Process for upgrading oil derived from pyrolysis of plastic waste

Abstract

A process for purifying a crude pyrolysis oil, the process comprising: (i) treating the crude pyrolysis oil with a liquid non-hydrocarbon polar compound; (ii) separating the resulting product into a purified pyrolysis oil fraction having a reduced content of contaminants relative to the crude pyrolysis oil and a fraction comprising the non-hydrocarbon liquid polar compound, the fraction comprising the non-hydrocarbon liquid polar compound containing at least a portion of the contaminants present in the crude pyrolysis oil.

Description

Technical Field

[0001] This disclosure relates to a process for producing and purifying pyrolysis oil derived from the pyrolysis of plastic waste to obtain modified pyrolysis oil having a reduced content of contaminants (such as nitrogen, oxygen, and halogens) based on its initial content in unmodified pyrolysis oil. This disclosure also relates to the use of said pyrolysis oil, particularly as a feedstock for (steam) pyrolysis plants. Background Technology

[0002] Plastics encompass a wide range of synthetic and semi-synthetic materials that use polymers as their primary component. Their plasticity allows plastics to be molded, extruded, or compressed into solid objects of various shapes. This adaptability, combined with a wide range of other properties such as light weight, durability, and low production costs, has led to their widespread use. Plastic production has increased dramatically over the past few decades. Simultaneously, this increase in plastic quantities has caused environmental problems because most plastics are resistant to natural degradation processes. Therefore, the material can persist for centuries or longer, filling landfills and even appearing in the food chain as microplastics.

[0003] Therefore, increasing efforts have been made to improve the recycling of polymer waste materials. Current recycling processes mainly rely on mechanical and chemical recycling. In mechanical recycling, plastics are mechanically transformed without altering their chemical structure, making them usable for the production of new products.

[0004] In chemical recycling, plastics are broken down into smaller fragments, and their structure and chemical properties are altered so that they can be used as raw materials for different industries or as feedstocks for manufacturing new polymer products. Chemical recycling typically involves the following steps: collecting plastic waste, then heating the plastic waste to break down the polymers, thereby obtaining smaller organic molecules, which can then be recycled in the petrochemical industry.

[0005] Typically, the main effluent from the pyrolysis step is a liquid stream, also known as pyrolysis oil, which can be refined and used as fuel or subjected to further steam cracking steps to produce fractions consisting of C2-C4 olefins.

[0006] In theory, polyolefins composed solely of carbon and hydrogen (such as polypropylene and polyethylene) can produce pyrolysis oils with low heterogeneous element content. However, plastic waste is typically a mixture of different types of polymers, including not only polyolefins but also PET, polyamides (nylon), PU polymers, PVC, etc. Furthermore, the polymers present in plastic waste often include heteroatom-containing additives, such as stabilizers and plasticizers, which have been introduced to improve polymer properties. These additives also frequently include nitrogen-, halogenated, and sulfur-containing compounds and heavy metals.

[0007] In summary, unpurified (crude) pyrolysis oil from the chemical recycling of plastic waste contains relatively high amounts of undesirable contaminants such as oxygen, nitrogen, halogens, and metals.

[0008] These substances are considered highly detrimental to the steam cracking process because they can cause process problems, such as generating NOx substances and damaging process equipment.

[0009] Furthermore, elements other than carbon and hydrogen can be detrimental to the processing of crude pyrolysis oil, as they may deactivate or poison catalysts used in further processing. For example, during steam cracking, halogenated compounds release hydrogen halides, which can damage the cracker through corrosion. Nitrogen-containing impurities can also poison downstream catalysts. Additionally, they can form explosive NOx when heated, potentially causing safety issues. Oxygen-containing substances may produce acidic / corrosive compounds, such as methanol, or form emulsions during quenching.

[0010] For the reasons mentioned above, a purification stage is usually required to reduce or completely remove contaminants, thereby improving the crude cracked oil so that it can be used smoothly in the refining process.

[0011] EP2650345 A1 relates to the removal of sulfur-containing substances from liquid hydrocarbons (such as crude oil and mineral oil) using eutectic solvents. Attempts to remove oxygen- and / or nitrogen-containing substances are not described. The efficiency of sulfur compound removal is unsatisfactory (40%) when the EC / Pyoil mass ratio is 1:1. Jelena D. Jovanovic et al. also described similar low efficiency when using DES / PO at 1:1 or lower in their paper "Extractive desulfurization of cracked tire oils using hydrodynamic cavitation with eutectic solvents" (Environmental Science & Pollution Research (2021) 28:59268-59276).

[0012] Removing oxygen, nitrogen, and other pollutants using solid adsorbents is the most commonly used technique in this field for this specific area.

[0013] US 2013 / 0043160 describes a process for removing sulfur, nitrogen, and metals from oil feedstocks (such as heavy oil, bitumen, and shale oil) by treating the feedstock with alkali metals and free radical capture substances.

[0014] WO 2017 / 100617 describes the removal of oxygen, sulfur, and nitrogen heteroatoms from fluids such as hydrocarbons using various adsorbents. US 6,248,230 describes a method for producing cleaner fuels by adsorbing naturally occurring polar compounds, namely sulfur- and nitrogen-containing compounds, as an efficient pretreatment upstream of a hydrodesulfurization unit.

[0015] Similar adsorption methods are described in WO2021 / 224287 and WO2021 / 216867.

[0016] However, adsorption methods have the following drawbacks: when the adsorbent is saturated, its removal and decontamination are arduous and do not allow for continuous processes. Furthermore, changing the type of adsorbent in the tower to meet specific requirements based on different types of pollutants in the raw material necessitates interrupting the process in that tower; therefore, a dual-tower system is required if a continuously running process is desired.

[0017] Therefore, there is a strong desire for an efficient liquid-liquid extraction process to modify plastic waste pyrolysis oil by reducing the nitrogen, oxygen, and halogen content, and preferably also reducing the heavy metal content. In particular, a process for efficiently removing such contaminants using a low EC / Pyoil mass ratio is desired. Furthermore, it is desirable to provide a high-quality plastic waste pyrolysis oil that can be economically converted into a high-value final product. Summary of the Invention

[0018] In one aspect, this disclosure provides a process for producing and purifying crude pyrolysis oil, the process comprising:

[0019] a) Provide molten plastic waste feedstock comprising at least a polyolefin fraction in an amount exceeding 70% by weight of the total weight of the plastic waste feedstock;

[0020] b) subject the molten product obtained in (a) to a temperature of 280°C to 600°C to obtain the depolymerization product;

[0021] (c) The depolymerization product is subjected to a condensation stage at a temperature ranging from 10°C to 250°C, preferably from 15°C to 200°C, and more preferably from 15°C to 150°C, to obtain the crude pyrolysis oil as a liquid fraction and a gas fraction, the crude pyrolysis oil containing oxygen-containing compounds and nitrogen-containing compounds as contaminants.

[0022] (d) The crude pyrolysis oil is contacted with a non-hydrocarbon liquid polar compound selected from eutectic compounds having the formula [A][B]x, wherein x ranges from 0.3 to 20, [A] is selected from metal salts, non-metal salts, and nonionic hydrogen bond acceptors (HBAs), and [B] is selected from metal salts, hydrated metal salts, and nonionic hydrogen bond donor compounds (NIHBDs), wherein the eutectic compound is immiscible with the crude pyrolysis oil; and

[0023] (e) Recover from the above steps (1) the purified pyrolysis oil fraction having a reduced content of nitrogen-containing and oxygen-containing compounds relative to the crude pyrolysis oil, and (2) the fraction containing the liquid non-hydrocarbon liquid polar compound, the fraction containing at least a portion of the contaminant present in the crude pyrolysis oil. Detailed Implementation

[0024] The plastic waste raw material preferably comprises a polyolefin fraction of more than 85% by weight, and especially more than 90% by weight, based on the total weight of the plastic waste raw material.

[0025] Preferably, in the polyolefin fraction, polyethylene (PE) and polypropylene (PP) are mixed in a weight ratio of 85:15 to 15:85, more preferably 80:20 to 20:80. The polyethylene may be one or more of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). The polypropylene (PP) may be a propylene homopolymer or a propylene copolymer having a lower amount of ethylene and / or butene. Furthermore, the raw material may contain other polyolefins such as polybutene. In a specific embodiment, the raw material may comprise a polymer blend incorporating other materials such as polystyrene (PS), ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), polyvinyl chloride (PVC), polyamide, or mixtures thereof. Furthermore, the plastic raw material does not contain tires or tire-like materials, which would generate significant amounts of sulfur-based contaminants. In a preferred embodiment, the raw material consists of a mixture of more than 80% by weight of polyethylene and polypropylene, wherein polypropylene accounts for more than 50% by weight of the polypropylene / polyethylene mixture.

[0026] Plastic waste may also contain limited amounts of non-pyrolytic inorganic components, such as water, glass, stone, and metal. "Limited amount" preferably means less than 15% by weight of the total weight of the dry plastic waste raw material, and more preferably less than 10% by weight.

[0027] Depolymerization

[0028] According to this disclosure, the process for depolymerizing plastic waste includes, optionally, pyrolyzing the plastic waste in the presence of a catalyst at a temperature preferably in the range of 300°C to 550°C, more preferably in the range of 350°C to 500°C.

[0029] The gaseous effluent from the pyrolysis reactor is then collected and separated into gaseous and liquid depolymerization products.

[0030] When performing depolymerization processes, care should be taken to avoid introducing oxygen-containing atmospheres into the depolymerization system. Barriers to potentially oxygen-containing atmospheres can be achieved through a range of measures, such as nitrogen gagging and a vacuum system connected to the extruder barrel.

[0031] More specifically, the plastic raw material mixture can be fed into the feeding system of the depolymerization reactor through a hopper or two or more hoppers connected in parallel, where the oxygen present in the plastic waste atmosphere is essentially eliminated inside the hopper.

[0032] In small-scale trials, the plastic raw material can be fed directly into the depolymerization reactor. For larger-scale trials, it is preferable to feed the depolymerization reactor through an extruder, which in turn is fed with the plastic raw material.

[0033] Preferably, the plastic waste is heated to a temperature at which substantially all the material melts before being injected into the depolymerization reactor. The extruder receives the chopped plastic waste into the feed hopper, conveys the material flow in the melting section, and heats the polymer through the combined action of mixed energy and heat provided by the barrel heater. Typically, the melting temperature ranges from 200°C to 350°C.

[0034] Additives may be optionally incorporated into the melt to reduce the corrosivity of plastic waste or improve depolymerization efficiency. Poison inhibitors may be used in combination with catalysts. Preferably, they may be selected from the group consisting of: Ca(OH)₂, Mg(OH)₂, Ba(OH)₂, Sr(OH)₂, CaO, Al₂O₃, aluminosilicates such as bentonite and Zr(HPO₄)₂, and mixtures thereof. 。 Among them, the use of Ca(OH)2, aluminosilicate, and Zr(HPO4)2 is preferred.

[0035] During the extrusion process, one or more degassing steps can be performed to remove residual moisture present in the product.

[0036] Before being fed into the reactor, the melt stream can be filtered to remove solid impurities present in the plastic waste.

[0037] It can be applied to any extrusion system, such as a single-screw extruder, a twin-screw extruder, a twin-screw extruder with a gear pump, or a combination thereof.

[0038] The depolymerization reactor is preferably a stirred vessel, operating at the temperature described above, having an inlet for the plastic raw material and (if used) a catalyst, and an outlet for the gaseous depolymerization products. An example of a depolymerization reactor is disclosed in WO2022 / 136333, the relevant portions of which are incorporated herein by reference.

[0039] According to this disclosure, the depolymerization step (b) can be carried out in the presence of a catalyst. The latter can be selected from those that are active as depolymerization / cracking catalysts in thermocatalytic processes. In particular, it can be selected from metal oxides, heteropoly acids, mesoporous silica, aluminosilicate catalysts such as halloysite and kaolinite, cement, metal-organic frameworks (MOFs), ionic liquids, and preferably zeolites. Particularly preferred zeolites are synthetic Y-type zeolites and ZSM-5.

[0040] In a particularly preferred embodiment, the amount of catalyst feed is no more than 10% by weight, preferably no more than 5% by weight, and especially no more than 2% by weight relative to the plastic waste feed.

[0041] As a result of the depolymerization process, a gaseous stream is generated, which is sent to a condensation unit that liquefies all or part of the stream.

[0042] The condensation section receives the exhaust gas from the depolymerization reactor and preferably partially condenses it into an oily depolymerization product (crude pyrolysis oil) consisting essentially of hydrocarbons. The gas fractions can be collected and stored separately. The condensation section may consist of one or more stages and can operate under pressurized or non-pressurized conditions and at different temperatures to recover the maximum amount of product based on the volatility of the formed compounds. The operating temperature of the condensation unit (3) can vary over a wide range, depending on the operating pressure. The temperature, i.e., atmospheric pressure, can be from 20°C to 200°C, more preferably from 50°C to 200°C, and especially from 60°C to 180°C. The temperature range can, of course, differ when different operating pressures are selected.

[0043] The depolymerization process can also be carried out in a reactor apparatus comprising two depolymerization reactors, preferably connected in series, wherein the second depolymerization reactor can operate under conditions similar to those of the previous depolymerization stage. When two reactors are used and a catalyst is present, there are several possibilities for the catalyst feeding method. According to a preferred embodiment, the catalyst is fed into the first reactor, preferably co-fed with the melted plastic waste, and then transferred to the second reactor along with the contents of the first reactor.

[0044] According to another embodiment, the catalyst can be fed into a second reactor, where it acts on the partially depolymerized material from the first reactor. When operating with such an apparatus, it is also preferable to recycle the catalyst and a portion of the liquid or semi-liquid material back to the first depolymerization reactor, from which the solid residue is discharged. Similar to the first depolymerization step, the gaseous effluent can be condensed in a subsequent condensation stage.

[0045] Liquid depolymerization products

[0046] The composition of liquid depolymerization products and the level of contaminants depend primarily on the composition of the feedstock, and partly on the depolymerization process and conditions.

[0047] Generally, the crude pyrolysis oil obtained from plastic waste raw materials according to this disclosure may have the following composition (based on the weight percentage of the total oil weight):

[0048] - Alkane content is 10% to 20%.

[0049] -Isoparaffin content is 3% to 8%.

[0050] -Olefin content ranges from 5% to 40%.

[0051] - Naphthalene content ranges from 2% to 15%.

[0052] - Aromatic hydrocarbon content ranges from 2% to 15%.

[0053] - Nitrogen compound content ranges from several ppm to 5%.

[0054] - The content of oxygen-containing compounds ranges from several ppm to 5%.

[0055] - Halogen content ranges from several ppm to 1%.

[0056] - Metal content ranges from several ppm to hundreds of ppm

[0057] - Sulfur content is less than 4 ppm, preferably less than 2 ppm, or absent.

[0058] The boiling range of the crude pyrolysis oil is from 30°C to 650°C, more preferably from 50°C to 350°C.

[0059] As previously stated, it has been found that by using the specific purifying agents disclosed herein, at least nitrogen and oxygen substances, which are the main contaminants, can be removed in an effective manner, at least partially.

[0060] As previously described, the crude pyrolysis oil is contacted with a non-hydrocarbon liquid polar agent selected from eutectic complexes having the formula [A][B]x, wherein x ranges from 0.5 to 20, [A] is selected from metal salts, non-metal salts, and nonionic hydrogen bond acceptors (NIHBA), and [B] is selected from metal salts, hydrated metal salts, and nonionic hydrogen bond donor compounds (NIHBD).

[0061] Preferably, such compounds are liquids at atmospheric pressure in the range of 10°C to 250°C, more preferably 15°C to 200°C.

[0062] In a particularly preferred embodiment, the eutectic composite comprises at least two compounds and exhibits a single melting point that is typically lower than the melting point of each of the individual compounds.

[0063] When [A] is a metal salt, it is preferably selected from compounds of the formula MXy, where M is a metal or metalloid element belonging to Groups 3-15 of the periodic table (Iupac), preferably Al or Zn, X is a halogen, preferably Cl, and y is the valence of the metal.

[0064] When [A] is a nonmetallic salt, it is preferably selected from nonmetallic salts formed by cations and anions as reported below:

[0065]

[0066] The R1 to R4 groups are independently selected from C1-C 20 Alkyl or arylalkyl and C6-C 20 Aryl or alkylaryl groups.

[0067] When A is a nonionic hydrogen bond acceptor (NIHBA), it is preferably selected from lactam compounds, such as caprolactam. Examples of such compounds are disclosed in WO2020 / 221916, the relevant portions of which are incorporated herein by reference.

[0068] When [B] is selected from metal salts, it is preferably selected from compounds of the formula MXy, where M is a metal or metalloid element belonging to Groups 3-15 of the periodic table (Iupac), preferably Al, Zn, Sn, Ga, In, Cu, X is a halogen, preferably Cl, and x is the valence of the metal.

[0069] Alternatively, hydrated metal salts of the formula MXy·nH2O can be selected [B], where M, X, and y have the same meaning as above, and n is 1 to 10.

[0070] When [B] is selected from nonionic hydrogen bond donor compounds (NIHBD), it is preferably selected from amides, carboxylic acids, and alcohols, including cyclic amides. Particularly preferred compounds are those reported below:

[0071]

[0072] It can be recognized that some compounds can belong to both lists [A] and [B]. This is due to the fact that there are many possibilities for forming eutectic complexes. However, it is clear that if [A] and [B] are the same, then eutectic complexes cannot be formed, nor do they exist.

[0073] In particularly preferred combinations, [A] is selected from nonmetallic salts, and [B] is selected from metallic salts, hydrated metallic salts, and nonionic hydrogen bond donor compounds (NIHBD). More preferably, the eutectic complex obtained from [A] is selected from nonmetallic salts formed by cations and anions, as reported below:

[0074]

[0075] The R1 to R4 groups are independently selected from C1-C 20 Alkyl or arylalkyl and C6-C 20 Aryl or alkylaryl groups; and [B] is selected from the following NIHBD compounds.

[0076]

[0077] For these eutectic compounds, the value of x ranges from 0.3 to 20, preferably from 0.5 to 15, more preferably from 1 to 10, and especially from 1 to 8.

[0078] Specific examples are listed below:

[0079]

[0080]

[0081]

[0082] The temperature at which the crude pyrolysis oil comes into contact with the liquid polar compound is 20°C to 250°C, more preferably 25°C to 150°C, and especially 25°C to 100°C.

[0083] The process can be performed in a single step or in multiple steps, with each step using the same or different eutectic compounds. For example, a single step can be performed using one or more eutectic compounds, and when multiple steps are performed, each step can be the same as or different from the other steps, and each step can be performed using one or more eutectic compounds. Preferably, step (i) is performed in multiple steps. In a preferred embodiment, two or more contact steps are performed, wherein multiple equal portions of fresh crude pyrolysis oil are sequentially contacted with a single equal portion of a liquid polar compound.

[0084] The total mass ratio between the crude pyrolysis oil and the eutectic complex results in an EC / Pyoil mass ratio ranging from 0.01:1 to 100:1 at the end of the process. In one specific embodiment, the EC / Pyoil mass ratio ranges from 1:1 to 100:1, preferably from 2:1 to 80:1, and more preferably from 2:1 to 50:1. In another specific embodiment, the EC / Pyoil mass ratio ranges from 0.01:1 to 1:1, preferably from 0.02:1 to 0.8:1, and more preferably from 0.02:1 to 0.5:1.

[0085] In another preferred embodiment, the EC / Pyoil mass ratio ranges from 0.05:1 to 3:1, preferably from 0.1:1 to 2:1, and more preferably from 0.2:1 to 1:1.

[0086] Removal efficiency (EOR) is determined by formula (C) O -C F ) / C O It means that C O The initial concentration of contaminants in the initial pyrolysis oil, and C F This represents the final concentration of contaminants in the treated pyrolysis oil. When the EC / Pyoil mass ratio is greater than 1:1, the EOR value is extremely high, typically exceeding 60%, preferably exceeding 70% to 99%. Notably, even with an EC / Pyoil mass ratio as low as 0.02, a removal efficiency of over 60% can be achieved; when this mass ratio is between 0.03 and 0.2, the EOR can typically reach 70% to 90%.

[0087] The total contact time can be reasonably determined by those skilled in the art based on other conditions employed, such as temperature, volume, mass ratio, type of ethylene carbonate, and type of pyrolysis oil. Generally, allowing for a longer contact time will allow for the extraction of higher amounts of contaminants by EC. However, those skilled in the art will be able to clearly establish, based on specific conditions, a time point after which, based on production capacity standards, extending the contact time would be inefficient. Generally, the applicant has achieved satisfactory results in pyrolysis oil purification with total contact times ranging from 0.2 to 10 hours, more specifically 0.5 to 6 hours.

[0088] Generally speaking, all techniques that can be used to bring two immiscible liquids into contact and perform liquid-liquid extraction can be used for the contact between ethylene carbonate and pyrolysis oil.

[0089] According to one preferred method, two immiscible liquids are brought into contact in a sealed container equipped with a stirrer and temperature control, and featuring a bottom design that facilitates the drainage of the denser liquid. After the desired time has elapsed, stirring is stopped, allowing the system to reach phase separation conditions. At this point, the denser liquid, i.e., ethylene carbonate, drains from the bottom of the container. Alternatively, the less dense liquid can be siphoned off from the top of the container. The same operation can be repeated multiple times as needed.

[0090] In an alternative implementation, extraction can be carried out in a liquid-liquid extraction column, wherein the denser ethylene carbonate is fed from the top of the column, flows downwards to encounter the pyrolysis oil phase, and is mixed with it by the action of rotating and stationary baffles. The denser phase containing extraction contaminants can be discharged from the bottom of the column, while the clean, lighter phase can be discharged from the top.

[0091] The pyrolysis oil undergoing extraction can be from the last condensation section of the pyrolysis unit, or, if the pyrolysis unit is equipped with two or more pyrolysis reactors, from the intermediate condensation between two pyrolysis stages in series.

[0092] Used ethylene carbonate does not require disposal; instead, it can be completely recovered through a contaminant removal process. This can be achieved using various technologies, but given the very low or negligible vapor pressure of ethylene carbonate, one preferred method for recovering clean ethylene carbonate is to perform a flash evaporation stage on the used ethylene carbonate, in which highly volatile contaminants are blown out.

[0093] This disclosure will be explained in more detail with reference to the accompanying drawings and embodiments provided below.

[0094] Characterization

[0095] The following analytical methods were used:

[0096] Liquid product characterization: Liquid products in the two traps were characterized by gas chromatography (GC) and proton nuclear magnetic resonance (1H NMR).

[0097] GC analysis of the liquid products obtained in each experiment was performed using an Agilent 7890B gas chromatograph (Agilent Technologies, Santa Clara, USA), equipped with a nonpolar RTX-DHA-50 column and coupled with a high-performance ionization (HES) 5977B mass spectrometer (Agilent Technologies, Santa Clara, USA) and a flame ionization detector. This technique was used to detect and focus on analyzing the most abundant oxygen and nitrogen-containing molecules.

[0098] NMR data were used to characterize the percentages of aromatic, alkane, and alkene protons in the liquid products. CDCl3 (0.6 g of depolymerized polymer / metal oxide mixture with 0.4 g of CDCl3) was added to the sample for analysis. Data acquisition was performed at 25 °C using a Bruker AV500 MHz NMR spectrometer with a 5 mm Prodigy probe (Bruker Corporation, Billerica, MA, USA). One-dimensional 1H NMR data were processed using TOPSPIN® software (Bruker) with an exponentially broadened window function. Quantitative measurements were performed with a 15-second relaxation delay, a 30° flip-angle pulse, and 32 scans to facilitate accurate integration. Spectral integrals of the protons in aromatic alkenes and alkanes were obtained and used to quantify the relative ratios of these protons.

[0099] The contaminant content in the pyrolysis oil was determined using GCXGC two-dimensional chromatography. The instrumentation and basic conditions described are presented in the paper published by Franchina et al. in *Analytical and Bioanalytical Chemistry* (2023) 415:4545-4555 (https: / / doi.org / 10.1007 / s00216-023-04519-8). Unlike the sample preparation described in that article, the pyrolysis oil was directly injected into the instrument in this experiment without solid-phase extraction and enrichment.

[0100] Example

[0101] Preparation of low melting point mixtures

[0102] The following general procedure was used to prepare the eutectic solvent for liquid-phase extraction: Two components [A] and [B] were mixed in a rotary evaporator at the target molar ratio and heated to 60°C or slightly above. The mixture was then held at this temperature for 3 hours or longer until a homogeneous and clear solution was obtained. The resulting liquid was then cooled to room temperature.

[0103] The following eutectic composites were prepared using the above method:

[0104]

[0105] Liquid-liquid extraction experiments are conducted according to either experimental procedure A or B.

[0106] Program A

[0107] In a 500cc Erlenmeyer flask, add the initial pyrolysis oil and place a magnetic stir bar inside. Then, pour the liquid eutectic complex into the flask, heat to the target temperature, and maintain this temperature for the specified time. Next, stop stirring and allow the two immiscible phases to separate within the specified time. Separate the pyrolysis oil from the liquid eutectic complex from the top. This process can be repeated.

[0108] Program B

[0109] In a 2-liter jacketed glass reactor equipped with mechanical stirring and temperature monitoring, the desired amount of crude pyrolysis oil is added. A liquid eutectic complex is then added, and the mixture is heated to the target temperature and stirred for a specified time. Stirring is stopped, allowing the liquid to separate within a few minutes, and then the denser phase (eutectic solvent) is discharged from the bottom of the glass reactor. The process can be repeated further if necessary.

[0110] Program C

[0111] In a 500cc Erlenmeyer flask, add the initial pyrolysis oil and place a magnetic stir bar inside. Then, pour the liquid eutectic complex into the flask, heat to the target temperature, and maintain this temperature for the specified time. Next, stop stirring and allow the two immiscible phases to separate for the required time. Separate the pyrolysis oil from the upper layer of the liquid eutectic complex.

[0112] After the initial treatment, fresh pyrolysis oil is added to the glass flask containing the used eutectic complex, maintaining an equal weight ratio. Stirring is then stopped, and the mixture is allowed to stand for the required time for the two immiscible phases to separate. The pyrolysis oil is then separated from the liquid eutectic complex from the upper layer.

[0113] Example 1

[0114] Proceed according to procedure A. Pyrolysis oil from waste plastics generated in the special experiment was treated using a liquid eutectic compound 1.1. The initial concentrations of major oxygen-containing compounds and nitrogen-containing molecules were 1.0% by weight, while the concentration of alkane hydrogens was 90 mol%.

[0115] The liquid eutectic complex was mixed with pyrolysis oil at a weight ratio of 10:1 and stirred at 60°C for 3 hours.

[0116] Following this step, the oil sample was analyzed and found that the alkyl hydrogen concentration increased to 92 mol%, and the total amount of oxygen-containing compounds and nitrogen-containing substances was 0.2 wt%.

[0117] After repeating the same treatment twice, the final pyrolysis oil showed an increase in the concentration of alkane hydrogens to 95 mol%, while oxygen- and nitrogen-containing products decreased to below the GC detection limit.

[0118] Example 2

[0119] Proceed according to procedure B. Treat the pyrolysis oil from the waste plastic terminal obtained in previous experiments with a liquid eutectic compound 1.1. The initial concentration of caprolactam was 1.4 wt%.

[0120] The liquid eutectic complex was mixed with pyrolysis oil at a mass ratio of 5:1 and stirred at 35°C for 1 hour. This treatment was repeated twice, and the final pyrolysis oil was analyzed by GC / MS; no trace of caprolactam was detected.

[0121] Example 3

[0122] Similar tests to those in Example 2 were conducted using liquid eutectic complex solvent 1.2, with the extraction temperature maintained at 55°C. Under these conditions, caprolactam was also not detected in the final pyrolysis oil of the raffinate.

[0123] Example 4

[0124] Procedure A was followed. Pyrolysis oil from waste plastics terminals in a specific production batch was treated with liquid eutectic compound 1.2. Initial concentrations of major oxygen-containing substances and nitrogen-containing molecules were measured by GC×GC to be 0.8 wt% and 0.4 wt%, respectively. The mass ratio of liquid eutectic compound to pyrolysis oil was 5:1, and the mixture was stirred at 55°C for 10 minutes. The extraction step was repeated 9 times, using fresh eutectic compound 1.2 in each step.

[0125] The decrease in the concentrations of oxygen- and nitrogen-containing products with the number of extractions is recorded:

[0126]

[0127] Example 5

[0128] The same procedure as in Example 4 was repeated, except that the ratio of the eutectic complex to oil was 2.5 g / g. The decrease in the concentrations of oxygen- and nitrogen-containing products with increasing extraction number was also recorded.

[0129]

[0130] Example 6

[0131] Proceed according to procedure A. Pyrolysis oil from waste plastics generated in the special experiment was treated using a liquid eutectic compound 1.3. The initial alkane hydrogen content, measured by nuclear magnetic resonance, was 94 mol%.

[0132] The liquid eutectic complex was mixed with cracked oil at a mass ratio of 5 / 1 and stirred at 60°C for 1 hour. After a single treatment, the alkane hydrogen concentration increased to 95 mol%.

[0133] Example 7

[0134] The procedure was the same as in Example 6, except that eutectic complex 1.4 was used in the treatment. After treatment, the alkane hydrogen content of the refined oil was also increased to 95 mol%.

[0135] Example 8

[0136] The process was carried out using the same steps as in Example 1, except that a eutectic compound 1.5 was used in the treatment. In the crude pyrolysis oil used in this specific example, the initial alkane hydrogen content, measured by nuclear magnetic resonance, was 90 mol%. After treatment, the alkane hydrogen content of the refined oil was also increased to 93 mol%.

[0137] Example 9

[0138] According to procedure A, a series of tests were conducted with different EC / Pyoil ratios. Pyrolysis oil from waste plastic terminals generated in a specialized experiment was treated using a liquid eutectic compound 1.2. The initial concentration of the main oxygen-containing substances was 1.54%, and the initial concentration of nitrogen-containing molecules was 0.18% by weight. Each treatment was carried out at 60°C for 30 minutes. The experimental results are shown below.

[0139]

[0140] Example 10

[0141] According to procedure C, a series of tests were conducted with different EC / Pyoil ratios. The crude pyrolysis oil, identical to that in Example 9, was treated with liquid eutectic compound 1.2. Each treatment was carried out at 60°C for 30 minutes. The experimental results are shown below.

[0142]

[0143] (*N) The number of pyrolysis oil samples that come into contact with the same ethylene carbonate sample.

Claims

1. A process for producing and purifying crude pyrolysis oil, the process comprising: a) Provide molten plastic waste feedstock, said molten plastic waste feedstock comprising at least a polyolefin fraction in an amount exceeding 70% by weight of the total weight of the plastic waste feedstock; b) subject the molten product obtained in (a) to a temperature of 280°C to 600°C to obtain the depolymerization product; (c) The depolymerization product is subjected to a condensation stage at a temperature ranging from 10°C to 250°C, preferably from 15°C to 200°C, and more preferably from 15°C to 150°C, to obtain the crude pyrolysis oil and gas fraction as liquid fractions, the crude pyrolysis oil containing oxygen-containing and nitrogen-containing compounds as contaminants. (d) Contacting the crude pyrolysis oil with a non-hydrocarbon liquid polar compound selected from eutectic compounds having the formula [A][B]x, wherein x ranges from 0.3 to 20, [A] is selected from metal salts, non-metal salts, and nonionic hydrogen bond acceptors (HBAs), and [B] is selected from metal salts, hydrated metal salts, and nonionic hydrogen bond donor compounds (NIHBDs), wherein the eutectic compound is immiscible with the crude pyrolysis oil; and (e) recovering from the above steps (1) the purified pyrolysis oil fraction, the purified pyrolysis oil fraction having a reduced content of nitrogen-containing and oxygen-containing compounds relative to the crude pyrolysis oil, and (2) the fraction containing the liquid non-hydrocarbon liquid polar compound, the fraction containing at least a portion of the contaminants present in the crude pyrolysis oil.

2. The process according to claim 1, wherein the liquid non-hydrocarbon polar compound is liquid at atmospheric pressure in the range of 10°C to 250°C, more preferably 15°C to 200°C.

3. The process according to any one of the preceding claims, wherein the eutectic composite is formed from at least two compounds and exhibits a single melting point lower than that of each of the respective compounds.

4. The process according to any one of the preceding claims, wherein [A] is a non-metallic salt, said non-metallic salt being selected from non-metallic salts formed from the following cations and anions. ： The R1 to R4 groups are independently selected from C1-C 20 Alkyl or arylalkyl and C6-C 20 Aryl or alkylaryl groups.

5. The process according to any one of the preceding claims, wherein [B] is selected from nonionic hydrogen bond donor compounds (NIHBD), said nonionic hydrogen bond donor compounds (NIHBD) are selected from amides, carboxylic acids and alcohols including cyclic amides.

6. The process according to claim 5, wherein [B] is selected from the following compounds:

7. The process according to any one of the preceding claims, wherein [A] is selected from the nonmetallic salts according to claim 4 and [B] is selected from the NIHBD compounds according to claim 6.

8. The process according to any one of the preceding claims, wherein in the eutectic composite, the value of x ranges from 0.5 to 15, more preferably from 1 to 10, and especially from 1 to 8.

9. The process according to claim 7, wherein the eutectic composite is selected from:

10. The process according to any one of the preceding claims, wherein step (d) is carried out at a temperature ranging from 20 to 250°C, more preferably from 25 to 150°C, and especially from 25 to 100°C.

11. The process according to any one of the preceding claims, wherein step (d) is performed as a plurality of steps, each of the plurality of steps using one or more eutectic compounds.

12. The process according to any one of the preceding claims, wherein in step (d), the total mass ratio of the eutectic complex to the crude pyrolysis oil is such that at the end of the process, the mass ratio of EC / Pyoil ranges from 0.01:1 to 100:1, preferably from 0.02:1 to 0.8:1, and more preferably from 0.02:1 to 0.5:

1.

13. The process according to any one of the preceding claims, wherein in step (d), the total mass ratio of the eutectic complex to the crude pyrolysis oil is such that at the end of the process, the mass ratio of EC / Pyoil is in the range of 1:1 to 100:1, preferably 2:1 to 80:1, and more preferably 2:1 to 50:

1.

14. The process according to any one of the preceding claims, wherein the total contact time of step (d) ranges from 0.5 to 10 hours, more specifically from 1 to 6 hours.

15. The process according to any one of the preceding claims, wherein step (e) is performed by removing the liquid non-hydrocarbon polar compound as a denser, immiscible phase.

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