Process for purifying synthetic crude oil streams

Abstract

The present invention relates to a method for purifying a synthetic crude oil stream, comprising the following steps: - providing a synthetic crude oil stream; - washing the synthetic crude oil stream with a first aqueous washing solution at a first temperature to obtain a first purified synthetic crude oil stream; and - washing the first purified synthetic crude oil stream with a second aqueous washing solution at a second temperature to obtain a second purified synthetic crude oil stream, wherein the first aqueous washing solution is alkaline, the second aqueous washing solution is acidic, and the second temperature is lower than the first temperature. The present invention also relates to a method for producing a synthetic crude oil stream, comprising the following steps: - producing a synthetic crude oil stream (1), preferably by depolymerization of plastic material, in particular plastic waste; and - purifying the synthetic crude oil stream (1) according to the method of the present invention.

Description

Technical Field

[0001] The present invention relates to a process for purifying synthetic crude oil streams. Background Art

[0002] Synthetic crude oil, sometimes also referred to as synthetic crude oil, can be obtained by different 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, from which synthetic crude oil can be obtained by upgrading. In addition, synthetic crude oil can also be produced from plastic materials, such as plastic waste, by cracking.

[0003] Synthetic crude oils often contain different impurities, which may adversely affect the refining process and refinery, or make the crude oil completely unsuitable for certain refining processes. The type and amount of impurities can vary greatly depending on the source of the synthetic crude oil and how it is obtained.

[0004] WO 2020 / 020769 A1 describes a process for purifying recycled or renewable organic material, comprising heating the material in the presence of an aqueous alkali metal hydroxide solution and hydrotreating the material in the presence of a hydrotreating catalyst to obtain a purified material having a reduced chlorine content.

[0005] WO 2021 / 105326 A1 describes a method for treating liquefied plastic waste, comprising pre-treating the liquefied plastic waste with an aqueous medium having a pH value of at least 7 at a temperature of at least 200° C., followed by hydrotreatment and post-treatment to obtain a steam cracker feed.

[0006] WO 2014 / 165859 A1 describes a method and an apparatus for treating synthetic crude oil, wherein the synthetic crude oil is washed with an alkaline aqueous process solution to reduce the acidity level. The method may also comprise two or more washing steps.

[0007] Other methods for purifying or treating oils are described in US 9 045 698 B2, US 2006 / 144761 A1 and GB 590 635 A.

[0008] However, the purification methods known in the prior art are often complicated and / or inadequate. In particular, impurities such as neutral compounds (e.g. esters, aldehydes, ketones, organic halogen compounds, amides, nitriles) or polycyclic amines are often not adequately removed, or are not removed at all. This is particularly problematic in the case of complex starting materials with a large variation in the impurity profile, such as in the case of synthetic crude oils obtained from plastic waste. Inadequate removal of impurities may lead to problems in the further processing of the purified crude oil. Another problem is the formation of deposits in the equipment observed in many purification processes, which makes cleaning the equipment more difficult and hinders efficient operation.

[0009] Therefore, there is still a need for new or improved methods for purifying synthetic crude oil. An object of the present invention is to provide such a method. In particular, an object of the present invention is to provide a method for purifying synthetic crude oil, which can particularly effectively and thoroughly remove impurities, especially impurities in the form of acidic or basic compounds, but also impurities in the form of neutral compounds. Another object of the present invention is to minimize the formation of deposits during the purification process. Another object is to provide a purification method that is as efficient and economical as possible. Summary of the invention

[0010] According to the invention, this object is achieved by a method for purifying a synthetic crude oil stream, comprising the following steps:

[0011] - Providing synthetic crude oil streams;

[0012] - washing the synthetic crude stream with a first aqueous wash solution at a first temperature to obtain a first purified synthetic crude stream; and

[0013] - washing the first purified synthetic crude stream with a second aqueous washing solution at a second temperature to obtain a second purified synthetic crude stream,

[0014] The first aqueous washing solution is alkaline, the second aqueous washing solution is acidic, and the second temperature is lower than the first temperature.

[0015] In another aspect, the present invention relates to a method for producing synthetic crude oil, comprising the steps of:

[0016] - producing a synthetic crude oil stream, preferably by depolymerization of plastic materials, in particular plastic waste; and

[0017] - A synthetic crude stream is purified according to the method for purifying a synthetic crude stream according to the invention.

[0018] In the process of the present invention, surprisingly it turns out that it is advantageous to carry out the alkaline washing step at a higher temperature and then the acidic washing step at a lower temperature. The surprising advantage comes from the fact that the alkaline washing step is carried out before the acidic washing step and the fact that the temperature in the alkaline washing step is higher than that in the acidic washing step.

[0019] About the order of washing steps, surprisingly found that, before the acidic washing step, alkaline washing step is carried out can cause better phase separation and the remarkable reduction of sediment.When carrying out the acidic washing step when there is no previous alkaline washing step, the inventor observes the formation of sediment, and sediment result is mainly the wax carboxylic acid of precipitation.Wax carboxylic acid is a long-chain carboxylic acid, for example, with a chain length of 20 to 75 carbon atoms.Except the unbranched and branched of paraffinic hydrocarbons, wax carboxylic acid can also have aromatic, olefinic and heteroatom functional groups.Wax carboxylic acid is included in many synthetic crude oils, particularly pyrolysis oil (for example, from the pyrolysis of plastics), because these compounds can be gradually formed in the pyrolysis process, for example, by reaction with the oxygen introduced or by functional polymers or additives already present.In synthetic crude oil, wax carboxylic acid exists in the combined form of salt usually.In the process of the present invention, it has been found that the crude oil stream of unpretreated synthesis treated with acidic washing aqueous solution can cause the wax carboxylic acid of combination to be protonated and therefore released. The wax carboxylic acids released in this way can, on the one hand, precipitate and form undesirable deposits, and on the other hand, it has been shown that the released wax carboxylic acids can act as surfactants and form mixed phases or can bind undesirable compounds such as water, heavy metals and nitrogen compounds in the oil phase. Unremoved wax carboxylic acids can also lead to equipment corrosion and act as catalyst poisons in other subsequent processing of the synthetic crude oil.

[0020] In the process of the present invention, it has been found that the release of bound wax carboxylic acids and related problems can be reduced by performing an alkaline washing step before the acid washing step. When washed with an alkaline aqueous washing solution, the wax carboxylic acids are mainly present in a deprotonated state, which can be removed by the aqueous phase, thereby reducing the adverse effects on the subsequent acid washing step. Therefore, the sequence of washing with the first aqueous washing solution and the second aqueous washing solution provided by the present invention can lead to reduced deposits in the equipment, better phase separation and thus better removal of impurities, reduced corrosion in the equipment, and protection of catalysts in other processing processes.

[0021] It has further been shown that carrying out the alkaline washing step at high temperatures is advantageous for the removal of wax carboxylic acids. High temperatures lead to better solubility of the wax carboxylic acids in the aqueous phase. It is therefore advantageous if the washing of the synthetic crude oil stream with the first aqueous washing solution is carried out at a temperature above 70° C. It has proven to be particularly advantageous if the temperature is above 95° C., since many wax carboxylates, in particular alkali metal salts, are particularly well soluble in water at these temperatures and can be removed particularly effectively by the aqueous phase.

[0022] In the prior art, alkaline washing aqueous solution is mainly used to reduce the acidity level in synthetic crude oil so far.In process of the present invention, it has been found that alkaline washing aqueous solution can even be used to remove neutral compounds, such as ester, aldehyde, ketone, organic halogen compound, amide and nitrile.In the method according to the present invention, this type of neutral compound can be hydrolyzed by the first aqueous washing solution.The product of alkaline hydrolysis includes the acidic compound removed in the alkaline washing process, such as carboxylic acid, and the basic compound that can be removed in the subsequent acid washing step, such as amine.

[0023] If the alkaline washing step is carried out at a higher temperature, this leads to further advantages: while acidic compounds such as carboxylic acids and phenols only need to be deprotonated during the alkaline washing in order to be removed with the aqueous washing solution, neutral compounds cannot be deprotonated under the washing conditions and must undergo a hydrolysis reaction. The hydrolysis reaction is temperature-dependent and proceeds faster at higher temperatures. Therefore, higher temperatures in the alkaline washing step allow for better removal of neutral compounds. In this context, it is advantageous to wash the synthetic crude oil stream with the first aqueous washing solution at a temperature above 70° C. Even higher temperatures, for example above 95° C., in particular above 100° C., have proven to be particularly suitable for removing neutral compounds.

[0024] In addition to removing the hydrolyzate from the alkaline washing step, washing the first purified synthetic crude oil stream with an acidic washing solution provided by the method of the present invention can remove other alkaline compounds, such as amines, pyridines and other alkaline impurities. The result is that polycyclic amines can be effectively removed in particular. Polycyclic amines can be present in synthetic crude oils to a greater extent, particularly in pyrolysis oils. They can be formed, for example, in a cracking process in the presence of a nitrogen source, which is, for example, an additive or a polymer, such as polyamide (PA), polyacrylonitrile (PAN) or acrylonitrile-butadiene-styrene copolymer (ABS). In the case of polycyclic amines, they can be, for example, polycondensed, saturated, monounsaturated and polyunsaturated or aromatic ring systems. They can be partially dissolved in the synthetic crude oil or suspended in the colloidal region, and generally lead to undesirable deposits, making the cleaning of the equipment more difficult. In addition, they may also cause clogging of the active surface of the catalyst in subsequent applications. In addition, they can also dissolve unwanted compounds in the organic product phase, such as salts, chlorides, heavy metals or sulfides. It has been found that polycyclic amines can be effectively removed by the method of the present invention. For the removal of polycyclic amines, it has proven to be advantageous if the acidic washing step is carried out at a temperature of at least 20° C. The removal efficiency is particularly high if the temperature is at least 50° C.

[0025] However, in the process of the present invention, it has surprisingly been shown that it is advantageous if the temperature in the acidic washing step is not too high, in particular lower than the temperature in the alkaline washing step. Thus, it has been found that high temperatures in the acidic washing step lead to reduced product yields and the formation of impurities. In the opinion of the inventors, without being bound by theory, this can be explained by the reaction of the olefin with the acid used, for example by hydroxysulfonation or by sulfation with sulfuric acid or by reaction with other acids. Alcohols, sulfonates, sulfates and hydroxysulfonates form impurities, which can lead to deposits, thus making cleaning more difficult and producing corrosion. It has therefore been shown that it is advantageous to carry out the acidic washing step at a temperature below 120°C. In particular, these adverse effects can be minimized if the temperature is below 100°C, even more preferably below 95°C.

[0026] Another advantage of the lower temperature in the acid washing step is that the material requirements for the washing equipment are significantly reduced. The presence of acidic solutions at high temperatures often requires the use of special materials or coatings, which can lead to significant cost increases.

[0027] Another advantage of the sequence of washing steps in the method according to the invention, particularly in combination with the preferred embodiment in which the alkaline and acidic washing steps are part of a continuous process, is that the method can be carried out particularly economically. Synthetic crude oils are usually obtained by high temperature processes, such as pyrolysis or cracking. If the production method according to the invention is downstream of such a method, it is not necessary to heat the synthetic crude oil stream, as long as the alkaline washing step is carried out before the acidic washing step. The synthetic crude oil stream obtained from the production process can be washed with a first aqueous washing solution directly or after being cooled to a first temperature, and the first purified synthetic crude oil stream thus obtained can be washed with a second aqueous washing solution after being further cooled to a second temperature. Since the synthetic crude oil stream does not have to be heated between the washing steps, the method can be carried out particularly economically and efficiently. With regard to the method according to the invention, it is therefore particularly preferred that the synthetic crude oil stream is not heated between the washing at the first temperature and the washing at the second temperature.

[0028] In a preferred embodiment of the process of the invention, the first temperature is above 70° C., preferably above 80° C., more preferably above 90° C., even more preferably above 95° C., even more preferably above 100° C., even more preferably above 105° C., even more preferably above 110° C., even more preferably above 115° C., even more preferably above 120° C., even more preferably above 125° C., even more preferably above 130° C., most preferably above 135° C. Providing such a high first temperature has the advantage that the wax carboxylic acids present in the synthetic crude oil stream can be better dissolved and can be removed by alkaline washing. Another advantage of a high first temperature is that the alkaline hydrolysis reaction proceeds particularly quickly and thus neutral compounds can be removed particularly well. It is particularly preferred that the first temperature is 70°C to 190°C, preferably 80°C to 180°C, more preferably 90°C to 170°C, even more preferably 95°C to 165°C, even more preferably 100°C to 160°C, even more preferably 105°C to 155°C, even more preferably 110°C to 150°C, most preferably 115°C to 145°C.

[0029] In a preferred embodiment of the method according to the invention, the second temperature is below 120°C, preferably below 110°C, more preferably below 100°C, even more preferably below 95°C, even more preferably below 90°C, even more preferably below 80°C, and most preferably below 75°C. The advantage of providing such a lower temperature is that the formation of impurities can be reduced and the product yield can be increased. Another advantage of the lower temperature is that the cleaning device is exposed to less harsh conditions, so cheaper materials or material coatings are required. At the same time, basic compounds such as amines and pyridines can still be effectively removed because, compared with neutral compounds, the removal of these compounds only requires protonation without hydrolysis reactions. It is particularly preferred that the second temperature is 20°C to 120°C, preferably 30°C to 110°C, more preferably 40°C to 100°C, even more preferably 50°C to 90°C, even more preferably 60°C to 80°C, even more preferably 65°C to 75°C. The advantage is that, on the one hand, the temperature is low enough to minimize the formation of impurities, and on the other hand, the temperature is high enough to effectively remove, in particular, polycyclic amines.

[0030] In a preferred embodiment, the average washing duration of the crude oil stream washed with the first aqueous washing solution is at least 0.5 minute, preferably at least 1 minute, more preferably at least 2 minutes, even more preferably at least 5 minutes, most preferably at least 12 minutes. Providing longer washing duration for alkaline washing can make the hydrolysis reaction be carried out more completely, thereby can better remove neutral compounds. Especially, therefore preferably average washing duration is 0.5 to 180 minute, preferably 1 to 120 minute, more preferably 2 to 60 minutes, even more preferably 5 to 30 minutes, most preferably 12 to 20 minutes.

[0031] The average washing duration is preferably the average time period between contacting the synthetic crude stream with the first aqueous washing solution and separating the first purified synthetic crude stream from the first aqueous washing solution. If the washing is carried out in a continuous process, the average washing duration preferably corresponds to the average residence time in the washing device, such as a mixer-settler.

[0032] In a preferred embodiment, the pressure at which the synthetic crude oil stream is washed with the first aqueous washing solution is higher than the pressure at which the first purified synthetic crude oil stream is washed with the second aqueous washing solution. Providing higher pressures during alkaline washing can achieve higher temperatures, thereby better removing insoluble wax carboxylic acids and neutral compounds. In contrast, in acidic washing, lower pressures are advantageous because this in turn can reduce the formation of unwanted impurities and because of lower material requirements, which can lead to considerable cost savings.

[0033] In a preferred embodiment, washing the synthetic crude stream with at least the first aqueous wash solution is performed in a pressure vessel. Providing a pressure vessel enables washing at higher pressures and temperatures, thereby better removing poorly soluble wax carboxylic acids and neutral compounds.

[0034] Preferably, washing the synthetic crude oil stream with the first aqueous washing solution is carried out at a pressure greater than 2 bar, preferably greater than 3 bar, more preferably greater than 5 bar, even more preferably greater than 7 bar, and most preferably greater than 10 bar. As mentioned above, providing such a high pressure enables high temperatures and good removal of insoluble wax carboxylic acids and neutral compounds. Particularly preferably, washing the synthetic crude oil stream with the first aqueous washing solution is carried out at a pressure of 2 to 50 bar, preferably 3 to 35 bar, more preferably 5 to 25 bar, even more preferably 7 to 20 bar, and most preferably 10 to 18 bar.

[0035] Preferably, washing the first purified synthetic crude oil stream with the second aqueous washing solution is carried out at a pressure of less than 12 bar, preferably less than 7 bar, more preferably less than 6 bar, and even more preferably less than 5 bar. As previously mentioned, providing such a low pressure allows cheaper materials to be used. Particularly preferably, washing the first purified synthetic crude oil stream with the second aqueous washing solution is carried out at a pressure of 1 bar to 12 bar, preferably 1.5 bar to 7 bar, more preferably 2 bar to 6 bar, and even more preferably 3 bar to 5 bar.

[0036] In the context of the present invention, it has proven to be particularly advantageous if the pH value of the first aqueous washing solution is greater than 8, preferably greater than 9, more preferably greater than 10, even more preferably greater than 11, even more preferably greater than 12, most preferably greater than 13. Providing such a high pH value can promote the hydrolysis reaction, whereby neutral compounds can be removed particularly well. Particularly preferably, the pH value of the first aqueous washing solution is from 8 to 14, preferably from 9 to 13, more preferably from 9.5 to 12, most preferably from 10 to 11.

[0037] In a preferred embodiment, the first aqueous washing solution contains sodium hydroxide. Particularly preferably, the concentration of sodium hydroxide is 0.5 to 10% by weight, in particular 1 to 5% by weight.

[0038] With regard to washing the first purified synthetic crude oil stream with the second aqueous washing solution, it has proven to be particularly advantageous if the pH value of the second aqueous washing solution is less than 6, preferably less than 5, more preferably less than 4, even more preferably less than 3, even more preferably less than 2, most preferably less than 1. This enables particularly effective removal of basic impurities, such as amines and pyridine. Particularly preferably, the pH value of the second aqueous washing solution is from 0 to 6, preferably from 1 to 5, more preferably from 2 to 4, most preferably from 2.5 to 3.5.

[0039] In a preferred embodiment, the second aqueous washing solution contains sulfuric acid. Preferably, the concentration of sulfuric acid is 0.5 to 10% by weight, in particular 1 to 5% by weight.

[0040] It has proven to be advantageous if the synthetic crude oil stream and the first aqueous washing solution are mixed in a volume ratio of 5:1 to 1:5, preferably 2.5:1 to 1:2.5, even more preferably 1.5:1 to 1:1.5. Such a mixing ratio allows particularly effective removal of wax carboxylic acids and hydrolysis of neutral compounds, and also allows particularly effective removal of other acidic impurities.

[0041] Advantageously, the first purified synthetic crude oil stream and the second aqueous washing solution are mixed in a volume ratio of 10:1 to 1:5, preferably 5:1 to 1:2.5, even more preferably 2.5:1 to 1:1.5. Such a mixing ratio is particularly effective in removing alkaline impurities.

[0042] The method according to the invention may also include further washing steps. For example, the first purified synthetic crude oil stream may undergo further washing or purification steps before washing with the second aqueous washing solution. However, preferably, no further purification steps, in particular no washing steps, no filtering steps and / or no hydrotreating steps, are performed between washing the synthetic crude oil stream with the first aqueous washing solution and washing the first purified synthetic crude oil stream with the second aqueous washing solution. This has the advantage, in particular, that alkaline products formed by alkaline hydrolysis of neutral compounds can be removed in an acidic washing step immediately following the alkaline washing step.

[0043] Preferably, the method according to the invention does not comprise any filtering step. Avoiding the filtering step results in a particularly simple and economical process. The filtering step can be avoided, in particular because the washing of the synthetic crude oil stream with the alkaline aqueous washing solution is carried out at higher temperatures. This enables the wax carboxylic acids, which usually dissolve more poorly at lower temperatures and which may require filtering if poorly removed, to be effectively removed.

[0044] The method according to the invention may also comprise a hydrotreating step for additionally removing impurities. However, it is preferred that the method according to the invention does not comprise a hydrotreating step. Avoiding a hydrotreating step results in a particularly simple and economical purification process. Even without providing a hydrotreating step, the washing step provided according to the invention is also able to remove impurities particularly well.

[0045] In a particularly preferred embodiment, the method according to the invention further comprises the step of washing the second purified synthetic crude oil stream with a third aqueous washing solution at a third temperature to obtain a third purified synthetic crude oil stream. Providing this further washing step enables particularly thorough removal of impurities that may still be present after the alkaline and acidic washing steps.

[0046] In this context, it is particularly preferred that the pH value of the third aqueous washing solution is from 3 to 13, preferably from 4 to 12, more preferably from 5 to 11, even more preferably from 6 to 10, even more preferably from 6.5 to 9, and most preferably from 7 to 8. pH values ​​within this range are particularly effective for removing small polar neutral molecules and inorganic and organic salts. It is particularly advantageous if the third aqueous washing solution is alkaline or substantially neutral, in particular substantially neutral.

[0047] In a preferred embodiment, the third aqueous washing solution contains a neutral amine. This has the advantage of better protecting subsequent equipment.

[0048] In a preferred embodiment, the third temperature is lower than the first temperature. This enables the process to be carried out efficiently and economically, as the crude oil stream does not have to be heated prior to washing with the third aqueous wash solution.

[0049] Preferably, the third temperature is less than 120° C., preferably less than 110° C., more preferably less than 100° C., even more preferably less than 90° C., even more preferably less than 80° C., and most preferably less than 75° C. Particularly preferably, the third temperature is 20° C. to 120° C., preferably 30° C. to 110° C., more preferably 40° C. to 100° C., even more preferably 50° C. to 90° C., even more preferably 60° C. to 80° C., even more preferably 65° C. to 75° C.

[0050] It has been shown to be advantageous that the pressure at which the synthetic crude oil stream is washed with the first aqueous washing solution is higher than that at which the second purified synthetic crude oil stream is washed with the third aqueous washing solution. Providing higher pressures during the alkaline washing process can achieve higher temperatures, thereby more thoroughly removing insoluble wax carboxylic acids and neutral compounds. However, when washing with the third aqueous washing solution, lower pressures are advantageous because this reduces the requirements for materials used, which can result in significant cost savings.

[0051] In a preferred embodiment, washing the second purified synthetic crude oil stream with the third aqueous washing solution is carried out at a pressure of less than 12 bar, preferably less than 10 bar, more preferably less than 8 bar, even more preferably less than 7 bar. Particularly preferred pressures range from 1 bar to 12 bar, preferably from 1.5 bar to 10 bar, more preferably from 2 bar to 8 bar, even more preferably from 3 bar to 7 bar.

[0052] It has proven to be advantageous to mix the second purified synthetic crude oil stream with the third aqueous washing solution in a volume ratio of 10:1 to 1:5, preferably 5:1 to 1:2.5, even more preferably 2.5:1 to 1:1.5. Such a mixing ratio allows particularly effective removal of residual impurities.

[0053] For the present invention, it is preferred that the method for purifying the synthetic crude oil stream is a continuous method. Compared with a batch process, the advantage is that higher productivity and shorter downtime can be achieved. Therefore, preferably, the following steps are part of a continuous method: washing the synthetic crude oil stream with a first aqueous washing solution, washing the first purified synthetic crude oil stream with a second aqueous washing solution, and if provided, washing the second purified synthetic crude oil stream with a third aqueous washing solution. It is also preferred that the method for producing synthetic crude oil according to the present invention is a continuous method, that is, if it is preferred to produce the synthetic crude oil stream by depolymerization of plastic materials, it is also part of a continuous method. Providing a continuous method has the advantage of avoiding heating the synthetic crude oil stream, because the synthetic crude oil stream obtained from the production method can be directly washed with the first aqueous washing solution or washed with the first aqueous washing solution after being cooled to the first temperature, or, after being cooled from the first temperature to the second temperature, the first purified synthetic crude oil stream can be washed with the second aqueous washing solution.

[0054] Typically, washing a crude oil stream with an aqueous wash solution includes mixing the crude oil stream with the wash solution and then separating the purified crude oil stream from the aqueous wash solution.

[0055] Preferably, the washing step of the method of the present invention is carried out in a mechanical mixer, a static mixer and / or a mixer-settler. It has been shown that it is particularly advantageous if the washing steps of the method of the present invention are each carried out in a mixer-settler. Typically, a mixer-settler comprises a continuously operated mixing zone and a continuously operated settling zone, thereby allowing the synthetic crude oil stream to be mixed with the corresponding aqueous washing solution, and allowing the subsequent settling process in a continuous process to separate the phases and separate the purified synthetic crude oil stream.

[0056] For the purposes of the present invention, "synthetic crude oil stream" preferably refers to a stream containing synthetic crude oil or a synthetic crude oil fraction (fraction). Preferably, the synthetic crude oil stream consists of synthetic crude oil or its fraction. Within the scope of the present invention, it is particularly preferred that the synthetic crude oil stream contains pyrolysis oil or its fraction, in particular, consists of pyrolysis oil or its fraction. Preferably, pyrolysis oil is a pyrolysis oil obtained from biomass (especially wood) and / or plastic. It has been proven. If the synthetic crude oil stream is a hydrocarbon mixture obtained by the depolymerization of biomass or plastic material, especially plastic material, the method according to the present invention is particularly suitable. Preferably, the synthetic crude oil stream is therefore a plastic pyrolysis product or its fraction, or a biomass pyrolysis product, in particular a wood pyrolysis product, or its fraction. However, the method according to the present invention is also very suitable for other synthetic crude oils and their fractions. In other preferred embodiments, the synthetic crude oil stream therefore contains shale oil or upgraded asphalt, preferably consisting of shale oil or upgraded asphalt.

[0057] Therefore, in the method for producing synthetic crude oil according to the invention, preferably the synthetic crude oil stream is produced by depolymerization of plastic material, preferably plastic waste. The person skilled in the art is familiar with the production of synthetic crude oil streams by depolymerization of plastic material. Such methods are known, for example, from WO 2012 / 149590 A1 and US 6,060,631 A.

[0058] Synthetic crude oils obtained from plastic materials usually contain many different impurities, in particular wax carboxylic acids, polycyclic amines and neutral compounds, which can be removed particularly well by the method according to the invention. This is particularly applicable to plastic waste, which usually contains a mixture of different plastics. In addition, plastic materials usually contain additives that may lead to impurities in the form of organic phosphates or phosphonates. Such phosphates or phosphonates can be hydrolyzed under alkaline conditions in the method according to the invention and can therefore be removed particularly effectively.

[0059] 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 proven to be particularly suitable for removing impurities generated by said plastic materials.

[0060] It is particularly preferred that the plastic material comprises PVC. This usually leads to impurities in the form of organochlorine compounds in the crude oil stream obtained from the plastic material. During the washing with the first aqueous washing solution, organochlorine compounds can be removed particularly well by alkaline hydrolysis.

[0061] It is particularly preferred if the plastic material comprises PET. This generally results in the presence of impurities in the form of ester compounds in the crude oil stream obtained from the plastic material, which impurities can also be removed particularly well by alkaline hydrolysis during washing with the first aqueous washing solution.

[0062] In particular, preferred plastic materials include PA, SAN and / or ABS. These plastic materials usually produce impurities in the form of amides and nitrile. In the process of the method of the present invention, these compounds can also be hydrolyzed during the washing process with the first aqueous washing solution. The basic compounds formed by the alkaline hydrolysis, in particular amines, can be effectively removed in the subsequent washing with an acidic washing aqueous solution. PA, SAN and ABS can also serve as nitrogen sources and promote the formation of polycyclic amines by rearrangement reactions, condensation reactions and / or free radical reactions (for example with PE, PP and PS). These can be effectively removed by washing with an acidic aqueous washing solution provided by the present invention.

[0063] Unless stated otherwise, all parameters mentioned herein refer to SATP conditions according to IUPAC (“Standard Ambient Temperature and Pressure”), in particular to a temperature of 25° C. and a pressure of 101,300 Pa.

[0064] Unless otherwise indicated, all percentages (%) herein refer to weight percentages.

[0065] Unless otherwise stated, all mixing ratios specified herein refer to volume mixing ratios, ie, volume ratios (volume:volume).

[0066] The temperatures specified in this context for the washing step preferably refer in each case to the temperature of the mixture of crude oil stream and aqueous washing solution after mixing and before phase separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The present invention is illustrated by the following figure, but of course, the present invention is not limited thereto.

[0068] Figure 1 A process flow diagram of a preferred embodiment of the method for producing synthetic crude oil according to the present invention is shown. Specific embodiments

[0069] exist Figure 1 In the embodiment shown, the synthetic crude oil stream 1 is obtained by depolymerization of plastic material. The plastic material is compacted, degassed and melted in an extruder 12. The plastic melt leaving the extruder 12 is mixed in a static mixer 13 with an external solvent 14, preferably heavy fuel oil, and / or with already cracked plastic material, which is recycled as a recycle stream 15 to reduce the viscosity of the plastic melt. The resulting mixture is introduced into a depolymerization reactor 16, in which the plastic material is preferably depolymerized at a temperature of 400° C. to 440° C. The cracked plastic material is obtained as a top product of a column 17. After separation of a gas stream 18 in a further column 19, the synthetic crude oil stream 1 is obtained.

[0070] In the embodiment shown, the synthetic crude oil stream 1 is mixed with the first aqueous washing solution 2 in the mixing zone of the first mixer-settler 8, preferably in a volume ratio of 1:1. The first aqueous washing solution 2 is preferably a sodium hydroxide solution with a pH value between 9 and 12. The mixture of the synthetic crude oil stream 1 and the first aqueous washing solution 2 preferably has a temperature of at least 95°C. Since the synthetic crude oil stream 1 is fed directly from the manufacturing process to the mixer-settler 8, no heating is required to reach this temperature. In particular, high temperatures increase the water solubility of wax carboxylic acids, which enter the aqueous phase in a deprotonated form due to the alkaline pH. In addition, high temperatures are conducive to the hydrolysis of impurities in the form of neutral compounds. Acidic hydrolysis products, such as carboxylic acids, are deprotonated due to the alkaline pH and also enter the aqueous phase as charged compounds. As a result, the purified oil phase is separated from the aqueous phase in the settling zone of the mixer-settler 8. The average residence time in the first mixer-settler 8 is preferably 5 to 30 minutes. The aqueous phase is removed as part of the wastewater stream 11 and the oil phase is separated as a first purified synthetic crude oil stream 3 .

[0071] The first purified synthetic crude oil stream 3 thus obtained is then mixed with the second aqueous washing solution 4 in the second mixer-settler 9. The second aqueous washing solution 4 is preferably an aqueous sulfuric acid solution with a pH value between 0 and 5. The temperature of the mixing of the first purified synthetic crude oil stream 3 and the second aqueous washing solution 4 is lower than the temperature of the mixing in the first washing step, preferably below 90° C. The lower temperature in the second washing step reduces the formation of additional impurities and increases the product yield. In addition, the material requirements for the second mixer-settler 9 are lower; in particular, expensive materials and coatings are not required. In addition, the second washing can be carried out at a lower pressure, which in turn leads to lower requirements for the materials used. In particular, basic impurities, such as amines or pyridine, are protonated by washing with an acidic washing solution and thus enter the aqueous phase as charged compounds. In addition, the remaining neutral compounds can also be hydrolyzed under acidic conditions. Subsequently, the purified oil phase is separated from the aqueous phase again in the settling zone of the mixer-settler 9, the aqueous phase is removed by the wastewater stream 11, and the second purified synthetic crude oil stream 5 is obtained from the oil phase.

[0072] In the embodiment shown, the second purified synthetic crude oil stream 5 is washed with a third aqueous washing solution 6 in a third mixer-settler 10. The third aqueous washing solution 6 is preferably a neutral washing solution, preferably substantially water. The temperature in this washing step preferably corresponds to the temperature of the second washing step, or is lower than the temperature of the second washing step. In this washing step, impurities are removed, some of which, such as acidic hydrolyzates, small polar neutral molecules and inorganic and organic salts, may still exist after the first two washing steps. Neutral washing also increases the safety of further using the third purified synthetic crude oil stream 7 obtained thereby. After washing, the aqueous phase is removed again as a part of the wastewater stream 11, and the third purified synthetic crude oil stream 7 is obtained from the oil phase.

Claims

1. A method for purifying a synthetic crude oil stream (1), comprising the following steps: - providing a synthetic crude oil stream (1); - washing the synthetic crude stream (1) with a first aqueous washing solution (2) at a first temperature to obtain a first purified synthetic crude stream (3); and - washing the first purified synthetic crude oil stream (3) with a second aqueous washing solution (4) at a second temperature to obtain a second purified synthetic crude oil stream (5), It is characterized in that The first aqueous washing solution (2) is alkaline, the second aqueous washing solution (4) is acidic, and the second temperature is lower than the first temperature, wherein the first temperature is higher than 100°C.

2. The method according to claim 1, characterized in that The first temperature is above 105°C.

3. The method according to claim 1 or 2, characterized in that: The average washing duration of washing the synthetic crude oil stream (1) with the first aqueous washing solution (2) is at least 0.5 minutes.

4. The method according to claim 1, characterized in that: The synthetic crude stream (1) is washed with the first aqueous wash solution (2) at a pressure that is higher than the pressure at which the first purified synthetic crude stream (3) is washed with the second aqueous wash solution (4).

5. The method according to claim 1, characterized in that: The pH value of the first aqueous washing solution (2) is greater than 8.

6. The method according to claim 1, characterized in that The pH value of the second aqueous washing solution (4) is less than 6.

7. The method according to claim 1, characterized in that The synthetic crude oil stream (1) and the first aqueous washing solution (2) are mixed in a volume ratio of 5:1 to 1:

5.

8. The method according to claim 1, characterized in that Between washing the synthetic crude stream (1) with the first aqueous washing solution (2) and washing the first purified synthetic crude stream (3) with the second aqueous washing solution (4), no further washing steps are performed.

9. The method according to claim 1, further comprising the steps of: - washing the second purified synthetic crude stream (5) with a third aqueous washing solution (6) at a third temperature to obtain a third purified synthetic crude stream (7).

10. The method according to claim 9, characterized in that The pH value of the third aqueous washing solution (6) ranges from 3 to 13.

11. The method according to claim 9 or 10, characterized in that: The third temperature is lower than the first temperature.

12. The method according to claim 9 or 10, characterized in that The synthetic crude stream (1) is washed with the first aqueous wash solution (2) at a pressure that is higher than the pressure at which the second purified synthetic crude stream (5) is washed with the third aqueous wash solution (6).

13. The method according to claim 9 or 10, characterized in that: The second purified synthetic crude oil stream (5) and the third aqueous wash solution (6) are mixed in a volume ratio of 10:1 to 1:

5.

14. A method for producing synthetic crude oil comprising the steps of: - producing a synthetic crude oil stream (1); and - Purifying the synthetic crude oil stream (1) according to the method according to any one of claims 1 to 13.

15. The method according to claim 14, characterized in that The synthetic crude oil stream (1) is produced by depolymerization of plastic materials.

16. The method according to claim 15, characterized in that The plastic material includes polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyamide (PA), styrene-acrylonitrile (SAN) and / or acrylonitrile-butadiene-styrene (ABS).

17. The method according to claim 15, characterized in that The plastic material includes plastic waste.

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