the range of 340°C to 360°C.

[0081] Preheating is preferably carried out through a heat exchanger, which is preferably an electric heat exchanger or a combustion heat exchanger.

[0082] In step A3), the treated pyrolysis product is washed with a polar washing solvent to obtain a purified pyrolysis product and a polar washing solvent phase. This washing step removes the remaining alkali metal hydroxide and the organic products formed during the reaction of the crude pyrolysis product with the alkali metal hydroxide in step A2).

[0083] Preferably, step A3) is performed in a mixing device. The mixing device is preferably a mixer or a static mixer.

[0084] Preferably, the polar washing solvent in step A3) comprises water, alkanols or mixtures thereof, or is composed of water, alkanols or mixtures thereof; more preferably, it comprises water or is composed of water.

[0085] Preferably, in step A3), the polar washing solvent further comprises an acid. The presence of an acid in the system is preferred if step A3) is to be performed in a neutralizing washing manner (i.e., to neutralize any remaining alkali metal hydroxides). Preferably, the acid comprises sulfuric acid, hydrochloric acid, or phosphoric acid, or is composed of sulfuric acid, hydrochloric acid, or phosphoric acid; more preferably, it comprises sulfuric acid, or is composed of sulfuric acid.

[0086] In step A4), the polar washing solvent phase is separated from the purified pyrolysis product. Preferably, step A4) is performed in a separation apparatus. The separation apparatus is preferably a settling tank or a mixing-sedimentation system, more preferably a mixing-sedimentation system.

[0087] The present invention also provides a method for producing pyrolysis feedstock, comprising the steps of: mixing 1 wt.% to 100 wt.% of purified pyrolysis oil based on the total weight of the pyrolysis feedstock and 0 wt.% to 99 wt.% of fossil naphtha based on the total weight of the pyrolysis feedstock, wherein the purified pyrolysis oil is obtained by the method according to the present invention.

[0088] All preferred embodiments of the purification method for crude pyrolysis oil according to the present invention are also preferred embodiments of the method for preparing pyrolysis feedstock (if applicable).

[0089] Preferably, the pyrolysis feedstock is a steam pyrolysis feedstock.

[0090] In one embodiment, based on the total weight of the pyrolysis feedstock, the pyrolysis feedstock (or steam pyrolysis feedstock) comprises at least 5 wt.% purified pyrolysis oil and no more than 95 wt.% fossil naphtha. Preferably, based on the total weight of the pyrolysis feedstock, the pyrolysis feedstock (or steam pyrolysis feedstock) comprises at least 10 wt.% purified pyrolysis oil and no more than 90 wt.% fossil naphtha. More preferably, based on the total weight of the pyrolysis feedstock, the pyrolysis feedstock (or steam pyrolysis feedstock) comprises at least 30 wt.% purified pyrolysis oil and no more than 70 wt.% fossil naphtha. In particular, based on the total weight of the pyrolysis feedstock, the pyrolysis feedstock (or steam pyrolysis feedstock) comprises at least 40 wt.% purified pyrolysis oil and no more than 60 wt.% fossil naphtha.

[0091] The present invention also provides the use of purified pyrolysis products as pyrolysis feedstock.

[0092] Preferably, the pyrolysis feedstock is a steam pyrolysis feedstock.

[0093] Typically, the impurities comprise inorganic compounds, which preferably comprise 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. Attached Figure Description

[0094] The present invention is further described and illustrated by the following non-limiting embodiments and accompanying drawings. The drawings show: Figure 1 This is a schematic diagram of the method according to the first embodiment of the present invention. Figure 2 This is a schematic diagram of the method according to the second embodiment of the present invention, and Figure 3 This is a schematic diagram of a method according to a third embodiment of the present invention.

[0095] Figures 1 to 3 The following figure labels were used: 1-Reactor 2-Heat Exchanger 4-Mixing device 5-Separation device 6-Preheater 7- Heated alkali metal hydroxide bath 8-Acid feed inlet 9-Polar washing solvent inlet 10-Washing Circulation Line 11-Purified pyrolysis product outlet 12-Discharge outlet 13 Crude pyrolysis product feed inlet 15-Pressure control valve 16-Vacuum-Liquid Separator 17-Solid Alkali Metal Hydroxide Feed Inlet 18-Hybrid Unit 19-Heating device. Detailed Implementation

[0096] As described in detail below, in Figure 1 The diagram schematically illustrates an exemplary method of a first embodiment of the present invention. Essentially, in the first embodiment of the present invention, a crude pyrolysis product in the gas phase is provided and contacted with molten alkali metal hydroxide at a high temperature, followed by washing with a polar washing solvent to obtain a purified pyrolysis product.

[0097] A crude pyrolysis product is provided and fed into a preheater (6) through a crude pyrolysis product feed inlet (13). Typically, the preheater (6) heats the crude pyrolysis product to a temperature of 330°C to 400°C so that the crude pyrolysis product is substantially in the gas phase before entering the reactor (1). If the provided crude pyrolysis product is already in the gas phase, an optional preheater (6) is not required, and the provided crude pyrolysis product already in the gas phase can be directly fed into the reactor (1). In this exemplary embodiment, the reactor (1) is a bubble column reactor. The gaseous pyrolysis product is continuously introduced into the bottom of the bubble column reactor and reacts with molten sodium hydroxide fed from a heated alkali metal hydroxide tank. During the reaction, halogens are removed from the pyrolysis product. The residence time of the pyrolysis product in the reactor (1) is less than 10 min, and the treated pyrolysis product leaves the reactor (1) and is transferred to a heat exchanger (2), where it is cooled to a temperature of 25°C to 100°C.

[0098] Subsequently, the liquid treated pyrolysis product is mixed with pure water as a polar washing solvent, which is introduced through the polar solvent washing inlet (9) and the washing circulation line (10). Additionally, sulfuric acid is added to the liquid treated pyrolysis product through the acid inlet (8) to neutralize any residual sodium hydroxide in the liquid treated pyrolysis product. The mixture of liquid treated pyrolysis product, sulfuric acid, and pure water is thoroughly mixed in a mixing device (4) to wash and neutralize the treated pyrolysis product. In this exemplary embodiment, the mixing device (4) is a static mixer. The resulting mixture of purified pyrolysis product and polar washing solvent phase is fed into a settling tank, which serves as a separation device (5). In the settling tank, the polar washing solvent phase, containing water and any residual acid, is separated from the purified pyrolysis product. The latter is discharged from the separation device (5) through the purified pyrolysis product outlet (11), and the polar washing solvent phase is discharged through the washing circulation line (10). The polar washing solvent phase can optionally be discharged through the drain outlet (12) or mixed with fresh pure water from the feed inlet (9) and recycled upstream of the mixing unit (4).

[0099] exist Figure 2The diagram schematically illustrates an exemplary method of a second embodiment of the present invention. Essentially, in the second embodiment of the invention, a crude pyrolysis product in liquid phase is provided and contacted with a solid alkali metal hydroxide at a high temperature, followed by washing with a polar washing solvent to obtain a purified pyrolysis product. The crude pyrolysis product is provided in liquid form through a crude pyrolysis product feed inlet (13). The liquid crude pyrolysis product is mixed with solid sodium hydroxide from a solid alkali metal hydroxide feed inlet (17). In this example, the mixing unit (18) is a homogenizing pump, which mixes the liquid crude pyrolysis product with the solid sodium hydroxide. The resulting mixture is fed into a heating device (19), which is a combustion heat exchanger, and heated to a temperature of 330°C to 400°C. The residence time of the mixture of liquid crude pyrolysis product and solid sodium hydroxide in the heating device (19) is in the range of 0.5 to less than 10 seconds. The obtained treated pyrolysis product is removed from the heating device (19) and transferred to a heat exchanger (2), where the treated pyrolysis product is cooled to a temperature of 25°C to 100°C. Optionally, a pressure control valve (15) can be used to regulate the pressure, keeping the treated pyrolysis products in the liquid phase. In this example, the pressure control valve (15) is located downstream of the heat exchanger (2). Subsequent washing, neutralization, and separation steps are as described above. Figure 1 The corresponding steps of the first embodiment of the present invention shown are the same. Therefore, referring to the above description of the first embodiment of the present invention and... Figure 1 Related instructions. Obtain purified pyrolysis products and remove them through the purified pyrolysis product outlet (11).

[0100] exist Figure 3 The diagram schematically illustrates an exemplary method according to a third embodiment of the present invention. Essentially, the third embodiment of the present invention can be considered a combination of the first and second embodiments. The third embodiment enables the parallel purification of crude pyrolysis products, wherein a first portion of the crude pyrolysis products is in the gas phase and a second portion is in the liquid phase.

[0101] exist Figure 3 In the example shown, a liquid crude pyrolysis product with a final boiling point (FBP) of approximately 500°C is provided and fed to a preheater (6) through a crude pyrolysis product feed inlet (13). The preheater (6) heats the liquid crude pyrolysis product to 350°C. Components in the liquid crude pyrolysis product with a final boiling point not exceeding 350°C will thus become gaseous, forming the first part of the crude pyrolysis product, while components with a final boiling point above 350°C will remain in the liquid phase, forming the second part of the crude pyrolysis product. The first part of the crude pyrolysis product in the gaseous phase and the second part of the crude pyrolysis product in the liquid phase are separated in a vapor-liquid separator (16).

[0102] Subsequently, the first portion of the crude pyrolysis product is treated with molten sodium hydroxide in reactor (1) as described in the first embodiment above to obtain a first treated pyrolysis product, and then the second portion of the crude pyrolysis product is treated with solid sodium hydroxide in heating device (19) as described in the second embodiment above to obtain a second treated pyrolysis product. The second treated pyrolysis product is then cooled in cooler (20), and the pressure is regulated using pressure control valve (15) to keep the treated pyrolysis product in the liquid phase. In this example, the first treated pyrolysis product and the second treated pyrolysis product are combined to obtain a combined treated pyrolysis product. This combined treated pyrolysis product is further processed according to the process of the second embodiment of the invention described above. A purified pyrolysis product is obtained and removed through the purified pyrolysis product outlet (11).

[0103] Example Materials The following examples used commercially available batches of crude pyrolysis oil (regenerated carbon fuel) from Renasci Oostende Recycling NV. The crude pyrolysis oil is characterized by a boiling point ranging from 50°C to 482.5°C. The properties of the different batches of crude pyrolysis oil used in the examples are given in Table 1 below.

[0104] Analytical methods Chlorine content in pyrolysis oil Instruments: TE Instruments' XPrep C-IC model (equipped with a 2019.010 combustion assembly and a 2019.080 component collector, featuring an Archie injection and liquid boat), and Metrohm's 19250020 ECO IC instrument. Test method: ASTM D7359-18 (Standard test method for determination of total fluorine, chlorine and sulfur in aromatic hydrocarbons and mixtures thereof by oxidative pyrolysis combustion-ion chromatography (CIC)) Each pyrolysis oil sample was measured three times.

[0105] Nitrogen content in pyrolysis oil Instrument: XPlorer NS from TE Instruments, equipped with an Azimuth injector and liquid boat. Test method: ASTM D5762-18a (Standard Test Method for the Determination of Nitrogen in Liquid Hydrocarbons, Petroleum and Petroleum Products by Chemiluminescence via Boat Inlet) ASTM D4629-17 (Standard Test Method for Determination of Trace Nitrogen in Liquid Hydrocarbons by Oxidation Combustion-Chemiluminescence Detection via Syringe / Inlet) ASTM D4629 is used to analyze pyrolysis oil with nitrogen concentrations below 1000 ppm, while ASTM D5762 is used to analyze pyrolysis oil with nitrogen concentrations above 1000 ppm.

[0106] Each sample was measured three times.

[0107] Sulfur content in pyrolysis oil Instrument: XPlorer NS from TE Instruments, equipped with an Azimuth injector and liquid boat. Test method: ASTM D5453-19a (Standard test method for the determination of total sulfur in light hydrocarbons, spark-ignition engine fuels, diesel engine fuels and engine oils by ultraviolet fluorescence method) Each sample was measured three times.

[0108] Final boiling point (FBP) The final boiling point was determined according to ASTM D2887.

[0109] Example The second embodiment of the present invention and Figure 2 The setup is shown. Liquid pyrolysis oil (40 ml, 31.6 g) was mixed with 0.29 g solid sodium hydroxide and then heated to 350°C using an autoclave reactor at a pressure of 8 to 9 bar. Therefore, the weight ratio between pyrolysis oil and solid sodium hydroxide was 109:1. Residence times varied between less than 0.5 min and 30 min, as shown in Table 1 below. The resulting mixture was cooled to room temperature and washed with 10 ml of water. The aqueous phase was separated from the treated pyrolysis oil by centrifugation. Chlorine, nitrogen, and sulfur impurities were measured as described above. As a comparative example, residence times were kept constant and different temperatures were used, as shown in Table 3. The "Reference Samples" in Tables 1 and 3 show the properties of the crude pyrolysis oil before purification.

[0110] Table 1: Solid NaOH treatment at 350℃

[0111] As can be seen from Table 1, most of the impurities were removed after a residence time of less than 0.5 min.

[0112] Table 2 below shows the correlation between residence time and final boiling point (FBP).

[0113] Table 2: Correlation between residence time and final boiling point (FBP)

[0114] Heating the reactor to 350°C and cooling it immediately.

[0115] **FBP is the average of the two experiments.

[0116] As shown in Table 2, the final boiling point of the pyrolysis products increases with increasing residence time. Since a higher final boiling point is generally undesirable, the residence time should be kept as short as possible. Referring to Table 1, after a residence time of less than 0.5 min, most impurities are removed without a significant increase in the final boiling point.

[0117] Table 3: Solid NaOH treatment at 1-hour residence time and different temperatures

[0118] As shown in Table 3, the removal efficiency increases with increasing temperature, especially for chlorine and sulfur concentrations. The inventors discovered that the combination of a reaction temperature of 330°C to 400°C and a residence time of less than 10 min produces the optimal removal efficiency when operating in continuous mode, while keeping the increase in the final boiling point of the pyrolysis products as low as possible.

Claims

1. A method for purifying crude pyrolysis products, the method comprising the following steps: A1) Provides a crude pyrolysis product comprising hydrocarbons and impurities, the crude pyrolysis product being obtained at least partially through the pyrolysis of plastic waste. A2) The crude pyrolysis product is contacted with an alkali metal hydroxide in a continuous mode at a temperature of 330°C to 400°C, preferably 340°C to 360°C, for a residence time of less than 10 min, to obtain a treated pyrolysis product and a residue containing reaction impurities. A3) Wash the treated pyrolysis product with a polar washing solvent to obtain a purified pyrolysis product and a polar washing solvent phase. A4) Separate the polar washing solvent phase and the purified pyrolysis product obtained in step A3).

2. The method according to claim 1, wherein the crude pyrolysis product is substantially in the gas phase. wherein step A2) comprises: In reactor (1), the crude pyrolysis product is continuously contacted with molten alkali metal hydroxide at a temperature of 330°C to 400°C, preferably 340°C to 360°C, for a residence time of 0.5 min to less than 10 min. Step A2) may also optionally include: cooling the treated pyrolysis product, preferably in a heat exchanger (2) and / or preferably to a temperature of 25°C to 100°C.

3. The method according to claim 1, wherein the crude pyrolysis product is substantially in the liquid phase. wherein step A2) comprises: In a mixing unit (18), the crude pyrolysis product is contacted with a solid alkali metal hydroxide in a continuous mode, and heated to a temperature of 330°C to 400°C, preferably 340°C to 360°C, using a heating device (19). The pressure within the heating device (19) is preferably 0.5 bar to 50 bar, and the residence time is 0.5 min to less than 10 min. Step A2) may also optionally include: cooling the treated pyrolysis product, preferably in a heat exchanger (2) and / or preferably to a temperature of 25°C to 100°C.

4. The method according to claim 1, wherein the first portion of the crude pyrolysis product is in the gas phase, and the second portion of the crude pyrolysis product is in the liquid phase. wherein step A2) comprises: In reactor (1), a first portion of the crude pyrolysis product is continuously contacted with molten alkali metal hydroxide at a temperature of 330°C to 400°C, preferably 340°C to 360°C, for a residence time of 0.5 min to less than 10 min to obtain a first treated pyrolysis product. Step A2) further includes: contacting a second portion of the crude pyrolysis product with a solid alkali metal hydroxide in a continuous mode in a mixing unit (18), and heating it to a temperature of 330°C to 400°C, preferably 340°C to 360°C, using a heating device (19), for a residence time of 0.5 min to less than 10 min, to obtain a second treated pyrolysis product. And step A2) may optionally include: cooling the first treated pyrolysis product, preferably in a heat exchanger (2) and / or preferably to a temperature of 25°C to 100°C, and / or Optionally, it may also include: cooling the second treated pyrolysis product, preferably in a heat exchanger (2) and / or preferably to a temperature of 25°C to 100°C. The process further includes step A2a): combining optionally cooled first-treated pyrolysis products and optionally cooled second-treated pyrolysis products to obtain combined treated pyrolysis products; optionally, cooling the combined treated pyrolysis products obtained in step A2a) to obtain cooled combined treated pyrolysis products. Step A3) includes washing the optionally cooled, combined, treated pyrolysis oil obtained in step A2a) with a polar washing solvent.

5. The method according to claim 2 or 4, wherein in step A2), the reactor (1) is a bubble column reactor.

6. The method according to any one of claims 2, 4 or 5, wherein in step A2), the reactor (1) further includes a heating device for controlling heating in the reactor (1), preferably the heating device includes microwave and / or electric heating.

7. The method according to claim 3 or 4, wherein in step A2), the mixing unit (18) is a homogenizing pump.

8. The method according to any one of claims 3, 4 or 7, wherein the heating device (19) in step A2) is a heat exchanger, preferably a tubular heat exchanger, preferably an electric or combustion heat exchanger, or an electric or combustion tubular heat exchanger.

9. The method according to any one of the preceding claims, wherein the alkali metal hydroxide in step A2) comprises sodium hydroxide, potassium hydroxide or a mixture thereof, or is composed of sodium hydroxide, potassium hydroxide or a mixture thereof; preferably it comprises sodium hydroxide or is composed of sodium hydroxide.

10. The method according to any one of the preceding claims, wherein the polar washing solvent in step A3) comprises water, alkanols or mixtures thereof, or is composed of water, alkanols or mixtures thereof; more preferably comprises water or is composed of water.

11. The method according to any one of the preceding claims, wherein the polar washing solvent in step A3) further comprises an acid, preferably sulfuric acid, hydrochloric acid or phosphoric acid, or is composed of sulfuric acid, hydrochloric acid or phosphoric acid; more preferably the acid comprises sulfuric acid, or is composed of sulfuric acid.

12. The method according to any one of claims 1, 2, 4 to 11, wherein prior to step A2), the crude pyrolysis product provided in step A1) is preheated to a temperature in the range of 330°C to 400°C.

13. The method according to any one of the preceding claims, wherein step A3) is carried out in a mixing device (4), preferably a mixer or a static mixer.

14. The method according to any one of the preceding claims, wherein step A4) is carried out in a separation device (5), which is preferably a settling tank or a mixed settling system, more preferably a mixed settling system.

15. The method according to claim 2, wherein the weight ratio between the crude pyrolysis product and the solid alkali metal hydroxide in step A2) is 50:1 to 1000:

1.

16. The method according to claim 3, wherein the weight ratio between the crude pyrolysis product and the solid alkali metal hydroxide is 50:1 to 1000:

1.

17. The method according to claim 4, wherein the weight ratio between the second portion of the crude pyrolysis product and the solid alkali metal hydroxide is 50:1 to 1000:

1.

18. A method for preparing a pyrolysis feedstock, the method comprising the steps of: The purified pyrolysis oil is mixed with 1 wt.% to 100 wt.% of the total weight of the pyrolysis feedstock and 0 wt.% to 99 wt.% of the total weight of the pyrolysis feedstock, wherein the purified pyrolysis oil is obtained by the method according to any one of claims 1 to 14.

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