Process and plant for the production of product olefins

Abstract

A process (100) for producing product olefins (8) is proposed in which a pyrolysis oil (2) is provided, a hydrogenation feed (5) is provided using the pyrolysis oil (2) or a portion thereof, the hydrogenation feed (5) is subjected to hydrogenation (130) to obtain a hydrogenation product (6), a cracker feed (7) is provided using the hydrogenation product (6) or a portion thereof, and the cracker feed (7) or a portion thereof is processed by steam cracking (140) to obtain the olefins (8). According to the invention, the hydrogenation feed (5) comprises paraffinic compounds, monounsaturated olefinic compounds and additional hydrogenatable compounds, wherein the hydrogenation (130) is performed as a selective hydrogenation of at least one of the additional hydrogenatable compounds, and the hydrogenation product (6) or the portion thereof used for providing the cracker feed (7) is transferred to the cracker feed (7) without undergoing any additional hydrogenation. The present invention also provides a corresponding plant.

Description

[0001] Description

[0002] Process and plant for the production of product olefins

[0003] The invention relates to a process and a plant for producing product olefins.

[0004] background

[0005] Processes and systems for the pyrolysis of plastic, in particular so-called solid plastic waste (SPW), are known and have been described many times. Among many others, reference can be made in this context to an article by BA 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 common practice in the art, are also referred to below as plastic pyrolysis oil or pyrolysis oil for short. The present invention is not limited to a specific method of obtaining such a pyrolysis oil, and utilization occurs by steam cracking.

[0006] WO 2022 / 063597 A1 relates to a process for processing a pyrolysis oil from plastics, comprising optional selective hydrogenation, hydroconversion, separation, fractionation, hydroprocessing, and further separation. WO 2023 / 208636 A1 also relates to a process for processing a pyrolysis oil from plastics, comprising hydrotreatment, separation or washing, removal of hydrogen sulfide, and removal of ammonia. Further processes for processing corresponding pyrolysis oils are known from US 2023 / 029587 A1 and WO 2021 / 204820 A1. US 5,985,136 A relates to processes for the hydrodesulfurization of naphtha.

[0007] The pyrolysis oil from plastic pyrolysis can be processed with additional feedstocks through steam cracking. The most widely used approach to date for commercial use of plastic-based pyrolysis oils is diluting 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.

[0008] By using light or hydrogenated feeds, a corresponding pyrolysis oil, which may have a lower quality (e.g. in terms of boiling range and impurities), can be brought into line with the requirements of a conventional cracker feed to a limited extent without too great a risk to the plant, especially if purification, for example adsorptive, is carried out at least to a limited extent.

[0009] However, due to various limitations, often only small amounts (typically in the single-digit percentage range) can be added to conventional applications, which severely limits the possible applications and quantities. Furthermore, known solutions often do not work satisfactorily in other respects.

[0010] There is therefore a need for improved processes in which pyrolysis oils, particularly those originating from plastic pyrolysis, can be converted more effectively and on a larger scale by steam cracking.

[0011] Disclosure of the invention

[0012] Against this background, a process and a plant for producing product olefins having the features of the independent patent claims are proposed. Further embodiments are the subject of the dependent patent claims and the following description.

[0013] The present invention and its embodiments are based in particular on the surprising discovery that the olefins in a pyrolysis oil from plastic pyrolysis, or certain of these olefins, in particular monounsaturated olefins, do not necessarily have to be hydrogenated to paraffins for use in steam cracking. Embodiments of the present invention comprise the provision of olefins by means of plastic pyrolysis. Hydrogenation is conventionally considered essential to ensure the processability of corresponding compounds in steam cracking. Conventional approaches, as disclosed, for example, in the publications cited above, provide, in particular, for the most complete hydrogenation possible.However, this proves to be particularly complex when processing pyrolysis oil from plastic pyrolysis, as pyrolysis oil from plastic pyrolysis has a very high olefin content, compared to refinery streams, for example. The resulting problems are explained in more detail below.

[0014] 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 pyrolysis of waste or biomass.

[0015] As recognized within the scope of the present invention, the processing of olefin-containing pyrolysis oils from plastics pyrolysis processes can be carried out in steam cracking in particular because the olefins contained, in particular monounsaturated olefins, are comparatively long-chain and can therefore be cleaved to the desired target products more easily than the olefin-containing fractions typically formed in steam cracking with shorter-chain compounds. Unexpectedly, a low tendency to coking is also observed. In addition, unexpectedly good yields are achieved, as also discussed further below. Aspects of the present invention and its embodiments therefore relate to processes and plants in which, although compounds containing disruptive heteroatoms and possibly polyunsaturated olefins are hydrogenated in a corresponding pyrolysis oil, at least not the monounsaturated olefins (which do not contain heteroatoms).

[0016] For the sake of clarity, the olefins contained in a pyrolysis oil are also referred to below as "feedstock olefins." These include the monounsaturated olefinic compounds that are not hydrogenated or hydrogenated only to a small extent in embodiments of the invention. These feedstock olefins typically differ from the olefins formed during steam cracking, which are also referred to below as "product olefins." A difference between feedstock olefins and product olefins can lie in particular in the chain length, with the feedstock olefins comprising more than 50% compounds with five or more carbon atoms, and the product olefins comprising more than 50% compounds with four or fewer carbon atoms.In particular, however, a weighted average chain length of the feedstock olefins lies above such an average chain length of the product olefins, whereby the former can in particular be a value of around five, six, seven, eight or more, and the latter a value of around two, three or four. A value "around" a certain number is intended to designate a value which, when rounded using standard methods, results in the stated number. The feedstock olefins can in particular comprise a significant proportion of alpha- and / or iso-olefins, i.e. a proportion of more than 50%, 60%, 70%, 80% or 90% based on the total proportion of olefins. However, this is not mandatory.

[0017] The present invention and its embodiments therefore propose a departure from conventional hydrogenation, which largely converts all feedstocks, which is even the aim of hydrogenation in conventional processes.

[0018] The proposed process for producing product olefins comprises providing a pyrolysis oil, providing a hydrogenation feed using the pyrolysis oil or a portion thereof, subjecting the hydrogenation feed to hydrogenation to obtain a hydrogenation product, providing a cracker feed using the hydrogenation product or a portion thereof, and processing the cracker feed or a portion thereof by steam cracking to obtain the product olefins.

[0019] The hydrogenation feed, and previously the pyrolysis oil from which the hydrogenation feed is formed, comprises paraffinic compounds, monounsaturated olefinic compounds and other hydrogenatable compounds, wherein the other hydrogenatable compounds may in particular comprise polyunsaturated olefinic compounds and / or heteroatom compounds.

[0020] Within the framework of the proposed process, the hydrogenation is carried out as a selective hydrogenation of at least one of the other hydrogenatable compounds. The hydrogenation product, or its portion used to provide the cracker feed, is transferred without further hydrogenation to the cracker feed, and thus to a steam cracking arrangement comprising one or more cracking furnaces or crackers, and is subjected to steam cracking there. In other words, a proportion of the monounsaturated olefinic compounds defined by the degree of selectivity of the selective hydrogenation reaches the steam cracker. This proportion is reduced only by the proportion that is undesirably converted during the selective hydrogenation.

[0021] For clarification, it should be mentioned that the selective hydrogenation in the proposed process is carried out using one or more hydrogenation reactors from which the hydrogenation product is withdrawn. In other words, the hydrogenation product is not withdrawn from a separation device and transferred from there to the steam cracker. The hydrogenation product can, in particular, have the same content of compounds such as paraffinic and monounsaturated compounds as the cracker feed. The hydrogenation product and cracker feed can, in particular, have the same or substantially the same absolute or relative contents of the paraffinic compounds and the monounsaturated olefinic compounds.

[0022] As is generally known to those skilled in the relevant field, even in a chemical reaction referred to as "selective," in this case hydrogenation, it cannot be completely avoided that a certain proportion of compounds that are not target compounds of the selective chemical reaction are nevertheless converted. In the present case, this means that a certain proportion of the monounsaturated olefinic compounds are also hydrogenated during the selective hydrogenation. In particular, this may mean that up to 25%, 20%, 15%, or 10% of the monounsaturated olefinic compounds present in the pyrolysis oil or the portion thereof used to provide the cracker feed are converted during the selective hydrogenation.

[0023] In other words, due to the proposed selective hydrogenation, the cracker feed will contain a significant proportion of monounsaturated olefinic compounds. If the proportion of monounsaturated olefinic compounds in the hydrogenation feed is X% by mass, mole, or volume, and this proportion in the hydrogenation product is Y%, Y may be less than X if the selective hydrogenation also converts a portion of the monounsaturated olefinic compounds. In this case, Y may be, for example, 25, 20, 15, 10, or 5 less than X. If the selective hydrogenation converts polyunsaturated olefinic compounds to monounsaturated olefinic compounds, Y may also be greater than X, for example, by up to 10 or 5 greater. The specific value in this case depends on the content of the polyunsaturated olefinic compounds and the reaction characteristics.It is understood that during the selective hydrogenation of the polyunsaturated olefinic compounds, these may also be partially or completely hydrogenated to the corresponding paraffins, in which case such compounds do not contribute to the content in the hydrogenation feed.

[0024] In the selective hydrogenation, it can be provided, in particular, that more than 95%, 90%, 80%, 70%, 60%, or 50% of the at least one further hydrogenatable compound, in particular one or more corresponding compound classes, is converted during the selective hydrogenation, so that their content in the hydrogenation product is correspondingly lower than in the pyrolysis oil. The above-mentioned percentages can denote a molar fraction, a volume fraction, or a mass fraction, or represent dimensionless quantities. The further hydrogenatable compounds can, in particular, comprise polyunsaturated olefinic compounds and heteroatom compounds. Dienes and acetylenes can be converted in the same or an additional upstream step.As will be explained below, it has surprisingly been found in this case that advantages arise even if only a comparatively small proportion of the monounsaturated feedstocks contained in the pyrolysis oil remain unhydrogenated, and these advantages increase accordingly if the unhydrogenated proportion increases.

[0025] A "heteroatom compound" as used herein can be, in particular, a compound that can have one or more heteroatoms, which can be selected from the group of nitrogen, oxygen, sulfur, and chlorine atoms, whereby different heteroatom compounds with the same heteroatom and / or multiple heteroatom compounds with different heteroatoms can be present. Acetylenes, i.e., alkynes, in particular do not fall under the term "olefins" used here. As mentioned, embodiments of the invention can also relate to a selective hydrogenation of polyunsaturated olefins or of acetylenes as hydrogenatable compounds, although the following explanations refer in particular to heteroatom compounds, which are also referred to below as "impurities."

[0026] The term "plastic pyrolysis oil" or "pyrolysis oil" is used here as is common practice in the field. Pyrolysis oil resulting from 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, but may also contain heavier components, such as those normally found at the light end of the vacuum gas oil fraction. If the term "pyrolysis oil" is used here, its composition typically does not, or not necessarily, correspond to that of known pyrolysis oils from steamer fields. These are typically very different mixtures. In particular, this also includes, at least in part, the components that are separated into the so-called gasoline fraction (pyrolysis gasoline) in pyrolysis oils from steamer fields, as well as heavier compounds than those typically 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 aromatics content), which cannot be directly determined from the boiling point.

[0027] The pyrolysis oil considered here may therefore already contain hydrocarbons with five or six carbon atoms and a boiling range of 30 to 100 °C, but need not contain them or may contain them only partially. Furthermore, components with six to 12 carbon atoms and a boiling point between 130 and 220 °C may be present. These components are also not necessarily present or may only be present in part. In particular, as mentioned, the compounds present may have boiling points such as those conventionally found in naphtha; for a definition, reference is made, for example, to the aforementioned article "Ethylene" in Ullmann's Encyclopedia of Industrial Chemistry. In particular, the pyrolysis oil may contain a significant amount of hydrocarbons with twelve or more carbon atoms, with the boiling range of these compounds being, in particular, essentially between 210 and 550 °C.These components are not necessarily present or may only be present in part. A pyrolysis oil as understood here can also contain extremely heavy compounds, as explained below. A certain separation of light and heavy compounds can be provided during the formation of the hydrogenation feed, but pyrolysis oil can also be used in unseparated form. The pyrolysis oil used here differs from a pyrolysis oil from a steam cracking process or other pyrolysis oils, in particular due to its comparatively high content of olefins (feedstock 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 above.

[0028] The term "hydrogenation product" refers here to a mixture of components taken from a hydrogenation reactor of the type used here, and which may have the above-discussed content of, in particular, monounsaturated olefins (i.e., of remaining feed olefins) as a hydrogenation feed, i.e., a component mixture fed to the hydrogenation reactor. In contrast, the content of the aforementioned impurities is correspondingly reduced.

[0029] Processes and equipment for steam cracking are described in the specialist 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. Any technical terms used below from the field of steam cracking, such as "cracking furnace," "coils," "propylene-ethylene ratio," etc., have the usual meanings known from the specialist literature.

[0030] The present invention and its embodiments enable at least a partial elimination of the previously existing limitation, as explained, on the usable quantities of pyrolysis oil as cracker feedstock to low percentages or only as a minor admixture. The invention and its embodiments thus enable the use of pyrolysis oils of the type described, which are increasingly available in increased quantities, in an improved manner, i.e., despite the lack of, or the occurrence of a lower proportion of, hydrogenation of feedstock olefins, with unexpected yield and low coking tendency.

[0031] The invention and its embodiments successfully address the often differing quality of pyrolysis oils compared to conventional feedstocks for steam cracking such as naphtha in terms of composition (in particular the content of olefins, dienes and acetylenes) and impurities (in particular chlorine-, nitrogen- and oxygen-containing components).

[0032] Conventional processes for the hydrogenation of pyrolysis oils, which are not used in the context of 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 can precede the fractionation and processing of all or some fractions in the steam cracker. Due to the strongly hydrogenating catalyst systems and reaction conditions in such processes, as mentioned, there is extensive, and in some cases even the desired complete, hydrogenation of the feedstock oils in the pyrolysis oil. This is accompanied by significant hydrogen consumption (which is extremely uneconomical) and a corresponding heat of reaction. While the heat development can still be manageable on a laboratory scale, very complex and possiblyRealistically no longer feasible measures are required to manage the heat development. The present invention and its embodiments overcome these disadvantages.

[0033] Corresponding approaches, as well as co-treatment with conventional refinery streams, are known from the patent literature. Compared to such processes, the invention and its refinements allow for a reduction in hydrogen demand and a simplified design of the hydrogenation reactors due to the reduced heat quantities.

[0034] The disadvantages mentioned do not occur in the field of conventional hydrotreating and hydrocracking of crude oil-based feedstocks, since these typically contain little or no feedstock oils.

[0035] By applying the conventional steps mentioned, a hydrogenated pyrolysis oil can be obtained which, after fractionation, resembles a conventional cracker feed in terms of its properties and can thus be used in large proportions as an admixture or even on its own as a feed for a cracking furnace. The prior art therefore specifically aims to bring the quality of the pyrolysis oils as close as possible to typical qualities of conventional feedstocks, e.g., to a typical naphtha quality. The aim of the hydrogenation steps in known processes is a substantial to complete reduction in the content of feed olefins (see, for example, 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 finding that this goal does not have to be achieved.

[0036] Due to the challenges mentioned above, conventional processes can be practically implemented with additional modifications such as multiple hydrogenation stages and dilution, e.g., with conventional feeds or recirculation of already hydrogenated streams, which significantly increases the complexity of a corresponding plant. The present invention and its embodiments, in contrast, can be implemented with particularly simple arrangements. Furthermore, the process allows for a higher throughput of pyrolysis oil per furnace.

[0037] These traditionally targeted very low feed olefin contents of typically less than 1%, which were found to be unnecessary in embodiments of the present invention, pose an additional challenge to the performance of the plants, particularly since the other impurities in the pyrolysis oil must also be reduced to the desired specification values ​​at the same time. The starting point for this is that olefinic feedstocks are traditionally considered unsuitable for the cracker, both with regard to cracker yield and coking or oxidation efficiency.

[0038] Risk of contamination in the plant. Within the scope of the present invention and its embodiments, it was nevertheless recognized that olefin-containing cracker feedstocks can be advantageously converted compared to naphtha, despite the often higher final boiling point, which is typically accompanied by a reduction in yield, as already mentioned and also discussed below.

[0039] As mentioned, the complete hydrogenation of the feedstock oils in pyrolysis oils is accompanied by a high exotherm due to the contents in the double-digit percentage range (e.g., 20 to 80% or 30 to 60% in embodiments of the present invention). This increases the complexity of the hydrogenation (e.g., multiple stages, dilution, and / or recycling) and reduces the service life and performance of the hydrogenation catalyst due to inadequate temperature control and excessively high (peak) temperatures. These disadvantages are avoided here. The conventionally extremely high hydrogen consumption in hydrogenation is also avoided, so that this can be covered by the cracker itself. The hydrogen supply is limited, especially in so-called liquid crackers, which are particularly suitable for the use of pyrolysis oils. In embodiments of the invention, therefore, no additional (external) supply of hydrogen to a corresponding plant is required.

[0040] Both the costs for providing the aforementioned process steps and their operation, including the provision of hydrogen, which typically represent a considerable cost factor, are significantly reduced in embodiments of the invention.

[0041] 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 feedstock olefins in the hydrogenation purification stage and thus fulfills the hydrogen balance across the complex, including the cracker. This avoids problems with exothermicity and catalyst loading in the hydrogenation stage and an otherwise necessary, more complex process with, for example, multiple hydrogenation stages. It also avoids feedstock dilution and / or recycling of the treated material stream. By appropriately adapting the furnace conditions or furnace design during steam cracking, olefin-containing feedstocks can be operated with the desired result, such as a high yield of product olefins.Embodiments of the invention thus contribute to creating an economical option for the use of such inserts and nevertheless taking into account the cleaning requirements of pyrolysis oils of varying quality.

[0042] In embodiments of the invention, the hydrogenation can be carried out in particular using one or more catalysts which comprise or comprise one or more transition group elements. In particular, elements of transition group VIII and VI and combinations thereof are suitable as catalyst material. The heteroatom-containing compounds can in particular be chlorine-, nitrogen-, oxygen- and / or sulfur-containing compounds. The selective hydrogenation serves for the targeted removal of corresponding compounds in the pyrolysis oil with no or only minimal hydrogenation of monounsaturated olefinic moieties. As mentioned, however, in this or a separate step, hydrogenation of diolefins and acetylenes can in particular take place. The catalyst types mentioned are known from the treatment of other streams in the refinery sector, such as gasoline from catalytic cracking (see, for example,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 preserving, in particular, the monounsaturated feedstocks. The use of such catalysts for the pretreatment of pyrolysis oils as cracker feedstock is not known to date. The references cited above differ fundamentally from the application described here in several respects (e.g., type of application: cracked gasoline, objective: maintaining the octane number, application: gasoline, contaminant: sulfur).

[0043] The one or more hydrogenatable compounds may be or comprise heteroatom compounds, wherein the selective hydrogenation comprises a selective hydrogenation of the one or more heteroatom compounds.-

[0044] In embodiments of the invention, the 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 a selective hydrogenation of the chlorine-containing compound or at least of the chlorine-containing compound. With such an embodiment, the particularly adverse influence of chlorine-containing impurities on the downstream process steps can be addressed. In other words, multiple heteroatom compounds can be present that comprise one or more chlorine-containing compounds, and the selective hydrogenation can be configured in particular such that, in particular, these one or more chlorine-containing compounds are reacted.In the case of multiple heteroatom compounds, of which a first compound or a first group of compounds contains chlorine and a second compound or a second group of compounds may not contain chlorine, a corresponding selective hydrogenation can thus be designed in particular such that the first compound or at least one compound of the first group of compounds is converted to a greater extent than the second compound or at least one compound of the second group of compounds. This can be achieved in particular because chlorine-containing compounds are easier to hydrogenate.

[0045] In embodiments of the present invention, the catalyst(s) may comprise nickel, molybdenum, and / or cobalt, in particular on a suitable support such as dialuminium trioxide. Thus, known and well-characterized catalysts or catalyst systems may be used.

[0046] In embodiments of the invention, the hydrogenation can be carried out at a temperature level of 150 to 400 °C, in particular 200 to 350 °C, and / or at a pressure level of 5 to 70 bar, in particular 10 to 40 bar. These conditions tend to be milder than those used in conventional hydrocracking and hydrotreating / hydrodesulfurization of crude oil distillates, preferably at 50 to 200 bar and 250 to 450 °C, resulting in advantages, for example, with regard to cooling and material selection.

[0047] In embodiments of the invention, the 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 to be realized.

[0048] Furthermore, in embodiments of the invention, a selective hydrogenation of polyunsaturated compounds such as dienes and / or acetylenes can be carried out. Particular advantages arise in embodiments in which 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 should not be excluded. Correspondingly low diene and acetylene contents enable advantageous conversion in steam cracking due to reduced coking tendency and shorter run times. In embodiments of the invention, it can be provided that a portion of the hydrogenation product is recycled upstream of the hydrogenation. In other words, a recycle gas flow of the gaseous portion of the reactor outlet stream of the hydrogenation reactor can be provided. Hydrogen or recycle gas can be supplied at one or more points.If necessary, the cycle gas recycling can also include stages for gas cleaning.

[0049] In embodiments of the present invention, the provision of the hydrogenation feed can include treatment in the form of removal of (further) impurities. This can involve targeted removal of impurities, in particular organic and inorganic salts and thus of alkali and alkaline earth metals or other metals, but also of chlorine-, nitrogen-, oxygen-, and silicon-containing trace components from the pyrolysis oil using suitable processes (filtration, water scrubbing, extraction, and adsorption processes). As a result, the service life of the hydrogenation catalyst used in a subsequent process step can be extended or its regeneration requirement reduced.

[0050] In further embodiments, the provision of the hydrogenation feed or the cracker feed can comprise a removal of high-boiling components ("high boilers"). The separation of the heavy fraction in the pyrolysis oil, in particular by distillation, takes place by means of a purification step arranged before or after the hydrogenation. One of the possible embodiments comprises in particular a separation to less than 10%, more particularly less than 5% of the corresponding high boilers, i.e. in such a way that in particular asphaltenes and metals are separated. An arrangement before the hydrogenation is particularly advantageous because it can possibly, for example, reduce the metal content or the proportion of inorganic impurities in the oil and thus improve the functioning and / or running time of the hydrogenation stage. Furthermore, several cuts of the feed can be produced if necessary and treated with adapted hydrogenation conditions.A further embodiment comprises a distillative separation after hydrogenation, in which components with a boiling point of more than 300 °C, in particular more than 350 °C, for example more than 380 °C, 390 °C, or 400 °C, are removed, to an appropriate and technically reasonable extent in order to facilitate evaporation of the cracker feedstock in the furnace. Fractionation into several fractions for different uses (e.g., in separate furnaces) is also a possible variant.

[0051] In particular, in embodiments of the invention, hydrogenated partial streams are recycled upstream of the hydrogenation reactor to a minimal extent, compared to the conventional process. In embodiments of the proposed process, more than 10% of the cracker feed can be prepared using components of the pyrolysis oil and / or components formed therefrom during hydrogenation.

[0052] In the 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 equipped as a conventional furnace with direct firing or with a different heating concept, such as an electrically heated furnace. In the case of an electrically heated furnace, the particular advantage can arise that preheating can be more targeted and decoupled from the classic waste heat concept, which benefits a critical feed such as pyrolysis oil with regard to reducing fouling and thus operability. This specific point is also advantageous with regard to feed streams that have not been pretreated by hydrotreating. Embodiments of the invention can comprise an optimized / adapted system for preheating and evaporation in the cracking furnace, as well as adapted cracking conditions for optimal product yield or to avoid fouling.

[0053] A hydrogen-containing fraction can be separated from a component mixture obtained during steam cracking and recycled to meet the hydrogen demand for hydrogenation, as mentioned above. The hydrogen supply to the hydrogenation unit can therefore be integrated into the cracker's hydrogen system, e.g., downstream of a demethanization and / or pressure swing adsorption process. It can also be advantageous to utilize low-grade hydrogen streams from the cracker that already contain impurities or portions of other hydrocarbons (particularly methane). Providing the cracker feed from the hydrogenation product can also include processing; in particular, removal of components from the hydrogenation product or from the portion thereof used to provide the cracker feed can be provided.These may also include components 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, volatile components and / or residual hydrogen can be removed by stripping.

[0054] As mentioned several times, the pyrolysis oil is primarily produced using plastic pyrolysis, but other pyrolysis processes and applications, such as biomass, are also possible. For information on such processes, please refer to relevant specialist literature.

[0055] The proposed plant for producing product olefins is configured to be fed with a pyrolysis oil, is configured to provide a hydrogenation feed using the pyrolysis oil or a portion thereof, is configured to hydrogenate the hydrogenation feed to obtain a hydrogenation product, is configured to provide a cracker feed using the hydrogenation product or a portion thereof, and is configured to steam crack the cracker feed or a portion thereof to obtain the product olefins. The hydrogenation feed comprises paraffinic compounds, monounsaturated olefinic compounds, and other hydrogenatable compounds.It is intended that the plant is designed to carry out the hydrogenation as a selective hydrogenation of at least one of the further hydrogenatable compounds and to transfer the hydrogenation product or its part used to provide the cracker feed into the cracker feed without further hydrogenation.

[0056] For further features and advantages of a corresponding system and embodiments thereof, reference is expressly made to the above explanations regarding the method proposed according to the invention and its embodiments, as these apply equally to them. The same applies to a system that, according to one embodiment of the invention, is configured to carry out a method according to any embodiment of the present invention.

[0057] Advantages of processes and plants according to the invention, as well as corresponding configurations, 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 absolutely 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. Little or no recycling of hydrogenated streams is required, resulting in a reduction in equipment and energy consumption. Dilution with conventional feedstock, which only represents unnecessary volume and may also be subject to side reactions, is unnecessary.It is possible to balance the hydrogen demand across the entire plant, eliminating the need for an additional hydrogen production facility and also enabling a self-sufficient supply throughout the entire complex.

[0058] Overall, the utilization of significant quantities of pyrolysis oils contributes to a circular economy, serves to prevent environmental pollution and waste disposal, and contributes to reducing carbon dioxide emissions and energy savings (compared to the use of conventional fossil feedstocks).

[0059] The basic concept and embodiments of the invention can be supplemented with further refinements regarding additional purification steps depending on the requirements / properties of the pyrolysis oil. Filtration, absorption / washing, extraction processes, physical and chemical adsorption / selective sorption are particularly relevant. Fractionation, particularly for the separation of heavy components, is also possible (separation of a heavy boiling point 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 of more than 300°C, in particular more than 350°C, for example more than 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.

[0060] Further specific scenarios include, in a first example, pyrolysis followed by distillation, followed by water washing to reduce inorganic salts, particularly chlorine, and water-soluble polar compounds, which in turn is followed by drying, targeted hydrogenation, and subsequent post-purification, e.g., by adsorptive means. A second scenario may include pyrolysis followed by distillation to remove heavy end components, followed by adsorptive coarse purification, e.g., for chlorine. The latter may then be followed by targeted hydrogenation and post-purification, e.g., by adsorptive or distillation.

[0061] Alternatively, hydrogenation can also take place outside the cracker environment, but rather at a pyrolysis oil producer or at centralized locations where several pyrolysis oils from different sources are hydrogenated. In this case, the upgraded quality also has a positive impact on transport and, in particular, storage properties prior to further use as a cracker feedstock.

[0062] In addition to pyrolysis oils, other feedstocks, such as bio-based pyrolysis oils, can also be appropriately processed for use as cracker feedstocks. Integration of utility and waste streams (wastewater, exhaust gas) with the cracker is possible, for example, by recirculating exhaust gas streams into the exhaust gas treatment or flare system or into the fuel gas network.

[0063] Alternatively, the additional hydrogen demand could be met by converting a methane or methane-rich fraction of the cracker into hydrogen and carbon dioxide (possibly supplemented by carbon capture).

[0064] Short description of the drawing

[0065] Embodiments of the invention are described below purely by way of example with reference to the accompanying drawing, in which Figure 1 illustrates a method according to an embodiment of the invention,

[0066] Figure 2 illustrates aspects of methods according to embodiments of the invention, Figure 3 illustrates aspects of methods according to embodiments of the invention.

[0067] Embodiments of the invention

[0068] The embodiments described below are described solely for the purpose of assisting the reader in understanding the claimed and previously discussed features. They are merely representative examples and are not intended to be exhaustive and / or limiting with regard to the features of the invention. It is to be understood that the advantages, embodiments, examples, functions, features, structures, and / or other aspects described above and below are not to be considered as limitations on the scope of the invention as defined in the claims or as limitations on equivalents to the claims, and that other embodiments may be utilized and changes may be made without departing from the scope of the claimed invention.

[0069] Different embodiments of the invention may include, have, consist of, or consist essentially of other useful combinations of the described elements, components, features, parts, steps, means, etc., even if such combinations are not specifically described herein.

[0070] Furthermore, the disclosure may cover other inventions which are not currently claimed but which may be claimed in the future, particularly if they are included within the scope of the independent claims.

[0071] Explanations relating to devices, apparatus, arrangements, systems, etc. according to embodiments of the present invention may also apply to methods, processes, methods, etc. according to the embodiments of the present invention, and vice versa. Identical, similarly acting, functionally corresponding, structurally identical or comparable elements, method steps, etc. may be identified by identical reference numerals. Figure 1 illustrates a method according to one embodiment of the invention in the form of a simplified schematic flow chart and is designated overall by 100. The method 100 is described using plastic pyrolysis. As mentioned, methods according to embodiments of the present invention are also suitable for use with other pyrolysis applications.

[0072] In the process 100, a pyrolysis feed 1 containing or consisting of plastic is subjected to a pyrolysis 110, in this case a plastic pyrolysis. Any separation steps can be associated with the pyrolysis, so that a pyrolysis oil 2 can be provided using the pyrolysis (and the separation steps).

[0073] In the example shown, the pyrolysis oil 2 is subjected to one or more optional treatment steps 120, which have already been explained above. These can, in particular, comprise adsorption or scrubbing. In this way, a treated pyrolysis oil 3 can be obtained. After optionally feeding a hydrogen cycle stream 4 to the treated pyrolysis oil 3, or, in particular if no treatment steps 120 are provided, also already to the pyrolysis oil 2, the treated pyrolysis oil 3, or, if no treatment steps 120 are provided, already the pyrolysis oil 2, is subjected as hydrogenation feed 5 to a hydrogenation 130, which is carried out as a selective hydrogenation of the type explained above using appropriate catalysts.

[0074] In the 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, but which, due to the specific nature of the hydrogenation, is depleted in or free of components containing heteroatoms compared to the hydrogenation feed 5. The monounsaturated olefinic compounds (feed olefins) fed into the hydrogenation feed 5 of the hydrogenation 130 are converted to at most a small extent.

[0075] By means of a separation device (not separately illustrated), hydrogen can be separated from the hydrogenation product 6 and returned to the hydrogen cycle stream. The liquid hydrogenation product is processed as 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 therein are not separately illustrated. 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 returned in the form of a stream 9.

[0076] Figures 2 and 3 illustrate the results of comparative tests with naphtha and olefin-containing pyrolysis oils. The results for naphtha are indicated by x symbols, the results for a first pyrolysis oil are indicated by upside-down, unfilled boxes, and the results for a second pyrolysis oil are indicated by upside-down, filled boxes. The results of two parallel tests are shown. The first and second pyrolysis oils differ primarily in that the feedstocks for the pyrolysis differed, particularly with regard to the proportions of polyethylene and polypropylene, respectively.

[0077] Figure 2 plots a temperature at the end of the cracking tubes in °C on the vertical axis versus a propylene-to-ethylene ratio in kg / kg on the horizontal axis. Figure 3 shows an ethylene yield in wt.% on the vertical axis versus a propylene-to-ethylene ratio in kg / kg on the horizontal axis.

[0078] As can be seen from Figures 2 and 3, 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 the structure, in particular the chain length, is appropriately suitable and the operation is carried out accordingly.

[0079] In contrast to the prior art, results obtained within the scope of this application surprisingly show that the influence of a double bond in a feed molecule generally decreases with increasing chain length, since the hydrogen-to-carbon ratio and the content of diolefins and acetylene-like compounds are primarily decisive. This also applies correspondingly to the coking tendency.

Claims

Patent 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 portion 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 portion thereof, and in which the cracker feed (7) or a portion thereof is processed by steam cracking (140) to obtain the product olefins (8), wherein the hydrogenation feed (5) comprises paraffinic compounds, monounsaturated olefinic compounds, and further hydrogenatable compounds, wherein the hydrogenation (130) is carried out as a selective hydrogenation of at least one of the further hydrogenatable compounds,and wherein the hydrogenation product (6) or its part used to provide the cracker feed (7) is transferred into the cracker feed (7) without further hydrogenation.

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 process (100) of claim 2, wherein the one or more further hydrogenatable compounds 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. Method (100) according to 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 process (100) according to any one of the preceding claims, wherein the provision of the hydrogenation feed (5) comprises a removal of impurities.

11. Method (100) according to one of the preceding claims, in which the cracker feed (7) is provided to more than 10% using 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 to the hydrogenation (130).

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 producing product olefins (8), 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 portion 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 portion thereof, and which is designed to process the cracker feed (7) or a portion thereof by steam cracking (140) to obtain the product olefins (8), wherein the hydrogenation feed (5) comprises paraffinic compounds, monounsaturated olefinic compounds and other hydrogenatable compounds, and wherein the plant is designed toto carry out the hydrogenation (130) as a selective hydrogenation of at least one of the further hydrogenatable compounds and to transfer the hydrogenation product (6) or its part used to provide the cracker feed (7) into the cracker feed (7) without further hydrogenation.

Images