Recovery of aliphatic hydrocarbons

Abstract

The present invention relates to a process for recovering aliphatic hydrocarbons from a liquid stream containing aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, comprising: a) liquid-liquid extraction of the liquid stream with an extractant, thereby recovering a portion of the aliphatic hydrocarbons; b1) combining the extract stream, containing the extractant, aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, with a deblending solvent to recover additional aliphatic hydrocarbons; b2) combining the remaining stream with additional deblending solvent to remove the heteroatom-containing organic compounds and optional aromatic hydrocarbons; and c) separating the remaining stream into a deblending solvent stream and an extractant stream. The present invention also relates to a process for recovering aliphatic hydrocarbons from plastics, including the above process, and to a process for steam cracking a hydrocarbon feed containing aliphatic hydrocarbons as recovered by one of the above processes.

Description

[[Technical Field]]

[0001] The present invention relates to a process for recovering aliphatic hydrocarbons from a liquid hydrocarbon feed stream comprising aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, to a process for recovering aliphatic hydrocarbons from plastics comprising the above process, and to a process for steam cracking a hydrocarbon feed comprising aliphatic hydrocarbons as recovered in one of the above processes. [[Background Art]]

[0002] Waste plastics can be converted into high value-added chemicals including olefins and aromatic hydrocarbons, for example via decomposition of plastics by pyrolysis. Pyrolysis of plastics can result in a product stream containing hydrocarbons having a wide boiling range. Hydrocarbons from such a pyrolysis product stream can be further cracked in a steam cracker to produce high-value chemicals including ethylene and propylene, which are monomers that can be used to make new plastics.

[0003] International Publication No. 2018 / 069794 discloses a process for producing olefins and aromatic hydrocarbons from plastics, in which a liquid pyrolysis product stream is separated into a first fraction having a boiling point <300°C and a second fraction having a boiling point ≥300°C. Only the first fraction is supplied to a liquid vapor decomposition unit, while the second fraction is recycled to a pyrolysis unit. In the process shown in Figure 1 of International Publication No. 2018 / 069794, this separation is carried out in a hydrocarbon liquid distillation unit. Separating the liquid pyrolysis product stream into two fractions is cumbersome (e.g., energy-intensive). A further disadvantage is that the heavier portion of the liquid pyrolysis product stream must be sent back to the pyrolysis unit for deeper pyrolysis. This results in yield loss due to gas formation and an increase in the amount of solid by-products (coke), and is ultimately not sent to the vapor decomposition unit. In one embodiment of the process described in the above-mentioned International Publication No. 2018 / 069794 (see Figure 2), a first fraction having a boiling point <300°C is first transported with hydrogen to a hydroprocessing unit to produce a treated hydrocarbon liquid stream, which is then supplied to a liquid vapor cracking unit. Such hydroprocesses are capital-intensive and cumbersome because they require the use of expensive hydrogen (H2).

[0004] Furthermore, US Patent Publication No. 2018 / 0355256 discloses a method for deriving fuel from plastic, which method comprises subjecting an amount of plastic to a pyrolysis process, thereby converting at least a portion of the plastic into crude fuel, and extracting the fuel in a directly usable form by: 1) a first extraction step including countercurrent liquid-liquid extraction using one or more extraction solvents to extract one or more impurities from the crude fuel, and 2) a second extraction step including countercurrent extraction of the contaminated extraction solvent obtained from the first extraction step. In the process shown in Figure 2 of US Patent Publication No. 2018 / 0355256, the crude fuel produced by pyrolysis of plastic (i.e., crude diesel) is first subjected to extraction with N-methyl-2-pyrrolidone (NMP) to extract one or more impurities including sulfur compounds and aromatics from the crude fuel. The contaminated NMP from the first extraction step is then subjected to a second extraction step using water to increase the polarity of the contaminated extraction solvent, thereby separating the impurities. In the final step, the NMP contaminated with water from the second extraction step is distilled using a standard distillation column to produce recycled water and recycled NMP.

[0005] The effluent from the extraction column used in the first extraction step, as disclosed in U.S. Patent Publication No. 2018 / 0355256 (Figure 2), may still contain a certain amount of valuable aliphatic hydrocarbons in addition to heteroatom-containing organic and aromatic contaminants. It is desirable to recover as much aliphatic hydrocarbon as possible and thus separate them from the heteroatom-containing organic and aromatic contaminants. In such recovery, these additional aliphatic hydrocarbons may then be recycled back to the first extraction step or combined directly with the raffinate flow (refined diesel) from the first extraction step to optimize the total recovery of aliphatic hydrocarbons. Such recovered additional aliphatic hydrocarbons may also be fed into a vapor cracking unit instead of being used as fuel, as disclosed in U.S. Patent Publication No. 2018 / 0355256. However, such recovery of additional aliphatic hydrocarbons may be complicated by steps following the first extraction step, resulting in one or more effluents containing aliphatic hydrocarbons, which still contain too much additional heteroatom-containing organic and aromatic pollutants, and therefore these effluents cannot be recirculated or combined as described above.

[0006] In addition, feed to a distillation column, such as that disclosed in U.S. Patent Publication 2018 / 0355256 (Figure 2), may still contain certain amounts of heteroatom-containing organic and aromatic contaminants. The distillation may result in some of these contaminants being separated along with the recirculated water, because the water and such contaminants may form an azeotropic mixture, thereby degrading the quality of the recirculated water flow. If the recirculated water is recirculated to a column used in a second extraction step, the concentration of these contaminants in the recirculated water increases in what is called “accumulation,” in addition to the accumulation of these contaminants in the recirculated NMP used in the first extraction step. This may result in lower efficiency in the first and second extraction steps. U.S. Patent Publication 2018 / 0355256 relates to a method for extracting fuel from plastics. Such accumulation of these contaminants (in the recirculated NMP) could result in the purified oil still containing relatively large amounts of these contaminants, which is of particular concern if such purified oil is supplied to a steam cracker instead of being used as fuel, due to the adverse effects of these contaminants on the yield, selectivity, and reliability of the steam cracker.

[0007] There is an ongoing need to develop improved processes for recovering aliphatic hydrocarbons from liquid streams containing aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, the liquid streams of which may result from the decomposition of waste plastics in certain mixed waste plastics, particularly before feeding such recovered aliphatic hydrocarbons into a vapor cracking unit. An object of the present invention is to provide such a process for recovering aliphatic hydrocarbons from such liquid streams, which is technically advantageous, efficient and affordable, and in particular, does not have one or more of the above-mentioned drawbacks, as discussed above in relation to International Publication No. 2018 / 069794 and U.S. Patent Publication No. 2018 / 0355256. Such a technically advantageous process would preferably result in relatively low energy demand and / or relatively low capital expenditure. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2018 / 069794 [Patent Document 2] U.S. Patent Application Publication No. 2018 / 0355256 [Overview of the Initiative]

[0009] Surprisingly, such a process involves a) liquid-liquid extraction of a liquid stream containing aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons with an extraction solvent a) containing one or more heteroatoms, thereby recovering a portion of the aliphatic hydrocarbons; and b) mixing the stream obtained from step a) containing the extraction solvent a), aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons with a demixing solvent b) to recover additional aliphatic hydrocarbons from the stream (demixing solvent b) containing one or more heteroatoms, and extraction in heptane. The inventors have found that the following can be achieved by mixing the stream obtained from step b1), which has miscibility in heptane lower than that of solvent a), extraction solvent a), demixing solvent b), heteroatom-containing organic compound, and optionally aromatic hydrocarbons, with an additional demixing solvent b) to remove the heteroatom-containing organic compound and optionally aromatic hydrocarbons, and by separating at least a portion of the stream obtained from step b2), which contains extraction solvent a) and demixing solvent b), into a stream containing demixing solvent b) and a stream containing extraction solvent a).

[0010] Accordingly, the present invention relates to a process for recovering aliphatic hydrocarbons from a liquid hydrocarbon feed stream containing aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, the process being: a) A step of bringing at least a portion of the liquid hydrocarbon feed stream into contact with an extraction solvent a) containing one or more heteroatoms, and subjecting the liquid hydrocarbon feed stream to liquid-liquid extraction with the extraction solvent a) to obtain a first stream containing aliphatic hydrocarbons and a second stream containing the extraction solvent a), aliphatic hydrocarbons, a heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. b1) Mix at least a portion of the second stream obtained from step a) with a demixing solvent b) which contains one or more heteroatoms and has lower miscibility in heptane than that of the extraction solvent a) in heptane, and separate the resulting mixture into a first stream containing aliphatic hydrocarbons and optionally aromatic hydrocarbons, and a second stream containing the extraction solvent a), demixing solvent b), heteroatom-containing organic compound, and optionally aromatic hydrocarbons. b2) A step of mixing at least a portion of the second stream obtained from step b1) with demixing solvent b), and separating the resulting mixture into a first stream containing heteroatom-containing organic compounds and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a) and demixing solvent b), (Steps b1) and b2) are substeps of step b) which include two or more substeps. c) Separating at least a portion of the second flow obtained from step b2) into a first flow containing demixing solvent b) and a second flow containing extraction solvent a), d) a step of recirculating at least a portion of the extraction solvent a) from the second stream obtained from step c) back to step a), and e) optionally a step of recirculating at least a portion of the demixing solvent b) from the first stream obtained from step c) back to one or more of the substeps of step b).

[0011] Advantageously, in this invention, hydrogenation (treatment with H2) is not required for the liquid-liquid extraction in step a). Furthermore, advantageously, liquid hydrocarbon streams with a wide boiling point range, such as plastic pyrolysis oil, can be processed in this process with relatively low yield loss and feed degradation. This suggests that by applying this invention, the cost of supplying hydrocarbons to the vapor cracking unit can be significantly reduced.

[0012] Furthermore, in step b) of the process of the present invention, the demixing solvent b) is not added in its entirety in a single step, but is mixed in a stepwise manner (stepwise or incrementally) with the extraction stream obtained from step a), which still contains a certain amount of valuable aliphatic hydrocarbons, so that in the first substep b1), the stream containing aliphatic hydrocarbons and optionally aromatic hydrocarbons (the first stream) is advantageously recovered, while the remaining stream (the second stream) containing extraction solvent a), demixing solvent b), heteroatom-containing organic compound, and optionally aromatic hydrocarbons is then mixed with another portion of demixing solvent b) in a further substep b2), thereby advantageously resulting in more efficient removal of heteroatom-containing organic compound and optionally aromatic hydrocarbons (in the first stream), leaving the stream containing extraction solvent a) and demixing solvent b) (the second stream), which is then separated from each other in step c). Therefore, in each substep b1), b2), and any further substep in step b), the composition of the stream (first stream) containing the compound to be separated, recovered, or removed (i.e., separated) from the stream (second stream) containing the extraction solvent a) and the demixing solvent b) will differ, as will be further described below. This is advantageous as it allows for the fractional separation of the component extracted in step a) into a number of different fractions, the number of which depends on the number of substeps in step b), and each of the fractions may have different values ​​and end uses.

[0013] Furthermore, in the present invention, the overall efficiency of separation step b) including substeps b1) and b2) is increased, which is advantageous because heteroatom-containing organic compounds and any aromatic hydrocarbons may ultimately be substantially not distributed, or their amounts reduced, into the stream containing the extraction solvent a) and demixing solvent b) obtained from the entire step b) of the process. The heteroatom-containing organic compounds and aromatic compounds may include the component with the highest polarity among all heteroatom-containing organic compounds and aromatic compounds extracted in step a) of the process. Therefore, advantageously, the entire step b) of the process of the present invention can deliver a relatively pure demixing solvent b) recirculation stream and a relatively pure extraction solvent a) recirculation stream in step c) of the process that are substantially free of, or contain reduced amounts of, heteroatom-containing organic compounds and aromatic hydrocarbons originating from the liquid hydrocarbon feed stream. Next, such a pure demixed solvent b) stream can be advantageously recycled and used to extract the extraction solvent a) in either step a) itself or in another additional step, thereby preventing the extraction solvent a) from entering the final hydrocarbon raffinate stream without contaminating such raffinate stream with heteroatom-containing organic compounds and aromatic hydrocarbons. With respect to the latter use of demixed solvent b) during recycling, the solvent is also hereafter referred to as washing solvent c). Similarly, such a pure extraction solvent a) stream from step c) can then advantageously be recycled back to step a) and used to extract further heteroatom-containing organic compounds and optionally aromatic hydrocarbons from a fresh feed.

[0014] Therefore, advantageously, the accumulation of heteroatom-containing organic compounds and any aromatic hydrocarbons in the recirculated flow in this process can be prevented or reduced as a result of the entire separation step b), which includes substeps b1) and b2), with the stepwise addition of demixed solvent b). Thus, there is no need to apply other cumbersome methods to mitigate the accumulation of these contaminants, or the need for such methods is substantially reduced. For example, there is no need to bleed a portion of the recirculated flow before recirculation, or the need for such methods is substantially reduced, so that (i) such a bleed flow is discarded, resulting in a loss of extraction solvent a), or (ii) the extraction solvent a) may be recovered from such a bleed flow, for example, by distillation, but that is cumbersome.

[0015] Furthermore, the present invention relates to a process for recovering aliphatic hydrocarbons from plastics, wherein at least a portion of the plastic contains a heteroatom-containing organic compound, and the process is (I) A step of decomposing the plastic and recovering hydrocarbon products including aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, (II) The step of subjecting a liquid hydrocarbon feed stream containing at least a portion of the hydrocarbon product obtained in step (I) to the above process for recovering aliphatic hydrocarbons from the liquid hydrocarbon feed stream.

[0016] Furthermore, the present invention relates to a process for vapor decomposition of a hydrocarbon feedstock, wherein the hydrocarbon feedstock comprises aliphatic hydrocarbons recovered in one of the above processes for the recovery of aliphatic hydrocarbons. [Brief explanation of the drawing]

[0017] [Figure 1] This document illustrates one embodiment of a process for recovering aliphatic hydrocarbons according to the present invention. [Figure 2] Another embodiment of the above process is shown. [Figure 3] This includes results from the experiments described in Example 2 below. [Figure 4]This includes results from the experiments described in Example 2 below. [Figure 5] This includes results from the experiments described in Example 2 below. [Modes for carrying out the invention]

[0018] Each of the processes of the present invention comprises a plurality of steps. In addition, the process may include one or more intermediate steps between consecutive steps. Furthermore, the process may include one or more additional steps before the first step and / or after the last step. For example, if the process comprises steps a), b), and c), the process may include one or more intermediate steps between steps a) and b) and between steps b) and c). Furthermore, the process may include one or more additional steps before step a) and / or after step c).

[0019] Within this specification, phrases such as “step y) includes providing at least a portion of the flow obtained from step x) to a process” mean “step y) includes providing some or all of the flow obtained from step x) to a process,” or similarly, “step y) includes providing part or all of the flow obtained from step x) to a process.” For example, the flow obtained from step x) may be divided into one or more parts, and at least one of these parts may be provided to step y). Furthermore, for example, the flow obtained from step x) may be provided to an intermediate step between step x) and step y) to obtain a further flow, and at least a portion of that flow may be provided to step y).

[0020] The processes of the present invention, as well as the flows and compositions used in such processes, are described using the terms “comprising,” “containing,” or “including” each of the one or more described steps and components, but they may also “essentially consist of” or “consist of” each of the one or more described steps and components.

[0021] In the context of the present invention, if the flow contains two or more components, these components should be selected in an amount not exceeding 100% of the total.

[0022] Furthermore, if upper and lower limits are cited for a property, the range of values ​​defined by a combination of either the upper limit or the lower limit is also included.

[0023] Within this specification, “substantially none” with respect to the amount of a particular component in a flow means an amount of the component in question that is at most 1,000, preferably at most 500, more preferably at most 100, more preferably at most 50, more preferably at most 30, more preferably at most 20, and most preferably at most 10 ppmw (parts per million by weight) based on the volume (i.e., weight) of the flow.

[0024] In this specification, “top flow” or “bottom flow” from a column refers to the flow exiting the column at a position 0% to 30%, more preferably 0% to 20%, or even more preferably 0% to 10%, based on the total length of the column, from the top or bottom of the column, respectively.

[0025] Unless otherwise specified, when a boiling point is referenced herein, it means the boiling point at a pressure of 760 mmHg (101.3 kPa).

[0026] Liquid hydrocarbon feedstock flow In the present invention, the liquid hydrocarbon supply stream includes aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons.

[0027] Preferably, the liquid hydrocarbon feed stream contains both aliphatic hydrocarbons having a boiling point of 30 to 300°C and aliphatic hydrocarbons having a boiling point greater than 300 to 600°C in a weight ratio of 99:1 to 1:99. The amount of aliphatic hydrocarbons having a boiling point of 30 to 300°C may be a maximum of 99% by weight, a maximum of 80% by weight, a maximum of 60% by weight, a maximum of 40% by weight, a maximum of 30% by weight, a maximum of 20% by weight, or a maximum of 10% by weight, based on the total amount of aliphatic hydrocarbons having a boiling point of 30 to 600°C. Furthermore, the amount of aliphatic hydrocarbons having a boiling point of 30 to 300°C may be at least 1% by weight, at least 5% by weight, at least 10% by weight, at least 20% by weight, or at least 30% by weight, based on the total amount of aliphatic hydrocarbons having a boiling point of 30 to 600°C.

[0028] Therefore, advantageously, the liquid hydrocarbon feedstock stream can contain varying amounts of aliphatic hydrocarbons within a wide boiling point range of 30 to 600°C. Thus, similar to the boiling point, the carbon number of the aliphatic hydrocarbons in the liquid hydrocarbon feedstock stream can also vary over a wide range, for example, between 5 and 50 carbon atoms. The carbon number of the aliphatic hydrocarbons in the liquid hydrocarbon feedstock stream can be at least 4, or at least 5, or at least 6, and at most 50, or at most 40, or at most 30, or at most 20.

[0029] The amount of aliphatic hydrocarbons in the liquid hydrocarbon feed stream may be at least 30% by weight, or at least 50% by weight, or at least 80% by weight, or at least 90% by weight, or at least 95% by weight, or at least 99% by weight, and may be less than 100% by weight, or at most 99% by weight, or at most 90% by weight, or at most 80% by weight, or at most 70% by weight. The aliphatic hydrocarbons may be cyclic, linear, or branched.

[0030] Aliphatic hydrocarbons in the liquid hydrocarbon feedstock stream may include non-olefinic (paraffinic) and olefinic aliphatic compounds. The amount of paraffinic aliphatic compounds in the liquid hydrocarbon feedstock stream may be at least 20% by weight, at least 40% by weight, at least 60% by weight, or at least 80% by weight, based on the total weight of the liquid hydrocarbon feedstock stream, and may be less than 100% by weight, or at most 99% by weight, or at most 80% by weight, or at most 60% by weight. Furthermore, the amount of olefinic aliphatic compounds in the liquid hydrocarbon feedstock stream may be less than 100% by weight, or at least 20% by weight, at least 40% by weight, at least 60% by weight, or at least 80% by weight, based on the total weight of the liquid hydrocarbon feedstock stream, and may be at most 99% by weight, or at most 80% by weight, or at most 60% by weight.

[0031] Furthermore, the olefinic compounds may include aliphatic compounds having one carbon-carbon double bond (monoolefins) and / or aliphatic compounds having two or more carbon-carbon double bonds, the latter of which may be conjugated or unconjugated. That is, the two or more carbon-carbon double bonds may be conjugated or unconjugated. The aliphatic compounds having two or more carbon-carbon double bonds may include compounds having double bonds at the alpha and omega positions. The amount of monoolefin in the liquid hydrocarbon feedstock stream may be at least 20% by weight, at least 40% by weight, at least 60% by weight, or at least 80% by weight, based on the total weight of the liquid hydrocarbon feedstock stream, and may be less than 100% by weight or at most 99% by weight, at most 80% by weight, or at most 60% by weight. Furthermore, the amount of conjugated aliphatic compounds having two or more carbon-carbon double bonds in the liquid hydrocarbon feedstock stream may be greater than 0% by weight, or at least 10% by weight, or at least 20% by weight, or at least 40% by weight, or at least 60% by weight, and may be up to 80% by weight, or up to 60% by weight, or up to 40% by weight, based on the total weight of the liquid hydrocarbon feedstock stream.

[0032] In this specification, an aliphatic hydrocarbon containing one or more heteroatoms is referred to as a "heteroatom-containing organic compound," as further described below. Unless otherwise explicitly or contextually indicated, the term "aliphatic hydrocarbon" in this specification does not include heteroatom-containing aliphatic hydrocarbons. Furthermore, unless otherwise explicitly or contextually indicated, the term "aliphatic hydrocarbon" in this specification does not include conjugated aliphatic compounds having two or more carbon-carbon double bonds.

[0033] In addition to the aliphatic hydrocarbons mentioned above, the liquid hydrocarbon feedstock stream also contains heteroatom-containing organic compounds and optionally aromatic hydrocarbons.

[0034] The amount of aromatic hydrocarbons in the liquid hydrocarbon feed stream may be 0% by weight, greater than 0% by weight, or at least 5% by weight, at least 10% by weight, at least 15% by weight, at least 20% by weight, at least 25% by weight, or at least 30% by weight, and may be up to 50% by weight, at most 40% by weight, at most 30% by weight, or at most 20% by weight. Aromatic hydrocarbons may include monocyclic and / or polycyclic aromatic hydrocarbons. An example of a monocyclic aromatic hydrocarbon is styrene. Polycyclic aromatic hydrocarbons may include non-condensed and / or condensed polycyclic aromatic hydrocarbons. An example of a non-condensed polycyclic aromatic hydrocarbon is oligostyrene. Styrene and oligostyrene may be derived from polystyrene. Examples of condensed polycyclic aromatic hydrocarbons are naphthalene and anthracene, as well as alkylnaphthalene and alkylanthracene. One or more aromatic rings in an aromatic hydrocarbon may be substituted with one or more hydrocarbyl groups, including alkyl groups (saturated) and alkylene groups (unsaturated).

[0035] In this specification, aromatic hydrocarbons containing one or more heteroatoms are referred to as “heteroatom-containing organic compounds,” as further described below. Unless otherwise explicitly or by context, the term “aromatic hydrocarbons” in this specification does not include heteroatom-containing aromatic hydrocarbons.

[0036] Furthermore, the amount of heteroatom-containing organic compounds in the liquid hydrocarbon feedstock stream is greater than 0% by weight, and can be at least 0.5% by weight, or at least 1% by weight, or at least 3% by weight, or at least 5% by weight, or at least 10% by weight, or at least 15% by weight, or at least 20% by weight, and can be up to 30% by weight, or up to 20% by weight, or up to 10% by weight, or up to 5% by weight.

[0037] The heteroatom-containing organic compound in the liquid hydrocarbon feedstock stream contains one or more heteroatoms, preferably oxygen, nitrogen, sulfur, and / or halogens (e.g., chlorine). The heteroatom-containing organic compound may also contain one or more of the following: amines, imines, nitriles, alcohols, ethers, ketones, aldehydes, esters, acids, amides, carbamates (sometimes called urethanes), and ureas.

[0038] Furthermore, the above heteroatom-containing organic compounds may be aliphatic or aromatic. An example of an aliphatic heteroatom-containing organic compound is oligomeric polyvinyl chloride (PVC). Oligomer PVC may be derived from polyvinyl chloride. Aromatic heteroatom-containing organic compounds may include monocyclic and / or polycyclic aromatic heteroatom-containing organic compounds. Examples of monocyclic aromatic heteroatom-containing organic compounds are terephthalic acid and benzoic acid. An example of a polycyclic aromatic heteroatom-containing organic compound is oligomeric polyethylene terephthalate (PET). Terephthalic acid, benzoic acid, and oligomeric PET may be derived from polyethylene terephthalate. Examples of nitrogen-containing organic compounds are compounds derived from polyamides, including polyurethane and nylon.

[0039] Unless otherwise explicitly indicated or contextually indicated, the term “heteroatom-containing organic compound” in this specification means a heteroatom-containing organic compound in or derived from a liquid hydrocarbon feedstock stream. Furthermore, unless otherwise explicitly indicated or contextually indicated, the term “heteroatom-containing organic compound” in this specification does not include extraction solvents, demixing solvents and / or washing solvents as defined herein.

[0040] Additionally, the liquid hydrocarbon feedstock stream may contain salts. These salts may include organic and / or inorganic salts. The salts may contain ammonium, alkali metals, alkaline earth metals, or transition metals as cations, and carboxylates, sulfates, phosphates, or halides as anions.

[0041] Preferably, at least a portion of the components in the liquid hydrocarbon feedstock stream, which include aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, are synthetic compounds and not natural compounds, such as those found in petroleum. For example, such synthetic compounds include compounds derived from the thermal decomposition of plastics synthesized from biomass, such as polyethylene synthesized by the dehydration of ethanol from bioethanol and the subsequent polymerization of the ethylene thus formed.

[0042] Furthermore, since heteroatom-containing organic compounds are easily removed in this process, the raw materials supplied to this process can advantageously tolerate relatively large amounts of such heteroatom-containing organic compounds. Therefore, waste plastics that can be pyrolyzed to produce raw materials for this process may include heteroatom-containing plastics such as polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polyurethane (PU). Specifically, mixed waste plastics containing relatively large amounts of such heteroatom-containing plastics, in addition to heteroatom-free plastics such as polyethylene (PE) and polypropylene (PP), can be pyrolyzed.

[0043] Step a) Extraction with extraction solvent a) In step a) of this process, at least a portion of a liquid hydrocarbon feed stream containing aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons is brought into contact with an extraction solvent a) containing one or more heteroatoms, and the liquid hydrocarbon feed stream is subjected to liquid-liquid extraction with the extraction solvent a) to obtain a first stream containing aliphatic hydrocarbons and a second stream containing the extraction solvent a), aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons.

[0044] In step a) of this process, a liquid hydrocarbon feedstock stream may be supplied to a first column (first extraction column). Furthermore, a first solvent stream containing the extraction solvent a) may be supplied to the first column at a higher position than the position where the liquid hydrocarbon feedstock stream is supplied, thereby enabling counterflow liquid-liquid extraction and resulting in a top flow (the "first flow" above) from the first column containing aliphatic hydrocarbons and a bottom flow (the "second flow" above) from the first column containing the extraction solvent a), aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons.

[0045] In step a), the weight ratio of the extraction solvent a) to the liquid hydrocarbon feedstock stream may be at least 0.05:1, at least 0.2:1, at least 0.5:1, at least 1:1, at least 2:1, or at least 3:1, and may be at most 5:1, at most 3:1, at most 2:1, or at most 1:1. Furthermore, the temperature in step a) may be at least 0°C, at least 20°C, at least 30°C, at least 40°C, or at least 50°C, and may be at most 200°C, at most 150°C, at most 100°C, at most 70°C, at most 60°C, at most 50°C, or at most 40°C. The pressure in step a) may be at least 100 mbara, at least 500 mbara, at least 1 bara, at least 1.5 bara, or at least 2 bara, and may be at most 50 bara, at most 30 bara, at most 20 bara, at most 15 bara, at most 10 bara, at most 5 bara, at most 3 bara, at most 2 bara, or at most 1.5 bara. The temperature and pressure in step a) are preferably such that both the hydrocarbon from the feed material stream and the extraction solvent a) are in a liquid state.

[0046] In step a), a portion of the aliphatic hydrocarbons, including heteroatom-containing organic compounds and optionally aromatic hydrocarbons, are recovered by liquid-liquid extraction with extraction solvent a). Preferably, the recovered aliphatic hydrocarbons include aliphatic hydrocarbons having a boiling point of 30 to 300°C and aliphatic hydrocarbons having a boiling point above 300 to 600°C in a weight ratio of 99:1 to 1:99. With respect to the aliphatic hydrocarbons in the liquid hydrocarbon feed stream, the above description of the weight ratio of aliphatic hydrocarbons having a boiling point of 30 to 300°C and aliphatic hydrocarbons having a boiling point above 300 to 600°C also applies to the recovered aliphatic hydrocarbons.

[0047] In step a), the liquid-liquid extraction yields a first stream containing aliphatic hydrocarbons and a second stream containing the extraction solvent a), aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. For the purposes of this specification, the former stream (first stream) containing the recovered aliphatic hydrocarbons may be referred to as the "raffinate stream," and the latter stream (second stream) may be referred to as the "extract stream." Such a raffinate stream has reduced content of aromatic hydrocarbons, conjugated aliphatic compounds having two or more carbon-carbon double bonds, and heteroatom-containing organic compounds. Such a raffinate stream contains no aromatic hydrocarbons, or contains them in amounts of up to 10% by weight, up to 5% by weight, or up to 1% by weight, or substantially no aromatic hydrocarbons. Furthermore, such a raffinate stream contains no conjugated aliphatic compounds having two or more carbon-carbon double bonds, or contains them in amounts of up to 15% by weight, up to 10% by weight, up to 5% by weight, or up to 1% by weight, or substantially no conjugated aliphatic compounds. Furthermore, such raffinate streams do not contain heteroatom-containing organic compounds, or contain them at a maximum of 1% by weight, or are substantially free of them.

[0048] The extraction solvent a) used in step a) of this process may be supplied to the first column as a first solvent stream in step a), but preferably has a density at least 3%, at least 5%, at least 8%, at least 10%, at least 15%, or at least 20% higher than the density of the liquid hydrocarbon feedstock stream. Furthermore, the density may be up to 50%, at least 40%, at least 35%, or at least 30% higher than the density of the liquid hydrocarbon feedstock stream.

[0049] Furthermore, the extraction solvent a) used in step a) contains one or more heteroatoms, which may be oxygen, nitrogen and / or sulfur. Furthermore, the extraction solvent a) is preferably thermally stable at a temperature of 200°C. Furthermore, the extraction solvent a) may have a boiling point of at least 50°C, or at least 80°C, or at least 100°C, or at least 120°C, and at most 300°C, or at most 200°C, or at most 150°C. Furthermore, the extraction solvent a) preferably has no or relatively low miscibility in heptane. Preferably, based on the weight of heptane, the extraction solvent a) has miscibility in heptane such that at most 30% by weight, or at most 20% by weight, or at most 10% by weight, or at most 3% by weight, or at most 1% by weight of the extraction solvent a) is miscible in heptane. The miscibility of a specific compound in another compound such as heptane can be determined by any conventional method known to those skilled in the art, including ASTM method D1476. In the present specification, when referring to the miscibility of one compound in another compound, this means miscibility at 25°C.

[0050] Furthermore, with respect to heptane when determined at 25°C, the extraction solvent a) in step a) has a Hansen solubility parameter distance R of at least 3 MPa 1 / 2 , preferably at least 5 MPa 1 / 2 , more preferably at least 10 MPa 1 / 2 , preferably at least 15 MPa 1 / 2 a、ヘプタン . Furthermore, the R for extraction solvent a) a、ヘプタン is less than 45 MPa 1 / 2 or at most 40 MPa 1 / 2 , preferably at most 35 MPa 1 / 2 , more preferably at most 30 MPa 1 / 2 , more preferably at most 25 MPa 1 / 2 . For example, the R for N-methylpyrrolidone (NMP) a、ヘプタン is 15 MPa 1 / 2 .

[0051] ​Furthermore, the extraction solvent a) is determined at 25°C, and the Hansen solubility parameter distance R for toluene is also determined. a、トルエン Compared to that, at least 1.5 MPa 1 / 2 Preferably at least 2 MPa 1 / 2 Hansen solubility parameter distance R for heptane a、ヘプタン The difference (i.e., R a、ヘプタン -R a、トルエン ) may have. Furthermore, R for the extraction solvent a) a、トルエン R compared a、ヘプタン The difference in this regard is a maximum of 4.5 MPa. 1 / 2 Preferably up to 4 MPa 1 / 2 That's fine.

[0052] Hansen solubility parameters (HSPs) can be used as a means to predict the relative solubility of one component compared to another. More specifically, each component is characterized by three Hansen parameters, each generally expressed in MPa. 0.5 It is expressed as δ d This indicates the energy from the intermolecular dispersion forces, δ p This indicates the energy from the dipolar intermolecular forces between molecules, δ h This indicates the energy from intermolecular hydrogen bonds. The affinity between compounds is expressed by the Hansen solubility parameter (HSP) distance R, defined by equation (1). a These can be described using multidimensional vectors that quantify the atomic and intermolecular interactions of these solvents: (R a ) 2 =4(δ d2 -δ d1 ) 2 +( δ p2 -δ p1 ) 2 +( δ h2 -δ h1 ) 2 (1) During the ceremony, R a = Distance in HSP space between compound 1 and compound 2 (MPa) 0.5 ) δd1 , δ p1 , δ h1 =Hansen (or equivalent) parameter (MPa) of compound 1 0.5 ) δ d2 , δ p2 , δ h2 =Hansen (or equivalent) parameter (MPa) of compound 2 0.5 )

[0053] Therefore, the R for a given solvent calculated with respect to the recovered compound (i.e., the recovered compound is compound 1 and the solvent is compound 2, or vice versa) a The smaller the value of this factor, the higher the affinity of the solvent for the recovered compound.

[0054] Hansen solubility parameters for numerous solvents can be found, in particular, in *CRC Handbook of Solubility Parameters and Other Cohesion Parameters, Second Edition* by Allan FM Barton, CRC press 1991; and *Hansen Solubility Parameters: A User's Handbook* by Charles M. Hansen, CRC press 2007.

[0055] Specifically, the extraction solvent a) used in step a) of this process is ammonia, or preferably diols and triols (including any isomers of monoethylene glycol (MEG), monopropylene glycol (MPG), butanediol, and glycerol); glycol ethers (including diethylene glycol, triethylene glycol, and tetraethylene glycol, including oligoethylene glycol), and their monoalkyl ethers (including diethylene glycol ethyl ether); amides (including N-alkylpyrrolidone, where the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, including N-methylpyrrolidone (NMP)); formamides, and di and monoalkylformamides; and acetamides (where the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, including dimethylformamide (dimethyl (Containing formamide, DMF), methylformamide and dimethylacetamide); dialkyl sulfoxide (the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, and includes dimethyl sulfoxide (DMSO)); sulfone (containing sulfolane); N-formylmorpholine (N-formyl It may contain one or more organic solvents selected from the group consisting of morpholine, NFM; furan ring-containing components and their derivatives (including furfural, 2-methylfuran, furfuryl alcohol, and tetrahydrofurfuryl alcohol); hydroxyesters (including methyl lactate and ethyl lactate, and lactates); trialkyl phosphates (including triethyl phosphate); phenol compounds (including phenol and guaiacol); benzyl alcohol compounds (including benzyl alcohol); amine compounds (including ethylenediamine, monoethanolamine, diethanolamine, and triethanolamine); nitrile compounds (including acetonitrile and propionitrile); trioxane compounds (including 1,3,5-trioxane); carbonate compounds (including propylene carbonate and glycerol carbonate); and cycloalkanone compounds (including dihydrolevoglucocenone).

[0056] More preferably, the extraction solvent a) comprises one or more of the above-mentioned dialkyl sulfoxides, specifically DMSO; sulfones, specifically sulfolanes; N-alkylpyrrolidones, specifically NMP; and furan ring-containing components, specifically furfural. Even more preferably, the extraction solvent a) comprises one or more of the above-mentioned N-alkylpyrrolidones, specifically NMP, and furan ring-containing components, specifically furfural. Most preferably, the extraction solvent a) comprises NMP.

[0057] Aqueous aqueous solutions of quaternary ammonium salts in specific trioctylmethylammonium chloride or methyltributylammonium chloride may also be used as the extraction solvent a) in step a).

[0058] In addition to the extraction solvent a), a washing solvent such as water may be added to step a). This washing solvent is referred to herein as washing solvent c) and will be further described below. In such a case, step a) results in a first stream preferably containing aliphatic hydrocarbons and a second stream containing washing solvent c), extraction solvent a), aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. Advantageously, the washing solvent c) added in step a) acts as an extraction solvent that extracts the extraction solvent a), thereby allowing the extraction solvent a) to be removed or substantially removed from the first stream obtained from step a) and recovered from the aliphatic hydrocarbons. If washing solvent c) is also added to step a), the weight ratio of extraction solvent a) to washing solvent c) in step a) may be at least 0.5:1, at least 1:1, at least 2:1, or at least 3:1, and may be up to 30:1, at most 25:1, at most 20:1, at most 15:1, at most 10:1, at most 5:1, at most 3:1, or at most 2:1.

[0059] If the washing solvent c) is also added to step a), the second solvent stream containing the washing solvent c) may be supplied to the first column (first extraction column) at a higher position than the position where the first solvent stream containing the extraction solvent a) is supplied, thereby enabling counterflow liquid-liquid extraction and resulting in a top flow (the "first stream") from the first column containing aliphatic hydrocarbons and a bottom flow (the "second stream") from the first column containing the washing solvent c), extraction solvent a), aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. In the above case, the first solvent stream in extraction step a) may contain, in addition to the extraction solvent a), a demixing solvent b), such as water, and / or the optional washing solvent c). The demixing solvent b) will be further described below. The demixing solvent b) and washing solvent c) may originate from one or more recirculated streams after step c) of this process.

[0060] If a washing solvent c) is also added to step a), it is preferable that the flow containing the added washing solvent c) does not contain, or substantially contains, heteroatom-containing organic compounds originating from the liquid hydrocarbon feedstock flow. This preference is particularly applicable when, as described above, the flow is supplied to the first extraction column at a relatively high position and these heteroatom-containing organic compounds could re-contaminate the raffinate (top) flow obtained from step a). Advantageously, in the present invention, if the demixing solvent b) is identical to the washing solvent c), particularly water, at least a portion of the demixing solvent b)-containing flow obtained from step c) (which may not contain, or may substantially not contain, heteroatom-containing organic compounds) can be used as such a washing solvent c) flow for supplying (recirculating) to step a).

[0061] As described above, the second stream obtained from step a) (the stream for the first (extraction) column described above corresponds to the bottom stream from such a column) comprises the extraction solvent a), an aliphatic hydrocarbon, a heteroatom-containing organic compound, and optionally an aromatic hydrocarbon. The stream may additionally include salts and / or conjugated aliphatic compounds having two or more carbon-carbon double bonds if such salts and / or compounds are present in the liquid hydrocarbon feed stream.

[0062] In the present invention, the extraction solvent a) is recovered from the second flow obtained from step a) and is then, advantageously, recycled back to step a) through steps b), c) and d) of the process.

[0063] Step b) - Demixing with demixing solvent b) Throughout step b) of this process, at least a portion of the second stream obtained from step a), which comprises an extraction solvent a), an aliphatic hydrocarbon, a heteroatom-containing organic compound, and optionally an aromatic hydrocarbon, is mixed with a demixing solvent b), which contains one or more heteroatoms and has lower miscibility in heptane than that of the extraction solvent a), and the resulting mixture is separated in at least two substeps, e.g., two to five substeps, preferably two or three substeps, into one stream containing the extraction solvent a) and the demixing solvent b), and another stream containing the compound to be separated from the previous stream. That is, in each of these substeps, there is mixing with the demixing solvent b), followed by separation of the resulting stream, and the separated stream containing the extraction solvent a) and the demixing solvent b) is fed into the next substep, where it is mixed with an additional portion of the demixing solvent b). Rather than adding the entire amount of demixing solvent b) in a single step, by adding demixing solvent b) in several steps in this manner, the relative amount of demixing solvent b) in each separated stream (second stream) containing extraction solvent a) and demixing solvent b) exiting the substep gradually increases, and after each substep, the second stream becomes less hydrophobic. This is advantageous because, at each substep, the composition of the stream (first stream) containing compounds that are separated and recovered or removed (i.e., separated) from the stream (second stream) containing extraction solvent a) and demixing solvent b) is different. Advantageously, the amount of aliphatic hydrocarbons in the first stream obtained from the first substep in step b) is relatively high, which allows for the recovery of such additional aliphatic hydrocarbons, which may be recycled to step a) and / or combined with the raffinate stream obtained from step a), preferably such raffinate stream, before being supplied to the following optional additional step in which the stream comes into contact with washing solvent c).On the other hand, the relative amounts of heteroatom-containing organic compounds and optionally aromatic hydrocarbons in the first stream obtained from the later (downstream) substep in step b) are relatively high, which makes it possible to remove these contaminants from the process without losing a considerable amount of additional aliphatic hydrocarbons already recovered in the preceding substep in step b).

[0064] Accordingly, in step b1) of this process, also referred to herein as substep b1), at least a portion of the second stream obtained from step a) is mixed with demixing solvent b), and the resulting mixture is separated into a first stream containing aliphatic hydrocarbons and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a), demixing solvent b), heteroatom-containing organic compounds, and optionally aromatic hydrocarbons.

[0065] Furthermore, in step b2) of the process, which is therefore also referred to herein as substep b2), at least a portion of the second stream obtained from step b1) is mixed with demixing solvent b), and the resulting mixture is separated into a first stream containing heteroatom-containing organic compounds and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a) and demixing solvent b).

[0066] Furthermore, the demixing solvent b) used in step b) contains one or more heteroatoms, which may be oxygen, nitrogen, and / or sulfur. Furthermore, it is preferable that the demixing solvent b) is miscible in heptane, or has relatively low miscibility, just like the extraction solvent a). Preferably, the demixing solvent b) is miscible in heptane such that, based on the weight of heptane, up to 10% by weight, up to 3% by weight, up to 1% by weight, up to 0.5% by weight, or up to 0.1% by weight of the demixing solvent b) is miscible in heptane. In the present invention, the miscibility of the demixing solvent b) in heptane is lower than that of the extraction solvent a) in heptane. The miscibility of solvents a) and b) in heptane can be determined by any general method known to those skilled in the art, including the ASTM method D1476 described above. Furthermore, preferably, the demixing solvent b) is miscible with the extraction solvent a). This means that up to 50% by weight of demixing solvent b) can be mixed in extraction solvent a) based on the total amount of demixing solvent b) and extraction solvent a).

[0067] Furthermore, the demixing solvent b) in step b) is determined at 25°C to be at least 10 MPa with respect to heptane. 1 / 2 Preferably at least 20 MPa 1 / 2 , more preferably at least 30 MPa 1 / 2 Preferably at least 40 MPa 1 / 2 Hansen solubility parameter distance R a、ヘプタン It may have the following characteristics. Furthermore, the R of the demixed solvent b) a、ヘプタン It can reach a maximum of 55 MPa. 1 / 2 More preferably up to 50 MPa 1 / 2 , more preferably up to 45 MPa 1 / 2 It may also be the case that the R for water a、ヘプタン 45MPa 1 / 2 That is the case.

[0068] As described above, the miscibility of extraction solvent a) and demixing solvent b) in heptane is different. Therefore, solvents a) and b) are not identical. Specifically, demixing solvent b) has a Hansen solubility parameter distance R for heptane determined at 25°C. a、ヘプタン It may have such R for extraction solvent a), which is a、ヘプタン Larger than. Preferably, R for solvents a) and b). a、ヘプタン The difference is at least 1 MPa. 1 / 2 , more preferably at least 5 MPa 1 / 2 , more preferably at least 10 MPa 1 / 2 , more preferably at least 15 MPa 1 / 2 , more preferably at least 20 MPa 1 / 2 , more preferably at least 25 MPa 1 / 2 Furthermore, preferably, R for solvents a) and b). a、ヘプタン The difference in this case is a maximum of 55 MPa. 1 / 2 More preferably up to 50 MPa 1 / 2 , more preferably up to 45 MPa 1 / 2 , more preferably up to 40 MPa 1 / 2 More preferably up to 35 MPa 1 / 2 More preferably up to 30 MPa 1 / 2 That is the case.

[0069] Specifically, the demixing solvent b) used in step b) of this process may contain water and one or more solvents selected from the group consisting of solvents from the group defined above for the extraction solvent a). Preferably, the demixing solvent b) contains water and one or more of the above-mentioned diols and triols, specifically monoethylene glycol (MEG) and glycerol. More preferably, the demixing solvent b) contains water, most preferably consisting of water. The other preferences and embodiments described above for the extraction solvent a) used in step a) also apply to the demixing solvent b), except that the demixing solvent b) is not identical to the extraction solvent a) because it has lower miscibility in heptane, and that the demixing solvent b) may contain water, preferably water.

[0070] In the process of the present invention, step b) includes two or more substeps, including steps b1) and b2), which are substeps of step b). Preferably, the process includes 2 to 10 substeps in step b), more preferably 2 to 5 substeps. The number of substeps in step b) is at least 2, may be at least 3 or at least 4, and may be at most 10, or at most 8 or at most 6.

[0071] For example, if step b) includes two substeps, in the first substep aliphatic hydrocarbons and any aromatic hydrocarbons may be removed via the first stream obtained from step b1), and in the second substep heteroatom-containing organic compounds may be removed via the first stream obtained from step b2).

[0072] Therefore, step b) of this process may include more than two substeps. For example, if step b) includes three substeps, the first substep may eliminate aliphatic hydrocarbons, the second substep may eliminate any aromatic hydrocarbons, and the third substep may eliminate heteroatom-containing organic compounds.

[0073] Furthermore, more specifically, if the process includes more than two substeps in step b), then step b) is: bi) Mix at least a portion of the second stream obtained from step a) with demixing solvent b), and separate the resulting mixture into a first stream containing aliphatic hydrocarbons and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a), demixing solvent b), aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. bii) Mix at least a portion of the second stream obtained from step bi) with demixing solvent b), and separate the resulting mixture into a first stream containing aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a), demixing solvent b), heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. The steps may also include: (b) mixing at least a portion of the second stream obtained from step (b) with demixing solvent (b), and separating the resulting mixture into a first stream containing heteroatom-containing organic compounds and optionally aromatic hydrocarbons, and a second stream containing extraction solvent (a) and demixing solvent (b), and Step c) may include separating at least a portion of the second stream obtained from step biii) into a first stream containing demixing solvent b) and a second stream containing extraction solvent a).

[0074] An additional advantage of the above process, including substeps bi), bii), and biii), is that the first stream obtained from step bii), which contains both (i) aliphatic hydrocarbons and (ii) heteroatom-containing organic compounds and optionally aromatic hydrocarbons, does not need to be discarded, but can still be used as fuel even if the relative amounts of heteroatom-containing organic contaminants and any aromatic contaminants are too high to feed into the steam cracking unit. Substep bi) corresponds to substep b1), while substep biii) corresponds to substep b2).

[0075] Accordingly, in the present invention, the various compositions of the first flows obtained from at least two substeps in step b) can be advantageously varied by increasing or decreasing the number of substeps, but can also be varied by changing the relative amount of demixed solvent b) mixed with the flow obtained from the preceding step in each of these substeps. Such variations result in different partition coefficients in each substep, preferentially leading certain compounds to either a more hydrophobic first flow or a less hydrophobic second flow. The need for such variations may then depend on the desired outlets for each of the first flows (decomposition unit feed, internal recirculation, fuel, potentially valuable products (e.g., solvent) or waste), the composition of the feed to the entire step b), and / or the composition of the liquid hydrocarbon feedstock flows supplied indirectly to step a).

[0076] Furthermore, each of the second flows obtained from the substep in step b) may additionally contain a salt. Any conjugated aliphatic compound having two or more carbon-carbon double bonds, together with heteroatom-containing organic compounds and optionally aromatic hydrocarbons, may lead to the first or second flows obtained from the substep in step b). In general, in the present invention, such conjugated aliphatic compounds can behave similarly to aromatic compounds, and therefore may lead to the same one or more flows as any optional aromatic hydrocarbons.

[0077] In each of the substeps of step b), the demixing solvent b) is added separately from the second stream obtained from step a) or the second stream obtained from a preceding substep of step b), and in addition to any demixing solvent b) that may be present in one of the latter streams, and is mixed with one of the latter streams. In each of the substeps of step b), at least a portion of the first stream obtained from step a) (the first stream containing the recovered aliphatic hydrocarbons and extraction solvent a) is subjected to liquid-liquid extraction with washing solvent c), and at least a portion of the second stream containing washing solvent c) and extraction solvent a) obtained from an optional additional extraction step described below may be added to provide the demixing solvent b) that needs to be added in step b).

[0078] The mixing in each of the substeps of step b) can be carried out in any manner known to those skilled in the art. For example, a mixer may be used upstream of a phase separation apparatus as described below. Furthermore, for example, in-line (or static) mixing may be carried out upstream of such a phase separation apparatus. Moreover, the mixing may be carried out in a column as described below.

[0079] Through such addition of demixing solvent b) and mixing in each of the substeps of step b), distinct phases are formed, comprising a more hydrophobic first phase and a less hydrophobic second phase containing the extraction solvent a) and demixing solvent b), which are separated in each substep into the first and second flows, respectively. Thus, advantageously, apart from the second flow obtained from step a) or the second flow obtained from the preceding substep in step b), the demixing solvent b) added in step b) functions as a so-called “demixing agent” (or “poor solvent”), thereby removing and recovering the more hydrophobic compounds from the extraction solvent a) and recirculating them.

[0080] Phase separation in each of the substeps of step b) can be carried out by any apparatus capable of separating two phases, including a decanter, a flotation device, a coalescer, and a centrifuge, preferably including a decanter. It is preferable that the phase separation in each of the substeps of step b) be carried out in a single step, for example, in a decanter, a flotation device, a coalescer, or a centrifuge. For example, when a decanter is used in step b), a first upper phase containing a more hydrophobic compound and a second lower phase containing an extraction solvent a), a demixing solvent b), and optionally a less hydrophobic compound (i.e., less hydrophobic than the compound in the first phase) can be separated into the first stream and the second stream, respectively.

[0081] Furthermore, each of the substeps in step b) may be carried out in a separate column comprising multiple separation steps. In the latter case, each substep includes mixing at least a portion of the second flow obtained from step a) or at least a portion of the second flow obtained from a preceding substep in step b) with the demixing solvent b) in the column, respectively, and separating the resulting mixture into the first and second flows, preferably obtaining a top flow from the column (the "first flow") and a bottom flow from the column (the "second flow"). Preferably, the flows rich in the demixing solvent b) and other extraction solvent a) are supplied to the column in parallel at the bottom of the column.

[0082] The internal structure within the column contributes to the mixing of the flow rich in the extraction solvent a) and the demixing solvent b). Such internal structures of columns are known in the art. The internal structure of the column may include packing materials such as Raschig rings, Paul rings, Lessing rings, Bialecki rings, and Dixon rings; sieve plates; or, in particular, random structure packing materials as described in Perry's Chemical Engineer's Handbook. Furthermore, the column may be provided with stirring means. For example, a shaft may extend along the column, or a rotor and stator fixed to the column may be provided.

[0083] Furthermore, in the present invention, a single column including multiple separation steps may be used for step b) as a whole, which includes multiple substeps. In such a case, the column that can be used may be the same as the column described above for the case where each of the substeps of step b) is performed in a separate column. When using such a single column, step b) of the process is b1) At least a portion of the second flow obtained from step a) and the demixing solvent b) are supplied to the first section of the column, mixed, the flow is withdrawn from the first section downstream of the position where the demixing solvent b) is supplied to the first section, and the withdrawn flow is separated into a first flow containing aliphatic hydrocarbons and optionally aromatic hydrocarbons, and a second flow containing extraction solvent a), demixing solvent b), heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. b2) may include supplying at least a portion of the second flow obtained from step b1) and the demixing solvent b) to the second section of a column located downstream of the first section, mixing them, withdrawing the flow from the second section at a position downstream of where the demixing solvent b) was supplied to the second section, and separating the withdrawn flow into a first flow containing heteroatom-containing organic compounds and optionally aromatic hydrocarbons, and a second flow containing the extraction solvent a) and the demixing solvent b).

[0084] In the above case where a single column is used for multiple substeps in step b), the second flow obtained from step b2) may be partially or completely supplied to the next section located downstream of the second section of the column, as further described below, or it may be recovered as a second flow containing the extraction solvent a) and the demixing solvent b), at least a portion thereof, supplied to step c).

[0085] Furthermore, in the above case where a single column is used for multiple substeps in step b), the first section of such a column may be located at the top or bottom of the column. Preferably, the demixed solvent b) and the second flow obtained from step a) are supplied in parallel to the first section of the column. In each substep of step b), phase separation may be carried out by any apparatus capable of separating the two phases, including a decanter, a flotation device, a coalescer and a centrifuge, preferably a decanter. Thus, phase separation occurs in such a phase separation apparatus located outside the column. Furthermore, the column may include one or more additional sections located downstream of the second section, in which case additional demixing solvent b) is also supplied separately to each of these additional sections in addition to the second flow obtained from the preceding substep, and these are mixed in such additional sections, and the flow from such additional sections is withdrawn at a position downstream of the position where demixing solvent b) is supplied to that additional section, and the withdrawn flow is separated into a first flow containing the compounds to be separated from demixing solvent b) and extraction solvent a), and a second flow containing extraction solvent a) and demixing solvent b).

[0086] Furthermore, the above description of temperature and pressure in extraction step a) also applies to the above substeps in step b) as a whole. Moreover, in step b) as a whole, the weight ratio of demixing solvent b), i.e., the total demixing solvent b), added in the substep, to extraction solvent a), based on the amount of extraction solvent a) in the second flow obtained from step a), may be at least 0.005:1, at least 0.01:1, at least 0.5:1, at least 1:1, or at least 2:1, and may be up to 10:1, up to 7:1, up to 5:1, up to 4:1, or up to 2:1. Preferably, the total amount of demixing solvent b) added throughout step b) and in all of the substeps of step b) may be 0.1 to 45% by weight, more preferably 1 to 40% by weight, more preferably 5 to 35% by weight, or more preferably 10 to 30% by weight, based on (i) the total amount of demixing solvent b) and (ii) the amount of extraction solvent a) in the second stream obtained from step a).

[0087] Therefore, throughout step b) of this process, additional aliphatic hydrocarbons may be advantageously recovered separately from heteroatom-containing organic compounds and any aromatic hydrocarbons, the latter of which may be advantageously removed from the recycled extraction solvent a), and thus, in later steps, it is not necessary to separate the extraction solvent a) from such removed compounds. Furthermore, advantageously, any aromatic hydrocarbons and conjugated aliphatic compounds having two or more carbon-carbon double bonds removed in step b) may be blended with pygas and processed into fuel or used to produce aromatic compounds. Similarly, heteroatom-containing organic compounds removed in step b) may optionally be converted into fuel after hydrogenation to remove heteroatoms. Furthermore, the compounds removed in step b) may be further separated into various fractions that can be used as solvents.

[0088] Step c) - Separation of extraction solvent a) and demixing solvent b). In step c) of this process, at least a portion of the second stream obtained from the last substep of step b) and containing the extraction solvent a) and the demixing solvent b) is separated into a first stream containing the demixing solvent b) and a second stream containing the extraction solvent a). If any washing solvent c) described below is used in the present invention, this washing solvent c) may be the same as or different from the demixing solvent b), preferably being the same, and such washing solvent c) may reach the second stream obtained from the last substep of step b) and then reach the first stream obtained from step c).

[0089] Therefore, the feed stream to step c) includes at least a portion of the second stream obtained from the last substep of step b). In step c), the demixing solvent b) and the extraction solvent a) can be separated from each other by any known method, preferably by evaporation, for example by distillation. The separation of the latter can be carried out in a distillation column. Advantageously, in distillation, at least a portion of any heteroatom-containing organic compounds and aromatic hydrocarbons in the feed stream to step c) are removed azeotropically with the demixing solvent b), particularly water.

[0090] Therefore, step c) preferably includes separating at least a portion of the second stream obtained from the last substep of step b) into a top stream containing demixed solvent b) and a bottom stream containing extraction solvent a) by distillation. If the feed stream to step c) additionally contains heteroatom-containing organic compounds and optionally aromatic hydrocarbons, the top stream additionally contains such compounds.

[0091] Furthermore, if the supply flow to step c) contains additional salts, the second flow obtained from step c) shall also contain such additional salts. If the supply flow to step c) or the second flow obtained from step c) contains any solid salts, they may be removed therefrom by any method, including filtration.

[0092] In the present invention, the amount of demixed solvent b) in the feed stream to step c) may be at least 10% by weight or at least 20% by weight, and may be up to 70% by weight, up to 50% by weight, or up to 40% by weight. The second stream obtained from step c) may still contain demixed solvent b) in an amount of, for example, up to 10% by weight, up to 5% by weight, up to 3% by weight, or up to 1% by weight. Advantageously, if the amount of demixed solvent b) in the second stream is relatively low, for example up to 5% by weight, such demixed solvent b) does not need to be removed before the extraction solvent a) from the same stream is recycled to step a) of this process.

[0093] As described above, if the feed stream to the distillation step as step c) in this process contains, in addition to the extraction solvent a) and the demixing solvent b), a heteroatom-containing organic compound and optionally aromatic hydrocarbons, then the top stream obtained from the distillation step contains the demixing solvent b), the heteroatom-containing organic compound, and optionally aromatic hydrocarbons. Advantageously, in distillation, at least a portion of the heteroatom-containing organic compound and aromatic hydrocarbons are removed azeotropically with the demixing solvent b), particularly water. In the latter case, the top stream can be separated into two phases, one phase containing the demixing solvent b) and the other phase containing the heteroatom-containing organic compound and optionally aromatic hydrocarbons. Such phase separation can be carried out by any apparatus capable of separating the two phases, such as a decanter, flotation device, coalescer and centrifuge, preferably including a decanter. Advantageously, the demixed solvent b) from such separated phase, including the demixed solvent b), may be recycled as further described below, while the other phase may be bled out of the process, thereby reducing the risk of any accumulation of heteroatom-containing organic compounds and aromatic hydrocarbons in the process.

[0094] Recirculation step In step d) of this process, at least a portion of the extraction solvent a) from the second flow obtained in step c) is recycled back to step a).

[0095] The second stream obtained from step c) may additionally contain aromatic hydrocarbons and / or heteroatom-containing organic compounds. If the stream containing the extraction solvent a) to be recycled to step a) contains a relatively large amount of such compounds, an additional demixing solvent b) may be added to step b) to prevent any accumulation of these contaminants in such recycled stream to step a). Furthermore, these contaminants may be removed by bleeding a portion of the stream containing the extraction solvent a) to be recycled to step a) before the extraction solvent a) is recycled to step a), and such a bleed stream may be discarded, or the extraction solvent a) may be recovered from such a bleed stream, for example, by distillation.

[0096] Furthermore, in an optional step e) of this process, at least a portion of the demixed solvent b) from the first stream obtained from step c) is recycled to one or more of the substeps of step b).

[0097] The latter recirculation of step b) to one or more substeps in step e) is preferred when the first stream obtained from step c) still contains a relatively large amount of heteroatom-containing organic compounds and / or aromatic hydrocarbons derived from the liquid hydrocarbon feed stream. However, if such a stream does not contain, substantially does not contain, or contains relatively small amounts of heteroatom-containing organic compounds and / or aromatic hydrocarbons (which is advantageously made possible by the entire separation step b) comprising at least two substeps), it is preferable to recirculate at least a portion of the demixing solvent b) from such a stream to step a) if a washing solvent c) such as water is added to step a) as described above, or if such washing solvent c) is added to an optional additional extraction step below to which it is added.

[0098] Separation of extraction solvent a) from the raffinate stream If the stream (raffinate stream) containing the recovered aliphatic hydrocarbons obtained from the liquid-liquid extraction with extraction solvent a) in step a) contains additional extraction solvent a), it is preferable that the extraction solvent a) is separated from that stream, which is the first stream obtained from step a), and optionally recycled back into step a). In this way, the recovered aliphatic hydrocarbons are advantageously separated from any extraction solvent a) in the raffinate stream, and the separated extraction solvent a) can advantageously be recycled back into step a).

[0099] The extraction solvent a) can be separated from the stream obtained from the first stream (which contains aliphatic hydrocarbons and extraction solvent a)) obtained from step a) by any method including distillation, extraction, absorption, and membrane separation.

[0100] Specifically, in the above case where the first stream obtained from step a) contains an aliphatic hydrocarbon and an extraction solvent a), in an additional step, at least a portion of the first stream is brought into contact with a washing solvent c) and subjected to liquid-liquid extraction with the washing solvent c) to obtain a first stream containing an aliphatic hydrocarbon and a second stream containing the washing solvent c) and an extraction solvent a).

[0101] In the present invention, an optional washing solvent c) that can be used in the additional extraction step described above, or that can be added separately to step a), or that can be added together with the extraction solvent a) in the flow to step a), may be the same as or different from the demixing solvent b), and is preferably the same. The above preferences and embodiments regarding the demixing solvent b) also apply to the optional washing solvent c). Preferably, the washing solvent c) contains water, and more preferably consists of water. Furthermore, more preferably, both the demixing solvent b) and the washing solvent c) contain water, and more preferably consist of water.

[0102] In the additional steps described above, the first flow obtained from step a) and containing aliphatic hydrocarbons and extraction solvent a) may be supplied to a second column (second extraction column). Furthermore, a second solvent flow containing washing solvent c) may be supplied to the second column at a higher position than the position to which the first flow obtained from step a) is supplied, thereby enabling counterflow liquid-liquid extraction and resulting in a top flow from the second column containing aliphatic hydrocarbons (the "first flow") and a bottom flow from the second column containing washing solvent c) and extraction solvent a) (the "second flow").

[0103] Therefore, advantageously, the washing solvent c) added in the additional step above acts as an extraction solvent for extracting the extraction solvent a), thereby advantageously allowing the extraction solvent a) to be eliminated or substantially eliminated from the recovered aliphatic hydrocarbons. In the additional step above, the weight ratio of the extraction solvent a) to the washing solvent c) may be at least 0.5:1 or at least 1:1 or at least 2:1 or at least 3:1, and may be at most 30:1 or at most 25:1 or at most 20:1 or at most 15:1 or at most 10:1 or at most 5:1 or at most 3:1 or at most 2:1. Furthermore, the above description of temperature and pressure in extraction step a) also applies to the additional (extraction) step above. If the process includes the additional step above, the first solvent stream in extraction step a) may include a demixing solvent b) in addition to the extraction solvent a), in which case the bottom stream from the first extraction column includes the demixing solvent b) as an additional.

[0104] In the additional step described above in which the washing solvent c) is added, it is preferable that the flow containing the added washing solvent c) does not contain or substantially contains heteroatom-containing organic compounds originating from the liquid hydrocarbon feedstock flow. This preference is particularly applicable when, as described above, the flow is supplied to the second extraction column at a relatively high position and these heteroatom-containing organic compounds may re-contaminate the raffinate (top) flow. Advantageously, in the present invention, at least a portion of the first flow obtained from step c) and containing the demixing solvent b) and optionally the washing solvent c) (which does not contain or substantially contains heteroatom-containing organic compounds originating from the liquid hydrocarbon feedstock flow) can be used as such a washing solvent c) flow for supplying (recirculating) to the additional step, in particular when the demixing solvent b) is identical to the washing solvent c), especially water.

[0105] Furthermore, at least a portion of the second flow containing the washing solvent c) and extraction solvent a) obtained from the above additional (extraction) step can be supplied to step b) to provide at least a portion of the demixing solvent b) that needs to be added in step b), particularly when the demixing solvent b) is identical to the washing solvent c). Advantageously, such washing solvent c) can function both as an extraction solvent for extracting the residual extraction solvent a) in the additional step, and as a so-called “demixing agent” (or “poor solvent”) in step b), i.e., as the demixing solvent b) as further discussed above.

[0106] If a washing solvent other than water is supplied to the extraction column for extracting the extraction solvent a) used in step a), it may be preferable in the additional step above, or in step a) itself, to supply water to the extraction column at a higher position than where the other solvent is supplied. In this way, advantageously, the water supplied at a higher position can extract any washing solvent other than water, thereby preventing such other washing solvent from entering the (final) raffinate stream. Alternatively, the latter raffinate stream may be washed with water in a separate step.

[0107] Upstream and downstream integration In the present invention, the liquid hydrocarbon feed stream may contain at least a portion of the hydrocarbon products formed in a process including the decomposition of plastics, preferably waste plastics, more preferably mixed waste plastics, wherein at least a portion of the plastics contains heteroatom-containing organic compounds.

[0108] Therefore, the present invention also relates to a process for recovering aliphatic hydrocarbons from plastics, wherein at least a portion of the plastics contains a heteroatom-containing organic compound, and the process is (I) A step of decomposing the plastic and recovering hydrocarbon products including aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, (II) The step of subjecting a liquid hydrocarbon feed stream containing at least a portion of the hydrocarbon product obtained in step (I) to the above process for recovering aliphatic hydrocarbons from the liquid hydrocarbon feed stream.

[0109] The preferences and embodiments described above as such in relation to this aliphatic hydrocarbon recovery process also apply to step (II) of the process for recovering aliphatic hydrocarbons from plastics. In step (I) above, the hydrocarbon product obtained may be a liquid, a solid, or a wax. In the latter case, the solid or wax is first heated to a liquid before being subjected to the aliphatic hydrocarbon recovery process of step (II).

[0110] In the process described above, at least a portion of the plastic supplied to step (I) contains a heteroatom-containing organic compound, which is preferably waste plastic, more preferably mixed waste plastic. In step (I), the decomposition of the plastic may involve a thermal decomposition process and / or a catalytic decomposition process. The decomposition temperature in step (I) may be 300-800°C, preferably 400-800°C, more preferably 400-700°C, and even more preferably 500-600°C. Furthermore, any pressure may be applied, which may be below atmospheric pressure, at atmospheric pressure, or above atmospheric pressure. The heat treatment in step (I) causes the plastic to melt and its molecules to decompose into smaller molecules. The decomposition in step (I) can be carried out as thermal decomposition or as liquefaction. In both thermal decomposition and liquefaction, a continuous liquid phase is formed. In addition, in thermal decomposition, a discontinuous gas phase is formed, which escapes the liquid phase and separates into a continuous gas phase. In liquefaction, no significant gas phase exists due to the application of relatively high pressure.

[0111] Furthermore, in step (I), subsequent condensation of the gas phase and / or cooling of the liquid phase provides a hydrocarbon product which may be liquid, solid, or wax, comprising aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, at least a portion thereof being subjected to the aliphatic hydrocarbon recovery process in step (II).

[0112] Step (I) above can be carried out in any known manner, for example, in the manner disclosed in International Publication No. 2018 / 069794 and International Publication No. 2017 / 168165 (these disclosures are incorporated herein by reference).

[0113] Advantageously, the aliphatic hydrocarbons recovered in one of the above processes for the recovery of aliphatic hydrocarbons may contain varying amounts of aliphatic hydrocarbons within a broad boiling point range and may be supplied to a vapor cracker without further pretreatment such as hydrogenation (hydroprocessing or hydroprocessing) as disclosed in International Publication No. 2018 / 069794. In addition to being used as a feedstock for a vapor cracker, the recovered aliphatic hydrocarbons may also be supplied to other purification processes, including hydrocracking, isomerization, hydrotreatment, thermal catalytic cracking, and fluid catalytic cracking. Furthermore, in addition to being used as a feedstock for a vapor cracker, the recovered aliphatic hydrocarbons may also be advantageously separated into different fractions, each of which may find different applications such as diesel, marine fuel, and solvents.

[0114] Accordingly, the present invention also relates to a process for vapor cracking a hydrocarbon feedstock, wherein the hydrocarbon feedstock comprises aliphatic hydrocarbons recovered in one of the above processes for the recovery of aliphatic hydrocarbons. Furthermore, the present invention also relates to a process for vapor cracking a hydrocarbon feedstock, comprising the steps of recovering aliphatic hydrocarbons from a liquid hydrocarbon feedstock stream in one of the above processes for the recovery of aliphatic hydrocarbons, and vapor cracking a hydrocarbon feedstock, wherein the hydrocarbon feedstock comprises aliphatic hydrocarbons recovered in the preceding step. In this specification, the phrase "vapor cracking a hydrocarbon feedstock comprising aliphatic hydrocarbons recovered in the preceding step" may mean "vapor cracking a hydrocarbon feedstock comprising at least a portion of the recovered aliphatic hydrocarbons." The hydrocarbon feedstock to the vapor cracking process may also comprise hydrocarbons from another source other than the present process for the recovery of aliphatic hydrocarbons. Such other sources may be naphtha, hydrowax, or a combination thereof.

[0115] Advantageously, if the liquid hydrocarbon feedstock stream contains aromatic hydrocarbons, particularly polycyclic aromatics, heteroatom-containing organic compounds, conjugated aliphatic compounds having two or more carbon-carbon double bonds, or combinations thereof, these are already removed by the aliphatic hydrocarbon recovery process described above before the recovered hydrocarbons are fed into the vapor cracking process. This is particularly advantageous in that such removed compounds, especially polycyclic aromatics, no longer cause fouling in the preheating, convection, and radiation sections of the vapor cracker, as well as in heat exchange and / or separation equipment downstream of the vapor cracker, for example, in transfer line exchangers (TLEs) used to rapidly cool effluents from the vapor cracker. When hydrocarbons condense, they can thermally decompose into a coke layer, which can cause fouling. Such fouling is a major factor determining the run-length of the cracker. Reducing the amount of fouling allows for longer run-time without shutting down maintenance and improves heat transfer in the exchangers.

[0116] Vapor decomposition can be carried out in any known manner. The hydrocarbon feed is typically preheated. The feed can be heated using any other combination of heat exchangers, furnaces, or heat transfer and / or heating devices. The feed is vapor-decomposed in a decomposition zone under decomposition conditions to produce at least olefins (including ethylene) and hydrogen. The decomposition zone may comprise any decomposition system known in the art that is suitable for decomposing the feed. The decomposition zone may comprise one or more furnaces, each dedicated to a specific feed or fraction of the feed.

[0117] Decomposition is carried out at high temperatures, preferably in the range of 650–1000°C, more preferably 700–900°C, and most preferably 750–850°C. Steam is usually added to the decomposition zone and acts as a diluent to reduce the hydrocarbon partial pressure, thereby increasing the yield of olefins. Steam also reduces the formation and accumulation of carbonaceous material or coke in the decomposition zone. Decomposition occurs in the absence of oxygen. Residence times under decomposition conditions are very short, typically on the order of milliseconds.

[0118] The decomposition unit yields a decomposition unit effluent that may contain aromatic compounds (produced in the steam decomposition process), olefins, hydrogen, water, carbon dioxide, and other hydrocarbon compounds. The specific products obtained depend on the feed composition, hydrocarbon-to-vapor ratio, and the decomposition temperature and furnace residence time. The decomposed products from the steam decomposition unit then pass through one or more heat exchangers, often referred to as TLEs ("transfer line exchangers"), to rapidly reduce the temperature of the decomposition products. The TLEs preferably cool the decomposition products to a temperature in the range of 400–550°C.

[0119] figure The process for recovering aliphatic hydrocarbons from a liquid hydrocarbon feed stream is further illustrated in Figures 1 and 2.

[0120] In the process shown in Figure 1, a liquid hydrocarbon feed stream 1 containing aliphatic hydrocarbons (including conjugated aliphatic compounds having two or more carbon-carbon double bonds (hereinafter referred to as "dienes")), aromatic hydrocarbons, and heteroatom-containing organic compounds; a first solvent stream 2 containing an organic solvent (e.g., N-methylpyrrolidone), which is the extraction solvent a) according to the present invention; and a second solvent stream 3 containing water, which is an optional washing solvent c) according to the present invention, are supplied to the extraction column 4. In column 4, the liquid hydrocarbon feed stream 1 is brought into contact with the first solvent stream 2 (organic solvent), thereby recovering the aliphatic hydrocarbons by liquid-liquid extraction of the dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds with the organic solvent. Furthermore, the water in the second solvent stream 3 removes the organic solvent from the top of column 4 by liquid-liquid extraction of the organic solvent with water. The stream 5 containing the recovered aliphatic hydrocarbons exits the upper part of column 4. Furthermore, a stream 6 containing the organic solvent, water, aliphatic hydrocarbons, dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds exits the bottom of column 4.

[0121] Furthermore, in the process shown in Figure 1, flow 6 and flow 14a containing additional water are combined, and the combined flow is supplied to the first decanter 13a. The water flow 14a and the lower water flows 14b and 14c are bystreams separated from water flow 14, and the water in these bystreams is the demixing solvent b) according to the present invention. In decanter 13a, the combined flow is separated into flow 15a containing aliphatic hydrocarbons and flow 16a containing organic solvents, water, aliphatic hydrocarbons, dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds. Next, flow 16a and flow 14b containing additional water are combined, and the combined flow is supplied to the second decanter 13b. In decanter 13b, the combined flow is separated into flow 15b containing aliphatic hydrocarbons, dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds and flow 16b containing organic solvents, water, dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds. Finally, flow 16b and flow 14c containing additional water are combined, and the combined flow is supplied to a third decanter 13c. In decanter 13c, the combined flow is separated into flow 15c containing dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds, and flow 16c containing organic solvents, water, and reduced amounts of dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds.

[0122] Furthermore, in the process shown in Figure 1, flow 16c is fed to the distillation column 7 and separated into a top flow 8 containing water, dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds, and a bottom flow 9 containing an organic solvent. The organic solvent from the bottom flow 9 is recycled through the organic solvent flow 2. Flow 8 is fed to the overhead decanter 17 and separated into a flow 18 containing dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds, and a flow containing water (which may additionally contain relatively small amounts of dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds). A portion of the water flow (flow 19a) is returned to the distillation column 7 as reflux, and the other portion (flow 19b) may be recycled through water flow 14 and / or water flow 3.

[0123] In the process shown in Figure 2, a liquid hydrocarbon feed stream 1, containing aliphatic hydrocarbons (including conjugated aliphatic compounds having two or more carbon-carbon double bonds, hereinafter referred to as "dienes"), aromatic hydrocarbons, and heteroatom-containing organic compounds, and a first solvent stream 2 (which is extraction solvent a according to the present invention), containing an organic solvent (e.g., N-methylpyrrolidone), are supplied to a first extraction column 4a. In column 4a, the liquid hydrocarbon feed stream 1 comes into contact with the first solvent stream 2 (organic solvent and water), thereby recovering the aliphatic hydrocarbons by liquid-liquid extraction of the dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds with the organic solvent, resulting in a top stream 5a containing the recovered aliphatic hydrocarbons and organic solvent, and a bottom stream 6 containing the organic solvent, water, dienes, aromatic hydrocarbons, and heteroatom-containing organic compounds. Stream 5a and a second solvent stream 3 (which is an optional washing solvent c according to the present invention), containing water, are supplied to a second extraction column 4b. mosquito In ram 4b, flow 5a comes into contact with the second solvent flow 3 (water), thereby removing the organic solvent by liquid-liquid extraction of the organic solvent with water. Stream 5b, containing the recovered aliphatic hydrocarbons, exits the upper column 4b. Furthermore, flow 14, containing the organic solvent and water, exits from the bottom of column 4b and is divided into substreams 14a, 14b, and 14c, where the water in these substreams is the demixing solvent b) according to the present invention. Flows 6 and 14a are combined, and the combined flow is fed to the first decanter 13a. Regarding processing after decanter 13a, downstream processing in the process in Figure 2 refers to the above description of the corresponding processing in the process in Figure 1. Optionally (not shown in Figure 2), an additional substream 14d can be separated from flow 14 and fed directly to distillation column 7.

[0124] The present invention will be further explained by the following examples. [Examples]

[0125] Example 1 In Example 1, waste plastic pyrolysis oil is used, which had the following composition as determined by two-dimensional gas chromatography (GC×GC) method where GC adopts a Flame Ionization Detector (FID): light components with less than 7 carbon atoms (<C7) (8.7 wt%), paraffin (25 wt%), olefin (26.3 wt%), naphthene (13.9 wt%), aromatic (12.2 wt%), polycyclic aromatic (1.9 wt%), heteroatom-containing organic compounds (12.1 wt%), chloride content (about 900 ppmw), nitrogen content (about 300 ppmw), oxygen content (about 1200 ppmw). Furthermore, the waste plastic pyrolysis oil has 777 kg / m 3 of density.

[0126] Under laboratory conditions, 250 mL of waste plastic pyrolysis oil, which is the liquid hydrocarbon feedstock according to the present invention, was mixed with 250 mL of dry N-methyl-2-pyrrolidone (NMP), which is the extraction solvent a) according to the present invention, for 5 minutes. Said NMP is also referred to as a solvent herein. NMP has a density of 1027 kg / m 3 . Then, the obtained mixture was allowed to stand to separate into (i) an upper oil phase comprising aliphatic hydrocarbons (also referred to as "first oil phase" herein) and (ii) a lower solvent phase comprising NMP and compounds extracted from the waste plastic pyrolysis oil into the solvent, including aliphatic hydrocarbons, heteroatom-containing organic compounds, and aromatic hydrocarbons (also referred to as extract or "first solvent phase" herein). The first oil phase had a lower density than the first solvent phase. The volume of the first solvent phase was 114 vol% based on the volume of the hydrocarbon feedstock. This means that compounds were extracted from the waste plastic pyrolysis oil into the solvent.

[0127] Next, the first solvent phase was separated from the first oil phase by decantation. Furthermore, water (which is demixing solvent b according to the present invention) was added to the separated first solvent phase in an amount of 7.4 vol% based on the volume of the first solvent phase. Therefore, the volume ratio of the first solvent phase to the added water was 13.5. After mixing for 5 minutes, the mixture was allowed to stand to separate into a second oil phase and a second solvent phase containing water and NMP. The volume of the second oil phase was approximately 10 vol% based on the volume of the mixture. The phases were separated by decantation.

[0128] Next, additional water was added to the separated second solvent phase in an amount of 65 vol% based on the volume of the second solvent phase. Therefore, the volume ratio of the second solvent phase to the added water was 1.5. After mixing for 5 minutes, the mixture was allowed to stand to separate into a third oil phase and a third solvent phase containing water and NMP. The volume of the third oil phase was approximately 3.6 vol% based on the volume of the mixture. The phases were separated by decantation.

[0129] The changes in the color appearance of several recovered oil phases can be considered qualitative evidence of changes in the composition of these oil phases. Oils rich in aliphatic compounds (without heteroatoms) have a translucent appearance (like water) and are colorless. In contrast, many compounds that have several double bonds between carbon atoms and / or between carbon atoms and heteroatoms are colored. The intensity of the darkness of the color of the excluded oil phase is somewhat proportional to the concentration of compounds containing such double bonds. In Example 1, the first oil phase was more transparent in appearance than the third oil phase, which was much darker in color, and showed a change in composition, as will be further confirmed in Examples 2 and 3 below.

[0130] Example 2 In Example 2, the same waste plastic pyrolysis oil used in Example 1 was contacted with the same dry organic solvent (NMP) in an extraction column at 40°C and atmospheric pressure. The pyrolysis oil was in the form of a dispersed phase (droplets) and was introduced to the bottom of the extraction column at a flow rate of 12 kg / h. The solvent (NMP) was in the form of a continuous phase and was introduced to the top of the column at a flow rate of 23.8 kg / h. The volume flow rate ratio of oil to solvent was 1:1.5. The extract phase was formed at the bottom of the extraction column, and the raffinate phase was formed at the top.

[0131] The extract contained N, Cl, and O contaminants from the NMP solvent and hydrocarbon feedstock. The relative amounts of these N, Cl, and O contaminants in the raffinate were substantially reduced compared to those in the feedstock, as shown in the table below.

[0132] [Table 1]

[0133] 1380 ml of the extract (first solvent phase) was taken as a sample. The extract contained a continuous phase (no phase separation, no second phase) and is represented by the first data point in Figure 3 below. A predetermined amount of desalinated water was added and mixed with the extract sample for approximately 5 minutes. The mixture was then separated into two phases, which were then separated by decantation. The excluded oil phase was removed for quantification and analysis. Additional water was then added to the resulting extract phase. These steps were repeated sequentially to produce a total of nine different excluded oil phases. The sequential amounts of desalinated water added in each step, as a percentage of the initial extract volume (which was 1380 ml), were correspondingly 2, 2, 2, 4, 7, 14, 22, 29, and 36 volume percent. The volume of each excluded oil phase was also recorded.

[0134] Figure 3 shows the cumulative amount of water added to the solvent phase on the x-axis, based on the initial extract volume (which was 1380 ml). For example, in the first water addition step, 2 vol% of water was added based on the initial extract volume. Furthermore, in the second water addition step, another 2 vol% of water was added based on that initial extract volume, resulting in a cumulative amount of added water of 4 vol% based on that initial extract volume.

[0135] Furthermore, Figure 3 shows the cumulative amount of the oil phase on the y-axis based on the initial extract volume (which was 1380 ml). As can be seen in Figure 3, by adding only about 2 volume% water to the first solvent phase in the first water addition step, a relatively large amount of hydrocarbon compounds other than NMP are favorably removed from the first solvent phase. Furthermore, by adding additional water in subsequent water addition steps, increasingly smaller relative amounts of such other compounds were removed.

[0136] As shown in Figure 3, not only were the relative amounts of the separated oil phases different for each water addition step, but advantageously, the composition of each of these oil phases was also different. This is shown in Figures 4 and 5.

[0137] Figure 4 shows the cumulative amount of the oil phase based on the volume of the first solvent phase ("extract") on the x-axis, and the cumulative amount of chloride-containing organic compounds based on the total volume of such chloride-containing organic compounds in the first solvent phase (measured by combustion ion chromatography, CIC) on the y-axis. Figure 4 shows that relatively few chloride-containing organic compounds are removed from the solvent phase in the first water addition step, whereas relatively more chloride-containing organic compounds are removed in the subsequent water addition step. Therefore, advantageously, the oil phase obtained from the first water addition step contains a relatively large amount of aliphatic hydrocarbons (and does not contain heteroatoms such as chlorine), thereby advantageously increasing the overall recovery rate of such aliphatic hydrocarbons compared to the case where the same total (cumulative) amount of water is added in a single water addition step, even though there is no stepwise addition of water.

[0138] Furthermore, Figure 5 shows the results of gas chromatography-field ionization mass spectrometry (FIMS) analysis of the separated oil phases obtained from the successive addition of water. In Figure 5, "Oil Phase Decanter 1" refers to the second oil phase separated in the first water addition step. "Oil Phase Decanter 3" refers to the fourth oil phase separated in the third water addition step, and "Oil Phase Decanter 5" refers to the sixth oil phase separated in the fifth water addition step. In Figure 5, the double bond equivalent (DBE) is plotted as a function of the number of carbon atoms in the compounds from the oil phase. Relatively large dots in Figure 5 indicate that the relative amount of compounds with a particular number of carbon atoms and DBE is relatively large. DBE represents the level of unsaturation in the organic compound. A higher DBE indicates a greater number of unsaturated carbon-carbon bonds and / or ring structures. Figure 5 also shows that the successive (stepwise) addition of water results in a shift in the composition of the oil phase, which contains organic compounds excluded by the solvent phase, which contains an increasing amount of water in addition to NMP. For example, paraffinic (unsaturated) organic compounds with a relatively high number of carbon atoms are mainly excluded into the oil phase in the first water addition step (see "Oil Phase Decanter 1" in Figure 5). As further water is added, the resulting solvent phase containing water and NMP begins to exclude a relatively large number of organic compounds having a relatively high number of unsaturated carbon-carbon bonds and / or ring structures, and / or relatively low numbers of carbon atoms (see "Oil Phase Decanters 3 and 5" in Figure 5).

[0139] Example 3 In Example 3, the findings from Examples 1 and 2 and the resulting effects of the present invention were confirmed as follows.

[0140] The process simulation in Aspen Plus V11 was configured as follows. The simulation uses a flow containing typical components of waste plastic pyrolysis oil (see "Waste Plastic Oil Supply Materials" in Tables 1, 2, and 3 below), which is the liquid hydrocarbon supply material flow according to the present invention. The components selected from the Aspen Plus component library are classified into paraffins, olefins and naphthenes, oxygen-containing aromatic compounds ("O-aromatic"), chlorine-containing aromatic compounds ("Cl-aromatic"), polycyclic aromatic compounds (not containing heteroatoms such as O and Cl), and other aromatic compounds (not containing heteroatoms such as O and Cl). The relative amounts of these components in the feed are shown in Table 1. The basic thermodynamic method selected is UNIF-LL, a characterization method generally recommended for liquid-liquid equilibrium applications.

[0141] The feed stream (oil) is introduced into the first extraction column, and solvent N-methyl-2-pyrrolidone (NMP), which is the extraction solvent a) according to the present invention, is added for simulation purposes at corresponding flow rates of 200 kg / h and 100 kg / h, respectively, in a solvent-to-oil mass ratio of 2:1. The oil phase ("raffinate") and the first solvent phase ("extract") are produced in a raffinate-to-extract mass ratio of 1:3.3. The raffinate is then introduced into the second extraction column and brought into contact with water, which is an optional washing solvent c) according to the present invention, in a water-to-raffinate mass ratio of 0.72:1. Another oil phase (final "raffinate product") and another solvent phase ("extract") containing NMP and mainly water are produced. This other solvent phase from the second extraction column is used as the demixing solvent b) and as a source of water to be added to each of the following decantation steps.

[0142] Water is added to the first solvent phase at a mass ratio of 50:1 relative to the first solvent [i.e., 2% water], and this water is the demixing solvent b) according to the present invention. After mixing and phase separation (by decantation), a first oil phase and a second solvent phase (containing NMP and water) are formed. Then, additional water is added to the second solvent phase at a mass ratio of 67:1 relative to the second solvent [i.e., 1.5% water]. After mixing and phase separation (by decantation), a second oil phase and a third solvent phase are formed. Then, additional water is added to the third solvent phase at a mass ratio of 4.6:1 relative to the third solvent [i.e., 18% water]. After mixing and phase separation (by decantation), a third oil phase and a fourth solvent phase are formed.

[0143] Table 1 shows the flow rates (parts by mass) of the first solvent phase and the first, second, and third oil phases, based on the flow rate of the waste plastic oil feed. Since the ratio of the flow rate of the first solvent phase to the flow rate of the waste plastic oil feed is greater than 2:1, this means that compounds are extracted from the waste plastic oil feed into the solvent. Table 1 also shows the relative amounts of various components in the first solvent phase and the first, second, and third oil phases, based on the amount of those components in the waste plastic oil feed (i.e., wof% = "weight relative to feed").

[0144] [Table 2]

[0145] As shown in Table 1, the first and second oil phases advantageously contain only relatively small amounts of organic chlorides (i.e., a total amount of only 6.3 wt% Cl-aromatics compared to 19.9 wt% in the third oil phase) and relatively small amounts of heteroatom-free aromatics (i.e., a total amount of only 9.6 wt% other aromatics compared to 14.5 wt% in the third oil phase, and a total amount of only 22.2 wt% polycyclic aromatics compared to 42.1 wt% in the third oil phase), which makes these first and second oil phases suitable for, for example, recirculation back into the process feed. Alternatively, these first and second oil phases may be mixed with the above-mentioned final raffinate product, due to the low level of heteroatom-containing contaminants, which can be further reduced to an acceptable level for such mixing. However, preferably, these first and second oil phases may be mixed with the raffinate obtained by the first extraction with NMP before being introduced into the second extraction column, taking into account the presence of NMP in the oil phases (see Table 2 below). Advantageously, in the case of these mixtures, the first and second oil phases constitute an increase of approximately 11% in oil recovery rate relative to the fresh feed (i.e., an additional 10.8 parts flow in total based on the feed material).

[0146] Furthermore, Table 2 shows the relative amounts of components in the waste plastic oil feed, the first solvent phase, and the first, second, and third oil phases, based on the amount of the feed or phase in question (i.e., w / w%).

[0147] [Table 3]

[0148] Table 3 below further identifies the above components selected in the process simulation in Aspen Plus V11.

[0149] [Table 4]

Claims

1. A process for recovering aliphatic hydrocarbons from a liquid hydrocarbon feed stream containing aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, a) A step of bringing at least a portion of the liquid hydrocarbon supply stream into contact with an extraction solvent a) containing one or more heteroatoms, and subjecting the liquid hydrocarbon supply stream to liquid-liquid extraction with the extraction solvent a) to obtain a first stream containing aliphatic hydrocarbons and a second stream containing the extraction solvent a), aliphatic hydrocarbons, a heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. b1) A step of mixing at least a portion of the second stream obtained from step a) with a demixing solvent b) which contains one or more heteroatoms and has lower miscibility in heptane than that of the extraction solvent a) in heptane, and separating the resulting mixture into a first stream containing aliphatic hydrocarbons and optionally aromatic hydrocarbons, and a second stream containing the extraction solvent a), demixing solvent b), heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, b2) A step of mixing at least a portion of the second stream obtained from step b1) with demixing solvent b), and separating the resulting mixture into a first stream containing heteroatom-containing organic compounds and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a) and demixing solvent b), Steps b1 and b2) are substeps of step b) that include two or more substeps. c) Separating at least a portion of the second flow obtained from step b2) into a first flow containing demixing solvent b) and a second flow containing extraction solvent a), d) Recirculating at least a portion of the extraction solvent a) from the second flow obtained from step c) back to step a), e) a process comprising the optional step of recirculating at least a portion of the demixed solvent b) from the first flow obtained from step c) to one or more of the substeps of step b).

2. The process according to claim 1, wherein step b) comprises 2 to 10 substeps.

3. Step b) is, bi) Mix at least a portion of the second stream obtained from step a) with demixing solvent b), and separate the resulting mixture into a first stream containing aliphatic hydrocarbons and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a), demixing solvent b), aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. bii) Mix at least a portion of the second stream obtained from step bi) with demixing solvent b), and separate the resulting mixture into a first stream containing aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a), demixing solvent b), heteroatom-containing organic compounds, and optionally aromatic hydrocarbons. The method includes: mixing at least a portion of the second stream obtained from step bi) with demixing solvent b); and separating the resulting mixture into a first stream containing heteroatom-containing organic compounds and optionally aromatic hydrocarbons, and a second stream containing extraction solvent a) and demixing solvent b); The process according to claim 1 or 2, wherein step c) includes separating at least a portion of the second flow obtained from step biii) into a first flow containing demixing solvent b) and a second flow containing extraction solvent a).

4. The extraction solvent a) has at least 5 MPa 1 / 2 R ａ、ヘプタン The demixing solvent b) has at least 20 MPa 1 / 2 R ａ、ヘプタン It has R ａ、ヘプタン However, this refers to the Hansen solubility parameter distance for heptane, which is determined at 25°C. R for the aforementioned demixed solvent b) ａ、ヘプタン The R for extraction solvent a) ａ、ヘプタン Larger R for solvents a) and b) ａ、ヘプタン The process according to any one of claims 1 to 3, wherein the difference is at least 1 MPa 1 / 2.

5. The extraction solvent a) is ammonia, diols and triols (including any isomers of monoethylene glycol (MEG), monopropylene glycol (MPG), butanediol and glycerol); glycol ethers (including diethylene glycol, triethylene glycol and tetraethylene glycol, including oligoethylene glycol), and their monoalkyl ethers (including diethylene glycol ethyl ether); amides (including N-alkylpyrrolidone, where the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, including N-methylpyrrolidone (NMP)); formamides, and di and monoalkylformamides, and acetamides (where the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, including dimethylformamide (DMF), methylformamide and dimethylacetamide); dialkyl sulfoxides (where the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, including dimethyl sulfoxide) A process according to any one of claims 1 to 4, selected from the group consisting of: sides (including DMSO); sulfones (including sulfolanes); N-formylmorpholine (NFM); furan ring-containing components and their derivatives (including furfural, 2-methylfuran, furfuryl alcohol and tetrahydrofurfuryl alcohol); hydroxyesters (including methyl lactate and ethyl lactate, including lactates); trialkyl phosphates (including triethyl phosphate); phenol compounds (including phenol and guaiacol); benzyl alcohol compounds (including benzyl alcohol); amine compounds (including ethylenediamine, monoethanolamine, diethanolamine and triethanolamine); nitrile compounds (including acetonitrile and propionitrile); trioxane compounds (including 1,3,5-trioxane); carbonate compounds (including propylene carbonate and glycerol carbonate); and cycloalkanone compounds (including dihydrolevoglucocenone).

6. The demixing solvent b) is water, and diols and triols (including any isomers of monoethylene glycol (MEG), monopropylene glycol (MPG), butanediol, and glycerol); glycol ethers (including diethylene glycol, triethylene glycol, and tetraethylene glycol, and oligoethylene glycol), and their monoalkyl ethers (including diethylene glycol ethyl ether); amides (including N-alkylpyrrolidone, where the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, and including N-methylpyrrolidone (NMP)); formamides, and di and monoalkylformamides, and acetamides (where the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, and including dimethylformamide (DMF), methylformamide, and dimethylacetamide); dialkyl sulfoxides (where the alkyl group may contain 1 to 8 or 1 to 3 carbon atoms, and dimethyl sulfoxide ( The solvent comprises one or more solvents selected from the group consisting of The process according to any one of claims 1 to 5, wherein the extraction solvent a) and the demixing solvent b) are not the same.

7. Washing solvent c) is added to step a) to produce a first stream containing aliphatic hydrocarbons and a second stream containing washing solvent c), extraction solvent a), heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, or The process according to any one of claims 1 to 6, wherein the first flow obtained from step a) comprises an aliphatic hydrocarbon and an extraction solvent a), at least a portion of the first flow is brought into contact with a washing solvent c), and subjected to liquid-liquid extraction with the washing solvent c) to obtain a first flow containing an aliphatic hydrocarbon and a second flow containing the washing solvent c) and the extraction solvent a).

8. The process according to claim 7, wherein the washing solvent c) is the same as or different from the demixing solvent b).

9. A process for recovering aliphatic hydrocarbons from plastic, wherein at least a portion of the plastic contains a heteroatom-containing organic compound, (I) A step of decomposing the plastic and recovering hydrocarbon products including aliphatic hydrocarbons, heteroatom-containing organic compounds, and optionally aromatic hydrocarbons, (II) A process comprising the step of providing a liquid hydrocarbon feedstock stream containing at least a portion of the hydrocarbon product obtained in step (I) to the process according to any one of claims 1 to 8.

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