Process for extracting wax from pyrolysis residues

Abstract

The present invention relates to a process for extracting wax from a pyrolysis residue, the process comprising the steps of: (a) providing a pyrolysis residue wherein the pyrolysis residue contains wax; (b) mixing the pyrolysis residue with a solvent at a temperature of at least 30 DEG 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 crystalline wax from the mixture.

Description

Technical Field

[0001] This invention relates to a method for extracting wax from pyrolysis residues. Background Technology

[0002] It is known in the prior art to separate wax from starting products by crystallization. For example, U.S. Patent Application Publication US2002 / 0096451A1 describes a method for purifying petroleum products. A solvent is added to the petroleum product at room temperature. The resulting mixture is then cooled, allowing the wax contained in the petroleum product to crystallize and separate.

[0003] WO2021 / 115982A1 discloses a similar dewaxing method in which a solvent is added to the pyrolysis residue obtained from the pyrolysis of plastic at room temperature. The resulting mixture is then cooled, and the wax contained therein is separated by crystallization.

[0004] In addition, other methods related to wax separation are described in US3,720,599A, US5,006,222A, US2,614,065A, and WO2017 / 168165A1 and WO2021 / 115982A1. Summary of the Invention

[0005] In existing methods, wax separation is primarily used to purify starting products. The purity of the separated wax may be relatively low. However, many applications require high-purity wax, necessitating additional complex cleaning processes after separation. There is a pressing need for a low-cost, simple method for preparing high-purity wax. The purpose of this invention is to provide such a method.

[0006] The method for extracting wax from pyrolysis residues according to the present invention comprises the following steps: (a) Providing a pyrolysis residue, wherein the pyrolysis residue contains wax; (b) At a temperature of at least 30°C, the pyrolysis residue is mixed with a solvent to obtain a mixture, wherein the wax is at least partially dissolved in the solvent; (c) Cool the mixture to allow at least a portion of the dissolved wax to crystallize; (d) Separate at least a portion of the crystallized wax from the mixture.

[0007] This invention is based on the discovery that pyrolysis residues (especially those obtained through the pyrolysis of plastics) are a highly valuable source of wax. By mixing the pyrolysis residues with a solvent at a temperature of at least 30°C, the wax can be largely or completely dissolved in the solvent, thereby separating high-purity wax from the pyrolysis residues. The resulting wax can serve as a sustainable alternative to waxes obtained directly from petroleum.

[0008] The pyrolysis residue can be obtained by pyrolysis of plastics (especially waste plastics). Pyrolysis can be carried out in a pyrolysis reactor, preferably at a temperature of 300-500°C, particularly 350-450°C. Therefore, a good balance can be achieved between economy and method efficiency.

[0009] The pyrolysis can be pyrolysis (i.e., thermal cracking without the addition of a catalyst) and / or catalytic pyrolysis (i.e., catalytic cracking). Pyrolysis is preferred to avoid contamination of the wax and / or solids by catalyst components.

[0010] Pyrolysis can be carried out in a virtually oxygen-free environment, especially in an inert atmosphere (such as a nitrogen atmosphere). The lack of oxygen or the isolation of oxygen prevents complete combustion and causes the polymers contained in the plastic to crack or depolymerize.

[0011] Within the scope of this invention, it has been proven advantageous to use the fractions (preferably heavy fractions) of the pyrolyzed plastic as pyrolysis residues. Therefore, in a preferred embodiment, the pyrolysis residue is obtained by pyrolyzing the plastic and separating at least one fraction (preferably a gaseous fraction) from the pyrolyzed plastic. The separated fraction preferably has a boiling point (or lower boiling range limit) lower than that of the pyrolysis residue.

[0012] In a particularly preferred embodiment, the boiling point (or lower boiling limit) of the pyrolysis residue is 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, and even more preferably at least 300°C. The boiling point (or lower boiling limit) of the pyrolysis residue is preferably in the range of 100°C-700°C, preferably in the range of 150°C-600°C, more preferably in the range of 200°C-500°C, more preferably in the range of 240°C-460°C, more preferably in the range of 270°C-430°C, and even more preferably in the range of 300°C-400°C. It has been found that fractions with this boiling point have particularly high wax content, and are therefore particularly suitable for the method described in this invention. It has been shown that it is particularly advantageous if the pyrolysis residue is mainly spindle oil (preferably with a boiling point or lower boiling limit in the range of 300°C-400°C). In this case, the wax content in the pyrolysis residue can, for example, reach about 50 wt%.

[0013] Boiling point (or boiling range) is preferably determined by standard ASTM D7500-15:2019. Standard ASTM D2887-22:2022 may also be used.

[0014] The plastic preferably comprises polyolefins and / or polystyrene (PS), wherein the polyolefins may comprise polyethylene (PE) and / or polypropylene (PP). Based on the total weight of the plastic, the plastic preferably contains at least 65 wt% of polyolefins and / or polystyrene, more preferably at least 70 wt%, and especially at least 90 wt%. As a result, a pyrolysis residue containing a large amount of aliphatic hydrocarbons (or a mixture of aliphatic hydrocarbons) can be obtained, i.e., containing a significant proportion of wax.

[0015] Based on the total weight of the plastic, the plastic preferably contains at least 20 wt% polyolefin, more preferably at least 50 wt%, even more preferably at least 70 wt%, and especially at least 90 wt%. As the proportion of polyolefin increases, the amount of wax obtained by the method of the present invention also increases, thereby improving the cost-effectiveness of the method.

[0016] During the development of this invention, it was discovered that a high polyethylene (PE) content has significant advantages because plastics with a high polyethylene content can yield a particularly high wax content during pyrolysis. Therefore, in a particularly preferred embodiment, the polyethylene content in the plastic is 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%.

[0017] The plastic may comprise other polymers selected from the group consisting of thermoplastics, thermosetting plastics and / or elastomers, and in particular may comprise acrylonitrile-butadiene-styrene copolymer (ABS), polyvinyl chloride (PVC), polyamide (PA) and / or polyester.

[0018] Prior to pyrolysis, the plastic can be plasticized, for example, in a mixer (particularly an extruder). For plasticization, the plastic is preferably heated to a temperature of at least 120°C, more preferably to 200-500°C, and even more preferably to 400-470°C. Subsequent pyrolysis can then be carried out in a more energy-efficient and time-saving manner. The plastic can also be degassed in the extruder to produce a homogeneous mass free of gaseous inclusions, thereby allowing for the acquisition of homogeneous pyrolysis products through subsequent pyrolysis.

[0019] Before pyrolysis, a diluent can be added to the plastic, especially the plasticized plastic, to reduce its viscosity. Based on the total weight of the plastic, the diluent is preferably added in an amount of at least 5 wt%, more preferably at least 9 wt%. The ratio of plastic to diluent is preferably at least 1:4, more preferably at least 1:9. By adding a diluent to the plastic, the fluidity of the polymer chains at a given temperature can be increased, thereby increasing the heat input to the plastic during pyrolysis. Furthermore, due to the reduced viscosity, the risk of overheating in the wall region of the pyrolysis reactor is reduced, as it is typically heated by heating devices arranged near the outer wall of the pyrolysis reactor. Reducing viscosity also reduces the risk of coking of the plastic during pyrolysis.

[0020] By adding a diluent to plastics, under the same measurement conditions, especially at temperatures in the range of 180 to 240°C, the viscosity of the plastic without diluent can preferably be reduced by at least 30%, more preferably by at least 50%, and particularly preferably by at least 80%. This can improve the pumpability of the plastic, thereby facilitating its processing.

[0021] When the diluent is added, the temperature of the plastic is preferably at least 120°C, more preferably between 150 and 300°C, particularly between 200 and 300°C. Alternatively or supplementarily, the diluent can be heated to a temperature preferably at least 120°C, more preferably at least 150°C, particularly between 200 and 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. Subsequent pyrolysis can also be carried out more energy-efficiently and rapidly.

[0022] The diluent can be added to the plastic via a feeding device. This feeding device may have a metering mechanism, such as a metering pump. For example, the plastic (especially plasticized plastic) can be fed into a mixer (such as a static mixer) and mixed there with the diluent. If the plastic is plasticized in an extruder, the diluent can be added directly to the extruder. For this purpose, the feeding device can be located, for example, in the compression or mixing zone of the extruder.

[0023] The diluent may contain hydrocarbons selected from alkanes, cycloalkanes, and / or aromatics. As a result of pyrolysis, such diluents can be converted into gaseous and / or liquid products that can be at least partially separated from the pyrolysis residue and reused. Specifically, the diluent may contain fractions obtained from crude oil, preferably heavy oil. Heavy oil can be oil obtained from petroleum in an oil refinery, such as residual oil from a pyrolysis system. The diluent preferably contains at least a portion of the liquid fraction of the pyrolysis residue. This can be separated, for example, in a hydrocyclone.

[0024] The boiling point (or lower boiling limit) of the diluent is preferably at least 300°C, and particularly at least 350°C. Therefore, after the mixture of plastic and diluent is introduced into the pyrolysis reactor, immediate evaporation of the diluent can be prevented; instead, the evaporation, cracking, and / or depolymerization of the diluent can only occur with the gradual residence time of the mixture in the pyrolysis reactor and the associated heating of the mixture. In this way, a homogeneous pyrolysis product can be obtained.

[0025] In addition to wax and solids, the pyrolysis residue provided in step (a) of this method may also contain a liquid fraction. Based on the total weight of the pyrolysis residue, the proportion of the liquid fraction is preferably at most 95 wt%, more preferably 30-95 wt%, and particularly 50-70 wt%. As the proportion of the liquid fraction decreases, the dissolution rate of at least a portion of the wax in the solvent increases, or less solvent can be added to the pyrolysis residue to allow the wax to dissolve at least partially in the solvent. Therefore, it also helps to separate at least a portion of the wax from a mixture with low solids content. This also reduces the amount of solvent used. Therefore, the method can be designed to be more efficient.

[0026] The pyrolysis residue provided in step (a) of this method can be obtained by pyrolyzing the plastic in a pyrolysis reactor and then increasing the solids concentration of the pyrolysis residue. Therefore, based on the total weight of the pyrolysis residue, the proportion of liquid fraction in the resulting pyrolysis residue can be reduced to preferably up to 95 wt%, more preferably 30-95 wt%, and especially 50-70 wt%. To increase the solids concentration, a hydrocyclone can be used, which can be connected downstream of the pyrolysis reactor.

[0027] If the pyrolysis residue is obtained through the pyrolysis of plastics, a gaseous fraction can be separated from the pyrolysis residue after pyrolysis and before step (a) of this method. The separation of the gaseous fraction can be carried out by evaporation, for example in a hydrocyclone that can be connected downstream of the pyrolysis reactor.

[0028] Separating gaseous fractions from pyrolysis residues and increasing the solids concentration in the residues can be accomplished, for example, by a single device or multiple single devices connected in series. Advantageously, the separation of gaseous fractions from pyrolysis residues and the increase in the solids concentration in the residues can be achieved in a single process step by means of a hydrocyclone that can be connected downstream of the pyrolysis reactor. Such hydrocyclones are described in WO 2023 / 036751 A1. By introducing a mixture containing pyrolysis residues and gaseous fractions through an inlet located in the upper region of the hydrocyclone shell, vortices are generated in the hydrocyclone, thereby separating the gaseous fractions from the pyrolysis residues and discharging them through an outlet located in the upper region of the hydrocyclone (e.g., on its top plate). The pyrolysis residues can then be discharged along the bottom direction of the hydrocyclone due to gravity, during which the tangential velocity of the formed vortices can continuously increase. Therefore, at least a portion of the pyrolysis residue (particularly at least a portion of the pyrolysis residue containing wax and solid matter) can be discharged through an outlet located at the bottom of the hydrocyclone, while at least a portion of the liquid fraction of the pyrolysis residue can enter an inner container located within the hydrocyclone and can be discharged from there through an outlet, for example, as a further diluent. The pyrolysis residue discharged through the outlet located at the bottom of the hydrocyclone can then be provided according to step (a) of this method. The hydrocyclone is preferably operated at a temperature in the range of 300 to 450°C, more preferably in the range of 320 to 420°C, and particularly preferably in the range of 360 to 400°C.

[0029] The pyrolysis residue can be cooled before the addition of solvent, either before step (a) of this method or between step (a) and step (b). Cooling can be carried out by a cooling unit. The pyrolysis residue is preferably cooled to a temperature not exceeding 220°C, more preferably not exceeding 200°C, and particularly preferably not exceeding 180°C. Cooling of the pyrolysis residue is especially necessary if it is obtained by immediately preceding plastic treatment (by pyrolysis, and if necessary, separation of gaseous fractions from the pyrolysis residue and / or increase of the solids concentration of the pyrolysis residue). By cooling the pyrolysis residue, undesirable evaporation and / or decomposition of the solvent during its addition can be reduced or even completely avoided. The pyrolysis residue is preferably cooled to a temperature not lower than 30°C, more preferably not lower than 80°C, further preferably not lower than 100°C, and particularly preferably not lower than 120°C. Further cooling to temperatures below these values ​​may impair the solubility of the wax in the solvent.

[0030] Solvent can be added to the pyrolysis residue via an introduction device. This introduction device may have a metering device (such as a metering pump). To mix the pyrolysis residue with the solvent in step (b) of this method, the pyrolysis residue can be fed into a container to which the aforementioned introduction device can be connected. This container is heatable so that the dissolution of the wax in the solvent can occur at a specific temperature.

[0031] The mixing in step (b) of this method is preferably carried out at a temperature of at least 50°C (i.e., 50°C or higher), more preferably at a temperature of at least 80°C (i.e., 80°C or higher). The fraction of wax with a melting point above room temperature (i.e., above 20-25°C) can then be dissolved in the solvent. The mixing in step (b) is preferably carried out at a temperature in the range of 50-200°C, more preferably in the range of 100-200°C, further preferably in the range of 80-200°C, and particularly preferably in the range of 80-120°C. Therefore, the wax can not only dissolve in the solvent in large quantities or even completely, but also ensures that the solvent does not evaporate due to excessively high temperatures. Even at temperatures of 100-120°C, the wax dissolves particularly well in the solvent, while from a process perspective, a temperature of 120-140°C may be optimal.

[0032] The mixing in step (b) of this method is preferably carried out at a pressure in the range of 1-25 bar, particularly at a pressure in the range of 5-16 bar. Therefore, the invention can be further improved, and rapid dissolution of the wax in the solvent can be achieved.

[0033] The boiling point (or boiling range) of the solvent is preferably in the range of 20-250°C, more preferably 50-150°C, and even more preferably 35-130°C. The lower the boiling point of the solvent, the lower the temperature at which the wax reaches a liquid state. Furthermore, as the boiling point of the solvent decreases, the crystallization ability of the wax is enhanced during the subsequent cooling of the mixture in step (c) of this method, thereby increasing the yield of the obtained wax. The boiling point (or boiling range) of the solvent can be determined according to the standards ASTM D5399-09:2017 or ASTM D2887-22:2022.

[0034] The solvent preferably contains aliphatic hydrocarbons or a mixture of two or more aliphatic hydrocarbons. When the wax has begun to crystallize, impurities dissolved in the solvent remain dissolved. This allows the wax to be separated with high purity, while the impurities remain in the mixture. The impurities may include organic impurities containing nitrogen, oxygen, sulfur, silicon, chlorine, bromine, and / or iodine, such as hybrid polymers (e.g., polyamides, polyethylene terephthalate, polyvinyl chloride, and / or acrylonitrile-butadiene-styrene copolymers) and / or additives (e.g., anti-aging agents, plasticizers, coloring pigments, and / or flame retardants).

[0035] Based on the total weight of the solvent, the solvent preferably contains at least 10 wt% aliphatic hydrocarbons or a mixture of two or more aliphatic hydrocarbons, more preferably at least 20 wt%, and even more preferably at least 50 wt%. As the proportion of aliphatic hydrocarbons increases, not only does the solvent's ability to dissolve waxes improve, but the solubility of solid substances in the solvent also decreases. On the other hand, when the proportion of aromatic hydrocarbons in the solvent is high, solid substances (especially asphaltenes or tar) will dissolve well in the solvent, which can make subsequent wax separation difficult and may even lead to contamination of the separated wax. When the proportion of cycloalkanes in the solvent is high, the wax can dissolve well, but the yield will be relatively low.

[0036] The aliphatic hydrocarbon is preferably selected from the group consisting of aliphatic hydrocarbons containing up to 15 carbon atoms per molecule, and especially from the group consisting of aliphatic hydrocarbons containing 4-12 carbon atoms per molecule. Therefore, the present invention can be carried out efficiently and enables the good separation of waxes from mixtures with low solids content.

[0037] The aliphatic hydrocarbon is preferably selected from n-pentane, n-hexane, n-heptane, n-octane, their isomers, or mixtures thereof (i.e., containing n-pentane, n-hexane, n-heptane, n-octane, isomers of these alkanes, and / or mixtures of multiple isomers of these alkanes). Since the boiling points of these aliphatic hydrocarbons are in the range of 35-130°C, this method can be carried out efficiently and economically. Then, the mixing in step (b) of this method can preferably be carried out at 120°C or lower, more preferably at 100°C or lower, to avoid solvent evaporation. Furthermore, due to the low molecular weight of these solvents, the wax not only dissolves well in them but also exhibits a good tendency to crystallize during the subsequent cooling process in step (c) of this method.

[0038] Based on the total weight of the solvent, the solvent preferably contains at least 10 wt% alcohol, more preferably at least 20 wt%. Therefore, polar impurities can dissolve in the solvent and thus separate from the wax, which crystallizes when the mixture is cooled. This can further improve the purity of the resulting wax. Based on the total weight of the solvent, the solvent preferably contains 10-30 wt% alcohol, more preferably 10-20 wt%. Particularly preferred is that the solvent contains at least 50 wt% aliphatic hydrocarbons and 10-30 wt% alcohol. Therefore, both non-polar wax and polar impurities can dissolve well in the solvent and be effectively separated during subsequent cooling of the mixture. A high-purity wax is ultimately obtained.

[0039] The alcohol is preferably selected from methanol, ethanol, propanol, or mixtures thereof. Propanol is particularly preferred because it reduces adhesion between wax crystals. This makes the separation of wax from solvent in step (d) of this method easier. Furthermore, after washing, the solvent remaining in the wax can also be well separated from the wax during the drying process.

[0040] In the mixture obtained in step (b) of this method, the ratio of pyrolysis residue to solvent may depend on the melting point of the wax. The higher the melting point of the wax, the more solvent may be required to dissolve it. The ratio of pyrolysis residue to solvent is preferably in the range of 5:1 to 1:5, more preferably 2:1 to 3:1, and especially 1:1. Then, the wax can be largely or even completely dissolved in the solvent.

[0041] If the pyrolysis residue contains solid matter, it can be at least partially separated from the mixture before step (c). Separation of the solid matter can be achieved by filtration, adsorption, and / or centrifugation. Preferably, the solid matter is separated by adsorption. An adsorbent, which may contain activated carbon and / or bleaching earth, is added to the pyrolysis residue. Therefore, the solid matter can be separated from the mixture efficiently and as thoroughly as possible.

[0042] The solid material may comprise inorganic salts, ceramic raw materials, asphalt, tar, and / or coke. Specifically, the solid material may include talc, iron oxide (such as ferric oxide), alumina, titanium dioxide, magnesium oxide, and / or calcium carbonate. If the provided pyrolysis residue is obtained by pyrolyzing a plastic, the solid may contain additives contained in the plastic. For example, additives may include fillers, coloring pigments, and / or other additives. Those skilled in the art know which additives are used depending on the different plastics and application areas.

[0043] After the solid material is separated from the mixture, it can be dried, for example, in an oven. This allows the solid to flow freely, making it easier to process. The solid material 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 no more than 120 minutes, particularly 5 to 60 minutes.

[0044] One or more components can be separated from a solid substance (especially a dried solid substance) by means of, for example, filtration and / or centrifugation. The separated components can be reused, for example, as an additive for plastics.

[0045] The solvent separated during the drying process of the solid material can be reused in step (b) of this method. Before the solvent is recycled back to this method, it can be purified, preferably by evaporation, especially rotary evaporation.

[0046] In step (c) of this method, 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 up to 25°C / min, more preferably up to 15°C / min, more preferably up to 10°C / min, more preferably up to 5°C / min, and more preferably up to 2°C / min. Cooling is preferably carried out at a rate in the range of 0.05-25°C / min, more preferably in the range of 0.1-15°C / min, more preferably in the range of 0.2-10°C / min, more preferably in the range of 0.4-5°C / min, and more preferably in the range of 0.5-2°C / min. At slower cooling rates, wax crystals can form well in this region, which facilitates better mechanical separation. Practice has also shown that slow cooling yields products with high purity. On the other hand, faster cooling leads to an increase in the amount of microcrystals formed, which are not only difficult to separate mechanically but may also carry more impurities.

[0047] Therefore, preferably, the cooling in step (c) of this method lasts for at least 5 minutes, more preferably at least 10 minutes, more preferably at least 30 minutes, and even more preferably at least 60 minutes. Cooling is preferably performed for 5-240 minutes, more preferably 10-180 minutes, more preferably 30-150 minutes, and even more preferably 60-120 minutes. The resulting wax crystals will have a scaly shape, which is characteristic of these method parameters.

[0048] In step (c) of this method, the mixture is preferably cooled to 10°C or lower, more preferably to 0°C or lower, and even more preferably to -10°C or lower. While wax can theoretically crystallize at slower cooling rates (especially up to 5°C / min), such as cooling from 100°C to only 50°C, the wax crystals will contain a significant amount of solvent, which reduces the purity of the wax, especially since the solvent may also contain impurities dissolved within it, which will also be trapped inside the wax crystals. When cooled to lower temperatures (e.g., 10°C or below), the presence of solvent can be reduced or even completely avoided, thereby significantly improving the purity of the resulting wax.

[0049] In step (d) of this method, at least a portion of the crystalline wax can be separated from the mixture. Separation may include filtration and / or centrifugation. The temperature during the separation process is preferably 80°C or lower, more preferably 30°C or lower. The temperature is preferably in the range of -10 to 80°C, particularly in the range of 0 to 30°C. This prevents the wax from redissolving in the solvent. Furthermore, the separation is preferably carried out at a pressure of up to 10 bar, more preferably at a pressure of 5 to 10 bar. This improves the efficiency of the method.

[0050] After separating the wax from the mixture in step (d) of this method, at least partially of the solvent contained in the mixture can be separated from the mixture. This separation can be carried out by evaporation or distillation. The separated solvent can be reused in step (b) of the method. Before recycling the solvent back into this method, additional purification treatment can be performed, preferably by evaporation, and particularly preferably by rotary evaporation.

[0051] The wax separated in step (d) of this method preferably has a boiling point (or lower limit of boiling range) of at least 270°C, more preferably at least 300°C, and even more preferably a boiling point (or lower limit of boiling range) in the range of 340-700°C. The boiling point (or boiling range) of the wax can be determined by the following standards: ASTM D7500-15:2019 (preferably for waxes with a boiling point or boiling range of 100-850°C (especially 100-735°C); ASTM D2887-22:2022 (preferably for waxes with a boiling point or boiling range of 55-538°C).

[0052] The separated wax preferably contains at least 15 carbon atoms per molecule, more preferably at least 20, and especially at least 40. The wax preferably contains 20-80 carbon atoms per molecule, especially 20-65. Such waxes are highly suitable for further use.

[0053] The separated wax can be supplied to refinery processing units, particularly fluidized bed catalytic cracking (FCC) units, thermal gas oil units (TGU units), hydrotreating units, and / or tubular coking units. The separated wax can also be applied in other technical fields, such as as a lubricant and / or additive. The separated wax can be further processed before further use. For example, the wax can be purified and / or separated into different carbon fractions.

[0054] Based on the total weight of the separated wax, the proportion of one (or more) carbon fractions contained in the separated wax is preferably at least 60 wt%, more preferably at least 70 wt%, even more preferably at least 80 wt%, and particularly at least 85 wt%. This proportion provides information about the purity of the separated wax, with a high proportion of carbon fractions corresponding to high purity of the separated wax. Therefore, high-purity wax can be obtained by the method of the present invention, and its purity can be further improved by subsequent washing of the wax. The proportion of carbon fractions can be determined by gravimetric analysis, which may include determining the pyrolysis residues, added solvents, and the mass of the separated wax.

[0055] Following step (d) of this method, the separated wax can be washed. In particular, the wax can be washed 1-3 times. As a result, the purity of the separated wax can be further improved.

[0056] During the cleaning process, the temperature of the wax is preferably 80°C or lower, more preferably 30°C or lower, and even more preferably within the range of -10 to 80°C, especially 0 to 30°C. This prevents the wax from dissolving back into the solvent. When cleaning the wax, the same or similar temperature as that used for separating the wax in step (d) of this method can be selected.

[0057] Alcohol is preferably used to clean the wax. This removes any remaining polar impurities, resulting in a wax of extremely high purity. The alcohol used for cleaning is preferably selected from methanol, ethanol, propanol, or mixtures thereof. This not only effectively removes residual polar impurities but also facilitates the separation of any solvent remaining in the wax during the drying process.

[0058] This method may also include an additional step (e): drying the separated wax. This removes the solvent that separates along with the wax crystals. Drying can be carried out thermally at elevated temperatures, or alternatively, at low temperatures and under vacuum. The type of drying depends on the further use of the wax. Vacuum drying is preferred to preserve the structure of the wax crystals. If the wax is subsequently used in liquid form, it can also be dried at elevated temperatures, and if necessary, melted. Thermal drying is preferably carried out at 150°C or lower and ambient pressure (0.7-1.1 bar). Vacuum drying is preferably carried out at 30°C or lower and pressures of 750 mbar or lower (especially 500 mbar or lower). The solvent separated during wax drying can be reused in step (b) of this method. Additional purification can be performed before recycling the solvent back into this method, preferably by evaporation, especially by rotary evaporation.

[0059] The present invention particularly relates to the following embodiments.

[0060] 1. A method for extracting wax from pyrolysis residues, the method comprising the following steps: (a) Providing a pyrolysis residue, wherein the pyrolysis residue contains wax; (b) At a temperature of at least 30°C, the pyrolysis residue is mixed with a solvent to obtain a mixture, wherein the wax is at least partially dissolved in the solvent; (c) Cool the mixture to allow at least a portion of the dissolved wax to crystallize; (d) Separate at least a portion of the crystallized wax from the mixture.

[0061] 2. The method according to embodiment 1, wherein the pyrolysis residue is obtained by pyrolyzing plastics (especially waste plastics).

[0062] 3. The method according to any of the foregoing embodiments, wherein the pyrolysis residue is obtained by pyrolyzing the plastic and separating at least one fraction (preferably a gaseous fraction) from the pyrolyzed plastic.

[0063] 4. The method according to any of the foregoing embodiments, wherein the boiling point of the pyrolysis residue is 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, and more preferably at least 300°C.

[0064] 5. The method according to any of the foregoing embodiments, wherein the boiling point of the pyrolysis residue is in the range of 100℃-700℃, preferably in the range of 150℃-600℃, more preferably in the range of 200℃-500℃, more preferably in the range of 240℃-460℃, more preferably in the range of 270℃-430℃, and more preferably in the range of 300℃-400℃.

[0065] 6. The method according to any of the foregoing embodiments, wherein the plastic comprises a polyolefin and / or polystyrene (PS), wherein the polyolefin may comprise polyethylene (PE) and / or polypropylene (PP).

[0066] 7. The method according to embodiment 6, wherein, based on the total weight of the plastic, the plastic comprises at least 65 wt% polyolefin and / or polystyrene, more preferably at least 70 wt%, and especially at least 90 wt%.

[0067] 8. The method according to any of the foregoing embodiments, wherein the plastic has a polyethylene (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%.

[0068] 9. The method according to any of the foregoing embodiments, wherein before adding the solvent, the pyrolysis residue is cooled to a temperature not exceeding 220°C, more preferably not exceeding 200°C, and particularly preferably not exceeding 180°C.

[0069] 10. The method according to any of the foregoing embodiments, wherein before adding the solvent, 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, and particularly preferably not less than 120°C.

[0070] 11. The method according to any of the foregoing embodiments, wherein the mixing in step (b) is carried out at a temperature of at least 50°C, more preferably at a temperature of at least 80°C, particularly in the range of 50°C-200°C, preferably in the range of 100°C-200°C, more preferably in the range of 80°C-200°C, and especially in the range of 80°C-120°C.

[0071] 12. The method according to any of the foregoing embodiments, wherein the mixing in step (b) is carried out at a pressure of 1 bar to 25 bar, preferably 5 bar to 16 bar.

[0072] 13. The method according to any of the foregoing embodiments, wherein the boiling point of the solvent is in the range of 20°C-250°C, preferably 50°C-150°C, and more preferably 35°C-130°C.

[0073] 14. The method according to any of the foregoing embodiments, wherein the solvent comprises an aliphatic hydrocarbon.

[0074] 15. The method according to any of the foregoing embodiments, wherein the solvent contains at least 10 wt% aliphatic hydrocarbons, preferably at least 20 wt%, more preferably at least 50 wt%, based on the total weight of the solvent.

[0075] 16. The method according to embodiment 14 or 15, wherein the aliphatic hydrocarbon is selected from the group consisting of aliphatic hydrocarbons containing up to 15 carbon atoms per molecule, preferably the group consisting of aliphatic hydrocarbons containing 4-12 carbon atoms per molecule.

[0076] 17. The method according to any one of embodiments 14 to 16, wherein the aliphatic hydrocarbon is selected from n-pentane, n-hexane, n-heptane, n-octane, isomers thereof, or mixtures thereof.

[0077] 18. The method according to any of the foregoing embodiments, wherein the solvent contains at least 10 wt% alcohol, preferably at least 20 wt%, based on the total weight of the solvent.

[0078] 19. The method according to embodiment 18, wherein the solvent contains 10wt%-30wt% alcohol, preferably 10wt%-20wt%, based on the total weight of the solvent.

[0079] 20. The method according to any one of embodiments 14 to 19, wherein the solvent comprises at least 50 wt% aliphatic hydrocarbons and 10 wt% to 30 wt% alcohols based on the total weight of the solvent.

[0080] 21. The method according to any one of embodiments 18 to 20, wherein the alcohol is selected from methanol, ethanol, propanol or mixtures thereof, especially propanol.

[0081] 22. The method according to any of the preceding embodiments, wherein the ratio of pyrolysis residue to solvent in the mixture obtained in step (b) is in the range of 5:1 to 1:5, preferably 2:1 to 3:1, especially 1:1.

[0082] 23. The method according to any of the preceding embodiments, wherein prior to step (c), the solids contained in the pyrolysis residue are at least partially separated from the mixture.

[0083] 24. The method according to embodiment 23, wherein the solid comprises inorganic salts, ceramic raw materials, bituminous substances, tar and / or coke.

[0084] 25. The method according to embodiment 23 or 24, wherein the separation of solids includes filtration, adsorption and / or centrifugation.

[0085] 26. The method according to embodiment 25, wherein the separation of the solids includes adsorption, wherein an adsorbent is added to the pyrolysis residue, and wherein the adsorbent preferably comprises activated carbon and / or bleaching clay.

[0086] 27. The method according to any one of embodiments 23 to 26, wherein the separated solid material is dried, preferably at a temperature of 50°C to 250°C, more preferably at a temperature of 100°C to 200°C; and / or the drying time is at most 120 minutes, preferably 5 to 60 minutes.

[0087] 28. The method according to any of the foregoing embodiments, wherein in step (c), the mixture is cooled to 10°C or lower, preferably to 0°C or lower, more preferably to -10°C or lower.

[0088] 29. The method according to any of the foregoing embodiments, wherein the mixture in step (c) is cooled at a rate of up to 25°C / min, preferably up to 15°C / min, more preferably up to 10°C / min, more preferably up to 5°C / min, more preferably up to 2°C / min; preferably in the range of 0.05°C / min to 25°C / min, more preferably 0.1°C / min to 15°C / min, more preferably 0.2°C / min to 10°C / min, more preferably 0.4°C / min to 5°C / min, more preferably 0.5°C / min to 2°C / min.

[0089] 30. The method according to any of the foregoing embodiments, wherein the cooling duration of step (c) is at least 5 minutes, more preferably at least 10 minutes, more preferably at least 30 minutes, and more preferably at least 60 minutes; the cooling duration is preferably 5 minutes to 240 minutes, more preferably 10 minutes to 180 minutes, more preferably 30 minutes to 150 minutes, and more preferably 60 minutes to 120 minutes.

[0090] 31. The method according to any of the foregoing embodiments, wherein the separation of crystallized wax in step (d) includes filtration and / or centrifugation.

[0091] 32. The method according to any of the foregoing embodiments, wherein the temperature in step (d) is 80°C or lower, preferably 30°C or lower, more preferably in the range of -10°C to 80°C, especially in the range of 0°C to 30°C.

[0092] 33. The method according to any of the foregoing embodiments, wherein after step (d), the solvent is at least partially separated from the mixture, and the separated solvent is preferably reused in step (b).

[0093] 34. The method according to any of the foregoing embodiments, wherein the boiling point of the separated wax is at least 270°C, preferably at least 300°C, and more preferably in the range of 340°C-700°C.

[0094] 35. The method according to any of the preceding embodiments, wherein each molecule of the wax contains at least 15 carbon atoms, preferably at least 20, and particularly at least 40.

[0095] 36. The method according to embodiment 35, wherein each molecule of the wax contains 20-80 carbon atoms, preferably 20-65.

[0096] 37. The method according to any of the foregoing embodiments, wherein, based on the total weight of the separated wax, the proportion of carbon fraction in the separated wax is at least 60 wt%, preferably at least 70 wt%, more preferably at least 80 wt%, and especially at least 85 wt%.

[0097] 38. The method according to any of the foregoing embodiments, wherein after step (d), the separated wax is washed, preferably with an alcohol, particularly selected from methanol, ethanol, propanol or mixtures thereof.

[0098] 39. The method according to any of the foregoing embodiments, wherein the temperature during the cleaning process of the separated wax is 80°C or lower, preferably 30°C or lower, more preferably in the range of -10°C to 80°C, especially 0°C to 30°C.

[0099] 40. The method according to any of the foregoing embodiments further includes step (e): drying the separated wax.

[0100] 41. The method according to embodiment 40, wherein in step (e), the wax is dried at a temperature of 150°C or lower and a pressure of 0.7 bar to 1.1 bar.

[0101] 42. The method according to embodiment 40 or 41, wherein in step (e), the wax is dried at a temperature of 30°C or lower and a pressure of 750 mbar or lower (preferably 500 mbar or lower).

[0102] 43. The method according to any of the embodiments 40 to 42, wherein the solvent separated during the wax drying process in step (e) is reused in step (b). Attached Figure Description

[0103] Figure 1 A flowchart of a pyrolysis method is shown, in which wax is obtained from the pyrolysis residue. Detailed Implementation

[0104] Depend on Figure 1 It is known that plastic containing at least 50 wt% polyolefin is fed into extruder 1, where it is plasticized and degassed. The plasticized plastic is heated to at least 120°C and then fed into static mixer 2. In static mixer 2, diluent 3 can be added to the plasticized plastic to reduce its viscosity. Alternatively, or in addition to diluent 3, a portion of the liquid fraction 4 separated from the pyrolysis residue can be mixed with the plasticized plastic to reduce its viscosity. The resulting mixture is then fed into pyrolysis reactor 5, where the plastic is pyrolyzed at a temperature of 350-450°C. As a result, a pyrolysis product 6 is obtained, containing gaseous fractions and pyrolysis residues, wherein the pyrolysis residues contain liquid fractions, waxes, and solid substances. The pyrolysis product 6 is fed into hydrocyclone 7 downstream of pyrolysis reactor 5. First, the gaseous fraction is at least partially separated in hydrocyclone 7. The separated portion 8 of the gaseous distillate can be further separated into light oil (e.g., boiling range 35-225°C) and heavy oil (e.g., boiling range 225-410°C) (not shown in the figure). Additionally, at least partially, the liquid distillate is separated within the hydrocyclone 7. The separated portion 4 of the liquid distillate can be discharged through the outlet 9 of the hydrocyclone 7 and reused in this method for viscosity reduction treatment of plastics, as previously described. At least a portion of the pyrolysis residue, which at least partially contains wax and solid matter, is discharged through the outlet 10 located at the bottom of the hydrocyclone 7.

[0105] Depend on Figure 1It is also known that the pyrolysis residue discharged through outlet 10 is sent to the first cooling unit 11 for cooling to a temperature in the range of 80-240°C. Subsequently, in container 12, a solvent 13 containing at least 20 wt% aliphatic hydrocarbons is added to the pyrolysis residue through introduction device 14 to obtain a mixture in which the wax is at least partially dissolved in solvent 13. The aliphatic hydrocarbons are selected from the group consisting of aliphatic hydrocarbons containing 4-12 carbon atoms per molecule. In the resulting mixture, the ratio of pyrolysis residue to solvent is in the range of 2:1 to 3:1. Container 12 is heated so that dissolution can be carried out at a temperature in the range of 80-200°C. In separation device 15, the solid matter is at least partially separated from the mixture by adsorption on activated carbon. Afterwards, the separated solid matter 16 is dried in oven 17 at a temperature in the range of 100-200°C. After drying, various components can be separated from the solid matter and reused (not shown in the figure). Solvent 13 separated during the drying process is returned to container 12 via introduction device 14 for reuse in step (b) of this method. Solvent 13 can be purified before recycling, for example by evaporation (not shown in the figure). Figure 1 As shown, the mixture is then cooled to -10°C or lower in the second cooling unit 18 at a maximum rate of 5°C / min, causing at least a portion of the wax dissolved in the solvent to crystallize. Subsequently, at least a portion of the crystallized wax is separated from the mixture through filter 19. The solvent 13 contained in the mixture is separated in evaporator 20 and returned to container 12 via inlet device 14.

[0106] Depend on Figure 1 Furthermore, the separated wax 21 is washed in a washer 22 using alcohol. Afterward, the washed and separated wax 21 is sent to a dryer 23 to dry the wax crystals. The resulting wax 24 can then be used for other applications (not shown in the figure). The solvent 13 separated during the drying process of the separated wax 21 is also returned to the container 12 via an introduction device 14. The solvent 13 can be purified before recycling, for example, by evaporation (not shown in the figure).

Claims

1. A method for obtaining wax from pyrolysis residues, the method comprising the steps of: (a) Providing a pyrolysis residue, wherein the pyrolysis residue contains wax; (b) The pyrolysis residue is mixed with a solvent at a temperature of at least 30°C to obtain a mixture, wherein the wax is at least partially dissolved in the solvent; (c) Cool the mixture to allow at least a portion of the dissolved wax to crystallize; (d) Separate at least a portion of the crystallized wax from the mixture.

2. The method according to claim 1, wherein the mixing in step (b) is carried out at a temperature of at least 80°C.

3. The method according to claim 1 or 2, wherein the boiling point of the solvent is in the range of 35°C to 130°C.

4. The method according to any one of claims 1 to 3, wherein the solvent comprises at least 50 wt% aliphatic hydrocarbons.

5. The method according to claim 4, wherein the aliphatic hydrocarbon is selected from n-pentane, n-hexane, n-heptane, n-octane, isomers thereof, or mixtures thereof.

6. The method according to any one of claims 1 to 5, wherein the solvent comprises at least 10 wt% alcohol.

7. The method according to claim 6, wherein the alcohol is propanol.

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

9. The method according to any one of claims 1 to 8, wherein the mixture in step (c) is cooled at a rate of up to 5°C / min.

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

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

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

13. The method according to any one of claims 1 to 12, wherein the boil point of the separated wax is 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. The method according to any one of claims 1 to 14, wherein the solvent separated during the drying of the wax in step (e) is reused in step (b).

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