Process for depolymerizing plastics material

Abstract

The present invention relates to a process for depolymerizing plastics material (1), the process comprising: - heating the plastics material (1) to form a plastic melt (3), - processing a pyrolysis feed (8) comprising the plastic melt (3) and an external solvent (5) in a pyrolysis reactor (9) to generate a pyrolysis product (10), - withdrawing a recycling stream (6) from the pyrolysis product (10) and including at least a portion of said recycling stream (6) in the pyrolysis feed (8), wherein the external solvent (5) is a hydrotreated lipid composition, preferably obtained by hydrotreating a lipid composition of biological origin.

Description

[0001] Process for depolymerizing plastics material

[0002] The present invention relates to a process for depolymeri zing plastics material .

[0003] Plastics materials have become integral to both industrial and consumer applications , resulting in the generation of substantial volumes of waste . A signi ficant portion of this waste is incinerated, contributing to the release of large amounts of carbon dioxide ( C02) , which exacerbates the environmental impact and highlights the pressing need for more sustainable recycling methods .

[0004] While mechanical recycling is widely practiced, it has inherent limitations . This process typically involves the physical reprocessing of plastics without altering their chemical structure . Steps such as sorting, cleaning, shredding, melting, and re-extruding are typically employed to convert waste plastics into new products . However, with each recycling cycle , the quality of the plastic deteriorates due to thermal and mechanical stress , leading to a reduction in material properties and ultimately limiting the number of times plastics can be mechanically recycled .

[0005] Chemical recycling has emerged as a promising alternative . Chemical recycling involves breaking down plastics at the molecular level , typically through depolymeri zation, to produce monomers or other valuable chemicals . This method can accommodate mixed or contaminated plastic waste streams that mechanical recycling struggles to handle , and it has the potential to recycle plastics multiple times without signi ficant loss in quality . As a result , chemical recycling represents a key pathway toward closing the loop in plastic waste management .

[0006] One of the primary approaches to chemical recycling is pyrolysis , which involves the thermal decomposition of plastics at high temperatures , typically between 400 and 600 ° C, to produce hydrocarbon products commonly referred to as "pyrolysis oils" , " synthetic crude oils" or " syncrudes" . These pyrolysis oils have a range of potential applications , including the use as alternative fuels or as feedstock for the production of new chemicals and materials . A notable advancement in pyrolysis-based recycling is described in WO 2012 / 149590 Al , which outlines a process where plastics material is melted and mixed with a crude oil fraction as an external solvent . The resulting mixture is then processed in a pyrolysis reactor . The use of an external solvent reduces the viscosity of the mixture , enhancing heat trans fer ef ficiency within the reactor . This reduction in viscosity helps minimi ze temperature gradients across the reactor, thereby reducing the risk of locali zed overheating and coking .

[0007] Nevertheless , despite such developments , there is still an urgent need to develop more ef ficient and environmentally sustainable processes for depolymeri zing plastics material , to promote their widespread adoption . Thus , new and improved processes for depolymeri zing plastics material are needed, in particular processes that address at least some of the limitations of the prior art and that enable the ef ficient and environmentally sustainable recycling of plastics material . It is an obj ect of the present invention to provide such processes .

[0008] Therefore , the present invention provides a process for depolymeri zing plastics material , the process comprising :

[0009] - heating the plastics material to form a plastic melt ,

[0010] - processing a pyrolysis feed comprising the plastic melt and an external solvent in a pyrolysis reactor to generate a pyrolysis product ,

[0011] - withdrawing a recycling stream from the pyrolysis product and including at least a portion of said recycling stream in the pyrolysis feed, wherein the external solvent is a hydrotreated lipid composition, preferably obtained by hydrotreating a lipid composition of biological origin .

[0012] The addition of external solvents to plastic pyrolysis feeds , as disclosed in WO 2012 / 149590 Al , was a signi ficant advancement for processes for depolymeri zing plastics material . As used herein, the "external solvent" can also be referred to as "diluent" or "reaction medium" . As mentioned above , the use of an external solvent reduces the viscosity of the pyrolysis feed, enhancing heat trans fer ef ficiency within the reactor, minimi zing temperature gradients across the reactor and reducing the risk of locali zed overheating and coking . As regards the type of external solvent , WO 2012 / 149590 Al suggests using a heavy oil with a content of aromatic hydrocarbons of at least 25% .

[0013] In the context of the present invention, it was unexpectedly found that the viscosity-reducing ef fects sought after in WO 2012 / 149590 Al can not only be achieved with heavy oils and other fossil-based solvents , but also with lipid compositions of biological origin . Surprisingly, it was found that such biological lipid compositions are able to ef fectively dissolve plastics polymers such as polyolefins , thereby signi ficantly reducing viscosity and improving heat trans fer during pyrolysis . Replacing the traditional fossil-based external solvents with lipid compositions of biological origin of fers signi ficant advantages , as biological lipid compositions are not only widely available at low costs , but also are renewable materials themselves . Thus , both the economic ef ficiency and the environmental sustainability of the process can be improved .

[0014] For the purposes of the inventive process , a hydrotreated lipid composition is used, which may be obtained by hydrotreating a lipid composition of biological origin . Preferably, the lipid composition comprises lipids selected from the group consisting of oils , fats , waxes , esters , acids , soaps , alcohols and ethers . The hydrotreatment typically involves saturation of double bonds contained in the lipids , in particular in fatty acid chains , leading to a more paraf finic composition . Additionally, the hydrotreatment may advantageously comprise hydrodeoxygenation (HDO) , especially of esters , carboxylic acids , ethers and alcohols .

[0015] As fatty acid chains are usually mostly unbranched, hydrotreated lipid composition can typically include a high proportion of n-paraf finic compounds . It has been found in the context of the invention that employing such external solvents can signi ficantly improve the ef ficiency of the overall process compared to the use of conventional fossil-based solvents , which often contain high amounts of olefinic and aromatic compounds , as well as iso-paraf finic compounds . According to the inventors , without wishing to be bound to a particular theory, these improvements are due to the high stability of paraf finic compounds , and particularly of n-paraf finic compounds , under pyrolysis conditions . During the pyrolysis of plastics materials , the decomposition typically occurs through radical mechanisms or ß-elimination, leading to the formation of smaller molecular fragments . The chain scission preferentially occurs at branch points or other energetically favorable positions within the polymer , ß-elimination results in the removal of hydrogen (H2) and the formation of double bonds , which can further react to form dienes , polyenes , and ultimately aromatic compounds . As a result of this process , compounds can undergo progressive aromati zation, eventually forming highly condensed aromatic systems , such as asphaltenes . Under conditions of prolonged thermal exposure , these systems can lose additional side chains , leaving behind a pure carbon framework, commonly referred to as coke .

[0016] The inventive process exploits the stability of n-paraf finic compounds in comparison to iso-paraf finic, olefinic, and aromatic compounds . In the case of n-paraf finic hydrocarbon chains , the absence of branching reduces the likelihood of cracking through ß-elimination, as this process is energetically less favorable in straight-chain hydrocarbons . On the other hand, isoparaf finic compounds , with their branched structures , are more prone to crack at the branch points , generating radicals that can propagate further decomposition .

[0017] Olefinic compounds , due to their unsaturation, are even more reactive under pyrolysis conditions . They are already one step closer to coke formation than paraf finic compounds . In particular, they can undergo cycli zation reactions , such as Diels-Alder reactions , resulting in the formation of ring structures . These rings , particularly cyclohexadienes , are often thermally and kinetically unstable and can further decompose , releasing hydrogen or breaking of f side chains . The continued aromati zation of these systems reduces the hydrogen content while increasing the carbon content , ultimately leading to the formation of coke .

[0018] Compared to olefinic compounds , aromatic compounds are yet another step closer to coke formation . Additionally, they can lead to the formation of phenyl and benzyl radicals . Phenyl radicals are highly reactive , while benzyl radicals exhibit resonance stabili zation, making them more stable . The presence of these aromatic radicals can promote the formation of polyaromatic structures , which, under the high-temperature conditions typical of cracking processes , can lead to the accumulation of coke .

[0019] The high stability of the external solvent under pyrolysis conditions has particular advantages in the context of the recycling stream that is withdrawn from the pyrolysis product . The inventive process comprises the step of withdrawing a recycling stream from the pyrolysis product and including at least a portion of said recycling stream in the pyrolysis feed . In this way, the recycling stream can ful fil a similar function as the external solvent described above , thereby reducing the consumption of external solvent . When the external solvent contains a high proportion of paraf finic compounds , especially n-paraf finic compounds , a greater amount of the external solvent can withstand the pyrolysis conditions and remain in the process through the recycling stream . In this case , the paraf finic compounds can remain in circulation longer, and even accumulate in circulation, thus reducing the amount of fresh external solvent that has to be added to the process .

[0020] The hydrotreated lipid composition is preferably obtained by hydrotreating a lipid composition of biological origin . Preferably, the lipid composition comprises lipids selected from the group consisting of oils , fats , waxes , esters , acids , soaps , alcohols and ethers .

[0021] In a preferred embodiment , the hydrotreated lipid composition is derived from plants , animals and / or microbes , especially from plants . Thus , preferably, the hydrotreated lipid composition is a hydrotreated lipid composition of plant , animal , and / or microbial origin, especially of plant origin .

[0022] In the context of the invention, the use of plant-derived lipids has proven to be particularly advantageous . According to the inventors , without wishing to be bound to a particular theory, lipid compositions of plant origin often have longer hydrocarbon chains , which causes the hydrotreated lipid compositions to have higher boiling ranges . This means that less pressure is required to keep the external solvent liquid at high temperatures, which allows keeping the process pressure lower, increasing safety and reducing the demands on the equipment used .

[0023] Preferably, the lipid composition comprises an oil or fat. Preferably, the lipid composition is an oil or fat. Preferably, the oil or fat is an oil or fat of biological origin, preferably of plant, animal, and / or microbial origin, especially of plant origin. As used herein, the terms "oil" and "fat" preferably refer to lipid compositions consisting predominantly of glycerides, especially diglycerides and / or triglycerides. The "oil or fat of biological origin" can preferably also be referred to as a "glyceride composition of biological origin", i.e., a composition comprising glycerides.

[0024] Thus, preferably, the lipid composition comprises glycerides, especially diglycerides and / or triglycerides. Preferably, the lipid composition comprises at least 10 wt% glycerides, based on the total weight of the lipid composition, preferably at least 25 wt%, more preferred at least 50 wt%, more preferred at least 80 wt%. Preferably the lipid composition consists essentially of glycerides. The glycerides are preferably of plant, animal, and / or microbial origin, as described above.

[0025] For the reasons detailed above, oils of plant origin are particularly preferred. Therefore, in a particularly preferred embodiment, the lipid composition comprises a vegetable oil, preferably it is a vegetable oil. Thus, the hydrotreated lipid composition preferably comprises a hydrotreated vegetable oil, preferably it is a hydrotreated vegetable oil.

[0026] Any suitable type of vegetable oil may be used. Preferably, the vegetable oil is selected from the group consisting of rapeseed oil, soybean oil, palm oil, coconut oil, corn oil, carinata oil, peanut oil, olive oil, sunflower oil, and / or castor oil.

[0027] In a particularly preferred embodiment, the oil or fat is Used Cooking Oil (UCO) . Preferably the UCO comprises or consists of oils and / or fats of biological origin, especially vegetable oils as detailed above.

[0028] In an alternative preferred embodiment, the oil or fat is of animal origin, preferably selected from hoof oil, tallow, fish oil, and / or lard. In yet another preferred embodiment, the oil or fat is of microbial origin, preferably selected from yeast oils, algae oils, and / or membrane lipids.

[0029] Preferably, the lipid composition, especially the oil or fat, is at least partially unsaturated. Thus, the lipid composition preferably comprises unsaturated fatty acid chains. When the lipid composition has a high degree of unsaturation, hydrotreating is particularly advantageous, as it increases the paraffinic content relative to the olefinic content, as described above.

[0030] As detailed above, it is particularly preferred when the oil or fat is made from fatty acids having long hydrocarbon chains, as this can allow for a higher boiling range of the external solvent, which means that less pressure is required to keep the external solvent liquid at high temperatures. In a preferred embodiment, the oil or fat comprises fatty acid chains with chain lengths of at least C16 (C16+-fatty acid chains) , preferably at least C18 (C18+-fatty acid chains) . Preferably, at least 30 wt%, more preferred at least 50 wt%, more preferably at least 70 wt% of fatty acid chains present in the oil or fat are C16+-fatty acid chains, preferably C18+-fatty acid chains.

[0031] In a further preferred embodiment, the lipid composition comprises fatty acids. Preferably, the lipid composition comprises at least 10 wt% fatty acids, based on the total weight of the lipid composition, preferably at least 25 wt%, more preferred at least 50 wt%, more preferred at least 80 wt%. Preferably the lipid composition consists essentially of fatty acids. Preferably, the fatty acids are C12+-fatty acids, preferably C14+-fatty acids, more preferred C16+-fatty acids, more preferred C18+-fatty acids. As detailed above, longer chain fatty acids were found to be advantageous in the context of the inventive process.

[0032] In a further preferred embodiment, the lipid composition comprises fatty acid esters. Preferably, the lipid composition comprises at least 10 wt% fatty acid esters, based on the total weight of the lipid composition, preferably at least 25 wt%, more preferred at least 50 wt%, more preferred at least 80 wt%. Preferably the lipid composition consists essentially of fatty acid esters. The fatty acid esters preferably are esters consisting of a C12+-fatty acid and an alcohol, preferably of a C14+-fatty acid and an alcohol, more preferred of a C16+-fatty acid and an alcohol, more preferred of a C18+-fatty acid and an alcohol. It is particularly preferred when the alcohol is methanol, i.e., when the ester is a fatty acid methyl ester (FAME) , preferably selected from the group consisting of methyl laurate, methyl myristate, methyl palmitate, methyl stearate, and methyl oleate .

[0033] In a further preferred embodiment, the lipid composition comprises waxes. As used herein, the term "wax" preferably refers to a fatty acid esterified with fatty alcohol. Preferably, the lipid composition comprises at least 10 wt% waxes, based on the total weight of the lipid composition, preferably at least 25 wt%, more preferred at least 50 wt%, more preferred at least 80 wt%. Preferably the lipid composition consists essentially of waxes. Preferably the waxes are esters consisting of a C12+- fatty acid and a Cl 8+-alcohol , preferably a C14+-fatty acid and a C20+-alcohol , more preferred a C12-C40-fatty acid and a C18- C40-alcohol, more preferred a C14-C35-f atty acid and a C20-C35- alcohol. It was found that such waxes are particularly well suited for inventive process, as they typically have particularly high melting and boiling ranges. Preferably, the waxes are selected from the group consisting of beeswax, wool wax, stearin waxes such as rapseed wax and palm wax, carnauba wax, and candle wax .

[0034] In a further preferred embodiment, the lipid composition comprises soaps. As used herein, the term "soap" preferably refers to a fatty acid salt. Preferably, the lipid composition comprises at least 10 wt% soaps, based on the total weight of the lipid composition, preferably at least 25 wt%, more preferred at least 50 wt%, more preferred at least 80 wt%. Preferably the lipid composition consists essentially of soaps. Preferably, the soaps are salts of C12+-fatty acids, preferably C14+- fatty acids, more preferred C16+-fatty acids, more preferred C18+-fatty acids. Soaps have turned out to be particularly advantageous for the purposes of the invention, as they were found to be particularly stable under pyrolysis conditions.

[0035] In a further preferred embodiment, the lipid composition comprises fatty or waxy alcohols . Preferably, the lipid composition comprises at least 10 wt% fatty or waxy alcohols , based on the total weight of the lipid composition, preferably at least 25 wt% , more preferred at least 50 wt% , more preferred at least 80 wt% . Preferably the lipid composition consists essentially of fatty or waxy alcohols . Fatty and waxy alcohols were also found to be stable under pyrolysis conditions and at the same time to solubili ze plastics material very well . Therefore , they are also particularly preferred for use in the inventive process . Preferably, the fatty or waxy alcohols are C12+-alcohols , preferably C14+-alcohols , more preferred Cl 6+-alcohols , more preferred Cl 8+-alcohols , more preferred C20+-alcohols , more preferred C24+-alcohols , more preferred C28+-alcohols .

[0036] In yet a further preferred embodiment , the lipid composition comprises ethers , preferably waxy ethers , preferably ethers having the chemical structure R-O-R' , wherein R and R' each independently represent a C8+-hydrocarbon chain, preferably a C12+-hydrocarbon chain, more preferred a Cl 6+-hydrocarbon chain, more preferred a C20+-hydrocarbon chain . Preferably, the lipid composition comprises at least 10 wt% of such ethers , based on the total weight of the lipid composition, preferably at least 25 wt% , more preferred at least 50 wt% , more preferred at least 80 wt% . Preferably the lipid composition consists essentially of of such ethers . Such ethers have high boiling points and were also found to be particularly stable under pyrolysis conditions .

[0037] As detailed above , it is particularly preferred when the lipid composition, especially the oil or fat , comprises fatty acid chains , in particular fatty acid chains having long hydrocarbon chains , as this can allow for a higher boiling range of the external solvent , which means that less pressure is required to keep the external solvent liquid at high temperatures . In a preferred embodiment , the lipid composition, especially the oil or fat , comprises fatty acid chains with chain lengths of at least C16 ( C16+- fatty acid chains ) , preferably at least C18 ( C18+- fatty acid chains ) . Preferably, at least 30 wt% , more preferred at least 50 wt% , more preferably at least 70 wt% of fatty acid chains present in the lipid composition are C16+- fatty acid chains , preferably C18+- fatty acid chains .

[0038] Preferably, the hydrotreating of the lipid composition comprises at least the partial hydrogenation of double bonds . Thus , preferably, the hydrotreated lipid composition is a hydrogenated lipid composition, preferably obtained by hydrogenating a lipid composition of biological original . As used herein, "hydrogenation" is preferably understood as a process that at least partially, preferably fully, saturates double bonds ( C=C ) in unsaturated fatty acid chains . This increases the proportion of paraf finic compounds relative to olefinic compounds in the external solvent , enhancing stability under pyrolysis conditions , as detailed above .

[0039] It is particularly preferred, when the lipid composition has undergone full hydrotreatment , i . e . , when it is a fully hydrotreated lipid composition . As used herein, " full hydrotreatment" is preferably understood as including hydrogenation, as described above , as well as deoxygenation . Deoxygenation may e . g . occur through hydrodeoxygenation or decarboxylation . Preferably, the " full hydrotreatment" includes the conversion of carboxylic acids , esters , ethers and alcohols . Preferably, the lipid composition comprises glycerides , especially diglycerides and / or triglycerides , and the hydrotreatment comprises cleavage of fatty acids from the glycerol backbone , followed by the removal of the carboxylic acid moieties through reduction or decarboxylation, preferably yielding paraf fins . Techniques for fully hydrotreating lipid compositions , such as the NExBTL process , are well known to the person skilled in the art .

[0040] Fully hydrotreating the lipid composition in this manner reduces the amount of oxygen-containing functional groups in the external solvent . This is advantageous , as such oxygen-contain- ing functional groups typically react under pyrolysis conditions to compounds such as H20, C02and / or CO, thus consuming thermal energy, making the pyrolysis process less energy ef ficient . Additionally, oxygen-containing functional groups can be prone to unwanted side-reactions under pyrolysis conditions , which can promote tar and coke formation .

[0041] In preferred embodiment , the hydrotreated lipid composition is obtained by a process comprising separating a lipid composition, preferably a lipid composition of biological origin, especially an oil or fat of biological origin as detailed above , into a heavy fraction and a light fraction and hydrotreating the heavy fraction . In this embodiment , the heavy fraction has a higher boiling range than the light product , in particular a boiling range with a higher T50 ( temperature at 50% volume distilled) than the light product . The separation of the lipid composition into the heavy fraction and the light fraction can be achieved with any method known in the art , preferably by distillation . For the hydrotreating of the heavy fraction, the same embodiments are preferred as detailed above for the hydrotreating of the lipid composition .

[0042] Hydrotreating a heavy fraction withdrawn from the lipid composition and using the resulting hydrotreated heavy fraction in the inventive process can advantageously increase the boiling range of the external solvent . As detailed above , this means that less pressure is required to keep the external solvent liquid at high temperatures , which allows keeping the process pressure lower, increasing safety and reducing the demands on the equipment used .

[0043] As mentioned above , WO 2012 / 149590 Al suggests using heavy oils having high contents of aromatic compounds as external solvents . However, in contrast to the teaching of WO 2012 / 149590 A 1 , it was found in the context of the present invention that low aromatic contents can of fer signi ficant advantages . More speci fically, for the reasons outlined above , it was found that reducing the content of aromatic compounds in the pyrolysis feed can signi ficantly reduce coke formation . Lipid compositions of biological origin are typically mostly aliphatic, which positively impacts the pyrolysis process . Therefore , it is preferred that the hydrotreated lipid composition comprises less than 5 wt% aromatic compounds , preferably less than 3 wt% , more preferred less than 2 wt% , more preferred less than 1 wt% . Preferably, the content of aromatic compounds is determined according to ASTM D6591- 19 or ASTM D5134-21 , especially ASTM D6591- 19 .

[0044] Preferably, the hydrotreated lipid composition has a Conradson Carbon Residue ( CCR) of less than 5 wt% , more preferred less than 3 wt% , more preferred less than 2 wt% , more preferred less than 1 wt% , more preferred less than 0 . 5 wt% . This reduces the amount of coke formation within the process , decreasing maintenance costs and increasing the ef ficiency of the process . Advantageously, lipid compositions of biological origin typically contain low amounts of sul fur . This is a signi ficant advantage over fossil-based solvents , which often contain high amounts of sul fur . High amounts of sul fur can lead to H2S formation, which can cause corrosion and is highly toxic . Thus , it is preferred that the hydrotreated lipid composition comprises less than 250 ppm, preferably less than 100 ppm, more preferred less than 50 ppm, more preferred less than 10 ppm, more preferred less than 1 ppm sul fur ( S ) .

[0045] Similarly, lipid compositions of biological origin typically also contain low amounts of nitrogen . As for sul fur, this is advantageous as in this way, few heteroatoms are introduced into the process and thus a higher quality product requiring less puri fication can ultimately be obtained . Thus , preferably the hydrotreated lipid composition contains less than 500 ppm, preferably less than 100 ppm, more preferred less than 50 ppm, more preferred less than 10 ppm nitrogen (N) .

[0046] It is further preferred that the hydrotreated lipid composition contains low amounts of oxygen . As detailed above , this is advantageous , as oxygen-containing compounds can react under pyrolysis conditions to compounds such as H2O, CO2and / or CO, thus consuming thermal energy, making the pyrolysis process less energy ef ficient . Additionally, oxygen-containing functional groups can be prone to unwanted side-reactions under pyrolysis conditions , which can promote tar and coke formation . As also described above , the amount of oxygen in the hydrotreated lipid composition can be reduced by deoxygenation in the course of hydrotreating . Therefore , in a preferred embodiment , the hydrotreated lipid composition comprises less than 1 wt% , preferably less than 0 . 5 wt% , more preferred less than 0 . 2 wt% , more preferred less than 0 . 05 wt% oxygen ( 0) .

[0047] For the reasons outlined above , it has been found to be highly advantageous , when the hydrotreated lipid composition comprises paraf finic compounds , as such compounds are better able to withstand the conditions during pyrolysis and remain in circulation for a longer period of time , thus reducing consumption of the external solvent . Therefore , it is preferred that the hydrotreated lipid composition comprises compounds having paraf finic hydrocarbon chains . As also outlined above , n- paraffinic compounds are particularly stable and therefore particularly preferred. It is therefore preferred that the hydrotreated lipid composition comprises compounds having n-paraf- finic hydrocarbon chains.

[0048] Of note, already moderate amounts, such as 10 wt%, of compounds comprising paraffinic (especially n-paraf f inic) hydrocarbon chains are highly advantageous, as it was found that due to their stability under pyrolysis conditions, these compounds can accumulate in the recycling stream, so that their concentration in the pyrolsis feed increases over time. Nevertheless, these advantageous effects are even more pronounced when higher amounts of such compounds are present. Therefore, the hydrotreated lipid composition preferably comprises at least 10 wt% compounds comprising an n-paraffinic hydrocarbon chain, preferably at least 15 wt%, more preferred at least 20 wt%, more preferred at least 30 wt%, more preferred at least 40 wt%, more preferred at least 50 wt%. As used herein, the wt% are based on the total weight of the hydrotreated lipid composition, i.e., the hydrotreated lipid composition comprises at least X wt% compounds comprising an n-paraffinic hydrocarbon chain based on the total weight of the hydrotreated lipid composition .

[0049] In the context of the invention, it is advantageous when the compounds comprising an n-paraffinic hydrocarbon chain have a high boiling point. This allows easily separating said compounds from shorter chain hydrocarbons obtained from depolymerizing the plastics material, which may be collected as the end product of the process in the form of synthetic crude oil. In this way, the compounds comprising an n-paraffinic hydrocarbon chain can be preferentially kept in the process as part of the recycling stream.

[0050] Therefore, the compounds comprising an n-paraffinic hydrocarbon chain have a boiling point of at least 285 °C, preferably at least 315 °C, more preferred at least 340 °C, more preferred at least 365 °C, more preferred at least 390 °C, more preferred at least 410 °C, more preferred at least 430 °C.

[0051] Thus, preferably, the hydrotreated lipid composition comprises at least 10 wt%, preferably at least 15 wt%, more preferred at least 20 wt%, more preferred at least 30 wt%, more preferred at least 40 wt%, more preferred at least 50 wt% compounds comprising an n-paraffinic hydrocarbon chain, wherein said compounds have a boiling point of at least 285 °C, preferably at least 315 °C, more preferred at least 340 °C, more preferred at least 365 °C, more preferred at least 390 °C, more preferred at least 410 °C, more preferred at least 430 °C. For clarification, this does not exclude that in addition to the indicated wt% of such compounds, the hydrotreated lipid composition may also comprise further n-paraffinic compounds having lower boiling points.

[0052] On the other hand, it is preferred that the compounds comprising an n-paraffinic hydrocarbon chain have a boiling point that is not too high. It was found that when the hydrotreated lipid composition comprises a larger proportion of lighter compounds, it can have a better solubilizing effect. Without wishing to be bound to a particular theory, it is assumed that smaller solvent molecules may diffuse more easily into the plastic polymers and disrupt the interactions therein through intercalation.

[0053] Therefore, it is preferred that the compounds comprising an n-paraffinic hydrocarbon chain have a boiling point of at most 800 °C, more preferred at most 750 °C, more preferred at most 700 °C, more preferred at most 650 °C, more preferred at most 600 °C. Preferably, the compounds comprising an n-paraffinic hydrocarbon chain have a boiling point between 285 °C and 800 °C, more preferred between 315 °C and 800 °C, more preferred between 340 °C and 775 °C, more preferred between 365 °C and 750 °C, more preferred between 390 °C and 700 °C, more preferred between 410 °C and 650 °C, more preferred between 430 °C and 600 °C.

[0054] In a preferred embodiment, the compounds comprising an n- paraffinic hydrocarbon chain have an n-paraffinic C16+- hydrocarbon chain, preferably an n-paraffinic Cl 8+-hydrocarbon chain, more preferred an n-paraffinic C20+-hydrocarbon chain, more preferred an n-paraffinic C22+-hydrocarbon chain. For the reasons mentioned above, providing heavier compounds having longer hydrocarbon chains allows to more easily keep these compounds in the process as part of the recycling stream. On the other hand, for ensuring a particularly good solubilization, as explained above, it is preferred that the hydrocarbon chains are not too long. Therefore, the compounds comprising an n-paraffinic hydrocarbon chain preferably have an n-paraffinic Cl 6-C12 O-hydrocarbon chain, preferably an n- paraffinic Cl 8-C8 O-hydrocarbon chain, more preferred an n- paraffinic C20-C65-hydrocarbon chain. Thus, preferably, the hydrotreated lipid composition comprises at least 10 wt%, preferably at least 15 wt%, more preferred at least 20 wt%, more preferred at least 30 wt%, more preferred at least 40 wt%, more preferred at least 50 wt% compounds comprising an n-paraffinic Cl 6-C120-hydrocarbon chain, preferably an n-paraffinic C18-C80- hydrocarbon chain, more preferred an n-paraffinic C20-C65- hydrocarbon chain. For clarification, this does not exclude that in addition to the indicated wt% of such compounds, the hydrotreated lipid composition may also comprise further compounds having shorter or longer n-paraffinic hydrocarbon chains .

[0055] In the context of the inventive process, the compounds comprising n-paraffinic hydrocarbon chains may preferably be selected from n-paraffins, aliphatic carboxylic acids, aliphatic alcohols, and derivatives thereof. In a preferred embodiment, the compounds comprising n-paraffinic hydrocarbon chains are selected from glycerides (especially diglycerides and / or triglycerides) , waxes, fatty acid esters (esepcially FAME) and combinations thereof; preferably comprising fatty acid chains or waxy acid chains, preferably having chain lengths as described above. In afurther embodiment, which is also preferred, the compounds comprising n-paraffinic hydrocarbon chains may be carboxylic acids, preferably fatty acids and waxy acids, preferaby having chain lengths as defined above. It is particularly preferred that the compounds comprising an n- paraffinic hydrocarbon chain are n-paraffins. N-paraffins can advantageously be obtained by fully hydrotreating lipid compositions of biological origin, as detailed above. As used herein, "n-paraffins" may also be referred to as "n-alkanes".

[0056] For the reasons outlined above, it is preferred that the hydrotreated lipid composition comprises a high amount of paraffinic compounds, especially compared to olefinic and aromatic compounds. While n-paraffinic compounds are particularly preferred, any types of paraffinic compounds can provide advantages over conventional solvents typically used in plastic pyrolysis processes, which are often highly aromatic. Therefore, it is preferred that the hydrotreated lipid composition comprises at least 20 wt% compounds comprising a paraffinic hydrocarbon chain, preferably at least 30 wt%, more preferred at least 40 wt%, more preferred at least 50 wt%, more preferred at least

[0057] 60 wt%, more preferred at least 70 wt%, more preferred at least

[0058] 80 wt%, more preferred at least 90 wt%, more preferred at least

[0059] 95 wt%, more preferred at least 98 wt%, more preferred at least

[0060] 99 wt%, more preferred 100 wt%.

[0061] All embodiments specified above for the compounds comprising an n-paraffinic hydrocarbon chain are also preferred for the compounds comprising a paraffinic hydrocarbon chain. Thus, preferably, the compounds comprising a paraffinic hydrocarbon chain have a boiling point of at least 285 °C, preferably at least 315

[0062] °C, preferably at least 340 °C, more preferred at least 365 °C, more preferred at least 390 °C, more preferred at least 410 °C, more preferred at least 430 °C. Preferably, the compounds comprising a paraffinic hydrocarbon chain have a boiling point of at most 800 °C, more preferred at most 750 °C, more preferred at most 700 °C, more preferred at most 650 °C, more preferred at most 600 °C. Preferably, the compounds comprising a paraffinic hydrocarbon chain have a boiling point between 285 °C and 800 °C, more preferred between 315 °C and 800 °C, more preferred between 340 °C and 775 °C, more preferred between 365 °C and 750 °C, more preferred between 390 °C and 700 °C, more preferred between 410 °C and 650 °C, more preferred between 430 °C and 600

[0063] In a preferred embodiment, the compounds comprising a paraffinic hydrocarbon chain have a paraffinic Cl 6+-hydrocarbon chain, preferably a paraffinic Cl 8+-hydrocarbon chain, more preferred a paraffinic C20+-hydrocarbon chain, more preferred a paraffinic C22+-hydrocarbon chain. The compounds comprising a paraffinic hydrocarbon chain preferably have a paraffinic C16- C120-hydrocarbon chain, preferably a paraffinic C18-C80- hydrocarbon chain, more preferred a paraffinic C20-C65- hydrocarbon chain. Preferably, the compounds comprising a paraffinic hydrocarbon chain are paraffins, glycerides (especially diglycerides and / or triglycerides) , or fatty acids, whereas paraffins obtained from full hydrotreatment of lipid compositions are particularly preferred.

[0064] While it is preferred that the hydrotreated lipid composition comprises a high amount of paraffinic compounds, n-paraf- finic compounds are preferred over iso-paraffinic compounds, for the reasons specified above. In particular, their branched structures make iso-paraffinic compounds more prone to radical formation and thus to breakdown under pyrolysis conditions. Therefore, it is preferred that the hydrotreated lipid composition comprises less than 60 wt%, preferably less than 50 wt%, more preferred less than 40 wt%, more preferred less than 30 wt%, more preferred less than 20 wt%, more preferred less than 10 wt%, more preferred less than 5 wt% compounds comprising an iso-paraffinic hydrocarbon chain. It is particularly preferred that the hydrotreated lipid composition comprises less than 60 wt%, preferably less than 50 wt%, more preferred less than 40 wt%, more preferred less than 30 wt%, more preferred less than 20 wt%, more preferred less than 10 wt%, more preferred less than 5 wt% iso-paraffins.

[0065] In a preferred embodiment, the hydrotreated lipid composition contains compounds comprising an n-paraffinic hydrocarbon chain and compounds comprising an iso-paraffinic hydrocarbon chain at a mass ratio of at least 1:1, more preferred at least 2:1, more preferred at least 4:1, more preferred at least 6:1, more preferred at least 8:1, more preferred at least 10:1.

[0066] As outlined above, it has been found in the context of the invention that olefinic compounds contained in the external solvent can be more prone to unfavorable reactions under pyrolysis conditions than paraffinic compounds. On the one hand, double bonds can stabilize radicals and thus promote radical formation. On the other hand, they can lead to diene formation and undergo cyclization reactions resulting in the formation of ring structures and ultimately leading to the formation of coke. As detailed above, hydrotreating the lipid composition advantageously ensures a low amount of olefinic compounds. Therefore, it is preferred that the hydrotreated lipid composition comprises less than 10 wt%, more preferred less than 5 wt%, more preferred less than 2 wt%, more preferred less than 1 wt%, more preferred substantially no compounds comprising an olefinic hydrocarbon chain. Preferably, the hydrotreated lipid composition comprises less than 10 wt%, more preferred less than 5 wt%, more preferred less than 2 wt%, more preferred less than 1 wt%, more preferred substantially no olefins.

[0067] In a preferred embodiment, the hydrotreated lipid composition contains compounds comprising a paraffinic hydrocarbon chain and compounds comprising an olefinic hydrocabon chain at a mass ratio of at least 4:1, more preferred at least 6:1, more preferred at least 8:1, more preferred at least 10:1, more preferred at least 20:1. It is especially preferred that the mass ratio between compounds comprising an n- paraffinic hydrocarbon chain and compounds comprising an olefinic hydrocabon chain is at least 4:1, more preferred at least 6:1, more preferred at least 8:1, more preferred at least 10:1, more preferred at least 20:1.

[0068] Preferably, the hydrotreated lipid composition has a bromine number of less than 100 g Br2 / 100 g, more preferred less than 90 g Br2 / 100 g, more preferred less than 80 g Br2 / 100 g, more preferred less than 70 g Br2 / 100 g, more preferred less than 60 g Br2 / 100 g, more preferred less than 50 g Br2 / 100 g, less than 40 g Br2 / 100 g, more preferred less than 30 g Br2 / 100 g, more preferred less than 20 g Br2 / 100 g, more preferred less than 15 g Br2 / 100 g, more preferred less than 10 g Br2 / 100 g, more preferred less than 5 g Br2 / 100 g, more preferred less than 3 g Br2 / 100 g, more preferred less than 2 g Br2 / 100 g, more preferred less than 1 g Br2 / 100 g, more preferred less than 0.5 g Br2 / 100 g. The bromine number, preferably determined according to ASTM D1159-07 (2017 ) , can be considered as a sum parameter for all unsaturated components contained in the hydrotreated lipid composition .

[0069] In addition to the above-described advantageous effects of the n-paraffinic compounds contained in the hydrotreated lipid composition having a high boiling point, it was found to also be advantageous when the hydrotreated lipid composition as a whole has a high boiling range. When the hydrotreated lipid composition has a higher boiling range, less pressure is required to keep the external solvent liquid at high temperatures. Thus, a higher boiling range of the hydrotreated lipid composition allows keeping the process pressure lower, increasing safety and reducing the demands on the equipment used .

[0070] Therefore, in a preferred embodiment, the hydrotreated lipid composition has a boiling range with an IBP (initial boiling point) of at least 150 °C, preferably at least 180 °C.

[0071] It is further preferred that the hydrotreated lipid composition has a boiling range with an FBP (final boiling point) of at most 800 °C, more preferred at most 750 °C, more preferred at most 700 °C, more preferred at most 650 °C, more preferred at mo st 600 °C.

[0072] Moreover, it is preferred that the hydrotreated lipid composition has a boiling range with a T10 (temperature at 10% volume distilled) of at least 200 °C, more preferred at least 225 °C, more preferred at least 250 °C, more preferred at least 275 °C. Preferably the T10 is between 200 °C and 500 °C, more preferred between 225 °C and 400 °C, more preferred between 250 °C and 300 °C.

[0073] It is further preferred that the hydrotreated lipid composition has a boiling range with a T50 (temperature at 50% volume distilled) of at least 285 °C, more preferred at least 315 °C, more preferred at least 350 °C, more preferred at least 380 °C, more preferred at least 400 °C. Preferably the T50 is between 285 °C and 600 °C, more preferred between 315 °C and 600 °C, more preferred between 350 °C and 550 °C, more preferred between

[0074] 380 °C and 500 °C, more preferred between 400 °C and 450 °C.

[0075] It is further preferred that the hydrotreated lipid composition has a boiling range with a T90 (temperature at 90% volume distilled) of at most 850 °C, more preferred at most 750 °C, more preferred at most 650 °C, more preferred at most 600 °C. Preferably, the T90 is between 350 °C and 850 °C, more preferred between 375 °C and 750 °C, more preferred between 400 °C and 650 °C, more preferred between 430 °C and 600 °C.

[0076] In a further preferred embodiment, the hydrotreated lipid composition has a Hydrogen / Carbon (H / C) ratio of at least 0.10, preferably at least 0.12, more preferred at least 0.14, more preferred at least 0.15, more preferred at least 0.16, more preferred at least 0.17. As used herein, the H / C ratio refers to the ratio of the hydrotreated lipid composition' s hydrogen content in wt% divided by the carbon content in wt%. A higher H / C ratio thus indicates a higher proportion of hydrogen relative to carbon. This was found to be advantageous, as in this case higher amounts of hydrogen are available during cracking, which can improve pyrolsis and reduce coke formation. A high H / C ratio can be achieved, e.g. by limiting the amount of unsaturated hydrocarbons in the hydrotreated lipid composition. Preferably, the hydrotreated lipid composition has an H / C ratio between 0.10 and 0.20, more preferred between 0.12 and 0.19, more preferred between 0.14 and 0.19, more preferred between 0.15 and 0.19, more preferred between 0.16 and 0.19, more preferred between 0.17 and 0.18.

[0077] The plastics material used in the inventive process preferably comprises polyethylene (PE) , polypropylene (PP) , polystyrene (PS) , polyvinyl chloride (PVC) , polyethylene terephthalate (PET) , polyamide (PA) , styrene acrylonitrile (SAN) and / or acrylonitrile butadiene styrene (ABS) . Preferably, the plastics material may be plastic waste, especially pre-consumer, post-consumer and / or post-industrial plastics. Preferably, the plastics material comprises polyolefins, preferably selected from polyethylene and polypropylene, and / or polystyrene.

[0078] The inventive process has been found to be particularly well suited for recycling polyolefin (PC) -based plastics material. In particular, it has been found that when the hydrotreated lipid composition contains a high amount of paraffinic compounds, PO- based plastics material can be particularly well solubilized. Thus, it is preferred that the plastics material comprises PO, preferably selected from PE and / or PP. Preferably, the plastics material comprises at least 20 wt% PO, more preferred at least 50 wt%, more preferred at least 70 wt%, more preferred at least 80 wt%, more preferred at least 90 wt%.

[0079] In the inventive process, the plastics material is heated to form a plastic melt, wherein the pyrolysis feed comprises the plastic melt. Preferably, the plastics material is heated in a mixer, especially in an extruder. This allows the subsequent pyrolysis to be carried out more energy-ef f iciently and in a shorter amount of time. In the mixer, especially the extruder, the plastics material can preferably also be degassed. This allows producing a uniform mass without gas inclusions, ensuring that a homogeneous pyrolysis product can be obtained through the subsequent pyrolysis.

[0080] Preferably, the plastics material is heated to a temperature of at least 80 °C to form the plastic melt, preferably at least 100 °C. Preferably, the plastics material is heated to a temperature between 80 °C and 450 °C, more preferred between 100 °C and 350 °C. Preferably, the plastics material is heated to the said temperature at a pressure of 10 to 30 bar, preferably 15 to 25 bar.

[0081] Preferably, the hydrotreated lipid composition is heated to a temperature of at least 80 °C, preferably at least 120°C, more preferred at least 150 °C, more preferred at least 200 °C before being added to the plastics material, especially the plastic melt. Preferably the hydrotreated lipid composition is heated to a temperature between 80 °C and 450 °C, preferably between 120 °C and 450 °C, more preferred between 150 °C and 400 °C, more preferred between 200 °C and 350 °C. This allows the mixing to proceed particularly quickly and efficiently.

[0082] In a preferred embodiment, the pyrolysis feed contains the plastic melt and the hydrotreated lipid composition at a weight ratio of between 1:1 and 200:1, more preferred between 2.5:1 and 100:1, more preferred between 5:1 and 20:1 (plastic melt:hy- drotreated lipid composition) . It has been found that providing such a ratio between the plastic melt and the hydrotreated lipid composition allows to effectively solubilize the plastic melt and decrease the viscosity of the pyrolysis feed.

[0083] Similarly, it is further preferred that the pyrolysis feed contains the hydrotreated lipid composition and the recycling stream at a weight ratio of between 1:2000 and 1:10, more preferred between 1:1500 and 1:20 (hydrotreated lipid composition : recycling stream) .

[0084] In a preferred embodiment of the inventive process, the external solvent is mixed with the recycling stream to form a diluent stream, wherein said diluent stream is added to the plastic melt .

[0085] At the timepoint when the diluent stream is added to the plastic melt, the plastic melt preferably has a temperature of at least 80 °C, preferably at least 120 °C, more preferred at least 150 °C, more preferred at least 200 °C. Preferably, the plastic melt has a temperature between 80 °C and 450 °C, preferably between 120 °C and 450 °C, more preferred between 150 °C and 400 °C, more preferred between 200 °C and 350 °C. Alternatively or in addition, the diluent stream can preferably be heated to a temperature of at least 80 °C, preferably at least 120°C, more preferred at least 150 °C, more preferred at least 200 °C before being added to the plastic melt. Preferably the diluent stream has a temperature between 80 °C and 450 °C, preferably between 120 °C and 450 °C, more preferred between 150 °C and 400 °C, more preferred between 200 °C and 350 °C. By increasing the temperature of the plastic melt and / or the diluent stream, the mixing can proceed more quickly and efficiently. This can also allow the subsequent pyrolysis to be carried out more efficiently.

[0086] In a preferred embodiment, the plastics material is depolymerized in the pyrolysis reactor at a temperature of at least 360 °C. However, even higher temperatures may be preferred to allow for more efficient and / or faster depolymerization. Thus, it is preferred if the plastics material is depolymerized at a temperature of at least 400 °C, more preferred at least 440 °C. Preferably the plastics material is depolymerized at a temperature between 360 °C and 510 °C, more preferred between 400 °C and 500 °C, more preferred between 440 °C and 480 °C.

[0087] The depolymerization of the plastics material may be by thermal cracking, without the addition of a catalyst, and / or by catalytic cracking. Thermal cracking is preferred. The depolymerization can be carried out under a substantially oxygen-free atmosphere, particularly under an inert atmosphere, such as under nitrogen. By limiting or excluding oxygen, complete combustion can be prevented more effectively.

[0088] In a preferred embodiment of the inventive process, the pyrolysis product is separated into a heavy product and a light product, preferably wherein the recycling stream is withdrawn from the heavy product.

[0089] The pyrolysis product may be separated into the heavy product and the light product using any suitable method known to the skilled person. For instance, it may be separated in a separation vessel, preferably wherein the separation vessel is a liquid-gas separation vessel, especially a cyclone. A particularly suitable type of separation vessel is disclosed in WO 2023 / 036751 Al.

[0090] Preferably, the light product has a boiling range with an FBP (final boiling point) below 250 °C, more preferred below 230 °C, more preferred below 210 °C. However, it is also preferred that the FBP is not too low, as this may reduce the amount of the final hydrocarbon product obtained through the process. Therefore, the light product preferably has a boiling range with a FBP above 150 °C, more preferred above 170 °C, more preferred above 190 °C. It is particularly preferred, if the light product has a boiling range with a FBP between 150 and 250 °C, more preferred between 170 and 230 °C, more preferred between 190 and 210 °C.

[0091] The heavy product preferably has a boiling range with an IBP (initial boiling point) of at most 250 °C, more preferred at most 230 °C, more preferred at most 210 °C. Preferably, the IBP is between 150 °C and 250 °C, more preferred between 170 °C and 230 °C, more preferred between 190 °C and 210 °C. Similarly, it is preferred that the heavy product has a boiling range with an T10 (temperature at 10% volume distilled) of at most 250 °C, more preferred at most 230 °C, more preferred at most 210 °C. Preferably, the T10 is between 150 °C and 250 °C, more preferred between 170 °C and 230 °C, more preferred between 190 °C and 210 °C. When the heavy product has a boiling range with such a low IBP and / or T10, this helps ensure that a large proportion of compounds originating from the hydrotreated lipid composition that survive the pyrolysis conditions, especially of the compounds comprising an n-paraffinic hydrocarbon chain, end up in the heavy product. This is particularly advantageous when the recycling stream is withdrawn from the heavy product, because in this case, a larger proportion of these compounds remains in circulation, reducing external solvent consumption. For the same reasons, the recycling stream preferably has a boiling range with an IBP (initial boiling point) of at most 250 °C, more preferred at most 230 °C, more preferred at most 210 °C. Preferably, the IBP is between 150 °C and 250 °C, more preferred between 170 °C and 230 °C, more preferred between 190 °C and 210 °C. Similarly, it is preferred that the recycling stream has a boiling range with an T10 (temperature at 10% volume distilled) of at most 250 °C, more preferred at most 230 °C, more preferred at most 210 °C. Preferably, the T10 is between 150 °C and 250 °C, more preferred between 170 °C and 230 °C, more preferred between 190 °C and 210 °C. As explained above, this helps ensure that the recycling stream can comprise a large proportion of compounds originating from the hydrotreated lipid composition having survived the pyrolysis conditions.

[0092] Unless specified otherwise, all parameters as used herein correspond to parameters at IUPAC SATP-conditions („Standard Ambient Temperature and Pressure") , in particular a temperature of 25 °C and a pressure of 101.300 Pa.

[0093] Percentages (indicated as "%", "wt%" and the like) as used herein correspond to weight per weight (w / w) unless specified otherwise. Similarly, ratios used herein correspond to weight ratios (w / w) unless specified otherwise.

[0094] References to percentages of a given component in any composition refer to the weight percent relative to the total weight of the respective composition unless specified otherwise. Thus, when it is specified that a certain composition comprises X wt% compound A, this means that compound A constitutes X wt% of said composition, i.e., that said composition contains X wt% compound A based on the total weight of said composition. For instance, if it is stated that "the hydrotreated lipid composition comprises at least 10 wt% compounds comprising an n-paraffinic hydrocarbon chain", this means that compounds comprising an n-par- affinic hydrocarbon chain constitute at least 10 wt% of the hydrotreated lipid composition.

[0095] As used herein, the phrase "at least a portion of" or similar phrases refer to any subset of a specified material, component, or stream, which may include part or all of the specified entity. This definition is intended to encompass not only partial quantities but also the entirety of the material , component , or stream in question . Consequently, whenever "at least a portion of" a stream or other entity is mentioned, it is also preferred to use the entire stream or entity . For instance , when it is mentioned that at least a portion of the recycling stream is included in the pyrolysis feed, it is also preferred that the recycling stream ( as a whole ) is included in the pyrolysis feed .

[0096] As used herein, "hydrotreating" or "hydrotreatment" is preferably understood as any process involving hydrogen processing, i . e . , treating a substrate with hydrogen (H2) , typically under pressure and with a catalyst .

[0097] As used herein, the term "compounds comprising an n-paraf- finic hydrocarbon chain" preferably refers to chemical entities that include at least one unbranched, saturated alkyl chain . Such compounds are herein also referred to as "n-paraf f inic compounds" . In addition, the "compounds comprising an n-paraf f inic hydrocarbon chain" can also be referred to as "compounds comprising a linear alkyl group" . Preferably, these compounds comprise a linear C12+-alkyl group, preferably a linear C14+-alkyl group, more preferred a linear C16+-alkyl group, more preferred a linear C18+-alkyl group .

[0098] Similarly, the term "compounds comprising an iso-paraf finic hydrocarbon chain" preferably refers to chemical entities that include at least one branched, saturated alkyl chain . Such compounds are herein also referred to as " iso-paraf finic compounds" . In addition, the "compounds comprising an iso-paraf- finic hydrocarbon chain" can also be referred to as "compounds comprising a branched alkyl group" . Preferably, these compounds comprise a branched C12+-alkyl group, preferably a branched C14+-alkyl group, more preferred a branched C16+-alkyl group, more preferred a branched C18+-alkyl group .

[0099] The term "paraf finic hydrocarbon chain" , as used herein, preferably encompasses both n-paraf finic and iso-paraf finic hydrocarbon chains . Compounds comprising a paraf finic hydrocarbon chain may also be referred to as "paraf finic compounds" .

[0100] The term "olefinic hydrocarbon chain" , as used herein, preferably refers to a hydrocarbon chain containing at least one carbon-carbon double bond ( C=C ) . Compounds comprising an olefinic hydrocarbon chain may also be referred to as "olefinic compounds" .

[0101] Any hydrocarbon chain referred to herein, such as an n-par- affinic-, iso-paraffinic-, paraffinic-, or olefinic hydrocarbon chain, preferably refers to a hydrocarbon chain comprising at least 12 carbon atoms, preferably at least 14, more preferred at least 16, more preferred at least 18 carbon atoms.

[0102] As used herein, the term "Cx-hydrocarbon chain" refers to hydrocarbon chains having the number of carbon atoms represented by the number "x". The term "Cx+-hydrocarbon chain" refers to hydrocarbon chains having x or more carbon atoms. The term "Cx- Cy-hydrocarbon chain" refers to hydrocarbon chains having from x to y carbon atoms. Thus, for instance, a "Cl 8+-hydrocarbon chain" refers to a hydrocarbon chain having at least 18 carbon atoms, i.e., an alkyl group having at least 18 carbon atoms. A "Cl 8-C12 O-hydrocarbon chain" refers to a hydrocarbon chain having from 18 to 120 carbon atoms, i.e., an alkyl group having from 18 to 120 carbon atoms.

[0103] Similarly, the term "Cx-fatty acid" refers to a fatty acid having a hydrocarbon chain having "x" carbon atoms. "Cx+-fatty acid" refers to a fatty acid having x or more carbon atoms. Thus, a "C16+-fatty acid" is a fatty acid having at least 16 carbon atoms, such as palmitic acid (hexadecanoic acid; C16:0) or stearic acid (octadecanoic acid; C18:0) . The term "Cx-Cy- fatty acid" refers to a fatty acid having from x to y carbon atoms, i.e., a "C12-C40-fatty acid" refers to a fatty acid having from 12 to 40 carbon atoms. Similarly, the term "Cx+-fatty acid chain" refers to a fatty acid chain having at least x carbon atoms, wherein the fatty acid chain may be part of a free fatty acid, a soap, an ester, an ether, and the like. For instance, it may be part of an oil or a fat, in particular a triglyceride. The term "Cx-Cy-fatty acid chain" refers to a fatty acid chain having from x to y carbon atoms.

[0104] Carbon number distributions referred to herein are preferably determined according to ASTM D5442-17 (2021 ) , unless specified otherwise.

[0105] Pressures given in "bar" indicate absolute pressures ("bara") , unless specified otherwise. Quantities given in "ppm" refer to parts per million on a weight basis (ppmw) , unless indicated otherwise. Thus, 1 ppm as used herein corresponds to 0.0001 wt%.

[0106] Boiling ranges mentioned herein are preferably determined according to ISO 3924:2019, in particular, Procedure A or Procedure B as defined in said standard, or ASTM D86-23ae; preferably ASTM D86-23ae.

[0107] Contents of aromatic compounds are preferably determined according to the standard ASTM D6591-19. Alternatively or in addition, they can also be determined according to ASTM D5134- 21.

[0108] Conradson Carbon Residue (CCR) , as specified herein, is preferably determined according to ISO 10370:2014 or ASTM D189- 06(2019) , preferably ASTM D189-06(2019) .

[0109] Bromine numbers, as specified herein, are preferably determined according to ASTM D1159-07 (2017 ) .

[0110] Hydrogen / carbon (H / C) ratios, as specified herein, are preferably determined as the ratio of the hydrogen wt% and the carbon wt%, wherein the hydrogen and carbon wt% are preferably determined according to ASTM D5291-21.

[0111] Elemental concentrations, such as concentrations of sulfur (S) , oxygen (0) or nitrogen (N) , expressed in ppm or wt%, are preferably determined by elemental analysis. The skilled person is familiar with methods suitable for the various elements. Sulfur (S) concentrations are preferably determined according to ASTM D5453-24. Oxygen (0) concentrations are preferably determined according to ASTM D5622-17. Nitrogen (N) concentrations are preferably determined according to ASTM D4629-17 .

[0112] Figure 1 shows a process flow diagram of an embodiment of the process for depolymerizing plastics material.

[0113] Figure 2 shows a thermogravimetric analysis (TGA) of vegetable oils.

[0114] Figure 3A shows boiling point distributions of hydrotreated lipid compositions used as external solvents. Figure 3B shows the carbon chain lengths of the same compositions. Six different hydrotreated lipid compositions were tested (Medium 1-6) . In the embodiment shown in Figure 1 , plastics material 1 is supplied to an extruder 2 , in which the plastics material is compacted, molten and / or degassed . The resulting plastic melt 3 is mixed with a diluent stream 4 , which comprises an external solvent 5 , and a recycling stream 6 comprising a fraction of depolymeri zed plastics material . The external solvent 5 is a hydrotreated lipid composition, obtained by hydrotreating a lipid composition of biological origin . The plastic melt 3 is mixed with the diluent stream 4 in a static mixer 7 to form a pyrolysis feed 8 . The pyrolysis feed 8 is processed in a pyrolysis reactor 9 at a temperature between 360 ° C and 510 ° C, whereby the plastics material 1 contained in the pyrolysis feed 8 is depolymeri zed through thermal cracking, yielding a pyrolysis product 10 . Next , the pyrolysis product 10 is conveyed to a separation vessel 11 , wherein the pyrolysis product 10 is separated into a heavy product 12 and a light product 13 . The light product 13 may be post-treated, e . g . , by washing and / or hydrotreating, and may be used as a synthetic crude oil for further applications such as the production of alternative fuels or new chemicals and materials . At least a part of the heavy product 12 is withdrawn as the recycle stream 6 , which is recycled and added to the plastic melt 3 as part of the diluent stream 4 .

[0115] Example 1 : TGA analysis of vegetable oils .

[0116] To determine which types of compounds would be most stable under pyrolysis conditions and thus most suitable for incorporation into the external solvent for the purposes of the invention, thermogravimetric analyses ( TGA) of di f ferent types of compounds were carried out .

[0117] In a first experiment , two vegetable oils were tested as potential external solvents , speci fically coconut oil and partially hydrogenated sunflower oil . Both oils had similar boiling ranges ( T50 in the range of 380 ° C to 420 ° C ) . However, due to the hydrogenation of the sunflower oil , they di f fered in the amount of olefinic hydrocarbon chains . Speci fically, the following amounts of unsaturated fatty acids were determined in the two oils :

[0118] Thus, the coconut oil contained significant amounts of a variety of compounds containing olefinic hydrocarbon chains, including 7.3 wt% octadecenoic acid. Such compounds were not detected for the partially hydrogenated sunflower oil, whose main component was determined as octadecanoic acid (76.2 wt%) , i.e., a compound having an n-paraffinic hydrocarbon chain. The difference in olefinic content was also reflected in the bromine numbers of the two oils. For the coconut oil, a bromine number of 3.7 g Br2 / 100g was determined, while for the partially hydrogenated sunflower oil the bromine number was only 2.9 g Br2 / 100g.

[0119] Both oils were tested in TGA experiments, the results of which are shown in Figure 2. These results clearly show that the partially hydrogenated sunflower oil, containing a higher proportion of compounds having paraffinic hydrocarbon chains, was significantly more stable than the coconut oil having a higher proportion of compounds having olefinic hydrocarbon chains.

[0120] Example 2: Hydrotreated lipid compositions as external solvents.

[0121] Six different media tested. Media 1 to 3 were fully hydrotreated vegetable oils. Medium 4 was a hydrotreated animal fat. Medium 5 and Medium 6 were fully hydrotreated heavy fractions of vegetable oils, i.e., they were derived from vegetable oils that were separated into a light fraction and a heavy fraction, and only the hydrotreated heavy fraction was used.

[0122] The six media were analyzed. The following results were obtained :

[0123] Boiling point distributions of the six media were analyzed through simulated distillation ( SimDist ) , with the results presented in Figure 3A. Additionally, the distribution of carbon chain lengths within the six media was determined and is shown in Figure 3B .

[0124] The analysis revealed that all six hydrotreated lipid compositions possessed properties that render them highly suitable for use as external solvents in the inventive process . Speci fically, these compositions exhibited very low aromatic and olefinic content , low heteroatom content , and a low Conradson Carbon Residue ( CCR) , all of which are advantageous in the context of plastic pyrolysis processes . Moreover, the hydrotreated heavy fractions (media 5 and 6 ) were found to contain long hydrocarbon chains and to exhibit high boiling points , making them particularly stable under pyrolysis conditions and therefore especially well suited as external solvents in the inventive process.

[0125] Example 3: Stability of n-paraffins and iso-paraffins under pyrolysis conditions.

[0126] Experiments were conducted to investigate the stability of different types of paraffins under pyrolysis conditions. Specifically, the stability of different n-paraffins and iso-paraffins was tested. As n-paraffins, octadecane and icosane were tested. As iso-paraffins, pristane and squalane were tested.

[0127] To simulate cracking conditions, a stainless-steel reactor with a glass inlet was filled with 10 g of the desired compound. The reactor was flushed three times with N2and was disposed with 5 bar N2pressure at room temperature. The reactor was heated to 460 °C for 1 h (heating rate 250 °C / h) , then cooled to room temperature and the overpressure was released. All phases were separated (liquid, solid) , balanced for the yield factors and analyzed.

[0128] The following mass balances were obtained based on 10 g starting material: Additionally, as a further stability parameter, the bromine number of the liquid phases was measured . A higher bromine number is indicative of a higher content of double bonds or reactive aromatic compounds formed under pyrolysis conditions .

[0129] The above results demonstrate the n-paraffins octadecane and ico- sane were significantly more stable under pyrolysis conditions than the iso-paraffins pristane and squalane .

Claims

Claims :

1. A process for depolymerizing plastics material (1) , the process comprising:- heating the plastics material (1) to form a plastic melt(3) ,- processing a pyrolysis feed (8) comprising the plastic melt(3) and an external solvent (5) in a pyrolysis reactor (9) to generate a pyrolysis product (10) ,- withdrawing a recycling stream (6) from the pyrolysis product (10) and including at least a portion of said recycling stream (6) in the pyrolysis feed (8) , wherein the external solvent (5) is a hydrotreated lipid composition, preferably obtained by hydrotreating a lipid composition of biological origin.

2. The process according to claim 1, wherein the hydrotreated lipid composition comprises a hydrotreated vegetable oil.

3. The process according to claim 1 or 2, wherein the hydrotreated lipid composition is obtained by hydrotreating a lipid composition comprising C16+-fatty acid chains.

4. The process according to any one of claims 1 to 3, wherein the hydrotreated lipid composition is a fully hydrotreated lipid composition .

5. The process according to any one of claims 1 to 4, wherein the hydrotreated lipid composition is obtained by a process comprising separating a lipid composition of biological origin into a heavy fraction and a light fraction, and hydrotreating the heavy fraction.

346. The process according to any one of claims 1 to 5, wherein the hydrotreated lipid composition comprises less than 5 wt% aromatic compounds.

7. The process according to any one of claims 1 to 6, wherein the hydrotreated lipid composition has a Conradson Carbon Residue (CCR) of less than 5 wt%.

8. The process according to any one of claims 1 to 7, wherein the hydrotreated lipid composition comprises less than 100 ppm sulfur (S) .

9. The process according to any one of claims 1 to 8, wherein the hydrotreated lipid composition comprises less than 1 wt% oxygen (0) .

10. The process according to any one of claims 1 to 9, wherein the hydrotreated lipid composition comprises less than 10 wt% compounds comprising an olefinic hydrocarbon chain.

11. The process according to any one of claims 1 to 10, wherein the hydrotreated lipid composition has a bromine number of less than 100 g Br2 / 100 g, preferably less than 90 g Br2 / 100 g.

12. The process according to any one of claims 1 to 11, wherein the hydrotreated lipid composition has a boiling range with a T50 (temperature at 50% volume distilled) of between 315 °C and 600 °C.

13. The process according to any one of claims 1 to 12, wherein the hydrotreated lipid composition has a Hydrogen / Carbon (H / C) ratio of at least 0.10.

14. The process according to any one of claims 1 to 13, whereinthe plastics material comprises at least 20 wt% polyolefins (PO) , preferably selected from polyethylene (PE) and polypropylene (PP) .

15. The process according to any one of claims 1 to 14, wherein the hydrotreated lipid composition is heated to a temperature of at least 120°C before being added to the plastic melt.

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