Process for refining a synthetic crude oil stream

Abstract

The present invention relates to a method for refining a synthetic crude oil stream (1), comprising the steps of: providing a synthetic crude oil stream (1), wherein the synthetic crude oil stream (1) contains diene compounds and has a diene number of 0.1 g / 100 g or greater; - contacting a synthetic crude oil stream (1) with a polysulfide stream (2) containing at least one polysulfide compound to form a mixture, wherein contact with the polysulfide stream (2) converts at least a portion of the diene compounds to diene-free products; - separating diene-free products from the mixture to obtain a refined synthetic crude stream (3).

Description

[Technical Field]

[0001] The present invention relates to a process for refining a synthetic crude oil stream. [Background technology]

[0002] Synthetic crude oil, sometimes called syncrude, can be obtained from a variety of processes. For example, synthetic crude oil can be shale oil, obtained from oil shale by pyrolysis. Another source is hydrocarbons obtained from oil sands, especially bitumen, which can be upgraded to obtain synthetic crude oil. Additionally, synthetic crude oil can also be produced from plastic materials (e.g., plastic waste) by cracking.

[0003] Synthetic crudes typically contain a variety of impurities that can adversely affect refining processes and systems or can render the crude completely unsuitable for a particular refining process. The type and content of impurities can vary widely depending on the source and method used to obtain the synthetic crude.

[0004] A particularly significant problem in the further processing of synthetic crude oil is so-called gum formation. Pyrolysis oils typically contain a variety of chemical compounds that can be prone to forming deposits. Such deposits can clog or otherwise damage subsequent refining systems, increasing the burden of cleanup efforts and shortening the plant's lifespan. Summary of the Invention [Problem to be solved by the invention]

[0005] The gum formation problem associated with synthetic crude oils has not yet been fully resolved. There remains a need for a method for reducing the tendency of synthetic crude oils to form gums. Accordingly, it is an object of the present invention to provide a method for reducing gum formation in synthetic crude oils. [Means for solving the problem]

[0006] Accordingly, the present invention provides a method for refining a synthetic crude oil stream, comprising the steps of: providing a syncrude stream, the syncrude stream containing diene compounds and having a diene number of 0.1 g / 100 g or greater; contacting the syncrude stream with a polysulfide stream containing at least one polysulfide compound to form a mixture, wherein contact with the polysulfide stream converts at least a portion of the diene compounds to diene-free products; separating diene-free products from the mixture to obtain a refined synthetic crude stream; and The present invention relates to a method, including:

[0007] In the context of the present invention, it has been found that synthetic crude oils have an increased tendency to form gum, especially when the content of diene compounds is high. Therefore, reactive dienes can act as gum formers and cause harmful deposits in refinery systems. For example, dienes can undergo Diels-Alder reactions, resulting in intermolecular cross-linking and ultimately deposits. Additionally, dienes can form stable complexes with catalysts in hydroprocessing units. Therefore, within the scope of the present invention, it has been found advantageous to reduce the diene content of synthetic crude oils.

[0008] In the method according to the present invention, this is accomplished by reacting the synthetic crude stream with polysulfide compounds. Polysulfide compounds have been shown to be highly suitable for converting reactive dienes into insoluble products or solids that can be easily separated from the synthetic crude stream. The dienes can react with the polysulfide compounds via an addition reaction to form thiols, which can then react with other molecules (e.g., alkenes). This crosslinks multiple molecules, resulting in the intended precipitation. Thus, in the method according to the present invention, gum formation is intentionally achieved, and the "gum," i.e., the insoluble reaction product of the diene and polysulfide compounds, is separated. The refined synthetic crude stream therefore has a lower diene content and is therefore less prone to gum formation.

[0009] US Pat. No. 5,417,844 mentions certain polysulfides in a different context, namely in connection with catalyst pretreatment.

[0010] The use of sulfur-containing compounds to remove olefins from hydrocarbon products is generally known in the prior art. For example, WO 2021 / 021449 describes a method for removing olefins from light hydrocarbon streams by mercaptanization using hydrogen sulfide in the presence of a catalyst. The olefins are converted to mercaptans, which are then oxidized and finally separated in the so-called Merox process. However, WO 2021 / 021449 does not relate to the processing of synthetic crude oils or to diene compounds, which are particularly problematic in relation to gum formation.

[0011] The present invention is also based on a completely different approach, specifically aimed at removing dienes from synthetic crude oils, by using polysulfide compounds to intentionally precipitate the diene compounds as diene-free products, thereby removing the diene compounds.

[0012] Treatment with polysulfide compounds also has a further positive effect on the quality of the synthetic crude stream, as it converts and subsequently removes neutral compounds such as esters, aldehydes, ketones, organohalogen compounds, amides, and nitriles, among others, which can undergo, for example, basic hydrolysis to polar or charged compounds that can be removed by washing with an aqueous phase.

[0013] The diene compounds contained in the synthetic crude oil stream are preferably conjugated or cumulated carbon-carbon double bonds, especially compounds containing conjugated carbon-carbon double bonds. Such compounds are particularly prone to gum formation, for example by the Diels-Alder reaction, and are particularly susceptible to removal by the process according to the invention.

[0014] Those skilled in the art are familiar with methods for determining the diene number. Preferably, the diene number is determined according to the ASTM UOP326-07 standard.

[0015] The synthetic crude stream has a densitometric value of at least 0.1 g / 100 g, preferably at least 0.2 g / 100 g, more preferably at least 0.3 g / 100 g, more preferably at least 0.4 g / 100 g, more preferably at least 0.5 g / 100 g, more preferably at least 0.6 g / 100 g, more preferably at least 0.7 g / 100 g, more preferably at least 0.8 g / 100 g, more preferably at least 0.9 g / 100 g, more preferably at least 1.0 g / 100 g, and more preferably at least 1.5 g / 100 g. The synthetic crude stream preferably has a diene number in the range of from 0.1 g / 100g to 15 g / 100g, more preferably from 1.0 g / 100g to 12 g / 100g, especially from 1.5 g / 100g to 1.5 g / 100g.

[0016] The refined synthetic crude stream preferably has a lower diene number than the synthetic crude stream. The refined synthetic crude stream preferably has a diene number of less than 5 g / 100 g, more preferably less than 4 g / 100 g, more preferably less than 3 g / 100 g, more preferably less than 2 g / 100 g, more preferably less than 1.5 g / 100 g, more preferably less than 1 g / 100 g, more preferably less than 0.9 g / 100 g, more preferably less than 0.8 g / 100 g, more preferably less than 0.7 g / 100 g, more preferably less than 0.6 g / 100 g, and more preferably less than 0.5 g / 100 g. The refined synthetic crude stream preferably has a diene number in the range of 0.01 g / 100 g to 5 g / 100 g, more preferably 0.1 g / 100 g to 2 g / 100 g, especially 0.2 g / 100 g to 1 g / 100 g.

[0017] It has been found advantageous for the contacting of the synthetic crude oil stream with the polysulphide stream to be carried out at a temperature of at least 80° C., preferably at least 100° C., more preferably at least 120° C., more preferably at least 140° C., more preferably at least 160° C., more preferably at least 180° C. In particular, it is preferred if the contacting of the synthetic crude oil stream with the polysulphide stream is carried out at a temperature in the range of from 80 to 450° C., preferably from 100 to 400° C., more preferably from 120 to 350° C., more preferably from 140 to 300° C., more preferably from 160 to 260° C., more preferably from 180 to 220° C. Higher temperatures can promote the reaction between the diene compounds and the polysulphide stream and therefore can reduce the diene content even more significantly.

[0018] In a preferred embodiment, the contact between the syncrude oil stream and the polysulfide stream is carried out for a period of at least 0.5 minutes, preferably at least 1 minute, more preferably at least 2 minutes, even more preferably at least 5 minutes, and most preferably at least 12 minutes. Providing a longer contact time allows for a more complete reaction between the diene compounds and the polysulfide stream, thereby further reducing the diene content. Therefore, particularly preferred contact times are 0.5 to 180 minutes, preferably 1 to 120 minutes, more preferably 2 to 60 minutes, even more preferably 5 to 30 minutes, and most preferably 12 to 20 minutes. The contact time is preferably the average time from initial contact of the syncrude oil stream with the polysulfide stream to separation of diene-free products from the mixture to obtain the refined syncrude oil stream. When the method is carried out as a continuous process, the contact time preferably corresponds to the average residence time in the wash equipment used, such as a mixer-settler.

[0019] In a preferred embodiment, the contacting of the syncrude stream with the polysulfide stream occurs in a pressure vessel, which allows for processing at higher pressures and temperatures, which can facilitate the removal of diene compounds.

[0020] The synthetic crude oil stream is preferably washed with the first aqueous wash solution at a pressure greater than 2 bar (0.2 MPa), preferably greater than 3 bar (0.3 MPa), more preferably greater than 5 bar (0.5 MPa), even more preferably greater than 7 bar (0.7 MPa), and most preferably greater than 10 bar (1.0 MPa). Providing such high pressures allows for high temperature processing, as described above. Particularly preferably, washing of the synthetic crude oil stream with the first aqueous wash solution is carried out at a pressure in the range of 2 bar to 50 bar (0.2 MPa to 5.0 MPa), preferably 3 bar to 35 bar (0.3 MPa to 3.5 MPa), more preferably 5 bar to 25 bar (0.5 MPa to 2.5 MPa), even more preferably 7 bar to 20 bar (0.7 MPa to 2.0 MPa), and most preferably 10 bar to 18 bar (1.0 MPa to 1.8 MPa).

[0021] The polysulfide stream may be an anhydrous stream, for example, obtained by dissolving sulfur in an amine. However, it is preferred that the polysulfide stream is an aqueous solution. This has the advantage, among other things, that further impurities (e.g., certain salts and polar compounds) can be particularly efficiently removed. In addition, the use of an aqueous solution is advantageous for removing neutral compounds such as esters, aldehydes, ketones, organic halogen compounds, amides, and nitriles by basic hydrolysis. The impurities can then be easily removed together with the aqueous phase.

[0022] The concentration of polysulfide compounds in the polysulfide stream is preferably 1 weight percent (% (w / w)) or greater, more preferably 5 weight percent or greater, more preferably 10 weight percent or greater, more preferably 15 weight percent or greater, more preferably 20 weight percent or greater, more preferably 25 weight percent or greater. The concentration is preferably 1 weight percent to 80 weight percent, more preferably 5 weight percent to 60 weight percent, more preferably 10 weight percent to 50 weight percent, more preferably 15 weight percent to 40 weight percent. The use of such high concentrations of polysulfides favors reaction with diene compounds contained in the synthetic crude oil stream, thereby enabling even greater reduction of the diene content.

[0023] In a preferred embodiment, the pH of the polysulfide stream is greater than 8, preferably greater than 9, more preferably greater than 10, more preferably greater than 11, more preferably greater than 12, more preferably greater than 13. The pH is preferably in the range of 8 to 14, preferably 10 to 13. The advantage of having such a basic pH is that the polysulfide compounds exist in a more highly deprotonated state and are therefore more nucleophilic. This promotes the basic hydrolysis of neutral compounds such as esters, aldehydes, ketones, organohalogen compounds, amides, and nitriles.

[0024] Any type of polysulfide compound can be used in the process according to the invention. The polysulfide compound is preferably an inorganic or organic polysulfide, in particular an inorganic polysulfide. Preferably, at least one polysulfide compound is an amine polysulfide, an alkali metal polysulfide, or an alkaline earth metal polysulfide. Calcium polysulfide, sodium polysulfide, and potassium polysulfide, in particular sodium polysulfide or potassium polysulfide, have proven particularly suitable. Sodium polysulfide or potassium polysulfide can be prepared, for example, by dissolving sulfur in NaOH caustic solution or KOH caustic solution. Amine polysulfides can be prepared, for example, by dissolving sulfur in an amine (e.g., ethanolamine or diethanolamine).

[0025] In a preferred embodiment, the volumetric blend ratio of the syncrude oil stream to the polysulfide stream is between 10:1 and 1:5, more preferably between 5:1 and 1:2.5, more preferably between 1.5:1 and 1:1.5. Such blend ratios have been found to be particularly good for treating syncrude oil streams.

[0026] In a preferred embodiment, the mixture formed from the syncrude oil stream and the polysulfide stream has a polar phase and a non-polar phase, and the diene-free products are primarily present in the polar phase. Preferably, separation of the diene-free products from the mixture is achieved by separating the polar phase. If the polysulfide stream is an aqueous solution, the polar phase may be the aqueous phase. Thus, the diene-free products can be separated in a particularly simple manner.

[0027] It has proven particularly advantageous if the contact with the polysulphide stream and subsequent separation of the polar phase takes place in a mixer settler, which typically comprises a continuously operating mixing section and a continuously operating settling section, thus allowing for the mixing of the syncrude stream with the polysulphide stream and the subsequent settling process (phase separation and separation of the refined syncrude stream in a continuous process).

[0028] In an advantageous embodiment, the separated polar phase is at least partially recycled and reused as at least part of the polysulfide stream. It has been found that the separated polar phase often still contains a significant proportion of unconsumed polysulfide compounds. Therefore, if the wastewater stream is partially recycled, the polysulfide compounds can be more effectively utilized. For example, the circulation can include 1 to 25 revolutions. This recycling has energy advantages, leading to cost savings and may also allow for system miniaturization. The proportion of consumed chemicals can also be compensated for by introducing fresh medium into the circulation.

[0029] In a preferred embodiment of the process according to the invention, the refined syncrude stream is washed with an aqueous wash solution to obtain a second refined syncrude stream. Such an additional wash step can more completely remove impurities contained in the syncrude stream.

[0030] The aqueous wash solution is preferably an acidic aqueous wash solution. In particular, it is preferred if the pH of the aqueous wash solution is less than 6, preferably less than 5, more preferably less than 4, more preferably less than 3.5. Such pH values ​​are particularly preferred if the polysulfide stream has a basic pH value. Thus, a basic wash in the form of a treatment with the polysulfide stream can be followed by an acidic wash.

[0031] Washing refined synthetic crude streams with acidic wash solutions can improve removal of basic compounds such as amines, pyridines, and other basic impurities. If basic hydrolysis of neutral compounds is performed as part of the treatment with the polysulfide stream, basic hydrolysis products, such as amines, can be further removed. In particular, this process can also efficiently remove polycyclic amines. Polycyclic amines may be more abundant in synthetic crudes, especially pyrolysis oils. They may be formed, for example, during the cracking process in the presence of a nitrogen source (e.g., additives or polymers such as polyamide (PA), polyacrylonitrile (PAN), or acrylonitrile-butadiene-styrene copolymer (ABS)). Polycyclic amines may be, for example, polycondensed saturated ring systems, polycondensed mono- or polyunsaturated ring systems, or polycondensed aromatic ring systems. Polycyclic amines may be partially dissolved in synthetic crudes or suspended in colloidal regions, often resulting in undesirable deposits that can make system cleaning difficult. In addition, polycyclic amines may cause coating of the active surface of the catalyst in subsequent applications. They may also dissolve undesirable compounds, such as salts, chlorides, heavy metals, or sulfides, in the organic product phase. It has been shown that an acidic wash step can efficiently remove polycyclic amines. It has been found to be advantageous for the acidic wash step to be carried out at a temperature of 20°C or higher for the removal of polycyclic amines. Removal is particularly efficient when the temperature is 50°C or higher.

[0032] However, in the course of the present invention, it has surprisingly been found that it is advantageous for the temperature in the acid wash step not to be too high, in particular to be lower than the temperature of contact with the polysulfide stream. It has been shown that high temperatures in the acid wash step can lead to a decrease in product yield and the formation of impurities. It has therefore been found to be advantageous to carry out the acid wash step at a temperature of less than 120°C. In particular, these adverse effects can be minimized if the temperature is less than 100°C, even more preferably less than 95°C.

[0033] An additional benefit of lower temperatures in the acid wash step is significantly lower material requirements for the wash equipment. The presence of acid solutions at elevated temperatures often necessitates the use of specialized materials or coatings, which significantly increases costs. Therefore, in a preferred embodiment, scrubbing the refined syncrude stream with an acid wash solution is performed at a lower temperature than contacting the syncrude stream with the polysulfide stream.

[0034] In a preferred embodiment, the aqueous cleaning solution contains sulfuric acid, the concentration of which is preferably 0.5 to 10% by weight, in particular 1 to 5% by weight.

[0035] It has also proven advantageous if the volumetric mixing ratio between the refined synthetic crude oil stream and the aqueous wash solution is between 10:1 and 1:5, preferably between 5:1 and 1:2.5, and even more preferably between 2.5:1 and 1:1.5, which allows for a particularly efficient removal of basic impurities.

[0036] The process according to the invention may also include further washing steps. For example, the refined syncrude stream may undergo further washing or refining steps before washing with the aqueous wash solution. However, it is preferred that no further refining steps (in particular washing, filtration, and / or hydrotreating steps) are carried out between the step of separating diene-free products to obtain the refined syncrude stream and the step of washing the refined syncrude stream with the aqueous wash solution. This has the advantage, inter alia, that basic products formed from neutral compounds by basic hydrolysis can be removed immediately after the basic wash step, preferably in an acidic wash step.

[0037] In a further preferred embodiment of the process according to the invention, the second refined syncrude stream is washed with a further aqueous wash solution to obtain a third refined syncrude stream. Such a further wash step makes it possible to particularly thoroughly remove impurities that may still be present after the acid wash step.

[0038] In this context, it is particularly preferred that the pH of the further aqueous washing solution is in the range of 3 to 13, preferably 4 to 12, more preferably 5 to 11, even more preferably 6 to 10, even more preferably 6.5 to 9, and most preferably 7 to 8. A pH in this range is particularly effective for removing small polar neutral molecules and inorganic and organic salts. It is particularly advantageous for the further aqueous washing solution to be basic or substantially neutral, in particular substantially neutral.

[0039] In a preferred embodiment of the method according to the invention, the refined syncrude stream, the second refined syncrude stream, or the third refined syncrude stream is fed to a hydrotreating unit. It has been found that reducing the diene content in the syncrude stream is particularly advantageous, particularly in the hydrotreating process in the hydrotreating unit, since dienes can form stable complexes with the catalyst in such systems. Therefore, using the method according to the invention in combination with hydrotreating can significantly improve the service life of the hydrotreating unit, and in particular the catalysts used.

[0040] In the context of the present invention, it is preferred if the process for refining the synthetic crude oil stream is a continuous process, which has the advantage of achieving higher productivity and less downtime compared to batch processes.

[0041] As described herein, washing each crude oil stream with a respective wash solution may involve mixing the crude oil stream with the wash solution, followed by separating the refined crude oil stream from the aqueous wash solution. Preferably, the wash steps of the process according to the invention are carried out in a mechanical mixer, a static mixer, and / or a mixer settler. As noted above for treatment with polysulfide streams, it has been found to be particularly advantageous if each of the wash steps of the invention is carried out in a mixer settler.

[0042] In the context of the present invention, "syncrude oil stream" is preferably understood to mean a material stream containing a synthetic crude oil or a fraction thereof. Preferably, the synthetic crude oil stream consists of a synthetic crude oil or a fraction thereof. Within the scope of the present invention, it is particularly preferred if the synthetic crude oil stream comprises, and in particular consists of, a pyrolysis oil or a fraction thereof. The pyrolysis oil is preferably a pyrolysis oil obtained from biomass (especially wood) and / or plastic. The process according to the present invention has proven particularly suitable when the synthetic crude oil stream is a hydrocarbon mixture obtained from the depolymerization of biomass or plastic materials, in particular plastic materials. Thus, the synthetic crude oil stream is preferably a plastic pyrolysis product or a fraction thereof, or a biomass pyrolysis product (especially wood pyrolysis product) or a fraction thereof. However, the process according to the present invention is also well suited to other synthetic crude oils and fractions thereof. Therefore, in a further preferred embodiment, the synthetic crude oil stream comprises, and preferably consists of, shale oil or upgraded bitumen.

[0043] Thus, in a particularly preferred embodiment, the synthetic crude stream is produced by depolymerization of plastic materials, in particular plastic waste. Those skilled in the art are familiar with the production of synthetic crude streams by depolymerization of plastic materials. Such methods are known, for example, from WO 2012 / 149590 and U.S. Pat. No. 6,060,631.

[0044] In a preferred embodiment, the plastic material comprises polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyamide (PA), styrene-acrylonitrile (SAN), and / or acrylonitrile-butadiene-styrene (ABS). The method according to the invention has been found to be particularly suitable for purifying pyrolysis oil from the exemplified plastic materials.

[0045] It is particularly preferred that the plastic material comprises PVC, which usually results in impurities in the form of organic chlorine compounds in the crude oil stream obtained from the plastic material, which can be particularly well removed by basic hydrolysis, for example, when the polysulfide stream is a basic aqueous solution.

[0046] It is also preferred if the plastic material comprises PET, which typically results in impurities in the form of ester compounds in the crude oil stream obtained from the plastic material, which can also be particularly easily removed by basic hydrolysis.

[0047] In particular, the plastic material preferably includes PA, SAN, and / or ABS. These plastic materials typically produce impurities in the form of amides and nitriles. During the process of the present invention, these compounds can also be hydrolyzed under basic conditions. When the process of the present invention includes acidic washing, the basic compounds formed from the basic hydrolysis, especially amines, can also be removed very efficiently. PA, SAN, and ABS can also function as nitrogen sources and contribute to the increased production of polycyclic amines, for example, through rearrangement reactions, condensation reactions, and / or radical reactions with PE, PP, and PS. These polycyclic amines can also be efficiently removed during acidic washing.

[0048] All parameters mentioned herein refer to SATP (Standard Ambient Temperature and Pressure) conditions according to IUPAC, in particular a temperature of 25° C. and a pressure of 101,300 Pa, unless otherwise stated.

[0049] Unless otherwise specified, all percentages (%) herein refer to weight percent.

[0050] Unless otherwise stated, all mix ratios specified herein relate to volume mix ratios, i.e., volume:volume ratios.

[0051] The invention is illustrated by the following figures, but it will be appreciated that the invention is not limited thereto. [Brief explanation of the drawings]

[0052] [Figure 1] FIG. 1 is a method flow diagram of a preferred embodiment of the method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0053] In the embodiment shown in Figure 1, a synthetic crude oil stream 1 is obtained by depolymerization of a plastic material. The plastic material is compressed, degassed, and melted in an extruder 12. The plastic melt obtained from the extruder 12 is mixed in a static mixer 13 with an external solvent 14 (preferably heavy oil) and / or previously cracked plastic material, which is recycled as a recycle stream 15, in order to reduce the viscosity of the plastic melt. The resulting mixture is introduced into a depolymerization reactor 16, where the plastic material is depolymerized, preferably at a temperature between 400°C and 440°C. The cracked plastic material is obtained as the overhead product of a column 17. After separation of a gas stream 18 in a further column 19, a synthetic crude oil stream 1 having a diene number of at least 0.1 g / 100 g is obtained.

[0054] In the illustrated embodiment, syncrude stream 1 is mixed with polysulfide stream 2 in a mixing section of first mixer settler 8, preferably at a volumetric mixing ratio of 1:1. Polysulfide stream 2 is preferably a basic aqueous solution containing sodium or potassium polysulfide. The mixture of syncrude stream 1 and polysulfide stream 2 preferably has a temperature of 80°C or higher. Diene compounds contained in syncrude stream 1 at least partially react with the polysulfides to form insoluble diene-free products. The oil phase is then separated from the aqueous phase in the settling section of mixer settler 8. The diene-free products are separated together with the aqueous phase. The average residence time in first mixer settler 8 is preferably 5 to 30 minutes. The aqueous phase is removed as part of wastewater stream 11, and the oil phase is separated as refined syncrude stream 3.

[0055] The refined synthetic crude oil stream 3 thus obtained is then mixed with an aqueous wash solution 4 in a second mixer settler 9. The aqueous wash solution 4 is preferably an aqueous sulfuric acid solution having a pH of 0 to 5. As a result, in the settling section of the mixer settler 9, the refined oil phase is again separated from the aqueous phase, the aqueous phase being removed via a wastewater stream 11, and a second refined synthetic crude oil stream 5 is obtained from the oil phase. In the illustrated embodiment, the second refined synthetic crude oil stream 5 is washed in a third mixer settler 10 with a further aqueous wash solution 6. The further aqueous wash solution 6 is preferably a neutral wash solution, preferably essentially water. After washing, the aqueous phase is again removed as part of the wastewater stream 11, and a third refined synthetic crude oil stream 7 is obtained from the oil phase.

Claims

1. 1. A method for refining a synthetic crude oil stream (1), comprising: providing said synthetic crude stream (1), wherein said synthetic crude stream (1) contains diene compounds and has a diene number of 0.1 g / 100 g or greater; contacting said synthetic crude oil stream (1) with a polysulfide stream (2) containing at least one polysulfide compound to form a mixture, wherein contact with the polysulfide stream (2) converts at least a portion of said diene compounds into diene-free products; - separating said diene-free product from said mixture to obtain a refined synthetic crude stream (3); A method comprising:

2. 2. The process of claim 1, wherein the contacting of the syncrude oil stream (1) with the polysulfide stream (2) is carried out at a temperature of 80°C or greater.

3. 3. The method according to claim 1 or claim 2, wherein the polysulfide stream (2) is an aqueous solution.

4. 4. The method according to any one of claims 1 to 3, wherein the concentration of the polysulfide compounds in the polysulfide stream (2) is 1 wt.% or more.

5. The method according to any one of claims 1 to 4, wherein the polysulfide stream (2) has a pH greater than 8.

6. The method of any one of claims 1 to 5, wherein the at least one polysulfide compound is an amine polysulfide, an alkali metal polysulfide, or an alkaline earth metal polysulfide.

7. 7. The method of any one of claims 1 to 6, wherein the at least one polysulfide compound is sodium polysulfide or potassium polysulfide.

8. The process according to any one of claims 1 to 7, wherein the volumetric mixing ratio of the synthetic crude oil stream (1) to the polysulfide stream (2) is between 10:1 and 1:

5.

9. 9. The method according to any one of claims 1 to 8, wherein the mixture formed from the syncrude oil stream (1) and the polysulfide stream (2) has a polar phase and a non-polar phase, the diene-free products being present mainly in the polar phase, and separation of the diene-free products from the mixture is achieved by separating the polar phase.

10. 10. The method of any one of claims 1 to 9, wherein the refined syncrude stream (3) is washed with an aqueous wash solution (4) to obtain a second refined syncrude stream (5).

11. 11. The method of claim 10, wherein the pH of the aqueous cleaning solution (4) is less than 6.

12. 12. The method of claim 10 or claim 11, wherein the second refined syncrude stream (5) is washed with another aqueous wash solution (6) to obtain a third refined syncrude stream (7).

13. 13. The method of any one of claims 1 to 12, wherein the refined syncrude stream (3), the second refined syncrude stream (5), or the third refined syncrude stream (7) is fed to a hydroprocessing unit.

14. The method according to any one of claims 1 to 13, wherein said synthetic crude stream (1) is produced by depolymerization of plastic material, in particular plastic waste.

15. 15. The method of claim 14, wherein the plastic material comprises polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyamide (PA), styrene-acrylonitrile (SAN), and / or acrylonitrile-butadiene-styrene (ABS).

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