Recovery of aliphatic hydrocarbons

Abstract

The invention relates to a process for the recovery of aliphatic hydrocarbons from a liquid hydrocarbon feedstock comprising aliphatic hydrocarbons, heteroatom containing polar components and optionally aromatic hydrocarbons, said process comprising the steps of: a) cooling the liquid hydrocarbon feedstock to obtain wax crystals, resulting in a cooled liquid and the wax crystals; b) separating the wax crystals and the cooled liquid obtained in step a) to produce a wax comprising aliphatic hydrocarbons and a dewaxed liquid comprising heteroatom containing polar components and optionally aromatic hydrocarbons; wherein the liquid hydrocarbon feedstock is not mixed with a solvent before or during step a), and wherein in steps a) and b) no solvent is used.

Description

[0001] RECOVERY OF ALIPHATIC HYDROCARBONS

[0002] Field of the invention

[0003] The present invention relates to a process for the recovery of aliphatic hydrocarbons from a liquid hydrocarbon feedstock; to a process for the recovery of aliphatic hydrocarbons from plastics; and to a process for steam cracking a hydrocarbon feed.

[0004] Background of the invention

[0005] Waste plastics can be converted via pyrolysis to high- value chemicals, including olefins and aromatic hydrocarbons. Pyrolysis of plastics can yield product streams having a wide boiling range, including gaseous and liquid product streams. Hydrocarbons from liquid pyrolysis product streams can be cracked to produce high-value chemicals, including ethylene and propylene which are monomers that can be used in making new plastics.

[0006] WO2021115982 discloses a process for the recovery of aliphatic hydrocarbons from a liquid hydrocarbon feedstock stream comprising aliphatic hydrocarbons, heteroatom containing polar components and optionally aromatic hydrocarbons, which stream may comprise a liquid product produced by the pyrolysis of plastic waste, said process comprising the steps of: a) mixing the liquid hydrocarbon feedstock stream with a solvent resulting in a liquid mixture; b) cooling the liquid mixture obtained in step a) to a temperature in the range of from +5 °C to -30 °C to obtain wax crystals in the mixture; c) separating wax crystals from the cooled liquid mixture obtained in step b) to produce a wax comprising aliphatic hydrocarbons and a dewaxed liquid mixture comprising solvent, heteroatom containing polar components and optionally aromatic hydrocarbons; d) separating solvent from the liquid mixture obtained in step c) and optionally recycling the separated solvent to step a) . Further, the present invention relates to a process for the recovery of aliphatic hydrocarbons from plastics, and to a process for steam cracking a hydrocarbon feed.

[0007] There is an ongoing need to develop improved processes for the recovery of aliphatic hydrocarbons from liquid feedstocks comprising aliphatic hydrocarbons, heteroatom containing polar components and optionally aromatic hydrocarbons which liquid feedstocks may originate from the pyrolysis of waste plastics, in specific mixed waste plastics. It is desired that with such process heteroatom containing polar components are separated from aliphatic hydrocarbons so that the aliphatic hydrocarbons become a suitable feedstock for a number of processes, including steam cracking, without the below-described disadvantages associated with the presence of heteroatom containing polar components in feedstocks comprising aliphatic hydrocarbons. Such removal of heteroatom containing polar components is achieved according to the invention of above-mentioned WO2021115982, whereby heteroatom containing polar components have been removed from the resulting wax comprising aliphatic hydrocarbons. However, a disadvantage of the dewaxing process as disclosed in WO2021115982 is that first the feedstock needs to be mixed with a solvent and that after dewaxing the solvent needs to be separated and recycled which is cumbersome .

[0008] It is an object of the present invention to provide such process for the recovery of aliphatic hydrocarbons from a liquid feedstock comprising aliphatic hydrocarbons, heteroatom containing polar components and optionally aromatic hydrocarbons, which is technically advantageous, efficient and affordable, in particular a process which does not have one or more of the above-mentioned disadvantages. Such technically advantageous process would preferably result in a relatively low energy demand and / or relatively low capital expenditure.

[0009] Summary of the invention

[0010] Surprisingly it was found that such process can be provided by subjecting a liquid hydrocarbon feedstock comprising aliphatic hydrocarbons and heteroatom containing polar components to dewaxing by cooling the feedstock without using a solvent, resulting in a wax comprising aliphatic hydrocarbons and a dewaxed liquid comprising heteroatom containing polar components.

[0011] Accordingly, the present invention relates to a process for the recovery of aliphatic hydrocarbons from a liquid hydrocarbon feedstock comprising aliphatic hydrocarbons, heteroatom containing polar components and optionally aromatic hydrocarbons, said process comprising the steps of: a) cooling the liquid hydrocarbon feedstock to obtain wax crystals, resulting in a cooled liquid and the wax crystals; b) separating the wax crystals and the cooled liquid obtained in step a) to produce a wax comprising aliphatic hydrocarbons and a dewaxed liquid comprising heteroatom containing polar components and optionally aromatic hydrocarbons ; wherein the liquid hydrocarbon feedstock is not mixed with a solvent before or during step a) , and wherein in steps a) and b) no solvent is used.

[0012] Thus, in the present invention, heteroatom containing polar components are advantageously removed from an aliphatic hydrocarbon feedstock containing such polar components by the above-described dewaxing process. This advantageously results in a wax comprising aliphatic hydrocarbons from which heteroatom containing polar components have been removed, preferably substantially all heteroatom containing polar components have been removed. This is advantageous as such heteroatom containing polar components may have adverse effects in further use of the aliphatic hydrocarbons, for example in a case where a heteroatom-containing aliphatic hydrocarbon stream is subjected to steam cracking. Oxygen containing compounds can result in a poor water oil separation, acids can impact the quench oil water pH, and aldehydes can result in the formation of so-called "green oil" (fouling) in the caustic section. Further, oxygen containing compounds can also promote the formation of radicals and initiate fouling by radical initiated polymerization. Nitrogen containing compounds could lead to formation of explosive N0xgums in the cold box. Amines can affect quench water pH and NH3 can form deposits with chlorides. Further, nitrogen may end up in effluent residue which, when used as fuel, will produce N0x. Chlorine containing compounds, when converted into chloride, can result in corrosion. Chloride is also a catalyst poison for any hydrotreating catalyst used in the backend. Further, chloride can form a deposit with ammonia. Metals (e.g. from salts) are known catalyst poisons and can also deposit in the preheater causing preheater fouling.

[0013] Further, advantageously, in the present invention heteroatom containing polar components can be removed by a dewaxing process which is less cumbersome than a hydrotreatment process that is usually applied to remove heteroatoms. A hydrotreatment process is generally conducted in the presence of a hydrotreating catalyst at a relatively high temperature, suitably of from 250 to 400 °C. Advantageously, such hydrotreatment necessary for removal of heteroatoms is completely obviated in the present process for the recovery of aliphatic hydrocarbons from a liquid hydrocarbon feedstock comprising aliphatic hydrocarbons and heteroatom containing polar components .

[0014] Further, since in the present process heteroatom containing polar components are easily removed by dewaxing, the feed to the present process can advantageously tolerate a relatively high amount of such heteroatom containing polar components. Thus, waste plastic that may be pyrolyzed to produce a feed to the present dewaxing process may comprise heteroatom-containing plastics, such as polyvinyl chloride (PVC) , polyethylene terephthalate (PET) and polyurethane (PU) . In specific, mixed waste plastic may be pyrolyzed that in addition to heteroatom-free plastics, such as polyethylene (PE) and polypropylene (PP) , contains a relatively high amount of such heteroatom-containing plastics.

[0015] Still further, in the present dewaxing process, no solvent is used. In particular, the liquid hydrocarbon feedstock is not mixed with a solvent before or during step a) . Further, in general, in steps a) and b) no solvent is used. The latter implies for example that a cooled mixture comprising a liquid and the wax crystals, suitably resulting from step a) , is not mixed with a solvent. By said "solvent" reference is made to a solvent which dissolves at least part of the liquid hydrocarbon feedstock comprising aliphatic hydrocarbons, heteroatom containing polar components and optionally aromatic hydrocarbons . By not having to use a solvent, as in above-mentioned WO2021115982 , the present dewaxing process is greatly simplified as there is no need to first mix the feedstock with a solvent and, after dewaxing to separate and recycle such solvent.

[0016] Further, the present invention relates to a process for the recovery of aliphatic hydrocarbons from plastics, said process comprising the steps of: i) converting the plastics by pyrolysis to a hydrocarbon product comprising a gas phase and a liquid phase; ii) separating at least a portion of the hydrocarbon product into a hydrocarbon gas stream and a hydrocarbon liquid stream; iii) subjecting at least a portion of the hydrocarbon liquid stream to the above-mentioned dewaxing process.

[0017] Still further, the present invention relates to a process for steam cracking a hydrocarbon feed, wherein the hydrocarbon feed comprises aliphatic hydrocarbons recovered in any one of the above-mentioned processes .

[0018] Detailed description of the invention

[0019] While the processes of the present invention and the feedstock (s) or stream(s) used in said processes are described in terms of "comprising", "containing" or "including" one or more various described steps and components, respectively, they can also "consist essentially of" or "consist of" said one or more various described steps and components, respectively.

[0020] In the context of the present invention, in a case where a feedstock or stream comprises two or more components, these components are to be selected in an overall amount not to exceed 100% .

[0021] Further, where upper and lower limits are quoted for a property then a range of values defined by a combination of any of the upper limits with any of the lower limits is also implied .

[0022] Unless indicated otherwise, where in the present specification reference is made to a boiling point this means the boiling point at 760 mm Hg pressure.

[0023] In step a) of the present process, a liquid feedstock which comprises aliphatic hydrocarbons, heteroatom containing polar components and optionally aromatic hydrocarbons (also herein referred to as the "liquid hydrocarbon feedstock") is cooled. The liquid hydrocarbon feedstock may comprise a liquefied solid or wax that is heated to make it liquid.

[0024] Preferably, the liquid hydrocarbon feedstock comprises both aliphatic hydrocarbons having a boiling point of from 30 to 300 °C and aliphatic hydrocarbons having a boiling point of from greater than 300 to 600 °C in a weight ratio of from 99:1 to 1:99. The amount of aliphatic hydrocarbons having a boiling point of from 30 to 300 °C, based on the total amount of aliphatic hydrocarbons having a boiling point of from 30 to 600 °C, may be at most 99 wt . % or at most 80 wt . % or at most 60 wt . % or at most 40 wt . % or at most 30 wt . % or at most 20 wt . % or at most 10 wt . % . Further, the amount of aliphatic hydrocarbons having a boiling point of from 30 to 300 °C, based on the total amount of aliphatic hydrocarbons having a boiling point of from 30 to 600 °C, may be at least 1 wt . % or at least 5 wt . % or at least 10 wt . % or at least 20 wt . % or at least 30 wt . % .

[0025] Thus, advantageously, the liquid hydrocarbon feedstock may comprise varying amounts of aliphatic hydrocarbons within a wide boiling point range of from 30 to 600 °C. Accordingly, as with the boiling point, the carbon number of the aliphatic hydrocarbons in the liquid hydrocarbon feedstock may also vary within a wide range, for example of from 5 to 50 carbon atoms. The carbon number of the aliphatic hydrocarbons in the liquid hydrocarbon feedstock may be at least 4 or at least 5 or at least 6 and may be at most 50 or at most 40 or at most 30 or at most 20.

[0026] The amount of aliphatic hydrocarbons in the liquid hydrocarbon feedstock, based on the total weight of the liquid hydrocarbon feedstock, may be at least 30 wt . % or at least 50 wt . % or at least 80 wt . % or at least 90 wt . % or at least 95 wt . % or at least 99 wt . % and may be smaller than 100 wt . % or at most 99 wt . % or at most 90 wt . % or at most 80 wt . % or at most 70 wt . % . The aliphatic hydrocarbons may be cyclic, linear and branched.

[0027] The aliphatic hydrocarbons in the liquid hydrocarbon feedstock may comprise non-olefinic (paraffinic) and olefinic aliphatic compounds. The amount of paraffinic aliphatic compounds in the liquid hydrocarbon feedstock, based on the total weight of the liquid hydrocarbon feedstock, may be at least 20 wt . % or at least 40 wt . % or at least 60 wt . % or at least 80 wt . % and may be smaller than 100 wt.% or at most 99 wt . % or at most 80 wt.% or at most 60 wt.%. Further, the amount of olefinic aliphatic compounds in the liquid hydrocarbon feedstock, based on the total weight of the liquid hydrocarbon feedstock, may be smaller than 100 wt.% or at least 20 wt.% or at least 40 wt.% or at least 60 wt.% or at least 80 wt.% and may be at most 99 wt.% or at most 80 wt.% or at most 60 wt.%.

[0028] Further, the olefinic compounds may comprise aliphatic compounds having one carbon-carbon double bond (mono-olefins) and / or aliphatic compounds having two or more carbon-carbon double bonds which latter compounds may be conjugated or nonconjugated. The aliphatic compounds having two or more carbon-carbon double bonds may include compounds having double bonds at alpha and omega positions . The amount of mono-olefins in the liquid hydrocarbon feedstock, based on the total weight of the liquid hydrocarbon feedstock, may be at least 20 wt.% or at least 40 wt.% or at least 60 wt.% or at least 80 wt.% and may be smaller than 100 wt.% or at most 99 wt.% or at most 80 wt.% or at most 60 wt.%. Further, the amount of conjugated aliphatic compounds having two or more carbon-carbon double bonds in the liquid hydrocarbon feedstock, based on the total weight of the liquid hydrocarbon feedstock, may be greater than 0 wt.% or at least 10 wt . % or at least 20 wt . % or at least 40 wt . % or at least 60 wt . % and may be at most 80 wt . % or at most 60 wt . % or at most 40 wt . % .

[0029] Within the present specif ication , an aliphatic hydrocarbon which contains one or more heteroatoms is a ''heteroatom containing polar component" a s further described below .

[0030] In addition to the above-described aliphatic hydrocarbons , the liquid hydrocarbon feedstock comprises heteroatom containing polar components and optionally aromatic hydrocarbons .

[0031] The amount of aromatic hydrocarbons in the liquid hydrocarbon feedstock , ba sed on the total weight of the liquid hydrocarbon feedstock , may be 0 wt . % or greater than 0 wt . % or at least 5 wt . % or at least 10 wt . % or at least 15 wt . % or at least 20 wt . % or at least 25 wt . % or at least 30 wt . % and may be at most 50 wt . % or at most 40 wt . % or at most 30 wt . % or at most 20 wt . % . The aromatic hydrocarbons may comprise monocyclic and / or polycyclic aromatic hydrocarbons . An example of a monocyclic aromatic hydrocarbon i s styrene . The polycyclic aromatic hydrocarbons may comprise non-fused and / or fused polycyclic aromatic hydrocarbons . An example of a non-fused polycyclic aromatic hydrocarbon i s oligostyrene . Styrene and oligostyrene may originate from polystyrene . Examples of fused polycyclic aromatic hydrocarbons are naphthalene and anthracene . The aromatic ring or rings in the aromatic hydrocarbons may be substituted by one or more hydrocarbyl groups , including al kyl groups ( saturated) and alkylene groups ( unsaturated) .

[0032] Within the present specif ication , an aromatic hydrocarbon which contains one or more heteroatoms is a "heteroatom containing polar component" as further de scribed below . Further, the amount of heteroatom containing polar components in the liquid hydrocarbon feedstock, based on the total weight of the liquid hydrocarbon feedstock, is greater than 0 wt . % and may be at least 0.5 wt . % or at least 1 wt . % or at least 3 wt . % or at least 5 wt . % or at least 10 wt . % or at least 15 wt . % or at least 20 wt . % and may be at most 30 wt . % or at most 20 wt . % or at most 10 wt . % or at most 5 wt . % .

[0033] The heteroatom containing polar components in the liquid hydrocarbon feedstock comprise heteroatom containing organic compounds. Additionally, the liquid hydrocarbon feedstock may comprise polar components comprising salts. The heteroatom containing organic compounds in the liquid hydrocarbon feedstock contain one or more heteroatoms, which may be oxygen, nitrogen, sulfur and / or a halogen, such as chlorine, suitably oxygen, nitrogen and / or a halogen. Preferably, said heteroatom containing organic compounds in the liquid hydrocarbon feedstock are synthetic compounds, and not natural compounds as present in for example fossil oil.

[0034] The above-mentioned salts may comprise organic and / or inorganic salts. The salts may comprise ammonium, an alkali metal, an alkaline earth metal or a transition metal as the cation and a nitrate, carboxylate, sulphate, phosphate or a halide as the anion. The heteroatom containing organic compounds contain one or more heteroatoms, which may be oxygen, nitrogen, sulfur and / or a halogen, such as chlorine. The heteroatom containing organic compounds may comprise amines, amides, nitriles, ethers, esters, ketones, acids and thiophene. The amines may include cyclic amines, such as pyrrole, and aromatic amines, such as pyridine. The amides may include cyclic amides, such as lactams.

[0035] Further, the above-mentioned heteroatom containing organic compounds may be aliphatic or aromatic. An example of an aliphatic, heteroatom containing organic compound is oligomeric polyvinyl chloride (PVC) . Oligomeric PVC may originate from polyvinyl chloride. Aromatic, heteroatom containing organic compounds may comprise 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 originate from polyethylene terephthalate. Examples of nitrogen containing organic compounds are compounds originating from polyurethane and nylon.

[0036] In step a) of the present dewaxing process, the liquid hydrocarbon feedstock is cooled to cause crystallization of a wax, said step a) resulting in a cooled liquid and wax crystals, suitably resulting in a cooled mixture comprising a liquid and the wax crystals. In step b) , said wax (wax crystals) and liquid are separated from each other.

[0037] In step a) of the present process, the liquid hydrocarbon feedstock may be cooled to a temperature which is below the wax crystallization temperature of the feedstock. The wax crystallization temperature may vary widely depending on the liquid hydrocarbon feedstock. As mentioned above, the liquid hydrocarbon feedstock may comprise a liquefied solid or wax that is heated to make it liquid. Thus, in case the feedstock is a solid or wax, fully or partly, it should first be heated to produce a liquid hydrocarbon feedstock prior to cooling step a) of the present process. It is preferred that the feedstock is made fully liquid or liquefied prior to step a) .

[0038] Generally, in step a) of the present process, the liquid hydrocarbon feedstock may be cooled to a temperature in the range of from +10 °C to -30 °C. Hence, preferably, step a) in the present process comprises cooling the liquid hydrocarbon feedstock to a temperature in the range of from +10 °C to -30 °C to obtain wax crystals, resulting in a cooled liquid and the wax crystals. More preferably, in step a) the feedstock is cooled to a temperature in the range of from +5 °C to -30 °C, more preferably 0 °C to -30 °C, more preferably -5 °C to -30 °C, more preferably -10 °C to -30 °C, more preferably -15 °C to -25 °C. During cooling in step a) stirring may be performed .

[0039] The cooling in step a) may be effected in many different ways. One preferred way comprises contacting the liquid hydrocarbon feedstock with a cooling element having a temperature in the range of from +10 °C to -30 °C. The above- mentioned preferences for cooling temperature equally also apply to the temperature of said cooling element.

[0040] One example of above-mentioned cooling element is a cooled plate. In step a) of the present process, the liquid hydrocarbon feedstock may be contacted with a plate cooled to below the wax crystallization temperature of the feedstock. A wax may then crystallize on the cooled plate. A wax crystallizer comprising a housing, in which one or more plates are suspended, may be used. Said plates in the wax crystallizer may be hollow inside and may be coupled to one or more pipes through which either a cooling medium or a heating medium can be sent to the cavity or cavities of the one or more plates . The liquid hydrocarbon feedstock may be sent to the inside of the housing of the wax crystallizer where it is contacted with one or more plates . Once the crystallization in said wax crystallizer is finalized, the plate may be heated so that part of the wax is liquefied and is combined with the liquid, which liquid is then subjected to separation step b) of the present process.

[0041] In step b) of the present process, the wax crystals and the cooled liquid obtained in step a) are separated to produce a wax comprising aliphatic hydrocarbons and a dewaxed liquid comprising heteroatom containing polar components and optionally aromatic hydrocarbons . Any separation method may be applied to achieve this. For example, filtration may be applied to separate the wax crystals from the dewaxed liquid. In case a cooled plate is used as a cooling element, as described above, the cooled liquid may be separated from the cooled plate which contains the wax. Subsequently, the cooled plate containing the wax may be heated to fully liquefy the wax, thereby producing a liquid, and steps a) and b) may be repeated one or more times. In this way, the purity of the final wax comprising aliphatic hydrocarbons may be increased.

[0042] In case aromatic hydrocarbons are present in the liquid hydrocarbon feedstock, the dewaxed liquid resulting from step b) comprises heteroatom containing polar components and aromatic hydrocarbons which liquid may be further separated to recover aromatic hydrocarbons, wherein the remaining heteroatom containing polar components may be used for further processing.

[0043] In the present invention, the liquid hydrocarbon feedstock may comprise a liquid product produced by the pyrolysis of plastic waste, preferably mixed plastic waste. Such liquid product may be provided in any known way, for example by the process as disclosed in WO2018069794 or WO2017168165.

[0044] Further, the present invention relates to a process for the recovery of aliphatic hydrocarbons from plastics, said process comprising the steps of: i) converting the plastics by pyrolysis to a hydrocarbon product comprising a gas phase and a liquid phase; ii) separating at least a portion of the hydrocarbon product into a hydrocarbon gas stream and a hydrocarbon liquid stream; iii) subjecting at least a portion of the hydrocarbon liquid stream to the above-described dewaxing process.

[0045] The preferences and embodiments as described above with reference to the present dewaxing process also apply to step iii) of the present process for the recovery of aliphatic hydrocarbons from plastics. In said step iii) , a liquefied solid or wax that is heated to make it liquid, may also be subjected to the above-described dewaxing process. Steps i) and ii) of the latter process may be carried out in any known way, for example in a way as disclosed in WO2018069794 and WO2017168165, the disclosures of which are herein incorporated by reference. For example, pyrolysis step i) may be carried out at sub-atmospheric pressure and a temperature of from 500 to 750 °C.

[0046] Advantageously, aliphatic hydrocarbons from the wax comprising aliphatic hydrocarbons obtained in one of the above-described processes for the recovery of aliphatic hydrocarbons, which may comprise varying amounts of aliphatic hydrocarbons within a wide boiling point range, may be fed to a steam cracker without a further pre-treatment , such as treatment with hydrogen (hydrotreating or hydroprocessing) as disclosed in WO2018069794. In addition to being used as a feed to a steam cracker, said recovered aliphatic hydrocarbons may also advantageously be separated into different fractions which each may find a different application, such as diesel, marine fuel, solvent, etc.

[0047] Accordingly, the present invention also relates to a process for steam cracking a hydrocarbon feed, wherein the hydrocarbon feed comprises aliphatic hydrocarbons from the wax comprising aliphatic hydrocarbons obtained in one of the above-described processes for the recovery of aliphatic hydrocarbons. Further, accordingly, the present invention also relates to a process for steam cracking a hydrocarbon feed, comprising the steps of: obtaining a wax comprising aliphatic hydrocarbons from a liquid hydrocarbon feedstock in one of the above-described processes for the recovery of aliphatic hydrocarbons; and steam cracking a hydrocarbon feed, wherein the hydrocarbon feed comprises aliphatic hydrocarbons from the wax obtained in the preceding step. The hydrocarbon feed to the steam cracking process may also comprise hydrocarbons from another source, other than the present process for the recovery of aliphatic hydrocarbons from a liquid hydrocarbon feedstock. Such other source may be naphtha, hydrowax or a combination thereof.

[0048] Advantageously, in a case wherein the liquid hydrocarbon feedstock comprises aromatic hydrocarbons, especially polycyclic aromatics, heteroatom containing polar components, conjugated aliphatic compounds having two or more carboncarbon double bonds, or a combination thereof, these have already been removed by the present dewaxing process as described above before feeding recovered hydrocarbons to a steam cracking process. This is particularly advantageous in that said removed compounds and components, especially polycyclic aromatics, can no longer cause fouling in the preheat, convection and radiant sections of a steam cracker and in the downstream heat exchange and / or separation equipment for a steam cracker, for example in transfer line exchangers (TLEs) which are used to rapidly cool the effluent from a steam cracker. When hydrocarbons condense, they may thermally decompose into a coke layer which may cause fouling. Such fouling is a major factor determining the run length of the cracker. Reducing the amount of fouling results in longer run times without maintenance shutdowns, and improved heat transfer in the exchangers.

[0049] The steam cracking may be performed in any known way. The hydrocarbon feed is typically preheated. The feed can be heated using heat exchangers, a furnace or any other combination of heat transfer and / or heating devices. The feed is steam cracked in a cracking zone under cracking conditions to produce at least olefins (including ethylene) and hydrogen. The cracking zone may comprise any cracking system known in the art that is suitable for cracking the feed. The cracking zone may comprise one or more furnaces, each dedicated for a specific feed or fraction of the feed.

[0050] The cracking is performed at elevated temperatures, preferably in the range of from 650 to 1000 °C, more preferably of from 700 to 900 °C, most preferably of from 750 to 850 °C. Steam is usually added to the cracking zone, acting as a diluent to reduce the hydrocarbon partial pressure and thereby enhance the olefin yield. Steam also reduces the formation and deposition of carbonaceous material or coke in the cracking zone. The cracking occurs in the absence of oxygen. The residence time at the cracking conditions is very short, typically on the order of milliseconds .

[0051] From the cracker, a cracker effluent is obtained that may comprise aromatics (as produced in the steam cracking process) , olefins, hydrogen, water, carbon dioxide and other hydrocarbon compounds. The specific products obtained depend on the composition of the feed, the hydrocarbon-to-steam ratio, and the cracking temperature and furnace residence time. The cracked products from the steam cracker are then passed through one or more heat exchangers, often referred to as TLEs ("transfer line exchangers") , to rapidly reduce the temperature of the cracked products. The TLEs preferably cool the cracked products to a temperature in the range of from 400 to 550 °C.

Claims

C L A I M S1. A process for the recovery of aliphatic hydrocarbons from a liquid hydrocarbon feedstock comprising aliphatic hydrocarbons, heteroatom containing polar components and optionally aromatic hydrocarbons, said process comprising the steps of : a) cooling the liquid hydrocarbon feedstock to obtain wax crystals, resulting in a cooled liquid and the wax crystals; b) separating the wax crystals and the cooled liquid obtained in step a) to produce a wax comprising aliphatic hydrocarbons and a dewaxed liquid comprising heteroatom containing polar components and optionally aromatic hydrocarbons ; wherein the liquid hydrocarbon feedstock is not mixed with a solvent before or during step a) , and wherein in steps a) and b) no solvent is used.

2. The process according to claim 1, wherein the weight ratio of aliphatic hydrocarbons having a boiling point of from 30 to 300 °C to aliphatic hydrocarbons having a boiling point of from greater than 300 to 600 °C in the liquid hydrocarbon feedstock is of from 99:1 to 1: 99.

3. The process according to claim 1 or 2, wherein in step a) the liquid hydrocarbon feedstock is cooled to a temperature in the range of from +10 °C to -30 °C.

4. The process according to any one of claims 1 to 3, wherein the liquid hydrocarbon feedstock comprises a liquid product produced by the pyrolysis of plastic waste.

5. A process for the recovery of aliphatic hydrocarbons from plastics, said process comprising the steps of: i) converting the plastics by pyrolysis to a hydrocarbon product comprising a gas phase and a liquid phase; ii) separating at least a portion of the hydrocarbon product into a hydrocarbon gas stream and a hydrocarbon liquid stream; iii) subjecting at least a portion of the hydrocarbon liquid stream to the process of any one of claims 1-4.

6. A process for steam cracking a hydrocarbon feed, wherein the hydrocarbon feed comprises aliphatic hydrocarbons from the wax comprising aliphatic hydrocarbons obtained in a process according to any one of claims 1-5.

7. A process for steam cracking a hydrocarbon feed, comprising the steps of: obtaining a wax comprising aliphatic hydrocarbons from a liquid hydrocarbon feedstock in a process according to any one of claims 1-5; and steam cracking a hydrocarbon feed, wherein the hydrocarbon feed comprises aliphatic hydrocarbons from the wax obtained in the preceding step.