Method and installation for producing olefins

Abstract

A process (100) for the production of product olefins is proposed, wherein a pyrolysis oil (2) is provided, wherein a hydrogenation feed (5) is provided using the pyrolysis oil (2) or a part thereof, wherein the hydrogenation feed (5) is subjected to hydrogenation (130) to obtain a hydrogenation product (6), wherein a cracker feed (7) is provided using the hydrogenation product (6) or a part thereof, and wherein the cracker feed (7) or a part thereof is processed by steam cracking (140) to obtain the olefins (8).The hydrogenation (130) is provided for in the selective hydrogenation of one or more heteroatom compounds and / or polyunsaturated compounds and / or acetylenes, wherein less than 90% of the monounsaturated olefinic compounds contained in the pyrolysis oil (2) or the portion thereof used to provide the cracker feed (3) are converted in the selective hydrogenation (130). A corresponding apparatus is also part of the present invention.

Description

[0001] The invention relates to a method and a plant for the production of product olefins. background

[0002] Processes and plants for the pyrolysis of plastics, in particular so-called solid plastic waste (SPW), are known and have been described extensively. Among many others, reference can be made in this context to an article by B.A. Perez et al., "Characterization of SPW pyrolysis oils: Products spectra and opportunities," in: D. Moscatelli and M. Pelucchi (eds.), "Towards Circular Economy: Closing the Loop with Chemical Recycling of Solid Plastic Waste," Adv. Chem. Eng. 60(1), 169-214, 2022. The present invention relates in particular to the processing and utilization of liquid pyrolysis products from such plastic pyrolysis, which, as is customary in the field, are hereinafter also referred to as plastic pyrolysis oil or, in short, pyrolysis oil. The present invention is not limited to a specific method of obtaining such pyrolysis oil, and its utilization is carried out by steam cracking.

[0003] The pyrolysis oil from plastic pyrolysis can be further processed by steam cracking. The most widespread approach to date for commercially applied plastic-based pyrolysis oils is to dilute them with conventional feedstocks such as naphtha, atmospheric gas oil (AGO), unhydrogenated or hydrogenated vacuum gas oil ((H)VGO), and other fractions, particularly from refinery processes.

[0004] By using lighter or hydrogenated feedstocks, a corresponding pyrolysis oil, which may be of lower quality (e.g., with regard to boiling range and impurities), can be brought into line with the requirements of a conventional cracker feedstock to a limited extent without posing too great a risk to the plant, especially if purification, e.g., adsorptive, is carried out at least to a limited extent.

[0005] Due to various limitations, only small amounts (typically in the single-digit percentage range) can often be added to conventional applications, which severely restricts the possible uses and quantities. Furthermore, existing solutions often fail to perform satisfactorily in other respects as well.

[0006] Therefore, there is a need for improved processes in which pyrolysis oils originating from plastic pyrolysis can be converted better and to a greater extent by steam cracking. Disclosure of the invention

[0007] Against this background, a process and a plant for the production of product olefins with the features of the independent claims are proposed. Embodiments are the subject of the dependent claims and the following description.

[0008] The present invention and its embodiments are based in particular on the surprising finding that the olefins in a pyrolysis oil from plastic pyrolysis do not necessarily need to be hydrogenated to paraffins for use in steam cracking. Embodiments of the present invention include providing olefins by means of plastic pyrolysis. Such hydrogenation is conventionally considered essential to ensure the processability of the corresponding compounds in steam cracking. Conventional approaches, in particular, aim for the most complete hydrogenation possible. However, this proves to be very complex, especially when processing pyrolysis oil from plastic pyrolysis, since such pyrolysis oil has a very high olefin content compared to, for example, refinery streams. The resulting problems are explained in more detail below.

[0009] The present invention is not limited to the use of pyrolysis oils from plastic pyrolysis, but can also extend to other pyrolysis oils with a comparatively high proportion of olefins, for example pyrolysis oils from the pyrolysis of waste or biomass.

[0010] As has been recognized within the scope of the present invention, the processing of olefin-containing pyrolysis oils from plastic pyrolysis processes during steam cracking is particularly advantageous because the olefins contained are comparatively long-chain and can therefore be more readily cleaved to the desired target products than the olefin-containing fractions typically formed during steam cracking, which tend to have shorter chains. Unexpectedly, a low tendency to coke is observed. Furthermore, unexpectedly good yields are obtained, as discussed below. Aspects of the present invention and its embodiments therefore relate to processes and plants in which, although compounds containing interfering heteroatoms are hydrogenated in a corresponding pyrolysis oil, the (heteroatom-free) olefins are preferably not hydrogenated.

[0011] For the sake of clarity, the olefins contained in a pyrolysis oil and, in embodiments of the invention, not hydrogenated or only hydrogenated to a small extent, will hereinafter be referred to as "feed olefins". These typically differ from the olefins formed during steam cracking, which will hereinafter be referred to as "product olefins". One difference can be, in particular, the chain length, whereby the feed olefins may contain more than 50% compounds with five or more carbon atoms, and the product olefins may contain more than 50% compounds with four or fewer carbon atoms.In particular, a weighted average chain length of the feed olefins, adjusted for their respective content, lies above a corresponding average chain length of the product olefins, with the former being around five, six, seven, eight, or more, and the latter around two, three, or four. A value "around" a certain number is intended to indicate a value that, when rounded to a standard rounding, yields the specified number. The feed olefins may, in particular, contain a significant proportion of alpha and / or iso-olefins, i.e., a proportion of more than 50%, 60%, 70%, 80%, or 90% of the total olefin content. However, this is not mandatory.

[0012] The present invention and its embodiments therefore propose a departure from conventional hydrogenation, which largely converts the input olefins, which is even the goal of hydrogenation in conventional processes.

[0013] The proposed process for producing product olefins comprises providing a pyrolysis oil, providing a hydrogenation feed using the pyrolysis oil or part thereof, subjecting the hydrogenation feed to hydrogenation to obtain a hydrogenation product, providing a cracker feed using the hydrogenation product or part thereof, and processing the cracker feed or part thereof by steam cracking to obtain the product olefins.

[0014] The hydrogenation process includes the selective hydrogenation of one or more impurities, particularly those from one or more classes of compounds, especially one or more heteroatom compounds, wherein less than 90%, particularly less than 80%, 75%, 50%, 25%, or 10% of the monounsaturated olefinic compounds in the pyrolysis oil or the portion thereof used to provide the cracker feed (i.e., feed olefins) are converted during the selective hydrogenation. It is also possible, in particular, for more than 95%, 90%, 80%, 70%, 60%, or 50% of the one or more impurities, particularly those from one or more corresponding classes of compounds, especially heteroatom compounds, to be converted during the selective hydrogenation. Dienes and acetylenes can be converted in the same or an additional upstream step.As will be explained below, and surprisingly found in the present case, advantages arise even if only a comparatively small proportion of the monounsaturated feed olefins contained in the pyrolysis oil remains unhydrogenated, and these advantages increase accordingly with an increase in the unhydrogenated proportion.

[0015] An "impurity" in the sense understood here can, in particular, be a heteroatom compound. A "heteroatom compound" in the terminology used here can, in particular, be a compound that may contain one or more heteroatoms, which may be selected from the group consisting of nitrogen, oxygen, sulfur, and chlorine atoms, and in which different heteroatom compounds with the same heteroatom and / or several heteroatom compounds with different heteroatoms may be present. Acetylenes, i.e., alkynes, do not fall under the term "olefins" as used here. As mentioned, embodiments of the invention may also relate to an alternative or additional selective hydrogenation of polyunsaturated olefins or of acetylenes, although the following explanations refer in particular to heteroatom compounds.

[0016] The terms "plastic pyrolysis oil" and "pyrolysis oil" are used here as is common practice in the field. Pyrolysis oil produced during the pyrolysis of plastics can overlap with known fractions such as naphtha and atmospheric gas oil in terms of the carbon numbers of the compounds it contains and their boiling points. However, it may also contain heavier components, such as those typically found at the lighter end of the vacuum gas oil fraction. When the term "pyrolysis oil" is used here, its composition typically does not correspond, or not necessarily corresponds, to that of known pyrolysis oils from steam crackers. It is typically a very diverse mixture. In particular, it also includes, at least in part, the components that are separated into the so-called gasoline fraction (pyrolysis gasoline) in pyrolysis oils from steam crackers, as well as heavier compounds than are usually found in pyrolysis oil.However, the overall composition of the plastic pyrolysis oil is significantly different, especially with regard to the structure of the compounds it contains (e.g., paraffin to aromatic ratio), which cannot be directly determined from the boiling point.

[0017] The pyrolysis oil under consideration here may contain hydrocarbons with five and six carbon atoms and a boiling range of 30 to 100 °C, but it does not necessarily contain them, or may only contain them partially. Furthermore, it may contain components with six to twelve carbon atoms and a boiling point between 130 and 220 °C. These components are also not necessarily present, or may only be present partially. In particular, as mentioned, the compounds contained may have boiling points conventionally found in naphtha, for which, for example, reference is made to the aforementioned article "Ethylene" in Ullmann's Encyclopedia of Industrial Chemistry. The pyrolysis oil may, in particular, contain a considerable amount of hydrocarbons with twelve or more carbon atoms, the boiling range of which may be primarily between 210 and 550 °C.These components are not necessarily included or may only be present in part. A pyrolysis oil, as understood here, can also contain exceptionally heavy compounds, as explained below. A certain degree of separation of lighter and heavier compounds may be intended, but the use of pyrolysis oil in its undivided form is also possible. The pyrolysis oil used here differs from pyrolysis oil from a steam cracking process or other pyrolysis oils, particularly in its comparatively high content of olefins (usage olefins), as explained below. For further characterization of a plastic pyrolysis oil, reference is made, for example, to the article by Perez et al. cited at the beginning.

[0018] The term "hydrogenation product" here refers to a mixture of components taken from a hydrogenation reactor of the type used in this case, and which may have essentially the same proportion of olefins (i.e., remaining feed olefins) as a hydrogenation feed, i.e., a mixture of components supplied to the hydrogenation reactor, or a reduced proportion thereof. Conversely, the content of the aforementioned impurities is correspondingly reduced.

[0019] Methods and equipment for steam cracking are described in the technical literature, for example in the article "Ethylene" in Ullmann's Encyclopedia of Industrial Chemistry, online since April 15, 2007, DOI 10.1002 / 14356007.a10_045.pub2. Where technical terms from the field of steam cracking are used below, such as "cracking furnace," "coils," "propylene-ethylene ratio," etc., they have their usual meanings as defined in the technical literature.

[0020] The present invention and its embodiments enable at least a partial removal of the previously existing limitation, as explained, on the usable quantities of pyrolysis oil as cracker feedstock, limiting it to low percentages or only as a minor admixture. The invention and its embodiments thus allow for the improved use of increasingly available pyrolysis oils of the type described, i.e., despite the absence or reduced hydrogenation of feed olefins, with unexpected yields and low coking tendency.

[0021] The invention and its embodiments successfully address the often differing quality of pyrolysis oils compared to conventional feedstocks for steam cracking such as naphtha with regard to composition (especially the content of olefins, dienes and acetylenes) and impurities (especially chlorine-, nitrogen- and oxygen-containing components).

[0022] Conventional methods for hydrogenating pyrolysis oils, which are not used in the present invention and its embodiments, include classic hydrogenating purification steps known from refinery technology, in particular so-called hydrotreating and hydrocracking, whereby these steps may precede fractionation and processing of all or some fractions in a steam cracker. Due to the strongly hydrogenating effect of the catalyst systems or reaction conditions in such processes, as mentioned, a largely complete hydrogenation of the feed olefins in the pyrolysis oil occurs, sometimes even as a desired outcome. This is accompanied by significant hydrogen consumption (which is extremely uneconomical) and a corresponding heat generation. While the heat generation may still be manageable on a laboratory scale, very complex and potentially costly measures are required in large-scale industrial applications.Realistically, no longer feasible measures are required to manage the heat generation. The present invention and its embodiments overcome these disadvantages.

[0023] Similar approaches, including co-treatment with conventional refinery streams, are known from patent literature. Compared to such processes, the invention and its embodiments allow for a reduction in hydrogen demand and a simplified design of the hydrogenation reactors due to the reduced heat quantities.

[0024] The aforementioned disadvantages do not arise when using conventional hydrotreating and hydrocracking of crude oil-based feedstocks, as these typically contain little or no feed olefins.

[0025] By applying the aforementioned conventional steps, a hydrogenated pyrolysis oil can be obtained which, after fractionation, closely resembles a conventional cracker feed in terms of its properties and can therefore be used in large proportions as an additive or even on its own as a feedstock for a cracking furnace. Thus, according to the prior art, the aim is to bring the quality of the pyrolysis oils as close as possible to the typical qualities of conventional feedstocks, e.g., to a typical naphtha quality. The objective of the hydrogenation steps in known processes is a substantial to complete reduction of the feedstock olefin content (see, e.g., WO 2016 / 142805 A1, WO 2016 / 132807 A1, WO 2021 / 165178 A1, WO 2022 / 084433 A1 and GB 2 601 407 A). The present invention and its embodiments are based on the understanding that this objective need not be achieved.

[0026] Due to the aforementioned challenges, conventional processes often require additional modifications such as multiple hydrogenation stages and dilution, for example, using conventional feeds or recirculating already hydrogenated streams, which significantly increases the complexity of the corresponding system. In contrast, the present invention and its embodiments can be implemented with particularly simple arrangements. Furthermore, the process allows for a higher throughput of pyrolysis oil per furnace.

[0027] These conventionally targeted very low levels of feed olefins, typically less than 1%, which have been found to be unnecessary in embodiments of the present invention, pose an additional challenge to the performance of the plants, especially since the other impurities in the pyrolysis oil must also be reduced to the desired specification values. The starting point for this is that olefinic feedstocks are conventionally considered unsuitable for the cracker, both with regard to cracker yield and the risk of coking or fouling in the plant.Within the scope of the present invention and its embodiments, it was nevertheless recognized that olefin-containing cracker inserts can be used to advantage compared to naphtha, despite the often higher boiling point, which is typically associated with a reduction in yield, as already mentioned and also discussed below.

[0028] The complete hydrogenation of the feed olefins in pyrolysis oils, due to their concentrations in the double-digit percentage range (e.g., 20 to 80% or 30 to 60% in embodiments of the present invention), is associated with a high heat input, as mentioned above. This increases the complexity of the hydrogenation process (e.g., multiple stages, dilution, and / or recycling) and reduces the service life and performance of the hydrogenation catalyst due to insufficient temperature control and excessively high (peak) temperatures. These disadvantages are avoided in the present invention. Furthermore, the conventionally high hydrogen consumption of the hydrogenation process is avoided, as this can be covered by the cracker itself. The hydrogen supply is particularly limited in so-called liquid crackers, which are especially suitable for use with pyrolysis oils. Therefore, in embodiments of the invention, no additional (external) hydrogen supply to the corresponding system is required.

[0029] In embodiments of the invention, both the costs for providing the aforementioned process steps and their operation, including the hydrogen supply, which typically represent a significant cost factor, are significantly reduced.

[0030] In summary, aspects of the present invention comprise a processing and purification concept for pyrolysis oils as feedstock for steam crackers. This concept reduces hydrogen consumption by minimizing the hydrogenation of feed olefins in the hydrogenation purification stage, thereby fulfilling the hydrogen balance across the entire complex, including the cracker. This avoids problems with heat dissipation and catalyst loading in the hydrogenation stage, as well as the otherwise necessary, more complex process with, for example, multiple hydrogenation stages. Feed dilution and / or recycling of the treated material stream are also avoided. By appropriately adjusting the furnace conditions or the furnace design during steam cracking, olefin-containing feedstocks can be processed with the desired results, such as high yields of product olefins.Embodiments of the invention thus contribute to creating an economical option for the use of such inserts while still taking into account the cleaning requirements of pyrolysis oils of varying quality.

[0031] In embodiments of the invention, hydrogenation can be carried out, in particular, using one or more catalysts comprising one or more transition metals. For example, elements of groups VIII and VI and combinations thereof are particularly suitable as catalyst materials. The compounds containing heteroatoms can be, in particular, chlorine-, nitrogen-, oxygen-, and / or sulfur-containing compounds. Selective hydrogenation serves to selectively remove corresponding compounds from the pyrolysis oil with no or only minimal hydrogenation of monounsaturated olefinic components. As mentioned, however, hydrogenation of diolefins and acetylenes can also be carried out in this or a separate step. The aforementioned catalyst types are known from the treatment of other streams in the refinery sector, such as gasoline from catalytic cracking (see, for example, [reference]).US 5,853,570 A, US 5,906,730 A, US 5,985,136 A, and US 6,013,598 A). This enables the reduction of heteroatoms while sparing, in particular, the monounsaturated feed olefins. The use of such catalysts for the pretreatment of pyrolysis oils as cracker feedstock is not yet known. The references cited above differ fundamentally from the application described here in several respects (e.g., type of feedstock: cracked gasoline, objective: preservation of octane number, application: gasoline, impurity: sulfur).

[0032] In embodiments of the invention, one heteroatom compound can be a chlorine-containing compound, or the multiple heteroatom compounds can comprise a chlorine-containing compound. The selective hydrogenation can comprise the selective hydrogenation of the chlorine-containing compound or at least the chlorine-containing compound. Such an embodiment can, in particular, address the especially detrimental influence of chlorine-containing impurities on downstream process steps. In other words, multiple heteroatom compounds can be present, comprising one or more chlorine-containing compounds, and the selective hydrogenation can, in particular, be designed such that these one or more chlorine-containing compounds are specifically reacted.In the case of several heteroatom compounds, where a first compound or group of compounds contains chlorine and a second compound or group of compounds does not, a corresponding selective hydrogenation can be designed such that the first compound, or at least one compound of the first group, is converted to a greater extent than the second compound, or at least one compound of the second group. This is particularly feasible because chlorine-containing compounds are more readily hydrogenated.

[0033] In embodiments of the present invention, the catalyst(s) can comprise nickel, molybdenum and / or cobalt, particularly on a suitable support such as, for example, a dialuminum trioxide support. Thus, known and well-characterized catalysts or catalyst systems can be used.

[0034] In embodiments of the invention, the hydrogenation can be carried out at a temperature level of 150 to 400 °C, particularly 200 to 350 °C, and / or at a pressure level of 5 to 70 bar, particularly 10 to 40 bar. These are generally milder conditions than those used in conventional hydrocracking and hydrotreating / hydrodesulfurization of crude oil distillates at preferably 50 to 200 bar and 250 to 450 °C, resulting in advantages, for example, with regard to cooling and material selection.

[0035] In embodiments of the invention, hydrogenation can be carried out in a single- or multi-stage fixed-bed arrangement; however, other designs such as a moving bed are also possible, meaning the concept is not limited to a specific reactor design. The fixed-bed arrangement can comprise one or more stages; the use of only one stage is preferred and is made possible in particular by the concept of the invention and its embodiments. This again allows for a particularly simple arrangement.

[0036] Furthermore, in embodiments of the invention, selective hydrogenation of polyunsaturated compounds such as dienes and / or acetylenes can be carried out. Particular advantages arise in embodiments where the diene and acetylene content is reduced to less than 1.0%, less than 0.5%, or less than 0.1%, although largely complete hydrogenation is not excluded. Correspondingly low diene and acetylene contents enable advantageous use in steam cracking due to reduced coking tendency and shorter cycle times.

[0037] In embodiments of the invention, it may be provided that a portion of the hydrogenation product is recycled upstream of the hydrogenation process. In other words, a recirculation system for the gaseous fraction of the reactor outlet stream of the hydrogenation reactor may be provided. Hydrogen or recirculated gas can be supplied at one or more points. Optionally, the recirculated gas system may also include gas purification stages.

[0038] In embodiments of the present invention, the provision of the hydrogenation feedstock can include a processing step. This step can involve the targeted removal of impurities, in particular organic and inorganic salts, and thus alkali and alkaline earth metals or other metals, as well as trace components containing chlorine, nitrogen, oxygen, and silicon, from the pyrolysis oil by suitable methods (filtration, water washing, extraction, and adsorption). As a result, the service life of the hydrogenation catalyst used in a subsequent process step can be extended, or its regeneration requirement reduced.

[0039] In further embodiments, the provision of the hydrogenation or cracker feed can include the removal of high-boiling components. The separation of the heavier fraction in the pyrolysis oil, particularly by distillation, is carried out by means of a purification step arranged before or after hydrogenation. One possible embodiment includes, in particular, a separation to less than 10%, and further, in particular, less than 5% of the corresponding high-boiling components, i.e., such that asphalthenes and metals, in particular, are separated. An arrangement before hydrogenation is especially advantageous, as this can, for example, reduce the metal content or the proportion of inorganic impurities in the oil and thus improve the functionality and / or service life of the hydrogenation stage. Furthermore, several cuts of the feed can be produced and treated with adapted hydrogenation conditions.Another embodiment involves a distillative separation after hydrogenation, in which components with a boiling point above 300 °C, particularly above 350 °C, for example above 380 °C, 390 °C, or 400 °C, are removed to an appropriate and technically feasible extent in order to facilitate the evaporation of the cracker feedstock in the oven. Fractionation into several fractions for different uses (e.g., in separate ovens) is also a possible option.

[0040] In particular, in embodiments of the invention, no or only a minor recirculation of hydrogenated partial streams takes place before the hydrogenation reactor compared to the conventional process.

[0041] In this process, one or more fired and / or at least partially electrically heated cracking furnaces can be used for steam cracking. A cracking furnace can therefore be a conventional furnace with direct firing or equipped with a different heating concept, such as an electrically heated furnace. In the case of an electrically heated furnace, the particular advantage arises that preheating can be carried out more precisely and decoupled from the conventional waste heat concept, which benefits a critical feed such as pyrolysis oil with regard to reducing fouling and thus improving operability. This specific point is also advantageous with regard to feed streams that have not been pretreated with hydrogenation. Embodiments of the invention can include an optimized / adapted system for preheating and vaporization in the cracking furnace, as well as adapted cracking conditions for optimal product yield or to avoid fouling.

[0042] A hydrogen-containing fraction can be separated from a component mixture obtained during steam cracking and recycled to meet the hydrogen demand of the hydrogenation process, as mentioned. This allows for the integration of the hydrogen supply for the hydrogenation unit into the cracker's hydrogen system, for example, downstream of a demethanation and / or pressure swing adsorption (PSA) unit. Utilizing lower-grade hydrogen streams from the cracker, which already contain impurities or other hydrocarbons (especially methane), can also be advantageous.

[0043] The provision of the cracker feed from the hydrogenation product can also include processing, specifically the removal of components from the hydrogenation product or the portion used to provide the cracker feed. These components can include those released during hydrogenation, such as hydrochloric acid, ammonia, hydrogen cyanide, hydrogen sulfide, water, carbon oxides and other gases, hydrocarbon fragments, and the like. In particular, the separation of volatile components and / or residual hydrogen can be achieved by stripping.

[0044] As mentioned several times, the pyrolysis oil is primarily produced using plastic pyrolysis, but other pyrolysis processes and inputs, such as biomass, are also possible. For further information on these processes, please refer to relevant technical literature.

[0045] The proposed plant for the production of product olefins is equipped for feeding with a pyrolysis oil, is equipped to provide a hydrogenation feed using the pyrolysis oil or part thereof, is equipped to subject the hydrogenation feed to hydrogenation to obtain a hydrogenation product, is equipped to provide a cracker feed using the hydrogenation product or part thereof, and is equipped to process the cracker feed or part thereof to product olefins by steam cracking.The plant is designed to carry out the hydrogenation as a selective hydrogenation of one or more heteroatom compounds and / or one or more polyunsaturated olefinic compounds, in particular one or more dienes, and / or one or more acetylenes, wherein in the selective hydrogenation less than 90%, in particular less than 80%, 75%, 50%, 25%, or 10% of monounsaturated olefinic compounds are converted in the pyrolysis oil or the part thereof, using which the cracker feed is provided.

[0046] For further features and advantages of a corresponding system and its embodiments, reference is expressly made to the above explanations concerning the method proposed according to the invention and its embodiments, since these apply in the same way.

[0047] The same applies to a system which, according to an embodiment of the invention, is equipped to carry out a process according to any embodiment of the present invention.

[0048] The advantages of the processes and systems according to the invention, as well as corresponding embodiments, have already been mentioned and are summarized again below. These advantages include a simpler reactor design for hydrogenation reactors due to lower cooling requirements. A multi-stage design is not strictly necessary, and a single-stage design represents a preferred embodiment of the invention. Furthermore, catalyst stress is reduced, resulting in improved performance and a longer service life. No or only minimal recycling of hydrogenated streams is required, leading to a reduction in equipment and energy consumption. Dilution using conventional methods, which only represents unnecessary volume and may also be subject to side reactions, is not required.It is possible to balance the hydrogen demand across the entire plant, thus eliminating the need for an additional hydrogen production facility and enabling a self-sufficient supply for the entire complex.

[0049] Overall, the utilization of significant quantities of pyrolysis oils contributes to a circular economy, helps to avoid environmental pollution and waste disposal / recycling, and contributes to reducing carbon dioxide emissions and saving energy (compared to the use of conventional fossil feedstocks).

[0050] The basic concept and embodiments of the invention can be supplemented with further embodiments regarding additional purification steps, depending on the requirements and properties of the pyrolysis oil. Particularly relevant are filtration, absorption / washing, extraction processes, and physical and chemical adsorption / selective sorption. Fractionation, especially for the separation of heavier components, is also possible (separation of a high-boiling end to remove asphaltenes and metals, typically to less than 10% or 5% of the corresponding pyrolysis oil fraction, or distillative separation of components after hydrogenation with a boiling point above 300 °C, particularly above 350 °C, for example, above 380 °C, 390 °C, or 400 °C, to facilitate the evaporation of the cracker feedstock in the furnace). These steps can be used individually or in combination, both before and after the hydrogenation unit.

[0051] Further specific scenarios include, in a first example, pyrolysis followed by distillation, subsequent water washing to reduce inorganic salts, especially chlorine, and water-soluble polar compounds, followed by drying, targeted hydrogenation, and then further purification, e.g., by adsorptive means. A second scenario could include pyrolysis followed by distillation to remove the heavier end and subsequent adsorptive coarse purification, e.g., for chlorine. This could then be followed by targeted hydrogenation and further purification, e.g., by adsorptive distillation.

[0052] Alternatively, hydrogenation can take place not in the cracker environment, but at a pyrolysis oil producer or at centralized facilities where several pyrolysis oils from different sources are hydrogenated. Here, the improved quality also has a positive effect on the transport and, in particular, storage properties before further use as cracker feedstock.

[0053] In addition to pyrolysis oils, other feedstocks, such as bio-based pyrolysis oils, can also be processed accordingly for use as cracker feedstock. Integration of utility and waste streams (wastewater, exhaust gas) with the cracker may be possible, for example, the recirculation of exhaust gas streams into the exhaust gas cleaning or flare system, or into the heating gas network.

[0054] Alternatively, the additional hydrogen requirement could be met by converting a methane- or methane-rich fraction of the cracker into hydrogen and carbon dioxide (possibly supplemented by carbon capture). Brief description of the drawing

[0055] Embodiments of the invention are described below by way of example only, with reference to the accompanying drawing, wherein Figure 1 a method according to one embodiment of the invention is illustrated, Figure 2 Aspects of methods according to embodiments of the invention are illustrated, Figure 3 Aspects of the process are illustrated according to embodiments of the invention. Embodiments of the invention

[0056] The embodiments described below are provided solely to assist the reader in understanding the claimed and previously explained features. They represent only representative examples and are not intended to be considered exhaustive or limiting with regard to the features of the invention. It is understood that the advantages, embodiments, examples, functions, features, structures, and / or other aspects described above and below are not to be considered limitations on the scope of the invention as defined in the claims or on equivalents to the claims, and that other embodiments may be used and modifications made without deviating from the scope of the claimed invention.

[0057] Different embodiments of the invention may include, feature, consist of, or essentially consist of further advantageous combinations of the described elements, components, features, parts, steps, means, etc., even if such combinations are not specifically described herein. Furthermore, the disclosure may include other inventions that are not currently claimed but may be claimed in the future, particularly if they are within the scope of the independent claims.

[0058] Explanations relating to devices, apparatus, arrangements, systems, etc., according to embodiments of the present invention may also apply to processes, procedures, methods, etc., according to embodiments of the present invention, and vice versa. Identical, functionally equivalent, structurally identical or comparable elements, process steps, etc., may be indicated by identical reference numerals.

[0059] In Figure 1 A process according to one embodiment of the invention is illustrated in the form of a simplified schematic flow chart and is designated as 100. Process 100 is described using plastic pyrolysis as an example. As mentioned, processes according to embodiments of the present invention are also suitable for use with other pyrolysis agents.

[0060] In process 100, a pyrolysis insert 1 containing or consisting of plastic is subjected to pyrolysis 110, in this case, plastic pyrolysis. Any number of separation steps can be assigned to the pyrolysis, so that a pyrolysis oil 2 can be provided using the pyrolysis (and the separation steps).

[0061] In the example shown, the pyrolysis oil 2 is subjected to one or more optional processing steps 120, which have already been explained above. These may include, in particular, adsorption or scrubbing. In this way, a processed pyrolysis oil 3 can be obtained. After an optional addition of a hydrogen cycle stream 4 to the processed pyrolysis oil 3, or, in particular if no processing steps 120 are provided, also to the pyrolysis oil 2, the processed pyrolysis oil 3, or, if no processing steps 120 are provided, the pyrolysis oil 2, is subjected as a hydrogenation feed 5 to a hydrogenation 130, which is carried out as a selective hydrogenation of the type described above with appropriate catalysts.

[0062] In hydrogenation 130, a hydrogenation product 6 is obtained in the form of a mixture of paraffins and olefins (feed olefins), which may also contain other components such as aromatics. However, due to the specific nature of the hydrogenation, it is depleted of components with heteroatoms or free of them compared to hydrogenation feed 5. The monounsaturated olefinic compounds (feed olefins) supplied to hydrogenation 130 in hydrogenation feed 5 are reacted only to a very small extent, if at all.

[0063] Hydrogen can be separated from the hydrogenation product 6 using a separation device (not shown separately) and returned to the hydrogen cycle stream. The liquid hydrogenation product is processed as a steam cracking feed 7 by steam cracking 140. Any other feeds can be used. Separation devices used in connection with steam cracking 140 and some of the products obtained here are not shown separately. In any case, one or more product olefins 8, for example ethylene, can be obtained in this way. A hydrogen or light gas fraction can be recycled in the form of a mass stream 9.

[0064] In the Figure 2 and 3The results of comparative tests with naphtha and olefin-containing pyrolysis oils are illustrated. Results for naphtha are represented by x symbols, results for a first pyrolysis oil by inverted, unfilled boxes, and results for a second pyrolysis oil by inverted, filled boxes. The results of two parallel tests are shown in each case. The first and second pyrolysis oils differ primarily in the feedstocks used for pyrolysis, particularly with regard to the proportions of polyethylene and polypropylene, respectively.

[0065] In Figure 2 The graph shows the temperature at the end of the cracked tubes in °C on the vertical axis versus the propylene-ethylene ratio in kg / kg on the horizontal axis. Figure 3shows an ethylene yield in wt.% on the vertical axis versus a propylene-ethylene ratio in kg / kg on the horizontal axis.

[0066] As from the Figure 2 and 3 It is evident that, in order to achieve a technically and economically satisfactory cracker operation, pyrolysis oils with high contents of feed olefins can be converted with good yields if they have a suitable structure, especially chain length, and if the operating conditions are appropriate.

[0067] In contrast to the prior art, the results obtained within the scope of the present application surprisingly show that the influence of a double bond in a feedstock molecule generally decreases with increasing chain length, since the hydrogen-carbon ratio and the content of diolefins and acetylene-like compounds are primarily decisive here. This also applies accordingly to the tendency to coke.

Claims

1. A process (100) for producing product olefins (8), in which a pyrolysis oil (2) is provided, in which a hydrogenation feed (5) is provided using the pyrolysis oil (2) or a part thereof, in which the hydrogenation feed (5) is subjected to hydrogenation (130) to obtain a hydrogenation product (6), in which a cracker feed (7) is provided using the hydrogenation product (6) or a part thereof, and in which the cracker feed (7) or a part thereof is processed by steam cracking (140), whereby the product olefins (8) are formed, characterized in that the hydrogenation (130) comprises a selective hydrogenation of one or more impurities, wherein in the selective hydrogenation (130) less than 90% of monoolefinic compounds contained in the pyrolysis oil (2) or the part thereof using which the cracker feed (3) is provided are converted.

2. The process (100) according to claim 1, wherein the hydrogenation (130) is carried out using one or more catalysts which comprise or comprise one or more transition group elements.

3. The method (100) of claim 2, wherein the one or more impurities are or comprise heteroatom compounds, wherein the selective hydrogenation comprises selective hydrogenation of the one or more heteroatom compounds.

4. The method (100) of claim 2 or 3, wherein the one heteroatom compound is a chlorine-containing compound or the plurality of heteroatom compounds comprise a chlorine-containing compound, wherein the selective hydrogenation comprises selective hydrogenation of the chlorine-containing compound.

5. Process (100) according to one of claims 2 to 4, wherein the catalyst(s) comprises one or more elements of subgroups VIII and / or VI as active component.

6. The process (100) according to any one of claims 2 to 5, wherein the hydrogenation (130) is carried out at a temperature level of 150 to 400 °C and / or at a pressure level of 5 to 70 bar.

7. The process (100) according to any one of claims 2 to 6, wherein the hydrogenation (130) is carried out in a single-stage or multi-stage fixed bed arrangement.

8. Process (100) according to one of the preceding claims, in which an additional selective hydrogenation of polyunsaturated compounds and / or acetylenes is carried out in the same or an upstream catalyst bed.

9. Process (100) according to one of the preceding claims, in which a portion of the hydrogenation product is recycled upstream of the hydrogenation (130).

10. The method (100) according to any one of the preceding claims, wherein the provision of the hydrogenation feed (5) comprises a processing step.

11. Process (100) according to one of the preceding claims, in which the cracker feed (7) consists of more than 10% components of the pyrolysis oil and / or components formed therefrom in the hydrogenation (130).

12. The method (100) according to any one of the preceding claims, wherein one or more fired and / or at least partially electrically heated cracking furnaces are used for the steam cracking (140).

13. Process (100) according to one of the preceding claims, in which a hydrogen-containing fraction is separated from a component mixture obtained during steam cracking (140) and recycled.

14. The method (100) according to any one of the preceding claims, wherein providing the cracker feed (7) comprises removing components from the hydrogenation product or the part thereof used to provide the cracker feed (7).

15. Plant for the production of product olefins, which is designed to be fed with a pyrolysis oil (2), which is designed to provide a hydrogenation feed (5) using the pyrolysis oil (2) or a part thereof, which is designed to subject the hydrogenation feed (5) to hydrogenation (130) to obtain a hydrogenation product (6), which is designed to provide a cracker feed (7) using the hydrogenation product (6) or a part thereof, and which is designed to process the cracker feed (7) or a part thereof by steam cracking (140), whereby the product olefins (8) are formed, characterized in thatthe plant is designed to carry out the hydrogenation (130) as a selective hydrogenation of one or more impurities, wherein in the selective hydrogenation (130) less than 90% of monounsaturated olefinic compounds contained in the pyrolysis oil (2) or the part thereof using which the cracker feed (3) is provided are converted.

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