Process for purifying petrochemical compositions obtained from chemical recovery of polymeric materials

Abstract

The method according to the invention comprises the following steps: (a) a gas stripping step in a gas stripping container (1); and (b) a liquid-liquid extraction step in the extraction vessel (2), wherein steps (a)-(b) can be carried out in any order. The liquid-liquid extraction step (b) can be implemented by using a protic solvent as an extraction medium or using an aprotic solvent as an extraction medium. The use of this method enables the purification of hydrocarbon compositions, in particular with respect to the content of chlorine-containing compounds. Reduction of chlorine content is desirable for treating hydrocarbon compositions in a variety of different chemical treatment operations, such as steam cracking. The presence of chlorine-containing compounds at higher levels may lead to equipment corrosion in such methods, which may cause, for example, equipment failures and / or shorten equipment maintenance intervals. In view of its significant impact on process economy, it is definitely desirable to reduce the amount of chlorine-containing compounds present as much as possible.

Description

[0001] This invention relates to a method for purifying petrochemical compositions.

[0002] In the chemical and refining industries, a variety of chemical conversion processes are in operation. These processes are highly optimized in terms of productivity, efficiency, and sustainability to achieve economical and profitable operations and obtain high-quality products. One specific aspect associated with this optimized production is the use of high-quality raw materials (also known as feedstocks) as inputs.

[0003] Many of these chemical and refining processes use petrochemical compositions as raw materials.

[0004] One particularly desirable type of feedstock currently being sought for the chemical and refining industries is that derived from waste streams. Using such feedstocks would greatly benefit material recycling; there is a strong desire to utilize waste materials as valuable raw materials for new processes. There is particular interest in using materials derived from waste plastics as feedstocks. This could be highly desirable in the petrochemical and refining industries because waste plastics are primarily material streams containing a large number of molecules in which carbon and hydrogen make up the majority of the atoms. Therefore, the atomic composition of these materials is very similar to that of typical hydrocarbon materials commonly used in the petrochemical and refining industries. Thus, materials produced from waste plastics are likely well-suited for application in this sector.

[0005] In recent years, there has been an upward trend in both technological development and industrial activity in the field of converting waste plastic materials into feedstocks usable in the petrochemical and refining industries. For example, through technologies such as plastic pyrolysis, waste plastic materials that are solid at room temperature can be converted into hydrocarbon-containing streams that are liquid at the same temperature, allowing them to be processed in chemical and refining processes used to convert liquid hydrocarbons. These products obtained from the pyrolysis of waste plastic materials can be called plastic-derived oils.

[0006] Typical examples of such methods include those for the production of light olefins and aromatics. Light olefins such as ethylene and propylene, and aromatics such as benzene, are well-known valuable basic chemicals widely used in the synthesis of chemical products, especially polymer products, the most abundant examples of which are polyethylene and polypropylene.

[0007] The most widely used method for producing light olefins and aromatics is the so-called cracking operation, typically a thermal cracking or catalytic cracking operation. In these cracking operations, hydrocarbon molecules (usually fossil hydrocarbons) present in the feed stream undergo specific conditions that break their atomic bonds and form smaller molecules. Due to chemical reaction kinetics, these processes typically produce a product composition containing the desired high content of light olefins and aromatics. After leaving the cracking unit, the product composition usually undergoes one or more separation operations to obtain a high-quality, high-purity chemical stream that can be processed into the desired final product (such as polymer materials).

[0008] Therefore, when feedstocks derived from waste plastics are used in such pyrolysis operations, polymer materials can be produced from waste polymer materials, thus establishing the circular application of polymers. It should be understood that this provides an attractive pathway for materials synthesis.

[0009] For waste plastic materials to be suitable for processing in chemical operations such as pyrolysis or catalytic cracking, the resulting products must meet very stringent material specifications. Pyrolysis operations are carried out industrially on a global scale; interruptions can lead to plant shutdowns and product defects, resulting in a significant decrease in process efficiency. Furthermore, pyrolysis is a highly sensitive process, and operating conditions must be maintained within strictly defined ranges. This also places demands on the raw materials that can be processed in such facilities.

[0010] On the other hand, the composition of processable waste plastic streams is often not very consistent; when they are generated by waste collection operations, whether at the consumer or industrial level, the composition of these streams is expected to vary considerably from batch to batch. This can conflict with the requirements of chemical processing operations that may use them as feedstocks, as these processes demand a high degree of consistency.

[0011] Therefore, it is necessary to ensure that the composition of products derived from waste plastics and used as feedstocks for chemical or refining operations such as pyrolysis processes is appropriately consistent and sufficiently pure.

[0012] One specific component that may be present in petrochemical feedstock compositions, such as streams derived from waste plastics, like plastic-derived oils, is chlorine. In petrochemical and refining operations, it is generally desirable to process feedstocks with particularly low chlorine content. Therefore, a technology is needed to remove chlorine from petrochemical compositions such as plastic-derived oils.

[0013] This invention relates to a method for removing chlorinated compounds from hydrocarbon compositions, and particularly to a method for removing chlorinated compounds from liquid hydrocarbon compositions.

[0014] Such a liquid hydrocarbon composition can be, for example, pyrolysis oil. In the context of this invention, pyrolysis oil refers to a product obtained by subjecting a waste plastic stream to pyrolysis conditions, wherein the plastic is decomposed into a range of hydrocarbon oils; that is, under these conditions, the chemical bonds in the polymer chains of the plastic break to form a low molecular weight product.

[0015] In the method of the present invention, the hydrocarbon composition undergoes multiple chemical unit operations to reduce the content of chlorinated compounds that may be contained therein.

[0016] The method of the present invention includes subjecting hydrocarbon composition A to:

[0017] (a) The air-lifting step in the air-lifting container (1); and

[0018] (b) Liquid-liquid extraction step in extraction vessel (2),

[0019] Steps (a)-(b) can be performed in any order.

[0020] The liquid-liquid extraction step (b) can be carried out using either a protic solvent or an aprotic solvent as the extraction medium.

[0021] In a preferred embodiment, the method of the present invention includes the following steps:

[0022] (a) The hydrocarbon composition A is subjected to a stripping step in a stripping container (1), wherein composition A is contacted with a nitrogen-containing stream B to obtain composition C;

[0023] (b) Composition C is subjected to a liquid-liquid extraction step in an extraction vessel (2), wherein an aprotic solvent or a protic solvent is used as the extraction medium to obtain composition E.

[0024] This method enables the purification of hydrocarbon compositions, particularly regarding the content of chlorine compounds. This reduction in chlorine content is desirable for processing hydrocarbon compositions in many different chemical processing operations, such as steam cracking. In these processes, high chlorine content can lead to equipment corrosion, potentially causing, for example, equipment failure and / or reduced maintenance intervals. Given its significant impact on process economics, it is clearly desirable to minimize the presence of chlorine compounds as much as possible.

[0025] exist Figure 1 and 2 Some embodiments of the invention are given below. Figure 1 and 2 middle:

[0026] A: Hydrocarbon composition A;

[0027] B: Nitrogen-containing logistics B;

[0028] C: The stripping composition C obtained from the stripping step (a);

[0029] D: Stream D containing nitrogen and compounds extracted from composition A by stripping step (a);

[0030] E: Composition E obtained from extraction step (b);

[0031] G: The purified stream G obtained from adsorption step (d);

[0032] H: Liquid hydrocarbon stream H obtained from liquefaction step (e);

[0033] 1: Airlift container

[0034] 2: Extraction container

[0035] 4: Adsorption container

[0036] 5: Condenser

[0037] Hydrocarbon Composition A

[0038] Hydrocarbon composition A can be, for example, a hydrocarbon-containing oil product obtained from the decomposition of waste plastics.

[0039] According to this invention, the hydrocarbon composition A used herein can be defined, for example, by its boiling range. The hydrocarbon composition is typically a hydrocarbon product and usually a mixture of compounds with different boiling points. For processing in process operations commonly used in the chemical and refining industries, the viscosity of these compositions should not be too high, and the composition should not be too volatile. Typical boiling ranges for suitable compositions may include an initial boiling point ≥25°C and a final boiling point ≤500°C, ≤400°C, or ≤350°C. The boiling point can be determined according to the method described in ASTM D86 (2012).

[0040] The initial boiling point reflects the lowest temperature at which compounds in a hydrocarbon-oil mixture begin to boil; therefore, it is the temperature at which the most volatile compound (usually the compound with the smallest molecular weight) begins to boil under atmospheric pressure. The terminal boiling point reflects the highest temperature that the hydrocarbon-oil composition can reach when boiling; therefore, it represents the boiling temperature of the compound with the largest molecular weight and the highest boiling point under atmospheric conditions.

[0041] The hydrocarbon composition A used in this invention preferably has an initial boiling point ≥30°C, more preferably ≥50°C. It is also preferred that the final boiling point of hydrocarbon composition A is ≤325°C, more preferably ≤300°C, even more preferably ≤250°C, even more preferably ≤225°C, or even ≤200°C. Specifically, a suitable hydrocarbon composition A may have an initial boiling point ≥30°C and a final boiling point ≤300°C, more preferably an initial boiling point ≥30°C and a final boiling point ≤250°C, and even more preferably an initial boiling point ≥50°C and a final boiling point ≤200°C.

[0042] Compositions with this initial boiling point and final boiling point range are considered suitable for handling in chemical and refining operations, including allowing proper transport, heating, cooling and separation processes without undesirable process interruptions.

[0043] Furthermore, it is considered that the hydrocarbon composition A suitable for use in this invention may contain, for example, a certain amount of n-chain alkanes, a certain amount of iso-chain alkanes, a certain amount of olefins, a certain amount of cycloalkanes, and / or a certain amount of aromatics. The composition may contain, for example, a certain amount of n-chain alkanes, a certain amount of iso-chain alkanes, a certain amount of olefins, a certain amount of cycloalkanes, and a certain amount of aromatics.

[0044] In the context of this invention, the n-chain alkanes that may be present in composition A may include, for example, n-alkanes having 3-40 carbon atoms. The iso-chain alkanes that may be present in composition A may have, for example, 3-40 carbon atoms. The cycloalkanes that may be present in composition A may have, for example, 3-40 carbon atoms. The aromatics that may be present in composition A may have, for example, 6-40 carbon atoms.

[0045] Relative to the total weight of hydrocarbon composition A, hydrocarbon composition A may contain, for example, ≥25.0 wt% and ≤95.0 wt% of n-chain alkanes. Hydrocarbon composition A preferably contains ≥25.0 wt% and ≤80.0 wt% of n-chain alkanes, more preferably ≥25.0 wt% and ≤70.0 wt%, and even more preferably ≥25.0 wt% and ≤50.0 wt%.

[0046] Relative to the total weight of hydrocarbon stream A, hydrocarbon composition A may contain, for example, ≥5.0 wt% and ≤40.0 wt% of isoparaffins. Hydrocarbon composition A preferably contains ≥5.0 wt% and ≤30.0 wt% of isoparaffins, more preferably ≥7.5 wt% and ≤25.0 wt%.

[0047] Hydrocarbon composition A may contain, for example, ≤50.0 wt% of olefins relative to the total weight of hydrocarbon composition A. Hydrocarbon composition A preferably contains ≤40.0 wt% of olefins, more preferably ≤35.0 wt%, and even more preferably ≤30.0 wt%.

[0048] Relative to the total weight of hydrocarbon composition A, hydrocarbon composition A may contain, for example, ≥5.0 wt% and ≤50.0 wt% of olefins. Hydrocarbon composition A preferably contains ≥10.0 wt% and ≤40.0 wt% of olefins, more preferably ≥15.0 wt% and ≤35.0 wt%.

[0049] Relative to the total weight of hydrocarbon composition A, hydrocarbon composition A may contain, for example, ≥5.0 wt% and ≤20.0 wt% of cycloalkanes. Hydrocarbon composition A preferably contains ≥5.0 wt% and ≤15.0 wt% of cycloalkanes, more preferably ≥7.5 wt% and ≤15.0 wt%.

[0050] Relative to the total weight of hydrocarbon composition A, hydrocarbon composition A may contain, for example, ≥5.0 wt% and ≤15.0 wt% of aromatics. Hydrocarbon composition A preferably contains ≥5.0 wt% and ≤12.5 wt% of aromatics, more preferably ≥7.5 wt% and ≤12.5 wt%.

[0051] Relative to the total weight of hydrocarbon composition A, hydrocarbon composition A may contain, for example:

[0052] ≥25.0 wt% and ≤95.0 wt%, preferably ≥25.0 wt% and ≤70.0 wt%, more preferably ≥25.0 wt% and ≤50.0 wt% of n-chain alkanes; and / or

[0053] ≥5.0 wt% and ≤20.0 wt%, preferably ≥5.0 wt% and ≤15.0 wt%, more preferably ≥7.5 wt% and ≤15.0 wt% of isoparaffins; and / or

[0054] ≥5.0 wt% and ≤50.0 wt%, preferably ≥10.0 wt% and ≤40.0 wt%, more preferably ≥15.0 wt% and ≤35.0 wt%, even more preferably ≥15.0 wt% and ≤25.0 wt% of olefins; and / or

[0055] ≥5.0 wt% and ≤20.0 wt%, preferably ≥5.0 wt% and ≤15.0 wt%, more preferably ≥7.5 wt% and ≤15.0 wt% of cycloalkanes; and / or

[0056] Aromatic hydrocarbons of ≥5.0 wt% and ≤15.0 wt%, preferably ≥5.0 wt% and ≤12.5 wt%, more preferably ≥7.5 wt% and ≤12.5 wt%.

[0057] In the context of this invention, atomic chlorine content should be understood as the fraction of the total weight of chlorine atoms present in the molecules of the hydrocarbon composition relative to the total weight of the hydrocarbon stream. Atomic nitrogen content should be understood as the fraction of the total weight of nitrogen atoms present in the molecules of the hydrocarbon stream relative to the total weight of the hydrocarbon stream.

[0058] Hydrocarbon composition A may contain, for example, a certain amount of contaminants. For example, hydrocarbon composition A may contain a certain amount of a chlorine-containing compound. The amount of the chlorine-containing compound can be expressed as the atomic chlorine content of hydrocarbon stream A. For example, measured according to ASTM UOP 779-08, the atomic chlorine content of hydrocarbon composition A may be 2000 ppmw, or <1500 ppm, or <1000 ppm, preferably <800 ppm, preferably <700 ppm, more preferably <600 ppm, even more preferably <500 ppm, even more preferably <400 ppm.

[0059] Hydrocarbon composition A may contain, for example, >150 ppm, preferably >200 ppm, more preferably >250 ppm of atomic chlorine.

[0060] For example, hydrocarbon composition A may contain >200 and <800 ppm, preferably >200 and <600 ppm, more preferably >200 and <500 ppm of atomic chlorine.

[0061] Hydrocarbon composition A may contain a certain amount of a nitrogen-containing compound. The amount of the nitrogen-containing compound may be expressed as the atomic nitrogen content of hydrocarbon composition A. For example, as measured by ASTM D5762 (2012), the atomic nitrogen content of hydrocarbon composition A may be <1600 ppmw, preferably <1500 ppm, more preferably <1400 ppm, even more preferably <1300 ppm, even more preferably <1200 ppm, or <1100 ppm, or <1000 ppm. For example, as measured by ASTM D4629 (2017), the atomic nitrogen content of hydrocarbon composition A may be <100 ppmw.

[0062] Hydrocarbon composition A may contain a certain amount of a compound containing olefinic unsaturated bonds. One indicator of the amount of olefinic unsaturated bonds is the bromine value of the hydrocarbon stream. The bromine value indicates the number of grams of bromine reacting with 100 grams of hydrocarbon sample when tested under ASTM D1159-07 (2012) conditions. For example, the bromine value of hydrocarbon composition A used in the method of the present invention may be <100, preferably <95, more preferably <90, and even more preferably <85.

[0063] Product C preferably contains <100ppm, more preferably <75ppm, even more preferably <50ppm, and still even more preferably <25ppm of atomic chlorine.

[0064] Hydrocarbon composition A can be, for example, a material stream obtained by processing waste plastic feedstock. For instance, hydrocarbon composition A can be obtained by processing a waste plastic stream in a pyrolysis unit.

[0065] Such a pyrolysis apparatus can be a continuously operating apparatus, wherein a waste plastic stream is continuously supplied to the apparatus, and at least one liquid stream containing pyrolysis products is continuously obtained from the apparatus. Alternatively, the pyrolysis apparatus can be a batch-operated apparatus, wherein a certain amount of waste plastic is introduced into the apparatus, subjected to pyrolysis conditions, and subsequently at least one liquid stream containing pyrolysis products is obtained from the apparatus.

[0066] The pyrolysis process carried out in the pyrolysis apparatus can be a low-severity pyrolysis process or a high-severity pyrolysis process. In a low-severity pyrolysis process, pyrolysis can be carried out at temperatures ≥250°C and ≤450°C, preferably ≥275°C and ≤425°C, more preferably ≥300°C and ≤400°C. Alternatively, the pyrolysis process can be a high-severity process carried out at temperatures ≥450°C and ≤750°C, preferably ≥500°C and ≤700°C, more preferably ≥550°C and ≤650°C.

[0067] The pyrolysis process can be a catalytic process. In such a pyrolysis process, for example, a certain amount of zeolite catalyst, such as ZSM-5 zeolite catalyst, can be used. In such a pyrolysis process, for example, a certain amount of spent FCC catalyst can be used. Specifically, a composition comprising a certain amount of ZSM-5 catalyst and a certain amount of spent FCC catalyst can be used. For example, a composition comprising a certain amount of ZSM-5 and a certain amount of spent FCC catalyst can be used, wherein the weight ratio of spent FCC catalyst to ZSM-5 catalyst is between 0.5 and 5.0, for example, 1.0 to 3.0.

[0068] Prior to any step (a)-(b), the method of the present invention may, for example, include a pyrolysis step of the waste plastic composition, wherein hydrocarbon composition A is obtained as a liquid product of pyrolysis.

[0069] Waste plastic raw materials used to produce hydrocarbon composition A in this method may include, for example, polyolefins, polyesters, thermoplastic elastomers, polyvinyl chloride, polystyrene, or polycarbonate.

[0070] Waste plastic raw materials that can be used to produce hydrocarbon composition A can be mixtures comprising polyolefins, polyesters, thermoplastic elastomers, polyvinyl chloride, polystyrene, or polycarbonate. Specifically, waste plastic raw materials that can be used to produce hydrocarbon composition A can be mixtures containing >25.0 wt% polyolefins by weight of the total waste plastic raw materials. Preferably, the waste plastic raw materials can contain >40.0 wt%, more preferably >50.0 wt%, even more preferably >60.0 wt%, or >70.0 wt% polyolefins. The waste plastic raw materials can contain a portion of non-thermoplastic materials. Such non-thermoplastic materials can be, for example, hydrocarbon-based materials, such as rubber materials, but can also include materials including paper, sand, and soil. An advantage of the present invention is that waste plastic raw materials containing up to 10 wt%, preferably up to 5.0 wt%, more preferably up to 2.0 wt% of materials selected from paper, sand, soil, and combinations thereof can be used in the method for preparing polypropylene. This allows these raw materials to be processed without the need for cleaning processes that may require the application of solvents or detergents.

[0071] For example, relative to the total weight of waste plastic raw materials, waste plastic raw materials may contain ≤10.0 wt% of the following components: glass, paper, metal, cardboard, compostable waste, wood, stone, textiles, rubber materials and superabsorbent sanitary products.

[0072] Relative to the total weight of waste plastic raw materials, waste plastic raw materials may contain, for example, ≥90.0 wt% polymeric materials.

[0073] Waste plastic raw materials may contain, for example, a certain amount of polyester. For instance, waste plastic raw materials may contain <20.0 wt%, preferably <15.0 wt%, more preferably <10.0 wt%, even more preferably <5.0 wt%, even more preferably <2.0 wt% of polyester. In some embodiments, the waste plastic raw materials may not contain polyester.

[0074] A specific type of polyester typically present in waste plastic feedstocks (e.g., those used to prepare hydrocarbon stream A used in this method) is polyethylene terephthalate, also known as PET. The waste plastic feedstock may contain, for example, a certain amount of PET. For instance, the waste plastic feedstock may contain <20.0 wt%, preferably <15.0 wt%, more preferably <10.0 wt%, even more preferably <5.0 wt%, even more preferably <2.0 wt% of PET. In some embodiments, the waste plastic feedstock may be PET-free.

[0075] Polyesters such as PET contain oxygen atoms in their polymer chains. Since excessive oxygen atoms in the compounds supplied to the pyrolysis furnace can cause problems including scaling and corrosion in the downstream processing of the pyrolysis hydrocarbon stream D leaving the furnace, the presence of oxygen-containing compounds in hydrocarbon stream A should be limited. Therefore, it is desirable to control or even minimize the amount of oxygen-containing polymers in the waste plastic feedstock used to prepare hydrocarbon stream A.

[0076] Waste plastic raw materials may contain, for example, a certain amount of polyamide. For instance, waste plastic raw materials may contain <20.0 wt%, preferably <15.0 wt%, more preferably <10.0 wt%, even more preferably <5.0 wt%, even more preferably <2.0 wt% of polyamide. In some embodiments, the waste plastic raw material may be polyamide-free.

[0077] Specific types of polyamides that are typically present in waste plastic feedstocks (such as those used to prepare hydrocarbon stream A applied in this method) are polyamide 6 and polyamide 6,6, which may also be referred to as PA6 and PA66, respectively. The waste plastic feedstock may contain, for example, a certain amount of PA6 or PA66. For example, the waste plastic feedstock may contain <20.0 wt%, preferably <15.0 wt%, more preferably <10.0 wt%, even more preferably <5.0 wt%, even more preferably <2.0 wt% of total PA6 and PA66. In some embodiments, the waste plastic feedstock may be free of PA6 and / or PA66.

[0078] Waste plastic raw materials may contain, for example, a certain amount of polyvinyl chloride, also known as PVC. For example, waste plastic raw materials may contain <5.0 wt%, preferably <2.0 wt%, more preferably <1.0 wt%, even more preferably <0.5 wt%, even more preferably <0.1 wt% of PVC. In some embodiments, waste plastic raw materials may be PVC-free.

[0079] Relative to the total weight of polymer materials in waste plastic raw materials, waste plastic raw materials may include, for example:

[0080] < 20.0 wt%, preferably < 10.0 wt%, of polyester; and / or

[0081] < 20.0 wt%, preferably < 10.0 wt%, of polyamide; and / or

[0082] < 2.0 wt%, preferably < 1.0 wt% of polyvinyl chloride.

[0083] The percentages of polyester, polyamide, and PVC in the waste plastic raw materials shown should be understood as the weight percentage of the total weight of polymer materials present in the waste plastic raw materials.

[0084] Waste plastic raw materials may also contain a certain amount of moisture, for example, waste plastic raw materials may contain up to 20.0 wt%, preferably up to 10.0 wt%, more preferably up to 5.0 wt% moisture.

[0085] Nitrogen-containing stream B can be, for example, gaseous nitrogen. The stripping step (a) is preferably carried out for at least 100 minutes, preferably at least 150 minutes, and even more preferably at least 200 minutes. For example, the stripping step (a) can be carried out for 100-300 minutes, preferably 150-300 minutes, and even more preferably 200-300 minutes. The stripping step (a) is preferably carried out in a stripping tower, more preferably in a stripping tower equipped with a condenser and a reboiler. The temperature of the condenser can be, for example, 50-160°C, preferably 70-140°C, and more preferably 80-120°C. The temperature of the reboiler can be, for example, 70-190°C, preferably 85-160°C, and more preferably 95-140°C.

[0086] Aprotic solvents may be selected, for example, from dimethyl sulfoxide, dimethylformamide, sulfolane, and n-methyl-2-pyrrolidone. Aprotic solvents are preferably selected from dimethyl sulfoxide and dimethylformamide.

[0087] A protic solvent may be applied, for example, in a certain amount relative to composition C, such that the aprotic solvent accounts for ≥40.0 vol% and ≤90.0 vol% of the contents of the first extraction vessel (2), preferably ≥50.0 vol% and ≤65.0 vol%, more preferably ≥55.0 vol% and ≤60.0 vol%.

[0088] Extraction step (b) can be carried out, for example, at temperatures >15°C and <60°C, preferably >20°C and <40°C.

[0089] Extraction step (b) can be carried out, for example, at pressures >50 kPa and <200 kPa, preferably >75 kPa and <150 kPa, such as at atmospheric pressure.

[0090] Extraction step (b) can be performed for, for example, >1.0 and <75.0 minutes, preferably >1.0 and <30.0 minutes, more preferably >5.0 and <20.0 minutes, and even more preferably >5.0 and <15.0 minutes.

[0091] In a preferred embodiment, dimethyl sulfoxide or dimethylformamide of the contents of the extraction vessel (2) with ≥55.0 vol% and ≤60.0 vol% is used as a solvent, and the extraction step (b) is performed for >5.0 and <15.0 minutes at temperatures >20°C and <40°C and pressures >75 kPa and <150 kPa.

[0092] The protic solvent can be selected from, for example, ethylene glycol, water, methanol, and ethanol. Ethylene glycol is preferred as the protic solvent.

[0093] The proton solvent can be applied, for example, in a certain amount relative to composition E, such that the proton solvent accounts for ≥40.0 vol% and ≤70.0 vol% of the contents of the second extraction vessel (3), preferably ≥50.0 vol% and ≤65.0 vol%, more preferably ≥55.0 vol% and ≤60.0 vol%.

[0094] In a preferred embodiment, ethylene glycol containing ≥55.0 vol% and ≤60.0 vol% of the contents of the extraction vessel (2) is used as the solvent, and the extraction step (b) is performed for >5.0 and <15.0 minutes at temperatures >20°C and <40°C and pressures >75 kPa and <150 kPa.

[0095] The stripping process (a) can also produce a stream D containing nitrogen and compounds stripped from component A. This stream D can then undergo an adsorption step (d) in an adsorption vessel (4) to obtain a purified stream G. The adsorption can be carried out using a zeolite-type adsorbent.

[0096] By feeding stream G into the condenser (5), it can be liquefied in the liquefaction step (e) to obtain liquid hydrocarbon stream H, which can be recycled back and mixed with hydrocarbon stream A fed into the stripping container (1).

[0097] The method of the present invention is preferably a continuous operation method.

[0098] The present invention is described below through the following non-limiting embodiments.

[0099] To verify the purpose of this invention, a plastic-derived oil product with an initial boiling point of 30°C and a final boiling point of 180°C was used as hydrocarbon stream A. The plastic-derived oil product has a total chlorine content of approximately 350 ppm, a total nitrogen content of less than 1000 ppm, and a bromine value of less than 85. The plastic-derived oil contains 43 wt% n-alkanes, 17 wt% isoalkanes, 19 wt% olefins, 10 wt% cycloalkanes, and 11 wt% aromatics. The density of the plastic-derived oil is approximately 750 kg / m³. 3 .

[0100] Air lifting steps

[0101] 150 ml of plastic-derived oil was placed into a 250 ml round-bottom flask. The oil was fed in gaseous form through a feed inlet near the bottom of the flask, with nitrogen supplied at a rate of 1.5 L / min. Stripping was performed at 20 °C and atmospheric pressure. Samples of the plastic-derived oil were collected at regular time intervals during the stripping process. The atomic chloride content of these samples was measured, as shown in Table 1 below.

[0102] Table 1: Nitrogen Extraction

[0103]

[0104] Extraction steps

[0105] After 290 minutes of gas extraction, the product of sample 7, containing 120 ppmw of atomic chlorine, was obtained by the gas extraction step and fed into a 100 ml penicillin flask serving as the extraction vessel. A certain amount of solvent was added according to Table 2, making it 58% vol% of the contents of the extraction vessel.

[0106] The extraction process was carried out at 20°C and atmospheric pressure for 60 minutes. Samples were taken from each extraction experiment. The atomic chlorine content of each sample was determined, as shown in Table 2 below.

[0107] Table 2: Extraction in non-proton or proton solvents

[0108]

Claims

1. A method comprising subjecting a hydrocarbon composition A to: (a) The air-lifting step in the air-lifting container (1); and (b) Liquid-liquid extraction step in extraction vessel (2) The steps (a)-(b) can be performed in any order.

2. The method of claim 1, wherein the liquid-liquid extraction step (b) is carried out using a protic solvent or an aprotic solvent as the extraction medium.

3. The method according to claims 1-2, comprising the following steps: (a) The hydrocarbon composition A is subjected to a stripping step in a stripping container (1), wherein the composition A is contacted with a nitrogen-containing stream B to obtain composition C; (b) Composition C is subjected to a liquid-liquid extraction step in an extraction vessel (2), wherein an aprotic solvent or a protic solvent is used as the extraction medium to obtain composition E.

4. The method according to any one of claims 1-3, wherein the hydrocarbon composition A is a hydrocarbon-containing oil product obtained by decomposing waste plastics.

5. The method according to any one of claims 1-4, wherein the hydrocarbon composition A contains >200 ppmw and <2000 ppmw, preferably >200 ppmw and <600 ppmw, of atomic chlorine as determined by ASTM UOP 779-08.

6. The method of any one of claims 1-5, wherein, relative to the total weight of hydrocarbon composition A, the hydrocarbon composition A comprises: ≥25.0 wt% and ≤95.0 wt%, preferably ≥25.0 wt% and ≤70.0 wt%, more preferably ≥25.0 wt% and ≤50.0 wt% of n-chain alkanes; and / or ≥5.0 wt% and ≤20.0 wt%, preferably ≥5.0 wt% and ≤15.0 wt%, more preferably ≥7.5 wt% and ≤15.0 wt% of isoparaffins; and / or ≥5.0 wt% and ≤50.0 wt%, preferably ≥10.0 wt% and ≤40.0 wt%, more preferably ≥15.0 wt% and ≤35.0 wt%, even more preferably ≥15.0 wt% and ≤25.0 wt% of olefins; and / or ≥5.0 wt% and ≤20.0 wt%, preferably ≥5.0 wt% and ≤15.0 wt%, more preferably ≥7.5 wt% and ≤15.0 wt% of cycloalkanes; and / or Aromatic hydrocarbons of ≥5.0 wt% and ≤15.0 wt%, preferably ≥5.0 wt% and ≤12.5 wt%, more preferably ≥7.5 wt% and ≤12.5 wt%.

7. The method according to any one of claims 1-6, wherein the air-lift step (a) is performed for at least 100 minutes, preferably at least 150 minutes, even more preferably at least 200 minutes, or for 100-300 minutes, preferably 150-300 minutes, even more preferably 200-300 minutes.

8. The method according to any one of claims 1-7, wherein the stripping step (a) is carried out in a stripping tower, more preferably in a stripping tower equipped with a condenser and a reboiler, wherein the temperature of the condenser can be, for example, 50-160°C, preferably 70-140°C, more preferably 80-120°C, and the temperature of the reboiler can be, for example, 70-190°C, preferably 85-160°C, more preferably 95-140°C.

9. The method according to any one of claims 2-8, wherein the aprotic solvent is selected from dimethyl sulfoxide, dimethylformamide, sulfolane, and n-methyl-2-pyrrolidone, preferably selected from dimethyl sulfoxide and dimethylformamide.

10. The method according to any one of claims 2-9, wherein the amount of the aprotic solvent relative to composition C is such that the aprotic solvent accounts for ≥40.0 vol% and ≤70.0 vol% of the contents of the extraction vessel (2), preferably ≥50.0 vol% and ≤65.0 vol%, more preferably ≥55.0 vol% and ≤60.0 vol%.

11. The method according to any one of claims 1-10, wherein at temperatures > 20°C and < 40°C and pressures > 75 kPa and < 150 kPa, dimethyl sulfoxide or dimethylformamide of the contents of the extraction vessel (2) is used as a solvent, and the extraction step (b) is carried out for a time of > 5.0 minutes and < 15.0 minutes.

12. The method of any one of claims 2-7, wherein the proton solvent is selected from ethylene glycol and water.

13. The method according to any one of claims 2-7, wherein the amount of the proton solvent relative to composition E is such that the proton solvent accounts for ≥40.0 vol% and ≤70.0 vol% of the contents of the second extraction vessel (3), preferably ≥50.0 vol% and ≤65.0 vol%, more preferably ≥55.0 vol% and ≤60.0 vol%.

14. The method according to any one of claims 2-7, wherein ethylene glycol of ≥55.0 vol% and ≤60.0 vol% of the contents of the second extraction vessel (3) is used as a solvent at temperatures >20°C and <40°C and pressures >75 kPa and <150 kPa, and the second extraction step (c) is carried out for a time of >5.0 minutes and <15.0 minutes.

15. The method of any one of claims 1-14, wherein a stream D containing nitrogen and a compound extracted by composition A is obtained by a stripping process (a), wherein the stream D further undergoes an adsorption step (d) in an adsorption vessel (4) to obtain a purified stream G, wherein optionally the stream G is then liquefied in a liquefaction step (e) by feeding it to a condenser (5) to obtain a liquid hydrocarbon stream H, wherein the liquid hydrocarbon stream H is optionally recycled and combined with the hydrocarbon stream A in the feed of the stripping vessel (1).

16. The method according to any one of claims 1-15, wherein prior to any step (a)-(b), the method comprises a pyrolysis step of the waste plastic composition, wherein the waste plastic composition preferably contains > 40.0 wt%, more preferably > 50.0 wt%, even more preferably > 60.0 wt% or > 70.0 wt% of polyolefin, wherein hydrocarbon composition A is obtained as a liquid product of pyrolysis.

17. The method of claim 16, wherein the pyrolysis is a low-severity pyrolysis process carried out at temperatures of ≥250°C and ≤450°C, preferably ≥275°C and ≤425°C, more preferably ≥300°C and ≤400°C; or a high-severity pyrolysis process carried out at temperatures of ≥450°C and ≤750°C, preferably ≥500°C and ≤700°C, more preferably ≥550°C and ≤650°C.

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