Method for extracting a wax from a pyrolysis residue

Abstract

The invention relates to a method for extracting a wax from a pyrolysis residue, comprising the steps of (a) providing the pyrolysis residue, wherein the pyrolysis residue comprises the wax, (b) mixing the pyrolysis residue with a solvent at at least 30°C to obtain a mixture, wherein the wax is at least partially dissolved in the solvent, (c) cooling the mixture to crystallise at least one portion of the dissolved wax, (d) separating at least one portion of the crystallised wax from the mixture.

Description

[0001] Process for obtaining a wax from a

[0002] Pyrolysis residue

[0003] The invention relates to a process for obtaining a wax from a pyrolysis residue.

[0004] It is known from the prior art to separate a wax from a starting product by crystallization. For example, US 2002 / 0096451 A1 describes a process for purifying a petroleum product. A solvent is added to the petroleum product at room temperature. The resulting mixture is then cooled to crystallize and separate a wax contained in the petroleum product.

[0005] A similar dewaxing process is disclosed in WO 2021 / 115982 A1, where a solvent is added at room temperature to a pyrolysis residue obtained from the pyrolysis of a plastic. The resulting mixture is then cooled to separate any wax contained therein by crystallization.

[0006] Further processes related to the separation of waxes are known from US 3,720,599 A, US 5,006,222 A, US 2,614,065 A, WO 2017 / 168165 A1 and WO 2021 / 115982 A1.

[0007] In the processes known in the prior art, the separation of the wax primarily serves the purpose of purifying the starting product. The separated wax may have a relatively low purity. However, for numerous applications, it may be necessary to use a wax with a high purity, which may necessitate further, complex purification of the separated wax. There is a need for inexpensive, simple processes for producing a wax with a high purity. One object of the invention is to provide such a process.

[0008] The process according to the invention for obtaining a wax from a pyrolysis residue comprises the steps

[0009] (a) providing the pyrolysis residue, wherein the pyrolysis residue comprises the wax,

[0010] (b) mixing the pyrolysis residue with a solvent at at least 30 °C to obtain a mixture, wherein the wax is at least partially dissolved in the solvent,

[0011] (c) cooling the mixture to crystallize at least a portion of the dissolved wax,

[0012] (d) separating at least a portion of the crystallized wax from the mixture.

[0013] The invention is based on the finding that a pyrolysis residue, in particular a pyrolysis residue obtained from plastic pyrolysis, represents a valuable source of wax. By mixing the pyrolysis residue with the solvent at at least 30 °C, the wax can dissolve largely or even completely in the solvent and can subsequently be separated from the pyrolysis residue with a high degree of purity. The resulting wax can represent a sustainable alternative to wax obtained directly from petroleum.

[0014] The pyrolysis residue can be obtained by pyrolyzing a plastic, especially a waste plastic. The pyrolysis can be carried out in a pyrolysis reactor, preferably at a temperature of 300 to 500 °C, especially 350 to 450 °C. This allows a good balance between cost-effectiveness and process efficiency to be achieved.

[0015] The pyrolysis can be thermal pyrolysis (i.e., thermal cracking without the addition of a catalyst) and / or catalytic pyrolysis (i.e., catalytic cracking). Thermal pyrolysis is preferred to avoid any contamination of the wax and / or the solid due to catalyst components.

[0016] Pyrolysis can be carried out largely in the absence of oxygen, especially in an inert atmosphere, such as nitrogen. A lack of oxygen or the absence of oxygen can prevent complete combustion and cause a polymer contained in the plastic to be cleaved or depolymerized.

[0017] Within the scope of the invention, it has proven advantageous if a fraction, preferably a heavy fraction, of the pyrolyzed plastic is used as the pyrolysis residue. In a preferred embodiment, the pyrolysis residue is therefore obtained by pyrolyzing a plastic and separating at least one fraction, preferably a gaseous fraction, from the pyrolyzed plastic. The separated fraction preferably has a lower boiling point (or a lower boiling range) than the pyrolysis residue.

[0018] In a particularly preferred embodiment, the pyrolysis residue has a boiling point (or a lower end of a boiling range) of at least 100°C, preferably at least 150°C, more preferably at least 200°C, more preferably at least 240°C, more preferably at least 270°C, more preferably at least 300°C. The pyrolysis residue preferably has a boiling point (or a lower end of a boiling range) in the range from 100°C to 700°C, preferably from 150°C to 600°C, more preferably from 200°C to 500°C, more preferably from 240°C to 460°C, more preferably from 270°C to 430°C, more preferably from 300°C to 400°C. It has been found that fractions with such a boiling point can have particularly high wax contents and are therefore particularly well suited for the process according to the invention. It has proven particularly advantageous if the pyrolysis residue is a spindle oil, preferably with a boiling point (ora lower end of a boiling range) in the range of 300 °C to 400 °C. In this case, the wax content of the pyrolysis residue can be, for example, approximately 50 wt%.

[0019] The boiling temperature (or boiling range) can preferably be determined using ASTM D7500-15: 2019. Alternatively, ASTM D2887-22: 2022 can be used.

[0020] The plastic preferably comprises a polyolefin and / or a polystyrene (PS), wherein the polyolefin may comprise a polyethylene (PE) and / or a polypropylene (PP). The plastic preferably comprises the polyolefin and / or the polystyrene in an amount of at least 65% by weight, more preferably at least 70% by weight, in particular at least 90% by weight, based on the total weight of the plastic. This makes it possible to obtain a pyrolysis residue which comprises a significant proportion of an aliphatic hydrocarbon (or a mixture of several aliphatic hydrocarbons), i.e. a significant proportion of the wax. The plastic preferably comprises at least 20% by weight of the polyolefin, more preferably at least 50% by weight, even more preferably at least 70% by weight, in particular at least 90% by weight, based on the total weight of the plastic.With increasing polyolefin content, the amount of wax obtained by the process according to the invention can be increased, which can improve the economic efficiency of the process.

[0021] In the course of the invention, it has been found that a high polyethylene (PE) content is particularly advantageous, since a particularly high wax content can be obtained when plastic with a high PE content is pyrolyzed. In a particularly preferred embodiment, the plastic therefore has a PE content of at least 10 wt%, preferably at least 20 wt%, more preferably at least 30 wt%, more preferably at least 40 wt%, more preferably at least 50 wt%, more preferably at least 60 wt%, and even more preferably at least 70 wt%.

[0022] The plastic may comprise another polymer from the group consisting of thermoplastics, thermosets and / or elastomers, in particular an acrylonitrile-butadiene-styrene copolymer (ABS), a polyvinyl chloride (PVC), a polyamide (PA) and / or a polyester.

[0023] Before pyrolysis, the plastic can be plasticized, for example, in a mixer, especially in an extruder. The plastic is preferably heated to a temperature of at least 120°C to plasticize it, more preferably to a temperature of 200 to 500°C, even more preferably 400 to 470°C. The subsequent pyrolysis can then be carried out more energy-efficiently and in a shorter time. The plastic can also be degassed in the extruder to produce a uniform mass without gas inclusions, so that a homogeneous pyrolysis product can be obtained by the subsequent pyrolysis.

[0024] Before pyrolysis, a diluent can be added to the plastic, in particular to the plasticized plastic, to reduce its viscosity. The diluent is preferably added to the plastic in an amount of at least 5% by weight, more preferably at least 9% by weight, based on the total weight of the plastic. The ratio of plastic to diluent is preferably at least 1:4, preferably at least 1:9. By adding the diluent to the plastic, the mobility of polymer chains can be increased at a given temperature, so that the heat input into the plastic can be improved during pyrolysis. Furthermore, due to the viscosity reduction, the risk of overheating of plastic in wall regions of the pyrolysis reactor can be reduced, since this is usually heated by a heating device arranged near an outer wall of the pyrolysis reactor.The risk of coking of the plastic during pyrolysis can also be reduced by reducing the viscosity.

[0025] By adding the diluent to the plastic, its viscosity can preferably be reduced by at least 30%, more preferably by at least 50%, particularly preferably by at least 80%, relative to the viscosity of the plastic without diluent under the same measurement conditions, in particular at a temperature in the range of 180 to 240 °C. This can improve the pumpability of the plastic, which can facilitate its processing.

[0026] When the diluent is added, the plastic preferably has a temperature of at least 120°C, more preferably a temperature of 150 to 300°C, in particular of 200 to 300°C. Alternatively or additionally, the diluent can be heated to a temperature of preferably at least 120°C, more preferably at least 150°C, in particular to a temperature of 200 to 300°C, before being added to the plastic. By increasing the temperature of the plastic and / or the diluent, the diluent can be mixed into the plastic more quickly and efficiently. The subsequent pyrolysis can also be carried out more quickly and in a more energy-efficient manner.

[0027] The diluent can be added to the plastic using a dosing device. The dosing device can have a metering device, such as a metering pump. For example, the plastic, in particular the plasticized plastic, can be fed to a mixer, e.g., a static mixer, and mixed there with the diluent. If the plastic is plasticized in an extruder, the diluent can be added directly in the extruder. For this purpose, the dosing device can be arranged, for example, in the compression zone or mixing zone of the extruder.

[0028] The diluent can comprise a hydrocarbon selected from an alkane, a cycloalkane and / or an aromatic. By means of pyrolysis, such a diluent can be converted into a gaseous and / or liquid product which can be at least partially separated from the pyrolysis residue and further utilized. In particular, the diluent can comprise a fraction obtained from crude oil, preferably a heavy oil. The heavy oil can be an oil obtained from petroleum in a petroleum refinery, e.g. a residual oil from a pyrolysis plant. The diluent preferably comprises at least part of a liquid fraction of the pyrolysis residue. This can be separated, for example, in a hydrocyclone.

[0029] The diluent preferably has a boiling point (or a lower end of a boiling range) of at least 300°C, in particular at least 350°C. This prevents the diluent from evaporating immediately after a mixture of plastic and diluent is introduced into the pyrolysis reactor; instead, evaporation, cleavage, and / or depolymerization of the diluent can only occur with increasing residence time of the mixture in the pyrolysis reactor and the concomitant heating of the mixture. This makes it possible to obtain a homogeneous pyrolysis product.

[0030] The pyrolysis residue provided in step (a) of the process can, in addition to the wax and the solid, also comprise a liquid fraction. The proportion of the liquid fraction is preferably a maximum of 95% by weight, more preferably 30 to 95% by weight, in particular 50 to 70% by weight, based on the total weight of the pyrolysis residue. As the proportion of the liquid fraction decreases, the rate at which at least part of the wax dissolves in the solvent can increase, or a smaller amount of solvent can be added to the pyrolysis residue in order to at least partially dissolve the wax in the solvent. This can also subsequently make it easier to separate at least part of the wax from the low-solids mixture. The use of solvent can also be reduced. The process can thus be made more efficient.

[0031] The pyrolysis residue provided in step (a) of the process can be obtained by pyrolyzing the plastic in a pyrolysis reactor and subsequently increasing the solids concentration of the pyrolysis residue. This allows the proportion of the liquid fraction of the resulting pyrolysis residue to be reduced to preferably a maximum of 95 wt.%, more preferably to 30 to 95 wt.%, in particular to 50 to 70 wt.%, based on the total weight of the pyrolysis residue. To increase the solids concentration, a hydrocyclone can be used, which can be connected downstream of the pyrolysis reactor.

[0032] If the pyrolysis residue is obtained by pyrolyzing a plastic, a gaseous fraction can be separated from the pyrolysis residue following pyrolysis and before step (a) of the process. The gaseous fraction can be separated by evaporation, for example, in a hydrocyclone, which can be connected downstream of the pyrolysis reactor.

[0033] The separation of the gaseous fraction from the pyrolysis residue and the increase in the solids concentration of the pyrolysis residue can be carried out, for example, using a separation device or using a plurality of separation devices connected in series. Advantageously, both the separation of the gaseous fraction from the pyrolysis residue and the increase in the solids concentration of the pyrolysis residue are carried out in just one process step by means of a hydrocyclone, which can be connected downstream of the pyrolysis reactor. Such a hydrocyclone is described in WO 2023 / 036751 A1. By introducing a mixture comprising the pyrolysis residue and the gaseous fraction via an inlet arranged in an upper region of a jacket of the hydrocyclone, a vortex flow can be generated in the hydrocyclone, as a result of which the gaseous fraction is separated from the pyrolysis residue and passed through aon the ceiling of which) arranged outlet. The pyrolysis residue can then be carried off under gravity in the direction of a base of the hydrocyclone, it being possible for a tangential velocity of a developing vortex flow to increase continuously. As a result, at least part of the pyrolysis residue, in particular at least a part of the pyrolysis residue at least partially comprising the wax and the solid, can be carried off via an outlet arranged in the base of the hydrocyclone, while at least part of the liquid fraction of the pyrolysis residue can reach an inner container arranged in the hydrocyclone and from there be carried off via an outlet, e.g. for further use as a diluent. The pyrolysis residue carried off via the outlet arranged in the base of the hydrocyclone can then be provided according to step (a) of the process.The hydrocyclone is preferably operated at a temperature in the range of 300 to 450 ° C, more preferably from 320 to 420 ° C, particularly preferably from 360 to 400 ° C.

[0034] The pyrolysis residue can be cooled before the addition of the solvent, either before step (a) of the process, or between steps (a) and (b). The cooling can be carried out by means of a cooling unit. The pyrolysis residue is preferably cooled to a temperature of not more than 220 °C, more preferably not more than 200 °C, particularly preferably not more than 180 °C. Cooling of the pyrolysis residue can be necessary in particular when the pyrolysis residue is obtained by immediately preceding processing of a plastic (by pyrolyzing and optionally subsequent separation of a gaseous fraction from the pyrolysis residue and / or increasing the solids concentration of the pyrolysis residue). By cooling the pyrolysis residue, undesired evaporation and / or decomposition of the solvent during addition to the pyrolysis residue can be reduced or completely prevented.The pyrolysis residue is preferably cooled to a temperature of not less than 30 ° C, more preferably not less than 80 ° C, even more preferably not less than 100 ° C, particularly preferably not less than 120 ° C. Further cooling below said temperature may impair the solubility of the wax in the solvent.

[0035] The solvent can be added to the pyrolysis residue by means of an introduction device. The introduction device can comprise a metering device, such as a metering pump. To mix the pyrolysis residue with the solvent in step (b) of the process, the pyrolysis residue can be fed to a container to which the introduction device can be connected. The container can be heatable so that the wax can dissolve in the solvent at a specific temperature.

[0036] The mixing in step (b) of the process is preferably carried out at at least 50°C (ie at 50°C or above), more preferably at least 80°C (ie at 80°C or above).

[0037] A fraction of the wax with a melting point above room temperature (i.e., above 20 to 25°C) can then be dissolved in the solvent. The mixing in step (b) is preferably carried out at a temperature in the range from 50 to 200°C, more preferably from 100 to 200°C, even more preferably from 80 to 200°C, particularly preferably from 80 to 120°C. This not only allows the wax to be largely or entirely dissolved in the solvent, but also ensures that the solvent does not evaporate due to excessively high temperatures. The wax dissolves particularly well in the solvent at a temperature of just 100 to 120°C, while a temperature of 120 to 140°C can be optimal from a process engineering perspective.

[0038] Mixing in step (b) of the process preferably takes place at a pressure in the range of 1 to 25 bar, in particular 5 to 16 bar. This further improves the process control and achieves rapid dissolution of the wax in the solvent.

[0039] The solvent preferably has a boiling point (or boiling range) in the range of 20 to 250°C, more preferably 50 to 150°C, and even more preferably 35 to 130°C. The lower the boiling point of the solvent, the lower the temperature at which the wax can be brought into a liquid state. Furthermore, as the boiling point of the solvent decreases, the ability of the wax to crystallize during subsequent cooling of the mixture in step (c) of the process can increase, thereby increasing the yield of recovered wax. The boiling point (or boiling range) of the solvent can be determined using ASTM D5399-09:2017 or ASTM D2887-22:2022.

[0040] The solvent preferably comprises an aliphatic hydrocarbon or a mixture of two or more aliphatic hydrocarbons. An impurity that dissolves in the solvent can then remain dissolved while the wax has already crystallized. Thus, the wax can be separated off in high purity and the impurity can remain in the mixture. The impurity can contain an organic impurity comprising nitrogen, oxygen, sulfur, silicon, chlorine, bromine and / or iodine, for example a heteropolymer (e.g. a polyamide, a polyethylene terephthalate, a polyvinyl chloride and / or an acrylonitrile-butadiene-styrene copolymer) and / or an additive (e.g. an age inhibitor, a plasticizer, a color pigment and / or a flame retardant).

[0041] The solvent preferably comprises at least 10 wt.%, preferably at least 20 wt.%, more preferably at least 50 wt.%, of the aliphatic hydrocarbon or a mixture of two or more aliphatic hydrocarbons, based on the total weight of the solvent. With an increasing proportion of aliphatic hydrocarbon, not only can the ability of the solvent to dissolve the wax improve, but the solubility of the solid in the solvent can also be reduced. With a high proportion of an aromatic compound in the solvent, however, the solid, particularly an asphaltene or tar, can dissolve readily in the solvent, which can complicate the subsequent separation of the wax or result in contaminated wax. With a high proportion of a cycloalkane in the solvent, the wax can dissolve readily, but the yield can be comparatively low.

[0042] The aliphatic hydrocarbon is preferably selected from the group of aliphatic hydrocarbons with up to 15 carbon atoms per molecule, in particular from 4 to 12 carbon atoms per molecule. This allows the process to be carried out efficiently and enables good separation of the wax from the solid mixture.

[0043] The aliphatic hydrocarbon is preferably selected from n-pentane, n-hexane, n-heptane, n-octane, an isomer thereof, or a mixture of the foregoing (i.e., a mixture comprising n-pentane, n-hexane, n-heptane, n-octane, an isomer of these alkanes, and / or several isomers of these alkanes). Since the boiling point of these aliphatic hydrocarbons is in the range of 35 to 130°C, the process can be carried out efficiently and economically. The mixing in step (b) of the process can then preferably take place at 120°C or below, more preferably at 100°C or below, to avoid evaporation of the solvent. Furthermore, due to the low molecular weight of these solvents, the wax can not only dissolve well in them, but can also have a good tendency to crystallize during the subsequent cooling in step (c) of the process.

[0044] The solvent preferably comprises at least 10% by weight of an alcohol, more preferably at least 20% by weight, based on the total weight of the solvent. This allows a polar impurity to be dissolved in the solvent and thereby separated from the wax, which crystallizes when the mixture is cooled. This can further increase the purity of the wax obtained. The solvent preferably comprises 10 to 30% by weight of the alcohol, more preferably 10 to 20% by weight of the alcohol, based on the total weight of the solvent. More preferably, the solvent comprises at least 50% by weight of the aliphatic hydrocarbon and 10 to 30% by weight of the alcohol. This allows both the non-polar wax and a polar impurity to be well dissolved in the solvent and well separated from one another during the subsequent cooling of the mixture. Overall, a wax with a high level of purity can then be obtained.

[0045] The alcohol can preferably be selected from methanol, ethanol, propanol, or a mixture thereof. Propanol is particularly preferred because it can reduce adhesions between wax crystals. This can allow for easier separation of the wax from the solvent in step (d) of the process. Furthermore, any solvent remaining in the wax after washing can subsequently be easily separated from the wax during drying of the wax.

[0046] The ratio of pyrolysis residue to solvent in the mixture obtained in step (b) of the process may depend on the melting temperature of the wax. The higher the melting temperature of the wax, the more solvent may be required to dissolve the wax. It is preferred if the ratio of pyrolysis residue to solvent is in the range from 5:1 to 1:5, preferably from 2:1 to 3:1, in particular 1:1. The wax can then dissolve largely or even completely in the solvent.

[0047] If the pyrolysis residue contains a solid, it can be at least partially separated from the mixture before step (c). Separating the solid can involve filtration, adsorption, and / or centrifugation. Preferably, the solid is separated by adsorption. An adsorbent, which may include activated carbon and / or bleaching earth, can be added to the pyrolysis residue. This allows the solid to be separated efficiently and as completely as possible from the mixture.

[0048] The solid may comprise an inorganic salt, a ceramic raw material, an asphaltene, a tar, and / or a coke. In particular, the solid may comprise talc, an iron oxide (e.g., iron(III) oxide), aluminum oxide, titanium dioxide, magnesium oxide, and / or calcium carbonate. If the pyrolysis residue provided is obtained by pyrolyzing a plastic, the solid may comprise an additive contained in the plastic. For example, the additive may comprise a filler, a color pigment, and / or an additive. A person skilled in the art will know which additives are used depending on the particular plastic and field of application.

[0049] After being separated from the mixture, the solid can be dried, for example, in an oven. This makes the solid free-flowing and thus easier to process. The solid is preferably dried at a temperature in the range of 50 to 250 °C, more preferably 100 to 200 °C, and even more preferably 130 to 160 °C. The drying time is preferably up to 120 minutes, in particular 5 to 60 minutes.

[0050] One or more components can be separated from the solid, especially from the dried solid, e.g., by filtration and / or centrifugation. Separated components can then be reused, e.g., as an additive for a plastic.

[0051] Solvent separated during drying of the solid can be reused in step (b) of the process. Before being recycled to the process, the solvent can be purified, preferably by evaporation, in particular by rotary evaporation.

[0052] In step (c) of the process, the mixture is cooled to crystallize at least a portion of the wax dissolved in the solvent. The mixture is preferably cooled at a rate of not more than 25°C / min, more preferably not more than 15°C / min, more preferably not more than 10°C / min, more preferably not more than 5°C / min, more preferably not more than 2°C / min. Cooling preferably takes place at a rate in the range of 0.05 to 25°C / min, more preferably from 0.1 to 15°C / min, more preferably from 0.2 to 10°C / min, more preferably from 0.4 to 5°C / min, more preferably from 0.5 to 2°C / min. Wax crystals can form well at a slow cooling rate in this range, which can enable better mechanical separation. It has also been shown that slow cooling can lead to a clean product.Faster cooling, on the other hand, can lead to an increased formation of microcrystals, which are more difficult to separate mechanically and can also carry more impurities.

[0053] It is therefore preferred if the cooling in step (c) of the process takes place over a period of at least 5 minutes, more preferably at least 10 minutes, more preferably at least 30 minutes, more preferably at least 60 minutes. Cooling preferably takes place over a period of 5 to 240 minutes, more preferably 10 to 180 minutes, more preferably 30 to 150 minutes, more preferably 60 to 120 minutes. The wax crystals formed in this process may have a flaky shape characteristic of these process parameters.

[0054] In step (c) of the process, the mixture is preferably cooled to 10°C or below, more preferably to 0°C or below, even more preferably to -10°C or below. Although the wax can in principle crystallize even when cooled at a slow cooling rate, in particular a maximum of 5°C / min, from, for example, 100 to just 50°C, a relatively large amount of solvent can become trapped in the wax crystals, which can reduce the purity of the wax, especially since the solvent may also contain a dissolved impurity, which can then also be trapped in the wax crystals. By cooling to a lower temperature (e.g. to 10°C or below), the entrapment of solvent can be reduced or completely prevented, so that the purity of the wax obtained can be significantly increased.

[0055] In step (d) of the process, at least a portion of the crystallized wax can be separated from the mixture. The separation can comprise filtration and / or centrifugation. The temperature during the separation is preferably 80°C or below, more preferably 30°C or below. The temperature is preferably in the range of -10 to 80°C, in particular 0 to 30°C. This can prevent the wax from redissolving in the solvent. Furthermore, the separation can preferably be carried out at a pressure of up to 10 bar, more preferably at 5 to 10 bar. This can improve the process efficiency.

[0056] After separating the wax from the mixture in step (d) of the process, any solvent present in the mixture can be at least partially separated from the mixture. The separation can be carried out by evaporation or distillation. Separated solvent can be reused in step (b) of the process. Before being recycled to the process, the solvent can be further purified, preferably by evaporation, in particular by rotary evaporation.

[0057] The wax separated in step (d) of the process may have a boiling point (or a lower end of a boiling range) of preferably at least 270°C, more preferably at least 300°C, even more preferably a boiling point (or a boiling range) in the range from 340 to 700°C. The boiling point (or boiling range) of the wax may be determined using the ASTM D7500-15: 2019 standard (preferably for a wax having a boiling point or boiling range of 100 to 850°C, in particular from 100 to 735°C) or using the ASTM D2887-22: 2022 standard (preferably for a wax having a boiling point or boiling range of 55 to 538°C).

[0058] The separated wax preferably has at least 15 carbon atoms per molecule, more preferably at least 20, in particular at least 40. Preferably, the wax has 20 to 80 carbon atoms per molecule, in particular 20 to 65. Such waxes are well suited for further use.

[0059] The separated wax can be fed into a refinery's processing plant, in particular a fluid catalytic cracking (FCC) plant, a thermal gasoil unit (TGU), a hydrogenation plant, and / or a coker. The separated wax can also be used in other technical fields, for example as a lubricant and / or additive. The separated wax can be processed before further use. For example, the wax can be purified and / or separated into various carbon fractions.

[0060] The separated wax preferably has a proportion of one (or more) carbon fractions of at least 60 wt.%, more preferably at least 70 wt.%, even more preferably at least 80 wt.%, in particular at least 85 wt.%, based on the total weight of the separated wax. This proportion provides information about the purity of the separated wax, wherein a high proportion of the carbon fraction corresponds to a high purity of the separated wax. By means of the process according to the invention, a wax with a high purity can thus be obtained, which can be increased even further by subsequently washing the wax. The proportion of the carbon fraction can be determined by means of a gravimetric analysis, wherein the gravimetric analysis can comprise a determination of the masses of the pyrolysis residue, the added solvent and the separated wax.

[0061] The separated wax can be washed after step (d) of the process. In particular, the wax can be washed one to three times. This can further increase the purity of the separated wax.

[0062] During washing, the temperature of the wax is preferably 80°C or below, more preferably 30°C or below, even more preferably in the range from -10 to 80°C, in particular from 0 to 30°C. This can prevent the wax from redissolving in the solvent. When washing the wax, a similar or the same temperature can be chosen as when separating the wax in step (d) of the process. Preferably, the wax is washed with an alcohol. This can wash out any remaining polar impurity, whereby a wax with a particularly high purity can be obtained. The alcohol used for washing is preferably selected from methanol, ethanol, propanol or a mixture thereof.This not only allows any remaining polar contamination to be washed out, but also allows any solvent remaining in the wax after washing to be easily separated from the wax during drying.

[0063] The process may comprise a further step (e): drying the separated wax. This allows solvent separated together with the wax crystals to be removed. Drying can be carried out thermally at an elevated temperature or, alternatively, at a low temperature under vacuum. The type of drying can depend on the further use of the wax. In order to retain the structure of the wax crystals, drying under vacuum is preferred. If the wax is subsequently used in liquid form, it can also be dried at an elevated temperature and, if necessary, melted in the process. Thermal drying is preferably carried out at a temperature of 150 °C or below and at ambient pressure (0.7 to 1.1 bar). Drying under vacuum is preferably carried out at a temperature of 30 °C or below and at a pressure of 750 mbar or below, in particular at 500 mbar or below.Solvent separated during drying of the wax can be reused in step (b) of the process. Before being recycled to the process, the solvent can be further purified, preferably by evaporation, in particular by rotary evaporation.

[0064] The invention particularly relates to the following embodiments:

[0065] 1 . A process for obtaining a wax from a pyrolysis residue, comprising the steps

[0066] ( a ) providing the pyrolysis residue , wherein the pyrolysis residue comprises the wax ,

[0067] (b) mixing the pyrolysis residue with a solvent at at least 30 °C to obtain a mixture, wherein the wax is at least partially dissolved in the solvent,

[0068] (c) cooling the mixture to crystallize at least a portion of the dissolved wax,

[0069] (d) separating at least a portion of the crystallized wax from the mixture.

[0070] 2. The method according to embodiment 1, wherein the pyrolysis residue is obtained by pyrolyzing a plastic, in particular a waste plastic.

[0071] 3. Process according to one of the preceding embodiments, wherein the pyrolysis residue is obtained by pyrolyzing a plastic and separating at least one fraction, preferably a gaseous fraction, from the pyrolyzed plastic.

[0072] 4. Process according to one of the preceding embodiments, wherein the pyrolysis residue has a boiling temperature of at least 100°C, preferably at least 150°C, more preferably at least 200°C, more preferably at least 240°C, more preferably at least 270°C, more preferably at least 300°C.

[0073] 5. Process according to one of the preceding embodiments, wherein the pyrolysis residue has a boiling point in the range from 100 °C to 700 °C, preferably from 150 °C to 600 °C, more preferably from 200 °C to 500 °C, more preferably from 240 °C to 460 °C, more preferably from 270 °C to 430 °C, more preferably from 300 °C to 400 °C.

[0074] 6. Method according to one of the preceding embodiments, wherein the plastic comprises a polyolefin and / or a polystyrene (PS), wherein the polyolefin may comprise a polyethylene (PE) and / or a polypropylene (PP).

[0075] 7. The method according to embodiment 6, wherein the plastic comprises the polyolefin and / or the polystyrene in an amount of at least 65 wt%, more preferably at least 70 wt%, in particular at least 90 wt%, based on the total weight of the plastic.

[0076] 8. Method according to one of the preceding embodiments, wherein the plastic has a PE content of at least 10 wt%, preferably at least 20 wt%, more preferably at least 30 wt%, more preferably at least 40 wt%, more preferably at least 50 wt%, more preferably at least 60 wt%, even more preferably at least 70 wt%.

[0077] 9. Process according to any one of the preceding embodiments, wherein the pyrolysis residue is cooled to a temperature of not more than 220 °C, more preferably not more than 200 °C, particularly preferably not more than 180 °C, before the addition of the solvent.

[0078] 10. Process according to any one of the preceding embodiments, wherein the pyrolysis residue is cooled to a temperature of not less than 30°C, more preferably not less than 80°C, even more preferably not less than 100°C, particularly preferably not less than 120°C, before the addition of the solvent.

[0079] 11. Process according to one of the preceding embodiments, wherein the mixing in step (b) takes place at at least 50 °C, more preferably at least 80 °C, in particular in the range from 50 to 200 °C, preferably from 100 to 200 °C, more preferably from 80 to 200 °C, in particular from 80 to 120 °C.

[0080] 12. Process according to one of the preceding embodiments, wherein the mixing in step (b) takes place at a pressure of 1 to 25 bar, preferably 5 to 16 bar.

[0081] 13. Process according to any one of the preceding embodiments, wherein the solvent has a boiling temperature in the range of 20 to 250 °C, preferably 50 to 150 °C, more preferably 35 to 130 °C.

[0082] 14. The process according to any preceding embodiment, wherein the solvent comprises an aliphatic hydrocarbon.

[0083] 15. A process according to any one of the preceding embodiments, wherein the solvent comprises at least 10 wt%, preferably at least 20 wt%, more preferably at least 50 wt%, of the aliphatic hydrocarbon, based on the total weight of the solvent.

[0084] 16. The process according to embodiment 14 or 15, wherein the aliphatic hydrocarbon is selected from the group of aliphatic hydrocarbons having up to 15 carbon atoms per molecule, preferably from 4 to 12 carbon atoms per molecule.

[0085] 17. The process according to any one of embodiments 14 to 16, wherein the aliphatic hydrocarbon is selected from n-pentane, n-hexane, n-heptane, n-octane, an isomer thereof, or a mixture of the foregoing.

[0086] 18. Process according to any one of the preceding embodiments, wherein the solvent comprises at least 10% by weight of an alcohol, preferably at least 20% by weight, based on the total weight of the solvent.

[0087] 19. The process according to embodiment 18, wherein the solvent comprises 10 to 30 wt% of the alcohol, preferably 10 to 20 wt% of the alcohol, based on the total weight of the solvent.

[0088] 20. The process according to any one of embodiments 14 to 19, wherein the solvent comprises at least 50 wt% of the aliphatic hydrocarbon and 10 to 30 wt% of the alcohol, based on the total weight of the solvent.

[0089] 21. The process according to any one of embodiments 18 to 20, wherein the alcohol is selected from methanol, ethanol, propanol or a mixture thereof, in particular propanol.

[0090] 22. Process according to one of the preceding embodiments, wherein the ratio of the pyrolysis residue to the solvent in the mixture obtained in step (b) is in the range from 5:1 to 1:5, preferably from 2:1 to 3:1, in particular 1:1.

[0091] 23. Process according to one of the preceding embodiments, wherein a solid contained in the pyrolysis residue before step

[0092] (c) is at least partially separated from the mixture.

[0093] 24. The method according to embodiment 23, wherein the solid comprises an inorganic salt, a ceramic raw material, an asphaltene, a tar and / or a coke.

[0094] 25. The method according to embodiment 23 or 24, wherein the separation of the solid comprises filtration, adsorption and / or centrifugation.

[0095] 26. The method according to embodiment 25, wherein the separation of the solid comprises adsorption, wherein an adsorbent is added to the pyrolysis residue, and wherein the adsorbent preferably comprises activated carbon and / or bleaching earth.

[0096] 27. The process according to any one of embodiments 23 to 26, wherein the separated solid is dried, preferably at a temperature of 50 to 250 °C, more preferably 100 to 200 °C, and / or for a period of up to 120 min, preferably 5 to 60 min.

[0097] 28. A process according to any preceding embodiment, wherein the mixture in step (c) is cooled to 10°C or below, preferably to 0°C or below, more preferably to -10°C or below.

[0098] 29. Process according to any one of the preceding embodiments, wherein the mixture in step (c) is cooled at a rate of at most 25 °C / min, preferably at most 15 °C / min, more preferably at most 10 °C / min, more preferably at most 5 °C / min, more preferably at most 2 °C / min, preferably in the range from 0.05 to 25 °C / min, more preferably from 0.1 to 15 °C / min, more preferably from 0.2 to 10 °C / min, more preferably from 0.4 to 5 °C / min, more preferably from 0.5 to 2 °C / min.

[0099] 30. Process according to any one of the preceding embodiments, wherein the cooling in step (c) takes place over a period of at least 5 min, more preferably at least 10 min, more preferably at least 30 min, more preferably at least 60 min, preferably over a period of 5 to 240 min, more preferably from 10 to 180 min, more preferably from 30 to 150 min, more preferably from 60 to 120 min.

[0100] 31. The process according to any one of the preceding embodiments, wherein the separation of the crystallized wax in step (d) comprises filtration and / or centrifugation.

[0101] 32. A process according to any one of the preceding embodiments, wherein the temperature in step (d) is 80°C or below, preferably 30°C or below, more preferably in the range from -10 to 80°C, in particular from 0 to 30°C.

[0102] 33. Process according to any one of the preceding embodiments, wherein the solvent is at least partially separated from the mixture after step (d), wherein separated solvent is preferably reused in step (b).

[0103] 34. The process according to any one of the preceding embodiments, wherein the separated wax has a boiling point of at least 270°C, preferably at least 300°C, more preferably a boiling point in the range of 340 to 700°C. 35. The process according to any one of the preceding embodiments, wherein the wax has at least 15 carbon atoms per molecule, preferably at least 20, in particular at least 40.

[0104] 36. The method of embodiment 35, wherein the wax has 20 to 80 carbon atoms per molecule, preferably 20 to 65.

[0105] 37. Process according to one of the preceding embodiments, wherein the separated wax has a proportion of a carbon fraction of at least 60 wt%, preferably at least 70 wt%, more preferably at least 80 wt%, in particular at least 85 wt%, based on the total weight of the separated wax.

[0106] 38. Process according to one of the preceding embodiments, wherein the separated wax is washed after step (d), preferably with an alcohol, in particular selected from methanol, ethanol, propanol or a mixture thereof.

[0107] 39. A process according to any one of the preceding embodiments, wherein the temperature during washing of the separated wax is 80°C or below, preferably 30°C or below, more preferably in the range from -10 to 80°C, in particular from 0 to 30°C.

[0108] 40. The method according to any one of the preceding embodiments, further comprising step (e): drying the separated wax.

[0109] 41. The process according to embodiment 40, wherein the wax is dried in step (e) at a temperature of 150°C or below and a pressure of 0.7 to 1.1 bar.

[0110] 42. The process according to embodiment 40 or 41, wherein the wax is dried in step (e) at a temperature of 30°C or below and a pressure of 750 mbar or below, preferably 500 bar or below.

[0111] 43. The process according to any one of embodiments 40 to 42, wherein solvent separated during drying of the wax in step (e) is reused in step (b).

[0112] Fig. 1 shows a flow diagram of a pyrolysis process in which wax is obtained from a pyrolysis residue.

[0113] As can be seen from Fig. 1, a plastic which comprises at least 50 wt% of a polyolefin is fed to an extruder 1 in which the plastic is plasticized and degassed. The plasticized plastic has a temperature of at least 120 °C and is then added to a static mixer 2. In the static mixer 2, a diluent 3 can be added to the plasticized plastic in order to reduce its viscosity. Alternatively or in addition to the diluent 3, a part of a liquid fraction 4 separated from a pyrolysis residue can be mixed with the plasticized plastic in order to reduce its viscosity. The resulting mixture is then fed to a pyrolysis reactor 5 in which the plastic is pyrolyzed at a temperature of 350 to 450 °C.This gives a pyrolysis product 6 comprising a gaseous fraction and a pyrolysis residue, the pyrolysis residue comprising a liquid fraction, a wax and a solid. The pyrolysis product 6 is fed to a hydrocyclone 7 downstream of the pyrolysis reactor 5. Firstly, the gaseous fraction is at least partially separated off in the hydrocyclone 7. The separated part of the gaseous fraction 8 can then be further separated into a light oil (e.g. with a boiling range of 35 to 225 °C) and a heavy oil (e.g. with a boiling range of 225 to 410 °C) (not shown). Furthermore, the liquid fraction is at least partially separated off in the hydrocyclone 7. The separated part of the liquid fraction 4 can be discharged via an outlet 9 of the hydrocyclone 7 and reused in the process for reducing the viscosity of the plastic, as previously described.At least a part of the pyrolysis residue, which at least partially comprises the wax and the solid, is discharged via an outlet 10 arranged in the bottom of the hydrocyclone 7.

[0114] As can also be seen in Fig. 1, the pyrolysis residue discharged via the outlet 10 is fed to a first cooling unit 11 for cooling to a temperature in the range from 80 to 240 ° C. A solvent 13 comprising at least 20 wt% of an aliphatic hydrocarbon is then added to the pyrolysis residue in a container 12 by means of an introduction device 14 in order to obtain a mixture in which the wax is at least partially dissolved in the solvent 13. The aliphatic hydrocarbon is selected from the group of aliphatic hydrocarbons having 4 to 12 carbon atoms per molecule. The resulting mixture has a ratio of pyrolysis residue to solvent in the range from 2:1 to 3:1. The container 12 is heated so that the dissolving can take place at a temperature in the range of 80 to 200 ° C.In a separation device 15, the solid is at least partially separated from the mixture by adsorption on activated carbon. The separated solid 16 is then dried in an oven 17 at a temperature in the range from 100 to 200 °C. After the separated solid 16 has been dried, individual components can be separated from the solid and reused (not shown). Solvent 13 separated during drying is reused in step (b) of the process by being returned to the container 12 via the introduction device 14. Before being returned, the solvent 13 can be purified, e.g. by evaporation (not shown). The mixture is dried according to Fig. 1 is then cooled in a second cooling unit 18 at a speed of maximum 5 ° C / min to - 10 ° C or below in order to crystallize at least part of the wax dissolved in the solvent .Subsequently, at least a portion of the crystallized wax is separated from the mixture by means of a filter 19. Solvent 13 contained in the mixture is separated in an evaporator 20 and also returned to the container 12 via the introduction device 14.

[0115] As can also be seen from Fig. 1, the separated wax 21 is washed in a washer 22, an alcohol being used for washing. The washed, separated wax 21 is then fed to a dryer 23 to dry the wax crystals. The obtained wax 24 can subsequently be used for further purposes (not shown). Solvent 13 separated during the drying of the separated wax 21 is also returned to the container 12 via the introduction device 14. Before being returned, the solvent 13 can be purified, e.g. by evaporation (not shown).

Claims

Patent claims:

1. A process for obtaining a wax from a pyrolysis residue, comprising the steps (a) providing the pyrolysis residue, wherein the pyrolysis residue comprises the wax, (b) mixing the pyrolysis residue with a solvent at at least 30 °C to obtain a mixture, wherein the wax is at least partially dissolved in the solvent, (c) cooling the mixture to crystallize at least a portion of the dissolved wax, (d) separating at least a portion of the crystallized wax from the mixture.

2. The process according to claim 1, wherein the mixing in step (b) takes place at at least 80°C.

3. The process according to claim 1 or 2, wherein the solvent has a boiling temperature in the range of 35 to 130 °C.

4. A process according to any one of claims 1 to 3, wherein the solvent comprises at least 50% by weight of an aliphatic hydrocarbon.

5. The process of claim 4, wherein the aliphatic hydrocarbon is selected from n-pentane, n-hexane, n-heptane, n-octane, an isomer thereof, or a mixture of the foregoing.

6. A process according to any one of claims 1 to 5, wherein the solvent comprises at least 10% by weight of an alcohol. The process of claim 6, wherein the alcohol is propanol.

8. The process according to any one of claims 1 to 7, wherein a solid contained in the pyrolysis residue is at least partially separated from the mixture before step (c), preferably wherein the separation of the solid comprises adsorption, wherein an adsorbent is added to the pyrolysis residue, and wherein the adsorbent preferably comprises activated carbon and / or bleaching earth.

9. The process according to any one of claims 1 to 8, wherein the mixture is cooled in step (c) at a rate of not more than 5 °C / min.

10. The process according to any one of claims 1 to 9, wherein the mixture is cooled to -10°C or below in step (c).

11. The process according to any one of claims 1 to 10, wherein the separation of the crystallized wax in step (d) comprises filtration and / or centrifugation.

12. The process according to any one of claims 1 to 11, wherein the temperature in step (d) is 80°C or below.

13. The method according to any one of claims 1 to 12, wherein the separated wax has a boiling point of at least 270 °C.

14. The method according to any one of claims 1 to 13, further comprising step (e): drying the separated wax.

15. A process according to any one of claims 1 to 14, wherein solvent separated during drying of the wax in step (e) is reused in step (b).

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