Method for extracting wax from pyrolysis residue

Abstract

The present invention relates to a method for obtaining wax from a thermal decomposition residue, comprising the steps of (a) preparing the thermal decomposition residue containing wax, (b) mixing the thermal decomposition residue with a solvent at 30°C or higher to obtain a mixture in which the wax is at least partially dissolved in the solvent, (c) cooling the mixture to crystallize at least a portion of the dissolved wax, and (d) separating at least a portion of the crystallized wax from the mixture.

Description

Technical Field

[0001] The present invention relates to a method for obtaining wax from pyrolysis residues.

Background Art

[0002] It is known from the prior art to separate wax from starting products by crystallization. For example, 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 to crystallize and separate the wax contained in the petroleum product.

[0003] A similar method of dewaxing is disclosed in WO2021 / 115982A1, where a solvent is added at room temperature to a pyrolysis residue obtained from the pyrolysis of plastics. The resulting mixture is then cooled to separate the wax contained in the mixture by crystallization.

[0004] Further methods for wax separation are known from US3,720,599A, US5,006,222A, US2,614,065A, WO2017 / 168165A1 and WO2021 / 115982A1.

Summary of the Invention

[0005] In the methods known in the prior art, the separation of wax mainly serves the purpose of purifying the starting product. The separated wax may have a relatively low purity. However, for many applications, it may be necessary to use wax with a high purity, and further complex cleaning of the separated wax may be required. There is a need for an inexpensive and simple method for producing wax with a high purity. The object of the present invention is to provide such a method.

[0006] The method according to the present invention for extracting wax from pyrolysis residues comprises (a) preparing the pyrolysis residue containing the wax, (b) A step of mixing the thermal decomposition residue with a solvent at 30°C or higher to obtain a mixture, wherein the wax is at least partially dissolved in the solvent, (c) A step of cooling the mixture to crystallize at least a portion of the dissolved wax, and (d) A step of separating at least a portion of the crystallized wax from the mixture. Includes. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows a flowchart of the pyrolysis method in which wax is obtained from the pyrolysis residue. [Modes for carrying out the invention]

[0008] This invention is based on the finding that pyrolysis residues, particularly those obtained from the pyrolysis of plastics, are a valuable source of wax. By mixing the pyrolysis residue with a solvent at 30°C or higher, the wax can be largely or even completely dissolved in the solvent and subsequently separated from the pyrolysis residue to have high purity. The resulting wax can be a sustainable alternative to wax obtained directly from petroleum.

[0009] The pyrolysis residue can be obtained by pyrolysis of plastics, particularly waste plastics. The pyrolysis can be carried out in a pyrolysis reactor at a temperature of preferably 300 to 500°C, and particularly 350 to 450°C. As a result, a good balance between cost-effectiveness and method efficiency can be achieved.

[0010] The thermal decomposition may be thermal decomposition (i.e., thermal cracking without catalyst addition) and / or catalytic decomposition (i.e., catalytic cracking). Thermal decomposition is preferred to avoid contamination of either wax or solids caused by the catalyst component.

[0011] The aforementioned thermal decomposition can be carried out in the absence of oxygen, particularly in an inert atmosphere, for example, under nitrogen. Complete combustion may be prevented due to the loss or removal of oxygen, and the polymer contained in the plastic may be cleaved or depolymerized.

[0012] Within the scope of the present invention, it has been demonstrated that a fraction of the pyrolysis-reduced plastic, preferably a heavy fraction, is advantageous when used as the pyrolysis residue. In a preferred embodiment, the pyrolysis residue is therefore obtained by pyrolysis of the plastic and separating at least one fraction, preferably a gaseous fraction, from the pyrolysis-reduced plastic. The separated fraction preferably has a lower boiling point (or a lower boiling point range) than the pyrolysis residue.

[0013] In a particularly preferred embodiment, the pyrolysis residue has a boiling point (or lower end of the boiling point range) of 100°C or higher, preferably 150°C or higher, more preferably 200°C or higher, more preferably 240°C or higher, more preferably 270°C or higher, and more preferably 300°C or higher. The pyrolysis residue preferably has a boiling point (or lower end of the boiling point range) in the range of 100°C to 700°C, preferably 150°C to 600°C, more preferably 200°C to 500°C, more preferably 240°C to 460°C, more preferably 270°C to 430°C, and more preferably 300°C to 400°C. It has been found that fractions having such boiling points can have a particularly high wax content and are therefore particularly suitable for the method according to the present invention. It has been demonstrated that it is particularly advantageous when the pyrolysis residue is spindle oil having a boiling point (or lower end of the boiling point range) in the range of 300°C to 400°C. In this case, the wax content of the pyrolysis residue may be, for example, about 50% by weight.

[0014] The boiling point (or boiling point range) can preferably be determined according to ASTM standard D7500-15:2019. Alternatively, ASTM standard D2887-22:2022 may be used.

[0015] The plastic preferably comprises polyolefin and / or polystyrene (PS), and the polyolefin may also comprise polyethylene (PE) and / or polypropylene (PP). The plastic contains the polyolefin and / or polystyrene in an amount of preferably 65% ​​by weight or more, more preferably 70% by weight or more, and particularly 90% by weight or more, based on the total weight of the plastic. As a result, a pyrolysis residue can be obtained that contains a significant proportion of aliphatic hydrocarbons (or a mixture of multiple aliphatic hydrocarbons), i.e., a significant proportion of the wax.

[0016] The plastic preferably contains 20% by weight or more, more preferably 50% by weight or more, even more preferably 70% by weight or more, and particularly 90% by weight or more of the polyolefin, based on the total weight of the plastic. As the proportion of polyolefin increases, the amount of wax obtained by the method according to the present invention may increase, and the cost-effectiveness of the method can be improved.

[0017] In the process of the present invention, it was found that a high polyethylene (PE) content is particularly advantageous because a particularly high wax content can be obtained during the thermal decomposition of a plastic having a high PE content. Therefore, in a particularly preferred embodiment, the plastic has a PE content of 10% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more, more preferably 40% by weight or more, more preferably 50% by weight or more, more preferably 60% by weight or more, and even more preferably 70% by weight or more.

[0018] The plastic may include thermoplastics, duromers and / or elastomers, and in particular, further polymers from the group consisting of acrylonitrile-butadiene-styrene copolymer (ABS), polyvinyl chloride (PVC), polyamide (PA), and / or polyester.

[0019] Prior to thermal decomposition, the plastic can be plasticized, for example, in a mixer, particularly in an extruder. For plasticization, the plastic is preferably heated to a temperature of 120°C or higher, more preferably 200-500°C, and even more preferably 400-470°C. The subsequent thermal decomposition can then be carried out more energy-efficiently and in a shorter time. In the extruder, the plastic can also be degassed to produce a gas-free, homogeneous mass, as a result of which a homogeneous thermal decomposition product can be obtained by subsequent thermal decomposition.

[0020] Prior to the aforementioned thermal decomposition, a diluent for viscosity reduction may be added to the plastic, particularly the plasticized plastic. The diluent is added to the plastic in an amount of preferably 5% or more by weight, more preferably 9% or more by weight, based on the total weight of the plastic. The ratio of plastic to diluent is preferably 1:4 or more, more preferably 1:9 or more. By adding the diluent to the plastic, the mobility of the polymer chains may be increased at a given temperature, and as a result, the heat injection into the plastic may be improved during thermal decomposition. Furthermore, the risk of overheating of the plastic in the wall region of the thermal decomposition reactor may be reduced due to the viscosity reduction, because such plastic is usually heated by a heating device located near the outer wall of the thermal decomposition reactor. The risk of coking of the plastic during thermal decomposition may also be reduced by reducing the viscosity.

[0021] By adding the diluent to the plastic, its viscosity can be reduced by preferably 30% or more, more preferably 50% or more, and especially preferably 80% or more, based on the viscosity of the plastic without the diluent, under the same measurement conditions, particularly at temperatures in the range of 180 to 240°C. This can improve the pumping capacity of the plastic, thereby facilitating its processing.

[0022] When the diluent is added, the plastic preferably has a temperature of 120 °C or higher, more preferably 150 - 300 °C, particularly 200 - 300 °C. Alternatively or additionally, the diluent can be heated to a temperature of preferably 120 °C or higher, more preferably 150 °C or higher, particularly 200 - 300 °C, before being added to the plastic. By increasing the temperature of the plastic and / or the diluent, the diluent can be mixed with the plastic more rapidly and efficiently. Subsequent thermal decomposition can also be carried out more energy - efficiently and faster.

[0023] The diluent can be added to the plastic using a supply device. The supply device may have a metering device such as a metering pump. For example, the plastic, particularly the plasticized plastic, can be supplied to a mixer, such as a static mixer, and mixed with the diluent therein. When the plastic is plasticized in an extruder, the diluent can be added directly to the extruder. For this purpose, the supply device can be arranged in, for example, the compression zone or the mixing zone of the extruder.

[0024] The diluent may contain hydrocarbons selected from alkanes, cycloalkanes, and / or aromatics. As a result of the thermal decomposition, such diluents can be converted into gaseous products and / or liquid products, and can be at least partially separated from the thermal decomposition residue and reused. In particular, the diluent may contain fractions obtained from crude oil, preferably heavy oil. The heavy oil can be an oil obtained from petroleum in petroleum refining, for example, the residual oil from a thermal decomposition system. The diluent preferably contains at least a part of the liquid fraction of the thermal decomposition residue. Such diluent can be separated, for example, in a hydrocyclone.

[0025] The diluent preferably has a boiling point (or the lower end of the boiling range) of 300 °C or higher, particularly 350 °C or higher. As a result, evaporation of the diluent can be prevented immediately after the mixture of the plastic and the diluent is introduced into the pyrolysis reactor, but evaporation, cracking and / or depolymerization of the diluent can only occur by the progress of the residence time of the mixture in the pyrolysis reactor and the associated heating of the mixture. As a result, a homogeneous pyrolysis product can be obtained.

[0026] Separate from the wax and the solid, the pyrolysis residue prepared in step (a) of the method may also contain a liquid fraction. The proportion of the liquid fraction is preferably 95% by weight or less, more preferably 30 - 95% by weight, particularly 50 - 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 a portion of the wax dissolves in the solvent may increase, or a smaller amount of solvent may be added to the pyrolysis residue to at least partially dissolve the wax in the solvent. As a result, separation of at least a portion of the wax from the low-solid mixture can also be facilitated. The use of the solvent can also be reduced as a result. Thereby, the method can be designed more efficiently.

[0027] The pyrolysis residue prepared in step (a) of the method may be obtained by pyrolyzing the plastic in a pyrolysis reactor and subsequently increasing the solid concentration of the pyrolysis residue. As a result, the proportion of the liquid fraction of the resulting pyrolysis residue can be reduced to preferably 95% by weight or less, more preferably 30 - 95% by weight, particularly 50 - 70% by weight, based on the total weight of the pyrolysis residue. A hydrocyclone may be used to increase the solid concentration and may be connected downstream of the pyrolysis reactor.

[0028] When the pyrolysis residue is obtained by the pyrolysis of plastic, a gaseous fraction may be separated from the pyrolysis residue after the pyrolysis and before step (a) of the method. The separation of the gaseous fraction may be carried out by evaporation, for example, in a hydrocyclone which may be connected downstream of the pyrolysis reactor.

[0029] The separation of the gaseous fraction from the pyrolysis residue and the increase in the solid concentration of the pyrolysis residue may be carried out, for example, by a separation device or by 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 solid concentration of the pyrolysis residue may be carried out in a single method step by a hydrocyclone, which may be connected downstream of the pyrolysis reactor. Such a hydrocyclone is described in WO2023 / 036751A1. A vortex flow may be generated in the hydrocyclone by introducing a mixture containing the pyrolysis residue and the gaseous fraction through an inlet located in the upper region of the hydrocyclone shell, thereby separating the gaseous fraction from the pyrolysis residue and discharging it through an outlet located in the upper region of the hydrocyclone (e.g., on the ceiling). The pyrolysis residue can then be discharged by gravity toward the bottom of the hydrocyclone, where the tangential velocity of the vortex flow being formed can increase continuously. As a result, at least a portion of the pyrolysis residue, particularly at least a portion of the pyrolysis residue containing at least a portion of the wax and the solid, 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 pass through an internal container located in the hydrocyclone and discharged from there through an outlet for further use, for example, as a diluent. The pyrolysis residue discharged through the outlet located at the bottom of the hydrocyclone can then be provided by step (a) of the method. The hydrocyclone is operated at a temperature preferably in the range of 300 to 450°C, more preferably 320 to 420°C, and particularly preferably 360 to 400°C.

[0030] The pyrolysis residue may be cooled before step (a) of the method, or between step (a) and step (b), before the addition of the solvent. Cooling may be carried out by a cooling unit. The pyrolysis residue is cooled to a temperature preferably 220°C or lower, more preferably 200°C or lower, and particularly preferably 180°C or lower. The cooling of the pyrolysis residue may be necessary in particular when the pyrolysis residue is obtained by the immediate processing of the plastic (by pyrolysis, and, if necessary, by subsequent separation of gaseous fractions from the pyrolysis residue and / or by increasing the solid concentration of the pyrolysis residue). By cooling the pyrolysis residue, undesirable evaporation and / or decomposition of the solvent upon addition to the pyrolysis residue may be reduced or completely prevented. The pyrolysis residue is cooled to a temperature preferably 30°C or higher, more preferably 80°C or higher, even more preferably 100°C or higher, and particularly preferably 120°C or higher. Further cooling below the temperatures described above may impair the solubility of the wax in the solvent.

[0031] The solvent may be added to the pyrolysis residue by an introduction device. The introduction device may have a metering device such as a metering pump. In step (b) of the method, the pyrolysis residue may be supplied to a container to which the introduction device can be connected in order to mix the pyrolysis residue with the solvent. The container may be heatable so that the dissolution of the wax in the solvent can occur at a certain temperature.

[0032] The mixing in step (b) of the method described above is preferably carried out at at least 50°C (i.e., 50°C or higher), more preferably at at least 80°C (i.e., 80°C or higher). A fraction of the wax having 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 100-200°C, even more preferably 80-200°C, and particularly preferably 80-120°C. As a result, not only can the wax be largely or completely dissolved in the solvent, but it can also be ensured that the solvent does not evaporate due to excessively high temperatures. The wax can dissolve particularly well in the solvent even at temperatures of 100-120°C, but temperatures of 120-140°C may be optimal from a procedural standpoint.

[0033] The mixing in step (b) of the method is preferably carried out at a pressure in the range of 1 to 25 bar, particularly 5 to 16 bar. As a result, the method can be further improved and rapid dissolution of the wax in the solvent can be achieved.

[0034] The solvent preferably has a boiling point (or boiling point 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 become liquid. Furthermore, as the boiling point of the solvent decreases, the ability of the mixture to crystallize during subsequent cooling in step (c) of the method may increase, and as a result, the yield of the resulting wax may increase. The boiling point (or boiling point range) of the solvent can be determined by ASTM standard D5399-09:2017 or ASTM D2887-22:2022.

[0035] The solvent preferably comprises an aliphatic hydrocarbon or a mixture of two or more aliphatic hydrocarbons. Impurities that dissolve in the solvent may then dissolve and remain while the wax has already crystallized. This allows the wax to be separated in high purity, while the impurities may remain in the mixture. The impurities may include organic impurities such as nitrogen, oxygen, sulfur, silicon, chlorine, bromine, and / or iodine, for example, heteropolymers (e.g., polyamides, polyethylene terephthalate, polyvinyl chloride, and / or acrylonitrile-butadiene-styrene copolymers) and / or additives (e.g., antioxidants, plasticizers, coloring pigments, and / or flame retardants).

[0036] The solvent preferably contains 10% by weight or more, preferably 20% by weight or more, and more preferably 50% by weight or more, of aliphatic hydrocarbons or a mixture of two or more aliphatic hydrocarbons based on the total weight of the solvent. As the proportion of aliphatic hydrocarbons increases, not only can the solvent's ability to dissolve the wax be improved, but the solubility of the solid in the solvent may also be reduced. On the other hand, if the proportion of aromatics in the solvent is high, the solid, in particular asphaltenes or tars, may dissolve well in the solvent, which may make subsequent separation of the wax more difficult, or as a result, the separated wax may be contaminated. If the proportion of cycloalkanes in the solvent is high, the wax may dissolve well, but the yield may be relatively low.

[0037] The aliphatic hydrocarbon is preferably selected from the group consisting of aliphatic hydrocarbons having 15 or fewer carbon atoms per molecule, particularly 4 to 12 carbon atoms per molecule. As a result, the method can be carried out efficiently, and good separation of the wax from the low-solid mixture can be achieved.

[0038] The aliphatic hydrocarbon is preferably selected from n-pentane, n-hexane, n-heptane, n-octane, their isomers, or mixtures thereof (i.e., mixtures including n-pentane, n-hexane, n-heptane, n-octane, isomers of these alkanes, and / or multiple isomers of these alkanes). Since the boiling points of these aliphatic hydrocarbons are in the range of 35 to 130°C, the method can be carried out efficiently and economically. The mixing in step (b) of the method is preferably carried out at 120°C or below, more preferably at 100°C or below, in order to avoid evaporation of the solvent. Furthermore, due to the low molecular weight of these solvents, the wax not only dissolves well in them but also has a good tendency to crystallize during the subsequent cooling in step (c) of the method.

[0039] The solvent preferably contains 10% by weight or more, more preferably 20% by weight or more, of alcohol based on the total weight of the solvent. As a result, polar impurities can be separated from the wax by dissolving in the solvent and crystallizing when the mixture cools. This can further increase the purity of the resulting wax. The solvent preferably contains 10-30% by weight of the alcohol, more preferably 10-20% by weight, based on the total weight of the solvent. Particularly preferably, the solvent contains 50% by weight or more of the aliphatic hydrocarbon and 10-30% by weight of the alcohol. As a result, both the non-polar wax and polar impurities can be well dissolved in the solvent and well separated from each other during subsequent cooling of the mixture. Overall, a wax of high purity can then be obtained.

[0040] The alcohol may be preferably selected from methanol, ethanol, propanol, or a mixture thereof. Propanol is particularly preferred because it can reduce adhesion between wax crystals. This may allow for easier separation of the wax from the solvent in step (d) of the method. Furthermore, any solvent remaining on the wax after washing can be easily separated from the wax during drying.

[0041] The ratio of thermal decomposition residue to solvent in the mixture obtained in step (b) of the method described above 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. A thermal decomposition residue to solvent ratio in the range of 5:1 to 1:5, preferably 2:1 to 3:1, and particularly preferably 1:1, is preferable. The wax can then be largely or even completely dissolved in the solvent.

[0042] If the pyrolysis residue contains a solid, it may be separated at least partially from the mixture before step (c). Separation of the solid may include filtration, adsorption, and / or centrifugation. Preferably, the solid is separated by adsorption. Adsorbents may be added to the pyrolysis residue and may include activated carbon and / or bleached earth. As a result, the solid can be separated from the mixture efficiently and as completely as possible.

[0043] The solid may include inorganic salts, ceramic raw materials, asphaltenes, tar, and / or coke. In particular, the solid may include talc, iron oxide (e.g., ferric oxide), aluminum oxide, titanium dioxide, magnesium oxide, and / or calcium carbonate. When the prepared pyrolysis residue is obtained by pyrolysis of a plastic, the solid may include additives contained in the plastic. For example, the additives may include fillers, coloring pigments, and / or other additives. Experts know which additives are used depending on the respective plastic and application field.

[0044] The solid, after being separated from the mixture, can be dried, for example, in an oven. As a result, the solid may become free-flowing and therefore easier to process. The solid is 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 120 minutes or less, particularly 5 to 60 minutes.

[0045] One or more components can be separated from the solid, particularly from the dried solid, for example, by filtration and / or centrifugation. The separated components can then be reused, for example, as an additive for plastics.

[0046] The solvent separated during the drying of the solid may be reused in step (b) of the method. Before being recycled into the method, the solvent may be purified, preferably by evaporation, and particularly by rotational evaporation.

[0047] In step (c) of the method described above, the mixture crystallizes upon cooling, crystallizing at least a portion of the wax dissolved in the solvent. The mixture is preferably cooled at a rate of 25°C / min or less, more preferably 15°C / min or less, more preferably 10°C / min or less, more preferably 5°C / min or less, and more preferably 2°C / min or less. Cooling is preferably carried out at a rate within the range of 0.05 to 25°C / min, more preferably 0.1 to 15°C / min, more preferably 0.2 to 10°C / min, more preferably 0.4 to 5°C / min, and more preferably 0.5 to 2°C / min. Wax crystals can form well at slower cooling rates in this region, which may allow for better mechanical separation. Slower cooling has also been shown to lead to a cleaner product. On the other hand, faster cooling may lead to increased formation of microcrystals, which are more difficult to separate mechanically and may also carry more impurities along with these microcrystals.

[0048] Therefore, the cooling in step (c) of the method is carried out for a period of 5 minutes or more, more preferably 10 minutes or more, more preferably 30 minutes or more, and more preferably 60 minutes or more. The cooling is preferably carried out for a period of 5 to 240 minutes, more preferably 10 to 180 minutes, more preferably 30 to 150 minutes, and more preferably 60 to 120 minutes. The wax crystals formed may have a scale-like shape characterized by these method parameters.

[0049] In step (c) of the method described above, the mixture is preferably cooled to 10°C or below, more preferably to 0°C or below, and even more preferably to -10°C or below. When the wax is cooled at a slow cooling rate, particularly at 5°C / min or less, for example from 100°C to just 50°C, it is possible in principle that crystallization may have already occurred, but a relatively large amount of solvent may be encapsulated in the wax crystals, which may reduce the purity of the wax, because the solvent may contain impurities dissolved in it, and consequently, these impurities may be encapsulated in the wax crystals. When cooled to a lower temperature (for example, to 10°C or below), solvent inclusion may be reduced or completely prevented, and as a result, the purity of the resulting wax may be significantly increased.

[0050] In step (d) of the method described above, at least a portion of the crystallized wax may be separated from the mixture. The separation may include filtration and / or centrifugation. The temperature during separation 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 0 to 30°C. This prevents the wax from redissolving in the solvent. Furthermore, the separation may be carried out at a pressure of preferably 10 bar or less, more preferably 5 to 10 bar. This can improve the efficiency of the method.

[0051] After separating the wax from the mixture in step (d) of the method, the solvent contained in the mixture may be separated from the mixture at least partially. The separation may be carried out by evaporation or distillation. The separated solvent may be reused in step (b) of the method. Before being recycled into the method, the solvent may be further purified, preferably by evaporation, and particularly by rotary evaporation.

[0052] The wax separated in step (d) of the above method may preferably have a boiling point (or lower end of the boiling point range) of 270°C or higher, more preferably 300°C or higher, and even more preferably in the range of 340 to 700°C. The boiling point (or boiling point range) of the wax may be determined by ASTM standard D7500-15:2019 (preferably 100 to 850°C, especially for waxes having a boiling point or boiling point range of 100 to 735°C) or by ASTM standard D2887-22:2022 (preferably 55 to 538°C for waxes having a boiling point or boiling point range).

[0053] The separated wax preferably has 15 or more carbon atoms per molecule, more preferably 20 or more carbon atoms, and particularly 40 or more carbon atoms. The wax preferably has 20 to 80 carbon atoms per molecule, and particularly 20 to 65 carbon atoms. Such wax is quite suitable for further use.

[0054] The separated wax may be supplied to the processing plants of the smelter, particularly to fluid catalytic cracking (FCC) plants, thermal gas oil units (TGU plants), hydrogenation plants, and / or cokers. The separated wax may also be used in other areas of technology, for example, as a lubricant and / or additive. The separated wax may be reprocessed before further use. For example, the wax may be purified and / or separated into different carbon fractions.

[0055] The separated wax has a carbon fraction of 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly 85% by weight or more, based on the total weight of the separated wax. This fraction provides information regarding the purity of the separated wax, where a higher fraction of the carbon fraction corresponds to a higher purity of the separated wax. The method according to the present invention can thus yield a wax having a high purity that can be further increased by the washing of the wax described later. The fraction of the carbon fraction can be determined by gravimetric analysis, which may include determining the mass of the pyrolysis residue, the added solvent, and the separated wax.

[0056] The separated wax may be washed after step (d) of the method. In particular, the wax may be washed 1 to 3 times. As a result, the purity of the separated wax may be further increased.

[0057] During washing, the temperature of the wax is preferably 80°C or lower, more preferably 30°C or lower, even more preferably -10 to 80°C, and particularly within the range of 0 to 30°C. This prevents the wax from redissolving in the solvent. When washing the wax, a temperature similar to or the same as that used when separating the wax in step (d) of the method may be selected.

[0058] Preferably, the wax is washed with alcohol. As a result, any remaining polar impurities can be washed away, and a wax of particularly high purity can be obtained. The alcohol used for washing is preferably selected from methanol, ethanol, propanol, or a mixture thereof. As a result, not only can any remaining polar impurities be thoroughly washed away, but any solvent remaining on the wax after washing can also be well separated from the wax during subsequent drying.

[0059] The method may include a further step (e): drying the separated wax. As a result, the solvent separated with the wax crystals can be removed. Drying may be carried out thermally at a high temperature, or alternatively at a low temperature under vacuum. The type of drying may depend on the further use of the wax. Drying under vacuum is preferred in order to maintain the structure of the wax crystals. When the wax is subsequently used in liquid form, the wax may also be dried at a high temperature and, if necessary, melted. Thermal drying is preferably carried out at a temperature of 150°C or less and at ambient pressure (0.7 to 1.1 bar). Drying under vacuum is preferably carried out at a temperature of 30°C or less and at a pressure of 750 millibars or less, particularly 500 millibars or less. The solvent separated during the drying of the wax may be reused in step (b) of the method. Before being recycled into the method, the solvent may be further purified, preferably by evaporation, particularly by rotational evaporation.

[0060] The present invention relates in particular to the following embodiments: 1. A method for obtaining wax from thermal decomposition residue, (a) A step of preparing the thermal decomposition residue containing the wax, (b) A step of mixing the thermal decomposition residue with a solvent at 30°C or higher to obtain a mixture, wherein the wax is at least partially dissolved in the solvent, (c) A step of cooling the mixture to crystallize at least a portion of the dissolved wax, and (d) A step of separating at least a portion of the crystallized wax from the mixture. The method, including the method described above.

[0061] 2. The method according to Embodiment 1, wherein the thermal decomposition residue is obtained by thermal decomposing plastic, particularly waste plastic.

[0062] 3. The method according to any of the above embodiments, wherein the pyrolysis residue is obtained by pyrolysis of a plastic and separation of at least one fraction, preferably a gaseous fraction, from the pyrolysis of the plastic.

[0063] 4. The method according to any of the above embodiments, wherein the thermal decomposition residue has a boiling point of 100°C or higher, preferably 150°C or higher, more preferably 200°C or higher, more preferably 240°C or higher, more preferably 270°C or higher, and more preferably 300°C or higher.

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

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

[0066] 7. The method according to Embodiment 6, wherein the plastic contains the polyolefin and / or polystyrene in an amount of 65% by weight or more, more preferably 70% by weight or more, and particularly 90% by weight or more, based on the total weight of the plastic.

[0067] 8. The method according to any of the above embodiments, wherein the plastic has a PE content of 10% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more, more preferably 40% by weight or more, more preferably 50% by weight or more, more preferably 60% by weight or more, and even more preferably 70% by weight or more.

[0068] 9. The method according to any of the above embodiments, wherein the thermal decomposition residue is cooled to a temperature of 220°C or lower, more preferably 200°C or lower, and particularly preferably 180°C or lower, before the addition of the solvent.

[0069] 10. The method according to any of the above embodiments, wherein the thermal decomposition residue is cooled to a temperature of 30°C or higher, more preferably 80°C or higher, even more preferably 100°C or higher, and particularly preferably 120°C or higher, before the addition of the solvent.

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

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

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

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

[0074] 15. The method according to any of the above embodiments, wherein the solvent contains 10% by weight or more, preferably 20% by weight or more, and more preferably 50% by weight or more of the aliphatic hydrocarbon, based on the total weight of the solvent.

[0075] 16. The method according to Embodiment 14 or Embodiment 15, wherein the aliphatic hydrocarbon is selected from the group consisting of aliphatic hydrocarbons having 15 or fewer carbon atoms per molecule, preferably 4 to 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, its isomers, or mixtures thereof.

[0077] 18. The method according to any of the above embodiments, wherein the solvent contains 10% by weight or more, preferably 20% by weight or more, of alcohol based on the total weight of the solvent.

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

[0079] 20. The method according to any one of Embodiments 14 to 19, wherein the solvent contains 50% by weight or more of the aliphatic hydrocarbon and 10 to 30% by weight of the alcohol, 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 a mixture thereof, and in particular is propanol.

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

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

[0083] 24. The method according to Embodiment 23, wherein the solid comprises an inorganic salt, a ceramic raw material, asphaltene, tar, and / or coke.

[0084] 25. The method according to Embodiment 23 or Embodiment 24, wherein separating the solid includes filtration, adsorption, and / or centrifugation.

[0085] 26. The method according to Embodiment 25, wherein the separation of the solid includes adsorption, an adsorbent is added to the pyrolysis residue, and the adsorbent preferably includes activated carbon and / or bleached earth.

[0086] 27. The method according to any one of Embodiments 23 to 26, wherein the separated solid is dried at a temperature preferably 50 to 250°C, more preferably 100 to 200°C, and / or for a period of 120 minutes or less, preferably 5 to 60 minutes.

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

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

[0089] 30. The method according to any of the above embodiments, wherein the cooling in step (c) is carried out over a period of 5 minutes or more, more preferably 10 minutes or more, more preferably 30 minutes or more, more preferably 60 minutes or more, preferably 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.

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

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

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

[0093] 34. The method according to any of the above embodiments, wherein the separated wax has a boiling point of 270°C or higher, preferably 300°C or higher, and more preferably in the range of 340°C to 700°C.

[0094] 35. The method according to any of the above embodiments, wherein the wax has 15 or more carbon atoms per molecule, preferably 20 or more carbon atoms, and in particular 40 or more carbon atoms.

[0095] 36. The method according to Embodiment 35, wherein the wax has 20 to 80 carbon atoms, preferably 20 to 65 carbon atoms, per molecule.

[0096] 37. The method according to any of the above embodiments, wherein the separated wax has a carbon fraction of 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and particularly 85% by weight or more, based on the total weight of the separated wax.

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

[0098] 39. The method according to any of the above embodiments, wherein the temperature during the washing of the separated wax is 80°C or less, preferably 30°C or less, more preferably -10 to 80°C, and particularly within the range of 0 to 30°C.

[0099] 40. Step (e): The method according to any of the above embodiments, further comprising drying the separated wax.

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

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

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

[0103] Figure 1 shows a flowchart of the pyrolysis method in which wax is obtained from the pyrolysis residue.

[0104] As can be seen from Figure 1, a plastic containing 50% or more by weight of polyolefin is fed into an extruder 1, where it is plasticized and degassed. The plasticized plastic, having a temperature of 120°C or higher, is then added to a static mixer 2. In the static mixer 2, a diluent 3 may be added to the plasticized plastic to reduce its viscosity. Alternatively, or in addition to, the portion of the liquid fraction 4 separated from the pyrolysis residue may be mixed with the plasticized plastic to reduce its viscosity. The resulting mixture is then fed into a pyrolysis reactor 5, where the plastic is pyrolyzed at a temperature of 350-450°C. As a result, a pyrolysis product 6 is obtained, which includes a gaseous fraction and pyrolysis residue, the pyrolysis residue containing a liquid fraction, wax, and solids. The pyrolysis product 6 is fed into a hydrocyclone 7 downstream of the pyrolysis reactor 5. First, the gaseous fraction is separated at least partially in the hydrocyclone 7. The separated portion of the gaseous fraction 8 may then be further separated into light oil (e.g., having a boiling point range of 35–225°C) and heavy oil (e.g., having a boiling point range of 225–410°C) (not shown). Furthermore, the liquid fraction is at least partially separated in the hydrocyclone 7. The separated portion of the liquid fraction 4 may be discharged through the outlet 9 of the hydrocyclone 7 and may be reused in the method for reducing the viscosity of the plastic as described above. At least a portion of the pyrolysis residue, at least partially containing the wax and the solid, is discharged through the outlet 10 located at the bottom 7 of the hydrocyclone.

[0105] As can be seen in Figure 1, the pyrolysis residue discharged from the outlet 10 is supplied to a first cooling unit 11 for cooling to a temperature in the range of 80 to 240°C. Subsequently, a solvent 13 containing 20% ​​by weight or more of aliphatic hydrocarbons is added to the pyrolysis residue in the container 12 by an introduction device 14 to obtain a mixture, where the wax is at least partially dissolved in the solvent 13. The aliphatic hydrocarbons are selected from the group consisting of aliphatic hydrocarbons having 4 to 12 carbon atoms per molecule. The resulting mixture has a pyrolysis residue to solvent ratio in the range of 2:1 to 3:1. The container 12 is heated so that the dissolution can be carried out 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 to activated carbon. The separated solid 16 is then dried in an oven 17 at a temperature in the range of 100 to 200°C. After the separated solid 16 is dried, individual components can be separated from the solid and reused (not shown in the figure). The solvent 13 separated during drying is returned to the container 12 via the introduction device 14 and reused in step (b) of the method. Before recycling, the solvent 13 may be purified, for example, by evaporation (not shown in the figure). According to Figure 1, the mixture is then cooled to below -10°C at a maximum rate of 5°C / min in a second cooling unit 18 in order to crystallize at least a portion of the wax dissolved in the solvent. Subsequently, at least a portion of the crystallized wax is separated from the mixture by a filter 19. The solvent 13 contained in the mixture is separated in an evaporator 20 and also returned to the container 12 via the introduction device 14.

[0106] As is further evident from Figure 1, the separated wax 21 is washed in a washing machine 22 using washing alcohol. The washed, separated wax 21 is then fed into a dryer 23 to dry the wax crystals. The resulting wax 24 can then be used for further purposes (not shown in the figure). The solvent 13 separated during the drying of the separated wax 21 is also returned to the container 12 via the introduction device 14. The solvent 13 may be purified, for example, by evaporation (not shown in the figure) before being recycled.

Claims

1. A method for obtaining wax from thermal decomposition residue, (a) A step of preparing the pyrolysis residue containing the wax, (b) A step of mixing the pyrolysis residue with a solvent at 30°C or higher to obtain a mixture, wherein the wax is at least partially dissolved in the solvent, (c) A step of cooling the mixture to crystallize at least a portion of the melted wax, and (d) A step of separating at least a portion of the crystallized wax from the mixture. The method, including the method described above.

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

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

4. The method according to any one of claims 1 to 3, wherein the solvent contains 50% by weight or more of aliphatic hydrocarbons.

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

6. The method according to any one of claims 1 to 5, wherein the solvent contains 10% by weight or more of 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 the solid contained in the pyrolysis residue is at least partially separated from the mixture prior to step (c), preferably the separation of the solid includes adsorption, an adsorbent is added to the pyrolysis residue, the adsorbent preferably includes activated carbon and / or bleached earth.

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

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

11. The method according to any one of claims 1 to 10, wherein step (d) involves separating the crystallized wax by 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 separated wax has a boiling point of 270°C or higher.

14. Step (e): The method according to any one of claims 1 to 13, further comprising 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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