Process and apparatus for producing product olefins

Abstract

A process (100) for producing a product olefin (8) is proposed in which a pyrolysis oil (2) is provided, a hydrogenation feedstock (5) is provided using the pyrolysis oil (2) or a portion of the pyrolysis oil (2), the hydrogenation feedstock (5) is hydrogenated (130), a hydrogenation product (6) is obtained, a cracking feedstock (7) is provided using the hydrogenation product (6) or a portion of the hydrogenation product (6), and the cracking feedstock (7) is separated from the pyrolysis oil (2). And subjecting the cracking feedstock (7) or a portion of the cracking feedstock (7) to a steam cracking (140) treatment to obtain an olefin (8). According to the invention, the hydrogenation feedstock (5) comprises a paraffin compound, a monounsaturated olefin compound, and further compounds that can be hydrogenated, the hydrogenation (130) being carried out as selective hydrogenation of at least one of the further compounds that can be hydrogenated, and the hydrogenation product (6) or part of the hydrogenation product (6) for providing the cracking feedstock (7) is fed to the cracking feedstock (7) without any additional hydrogenation. The invention further provides a corresponding device.

Description

Technical Field

[0001] This invention relates to a method and apparatus for producing the product olefin. Background Technology

[0002] Methods and apparatus for the pyrolysis of plastics, particularly the so-called solid plastic waste (SPW), are known and have been described extensively. Without needing to consult numerous documents, reference can be made to the article “Characterization of SPW pyrolysis oils: Products spectra and opportunities” by BA Perez et al., in D. Moscatelli and M. Pelucchi (eds.), “Towards Circular Economy: Closing the Loop with Chemical Recycling of Solid Plastic Waste,” *Advanced Chemical Engineering*, Vol. 60, No. 1, pp. 169-214, 2022. This invention particularly relates to the reprocessing and utilization of liquid pyrolysis products from the pyrolysis of such plastics, which, according to art practice, are hereinafter referred to as plastic pyrolysis oils or simply pyrolysis oils. The invention is not limited to a specific method of obtaining such pyrolysis oils, and the utilization is achieved through steam cracking.

[0003] WO2022 / 063597A1 relates to a method for treating pyrolysis oil from plastics, including optional selective hydrogenation, hydroconversion, separation, fractionation, hydrotreatment, and re-separation. WO2023 / 208636A1 also relates to a method for treating pyrolysis oil from plastics, including hydrotreatment, separation or washing, separation of hydrogen sulfide, and separation of ammonia. Other methods for treating the corresponding pyrolysis oils are also found in US2023 / 029587A1 and WO2021 / 204820A1. US5,985,136A relates to a method for hydrodesulfurizing naphtha.

[0004] Pyrolysis oil from plastic pyrolysis can be further processed with other feedstocks via steam cracking. To date, the most common practice for commercial applications of plastic-based pyrolysis oil is to dilute it with conventional feedstocks such as naphtha, atmospheric gas oil (AGO), unhydrogenated or hydrogenated vacuum gas oil ((H)VGO), and especially other fractions from refining processes.

[0005] By using light or hydrogenated feedstocks, the corresponding pyrolysis oils of lower quality (e.g., in terms of boiling range and impurities) can be made to meet the requirements of conventional cracking feedstocks to a limited extent without posing excessive risks to the unit, especially when at least a limited degree of purification (e.g., adsorption purification) has been carried out.

[0006] However, due to various limitations, only small amounts (typically single-digit percentages) can usually be added to conventional raw materials, which has severely limited application possibilities and dosage. Furthermore, known solutions often prove ineffective from other perspectives.

[0007] Therefore, there is an urgent need for improved methods that can better and more fully utilize steam cracking to convert pyrolysis oil, especially pyrolysis oil derived from plastic pyrolysis. Summary of the Invention

[0008] Against this background, a method and apparatus for producing the product olefin, having the features of the independent claim, are proposed. Examples are the subject of the dependent claims and the description herein.

[0009] This invention and its embodiments are based, in particular, on the unexpected discovery that olefins, or certain olefins, particularly monounsaturated olefins, from pyrolysis oils derived from plastic pyrolysis do not necessarily need to be hydrogenated to alkanes when used for steam cracking. Embodiments of this invention include providing olefins via plastic pyrolysis. Hydrogenation has traditionally been considered a necessary step to ensure the processability of the corresponding compounds during steam cracking. Conventional methods, such as those disclosed in the foregoing literature, particularly require hydrogenation to be performed as completely as possible. However, this has proven to be very complex, especially when processing pyrolysis oils from plastic pyrolysis, because these oils have a very high olefin content compared to, for example, refinery streams. The resulting problems will be described in more detail below.

[0010] This invention is not limited to using pyrolysis oil from plastic pyrolysis, but can also be extended to other pyrolysis oils with a relatively high olefin content, such as pyrolysis oils from waste or biomass pyrolysis.

[0011] As already recognized in the context of this invention, the processing of olefin-containing pyrolysis oils from plastic pyrolysis methods during steam cracking is feasible, particularly because the olefins present therein, especially monounsaturated olefins, have relatively long chains and are therefore more readily cracked to produce the desired target products than olefin-containing fractions, which typically form during steam cracking and tend to have shorter chains. Unexpectedly, a slight tendency to coking was also observed. Furthermore, as discussed below, unexpectedly good yields were obtained. Therefore, aspects of the invention and its embodiments relate to methods and apparatus in which, while compounds containing interfering heteroatoms and possibly polyunsaturated olefins are hydrogenated in the corresponding pyrolysis oil, at least monounsaturated olefins (without heteroatoms) are not hydrogenated.

[0012] For clarity, the olefins contained in the pyrolysis oil are referred to hereinafter as "feed olefins". These include monounsaturated olefin compounds, which, in some embodiments of the invention, are unhydrogenated or only minimally hydrogenated. These feed olefins are generally distinct from the olefins formed during steam cracking, which are hereinafter referred to as "product olefins". One distinction between feed olefins and product olefins is particularly evident in chain length, wherein feed olefins may comprise more than 50% of compounds having five or more carbon atoms, while product olefins may comprise more than 50% of compounds having four or fewer carbon atoms. In particular, however, the weight-average chain length of feed olefins is higher than that of product olefins, wherein the former may in particular be about five, six, seven, eight or higher, while the latter may be about two, three or four. "About" means a value that is close to the specified value after being rounded in the usual manner. Feed olefins may in particular comprise a substantial proportion of α-olefins and / or isoolefins, i.e., more than 50%, 60%, 70%, 80% or 90% relative to the total olefins. However, this is not mandatory.

[0013] Therefore, the present invention and its embodiments propose a different approach from conventional hydrogenation, which aims to convert all feedstock olefins as much as possible; in conventional methods, this is even the goal of hydrogenation.

[0014] The proposed method for producing the product olefins includes: providing pyrolysis oil, using the pyrolysis oil or a portion thereof to provide a hydrogenation feedstock, hydrogenating the hydrogenation feedstock to obtain a hydrogenation product, using the hydrogenation product or a portion thereof to provide a cracking feedstock, and subjecting the cracking feedstock or a portion thereof to steam cracking to obtain the product olefins.

[0015] The hydrogenation feedstock, and the pyrolysis oil that forms the hydrogenation feedstock prior to it, includes alkane compounds, monounsaturated olefin compounds, and other compounds that can be hydrogenated, wherein the other compounds that can be hydrogenated may in particular include polyunsaturated olefin compounds and / or heteroatom compounds.

[0016] The proposed method specifies that hydrogenation is carried out as selective hydrogenation of at least one of other compounds capable of being hydrogenated, and the hydrogenation product, or a portion thereof, used to provide the cracking feedstock is fed to the cracking feedstock without further hydrogenation, thereby being fed into a steam cracking apparatus having one or more cracking furnaces or pyrolyzers, where it undergoes steam cracking. In other words, a certain proportion of monounsaturated olefin compounds arrives at the steam cracker, the proportion being defined by the selectivity of the selective hydrogenation. This proportion is reduced only by the proportion of unintended conversions occurring during the selective hydrogenation process.

[0017] For clarity, it should be noted that in the proposed method, selective hydrogenation is carried out using one or more hydrogenation reactors from which the hydrogenation product is removed. In other words, specifically, the hydrogenation product is not removed from a separation unit and conveyed to a steam cracker. This hydrogenation product may, in particular, have the same compound content as the cracking feedstock, such as alkanes and monounsaturated compounds. Specifically, the hydrogenation product and the cracking feedstock may have the same or substantially the same absolute or relative content of alkanes and monounsaturated olefins.

[0018] As is generally known to those skilled in the art, even in chemical reactions described as "selective"—specifically, hydrogenation in this application—it is impossible to completely avoid the conversion of a certain proportion of non-target compounds in such selective reactions. In this application, this means that a certain proportion of monounsaturated olefin compounds will also be hydrogenated during selective hydrogenation. This particularly likely means that up to 25%, 20%, 15%, or 10% of the monounsaturated olefin compounds in the pyrolysis oil, or a portion of the pyrolysis oil used to provide feedstock for cracking, may be converted during selective hydrogenation.

[0019] In other words, due to the proposed selective hydrogenation, the cracking feedstock will contain a significant proportion of monounsaturated olefins. If the proportion of monounsaturated olefins in the hydrogenation feedstock is X% by weight, mole, or volume, and this proportion is Y% in the hydrogenation product, then if selective hydrogenation also converts some monounsaturated olefins, Y can be less than X. In this case, Y could be, for example, 25, 20, 15, 10, or 5 less than X. If, during selective hydrogenation, polyunsaturated olefins are converted to monounsaturated olefins, Y can also be greater than X, for example, by a maximum of 10 or 5. In this case, the specific value depends on the content of polyunsaturated olefins and the reaction characteristics. It should be understood that during the selective hydrogenation of polyunsaturated olefins, these compounds may also be partially or completely hydrogenated to form the corresponding alkanes; in this case, such compounds will not contribute to the content of the hydrogenation feedstock.

[0020] In selective hydrogenation, it can be specifically specified that during selective hydrogenation, more than 95%, 90%, 80%, 70%, 60%, or 50% of at least one other compound capable of hydrogenation, particularly one or more compounds of the corresponding class, are converted, thus the content of this compound in the hydrogenation product is correspondingly lower than its content in the pyrolysis oil. The above percentages can express molar, volumetric, or weight percentages, or can represent dimensionless quantities. Other compounds capable of hydrogenation can include, in particular, polyunsaturated olefins and heteroatom compounds. Dienes and alkynes can be converted in the same step or in additional upstream steps. As will be explained below, and as unexpectedly discovered in this application, even if only a relatively small proportion of the monounsaturated feedstock olefins in the pyrolysis oil are not hydrogenated, advantages can still be provided, and these advantages increase accordingly with the increase of the unhydrogenated proportion.

[0021] In the terminology used herein, "heteroatom compound" may specifically refer to a compound having one or more heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and chlorine atoms. Different heteroatom compounds having the same heteroatom and / or multiple heteroatom compounds having different heteroatoms may exist. Specifically, alkynes, i.e., alkyne hydrocarbons, are not within the scope of the term "olefin" as used herein. As previously mentioned, embodiments of the invention may also relate to the selective hydrogenation of polyunsaturated olefins or alkynes that are capable of being hydrogenated, although the following description specifically refers to heteroatom compounds, which are also referred to hereinafter as "impurities".

[0022] The terms “plastic pyrolysis oil” or “pyrolysis oil” are used herein in accordance with common usage in the art. Pyrolysis oil produced during the pyrolysis of plastics may overlap with known fractions such as naphtha and atmospheric gas oil in terms of the number of carbon atoms in the compounds present and their boiling points, but may also contain heavier components, such as those typically found at the light end of vacuum gas oil fractions. However, when the term “pyrolysis oil” is used herein, its composition generally does not correspond to, or does not necessarily correspond to, the composition of known pyrolysis oil from a steam cracker. Generally speaking, the pyrolysis oil is a distinctly different mixture. In particular, the pyrolysis oil also includes at least some of the components that, in the case of pyrolysis oil from a steam cracker, are separated into the so-called gasoline fraction (pyrolytic gasoline), as well as compounds heavier than those typically found in pyrolysis oil. However, the overall composition of plastic pyrolysis oil is significantly different, especially in terms of the structure of the compounds it contains (e.g., the ratio of alkanes to aromatics), which cannot be directly determined from the boiling point.

[0023] Therefore, the pyrolysis oil considered here may already contain hydrocarbons with five or six carbon atoms and a boiling range of 30°C to 100°C, but it is not necessary to contain these hydrocarbons, or it may contain only a portion of them. In addition, the pyrolysis oil may contain components with six to twelve carbon atoms and a boiling point between 130°C and 220°C. These components are also not necessary, or only some of these components may be present. In particular, as mentioned above, the boiling point of the contained compounds may be comparable to that commonly found in naphtha; for a definition of such compounds, see, for example, the article entitled "Ethylene" in the aforementioned *Ullmann's Encyclopedia of Industrial Chemistry*. The pyrolysis oil may contain a considerable number of hydrocarbons with twelve or more carbon atoms, wherein the boiling range of these compounds is generally between 210°C and 550°C. These components are also not necessary, or only some of these components may be present. The pyrolysis oil understood here may also contain extremely heavy compounds, as described below. The formation of the hydrogenation feedstock allows for some separation of light and heavy components, but also provides the use of unseparated pyrolysis oil. The pyrolysis oil used in this case differs from that used in steam cracking or other pyrolysis oils, particularly in its relatively high olefin content (feedstock olefins), as described below. Further characterization of the plastics pyrolysis oil can be found in the article by Perez et al., mentioned at the beginning of this text.

[0024] The term "hydrogenation product" here refers to a mixture of components taken from a hydrogenation reactor of the type used in this application, which may contain, in proportion, the amounts of monounsaturated olefins (i.e., residual feedstock olefins) discussed above, similar to the hydrogenation feedstock, i.e., the mixture of components fed into the hydrogenation reactor. In contrast, the content of the aforementioned impurities is correspondingly reduced.

[0025] Methods and apparatus for steam cracking are documented in professional literature, such as in the article entitled "Ethylene" in Ullmann's Encyclopedia of Industrial Chemistry, published online since April 15, 2007, DOI 10.1002 / 14356007.a10_045.pub2. Technical terms in the field of steam cracking used below, such as "cracking furnace," "coil," and "propylene-ethylene ratio," refer specifically to their commonly understood meanings in professional literature.

[0026] As described herein, the present invention and its embodiments can at least partially overcome existing limitations on the usable amount of pyrolysis oil as a cracking feedstock, i.e., no longer limited to low percentages or only as a small amount of blending. Therefore, the present invention and its embodiments can utilize the increasing quantity of the aforementioned type of pyrolysis oil in an improved manner, i.e., achieving unexpected yields and lower coking tendency even without hydrogenation of the feedstock olefins or with a low hydrogenation ratio of the feedstock olefins.

[0027] The present invention and its embodiments successfully address the quality differences that are commonly found between pyrolysis oil and conventional feedstocks for steam cracking, such as naphtha, particularly in terms of composition (especially the content of olefins, dienes and alkynes) and impurities (especially chlorine-containing, nitrogen-containing and oxygen-containing components).

[0028] Conventional methods for hydrogenating pyrolysis oils are not employed in the context of this invention and its embodiments. These methods include classic hydropurification steps known in refining technology, particularly so-called hydrocracking and hydrocracking, where fractionation may occur prior to these steps, and all or part of the fractions in the steam cracker may be processed. Due to the strong hydrogenating effect of the catalyst systems or reaction conditions in such methods, as previously mentioned, the feedstock olefins in pyrolysis oils often undergo complete hydrogenation, and in some cases, even the desired complete hydrogenation. This is accompanied by significant hydrogen consumption (extremely uneconomical) and corresponding heat of reaction. While heat generation can be controlled on a laboratory scale, large-scale applications require extremely complex measures to manage heat generation, which may be impractical in reality. This invention and its embodiments overcome these drawbacks.

[0029] Similar methods are known in patent literature, such as co-processing with conventional refining streams. Compared to these methods, the present invention and its embodiments reduce hydrogen demand and simplify the design of the hydrogenation reactor due to reduced heat generation.

[0030] The aforementioned drawbacks do not occur when applied to conventional hydrotreating and hydrocracking of crude oil-based feedstocks, because these feedstocks typically contain little or no feedstock olefins.

[0031] The conventional steps described above yield hydrogenated pyrolysis oil. After fractionation, this oil's properties are close to those of conventional cracking feedstocks, making it suitable for extensive use as an additive or even as a standalone feedstock for cracking furnaces. Therefore, according to existing technology, a targeted objective is to make the quality of the pyrolysis oil as close as possible to the typical quality of conventional feedstocks, such as typical naphtha. The purpose of the hydrogenation step in known methods is to significantly reduce or completely remove the olefin content of the feedstock (see, for example, WO2016 / 142805A1, WO2016 / 132807A1, WO2021 / 165178A1, WO2022 / 084433A1 and GB2601407A). This invention and its embodiments are based on the finding that this objective is not necessarily required.

[0032] Due to the aforementioned challenges, conventional methods require additional improvements in practice, such as multi-stage hydrogenation and dilution, for example, using conventional feedstocks or recycling the hydrogenated stream, thus significantly increasing the complexity of the corresponding equipment. In contrast, the present invention and its embodiments can be implemented with a particularly simple apparatus. Furthermore, the method allows each furnace to process higher throughput pyrolysis oil.

[0033] Traditionally, these feedstocks require extremely low olefin content, typically below 1%. However, in the embodiments of this invention, this requirement is not necessary, posing an additional challenge to the performance of the unit, especially since other impurities in the pyrolysis oil must also be reduced to the required specifications. The starting point is that olefin-containing feedstocks are generally considered unsuitable for pyrolysis, both in terms of cracking yield and the risk of coking or contamination within the unit. However, in the context of this invention and its embodiments, it has been found that such feedstocks, despite typically having higher boiling points than naphtha (which are generally associated with yield reductions, as previously mentioned and discussed below), can still be advantageously converted.

[0034] As previously mentioned, the complete hydrogenation of feedstock olefins in pyrolysis oils, due to their double-digit percentage content (e.g., 20% to 80%, or 30% to 60% in embodiments of the invention), is accompanied by high heat of reaction. This increases the complexity of hydrogenation (e.g., multi-stage, dilution, and / or recycling) and shortens the lifespan and reduces the performance of the hydrogenation catalyst due to insufficient temperature control and excessively high (peak) temperatures. In this application, these disadvantages are avoided. Simultaneously, the typically extremely high hydrogen consumption in hydrogenation is avoided, as hydrogen can be supplied by the cracker itself. Especially in devices particularly suitable for the use of pyrolysis oils, known as liquid crackers, hydrogen supply is limited. Therefore, in embodiments of the invention, there is no need for an additional (external) supply of hydrogen to the corresponding device.

[0035] In embodiments of the present invention, the cost of providing the above-described method steps and the operation including the supply of hydrogen is significantly reduced, the supply of hydrogen typically representing a significant cost factor.

[0036] In summary, aspects of the present invention include a treatment and purification scheme for pyrolysis oil as feedstock for steam crackers. This scheme reduces hydrogen consumption by minimizing the hydrogenation of feedstock olefins during the hydrogenation purification stage, thereby achieving hydrogen balance throughout the unit, including the cracker. This avoids problems such as reaction heat and catalyst stress during the hydrogenation stage, and also avoids potentially more complex processes, such as requiring multiple hydrogenation stages. It also avoids feedstock dilution and / or recycling of the processed material stream. With appropriate adjustments to furnace conditions or furnace design during steam cracking, desired results, such as high yields of product olefins, can be obtained using olefin-containing batches. Therefore, embodiments of the present invention help provide an economically feasible solution for using such feedstocks while accommodating purification requirements for pyrolysis oils of varying qualities.

[0037] In embodiments of the invention, hydrogenation is carried out, in particular, using one or more catalysts comprising one or more transition elements. Specifically, Group VIII and Group VI elements, and combinations thereof, are suitable as catalyst materials. Heteroatom-containing compounds can be, in particular, compounds containing chlorine, nitrogen, oxygen, and / or sulfur. Selective hydrogenation is used to selectively remove the corresponding compounds from the pyrolysis oil when the monounsaturated olefin component does not undergo hydrogenation or only undergoes slight hydrogenation. However, as previously mentioned, hydrogenation of dienes and alkynes can be carried out in this step or in separate steps. The types of catalysts mentioned are known in the processing of other streams in the refining industry, such as gasoline obtained from catalytic cracking (see, for example, US5,853,570A, US5,906,730A, US5,985,136A, and US6,013,598A). This makes it possible to reduce heteroatoms while retaining the monounsaturated olefins used. To date, there has been no application of such catalysts for the pretreatment of pyrolysis oil as a cracking feedstock. The cited literature differs fundamentally from the application described in this paper in several aspects (e.g., feedstock type: cracked gasoline; purpose: octane number maintenance; application: gasoline; impurities: sulfur).

[0038] Therefore, one or more compounds that can be hydrogenated are heteroatom compounds or include heteroatom compounds, wherein selective hydrogenation includes selective hydrogenation of one or more heteroatom compounds.

[0039] In embodiments of the invention, one heteroatom compound may be a chlorinated compound, or multiple heteroatom compounds may include chlorinated compounds. Selective hydrogenation may include selective hydrogenation of the chlorinated compound or at least the chlorinated compound. This design is particularly useful for addressing the particularly adverse effects of chlorinated impurities on downstream process steps. In other words, multiple heteroatom compounds comprising one or more chlorinated compounds may be present, and selective hydrogenation may be specifically designed to cause these one or more chlorinated compounds to react. When multiple heteroatom compounds are present where the first compound or group of compounds is chlorinated while the second compound or group of compounds may not be chlorinated, the corresponding selective hydrogenation can therefore be specifically designed to convert at least one compound in the first compound or group of compounds to a greater extent than at least one compound in the second compound or group of compounds. This is particularly achievable because chlorinated compounds are relatively easy to hydrogenate.

[0040] In embodiments of the invention, one or more catalysts may include nickel, molybdenum, and / or cobalt, particularly supported on a suitable support such as alumina. Therefore, known and well-characterized catalysts or catalyst systems can be used.

[0041] In embodiments of the invention, hydrotreating can be carried out at temperature levels of 150°C to 400°C, particularly 200°C to 350°C, and / or at pressure levels of 5 bar to 70 bar, particularly 10 bar to 40 bar. These conditions are generally milder than those used in conventional hydrocracking and hydrotreating / hydrodesulfurization of crude oil fractions, preferably 50 bar to 200 bar and 250°C to 450°C, thus providing advantages, for example, in terms of cooling and material selection.

[0042] In embodiments of the invention, hydrogenation can be carried out in a single-stage or multi-stage fixed-bed unit; however, other designs such as moving beds are also feasible, meaning the concept is not limited to a particular reactor design. A fixed-bed unit may include one or more stages; preferably, only one stage is used, and this is particularly achievable through the concepts of the invention and its embodiments. Similarly, this makes it possible to implement a particularly simple unit.

[0043] Furthermore, in embodiments of the invention, selective hydrogenation can be performed on polyunsaturated compounds such as dienes and / or alkynes. Particular advantages arise in embodiments where the diene and alkyne content is reduced to less than 1.0%, less than 0.5%, or less than 0.1%, wherein primarily complete hydrogenation is also possible. Correspondingly lower diene and alkyne contents allow for favorable conversion during steam cracking due to reduced coking tendency and shorter operating cycles.

[0044] In embodiments of the invention, a portion of the hydrogenation product may be recycled upstream of the hydrogenation process. In other words, a recirculating gas stream may be provided to the gaseous portion of the outlet stream from the hydrogenation reactor. Hydrogen or recirculating gas may be fed at one or more points. The recirculating gas recovery may optionally include a stage for gas purification.

[0045] In embodiments of the invention, providing the hydrogenation feedstock may include treatment to remove (further) impurities. This can be achieved by selectively removing impurities, particularly organic and inorganic salts, from the pyrolysis oil using suitable methods (filtration, washing, extraction, and adsorption), thereby removing alkali metals, alkaline earth metals, or other metals, as well as trace components containing chlorine, nitrogen, oxygen, and silicon. This can extend the lifespan of the hydrogenation catalyst used in subsequent process steps or reduce its regeneration requirements.

[0046] In a further embodiment, the provision of the hydrotreating or pyrolysis feedstock may include the removal of high-boiling-point components (“high-boiling-point substances”). Separation of heavy components from the pyrolysis oil, particularly by distillation, is achieved through purification steps located upstream or downstream of the hydrotreating process. One possible embodiment particularly includes separating the corresponding high-boiling-point substances to less than 10%, more particularly less than 5%, specifically removing asphaltenes and metals. This is particularly advantageous upstream of hydrotreating because it can, for example, reduce the metal content or proportion of inorganic impurities in the oil, thereby improving the functionality and / or service life of the hydrotreating stage. Furthermore, multiple fractions of the feedstock can be produced, and each fraction can be treated with suitable hydrotreating conditions as needed. Another embodiment includes separation by distillation after hydrotreating, wherein in each case, components with boiling points above 300°C, particularly above 350°C, such as those above 380°C, 390°C, or 400°C, are removed to an appropriate and technically reasonable extent to facilitate evaporation of the pyrolysis feedstock in the furnace. Fractionating the fractions into multiple fractions for different purposes (e.g., in different cracking furnaces) is also a possible variation.

[0047] In particular, in embodiments of the invention, compared to conventional methods, little or no recycling of the post-hydrogenation feedstock occurs upstream of the hydrotreating reactor. In embodiments of the proposed method, more than 10% of the pyrolysis feedstock can be provided using components of the pyrolysis oil and / or components formed from the pyrolysis oil during hydrotreating.

[0048] In this method, a pyrolysis furnace using one or more flame-heated and / or at least partially electrically heated furnaces is employed for steam pyrolysis. Therefore, the pyrolysis furnace can be equipped with direct heating like a conventional furnace, or with a different heating concept, such as an electrically heated furnace. In the case of an electrically heated furnace, an additional advantage arises: preheating can be performed more specifically and decoupled from the classic waste heat concept, which is beneficial for reducing fouling and improving operability for key feedstocks such as pyrolysis oils. This is also advantageous for feedstock streams that have not been hydrogenated but have undergone pretreatment. Embodiments of the invention may include optimized / adapted systems for preheating and evaporation within the pyrolysis furnace, and pyrolysis conditions adapted to obtain optimal product yields or prevent fouling.

[0049] As previously mentioned, hydrogen-containing fractions can be separated from the component mixture obtained during steam cracking and recycled to meet the hydrogen demand for hydrogenation. Therefore, the hydrogen supply for the hydrogenation unit can be integrated into the hydrogen system of the cracker, for example, downstream of demethanization and / or pressure swing adsorption. Utilizing a lower-grade hydrogen stream from the cracker that already contains impurities or other hydrocarbon proportions (especially methane) may also be advantageous.

[0050] Providing pyrolysis feedstock from hydrogenation products may also include processing; in particular, the hydrogenation products or a portion thereof used to provide pyrolysis feedstock may undergo component removal. These components may also include components released during hydrogenation, such as hydrochloric acid, ammonia, hydrogen cyanide, hydrogen sulfide, water, carbon oxides and other gases, hydrocarbon fragments, etc. In particular, volatile components and / or residual hydrogen may be separated by stripping.

[0051] As mentioned several times above, pyrolysis oil is primarily provided through the pyrolysis of plastics, but other pyrolysis methods and feedstocks, such as biomass, are also feasible. Relevant technical literature can be consulted for specific methods.

[0052] The proposed apparatus for producing the product olefins is designed as follows: pyrolysis oil is used as feedstock; a hydrogenation feedstock, or a portion thereof, is provided using the pyrolysis oil; the hydrogenation feedstock is hydrogenated to obtain a hydrogenated product; the hydrogenated product, or a portion thereof, is used to provide a cracking feedstock; and the cracking feedstock, or a portion thereof, is treated by steam cracking to obtain the product olefins. The hydrogenation feedstock includes alkane compounds, monounsaturated olefin compounds, and other compounds capable of hydrogenation. The apparatus is designed such that hydrogenation is carried out as selective hydrogenation of at least one of the other compounds capable of hydrogenation, and the hydrogenated product, or a portion thereof, used to provide the cracking feedstock is fed to the cracking feedstock without further hydrogenation.

[0053] For further features and advantages of the corresponding apparatus and its embodiments, reference is made hereto to the foregoing description of the methods and embodiments of the present invention, as they are equally applicable herein.

[0054] This also applies to an apparatus according to an embodiment of the present invention, which is used to perform the method described in any embodiment of the present invention.

[0055] The advantages of the method and apparatus according to the invention, and corresponding embodiments, have been described above and are summarized again below. These advantages include: simple design of the hydrogenation reactor due to low cooling requirements; multi-stage design is not absolutely necessary, while a single-stage design represents a preferred embodiment of the invention. Furthermore, this results in low catalyst stress, leading to better performance and longer service life. The hydrogenated stream requires no or very little recycling, thus reducing equipment and energy consumption. Dilution with conventional feedstocks is unnecessary, as such feedstocks only add unnecessary volume and can potentially trigger side reactions. Hydrogen demand can be balanced throughout the unit, eliminating the need for additional hydrogen production facilities and enabling the entire complex to achieve self-sufficiency.

[0056] Overall, the recovery of large quantities of pyrolysis oil is beneficial to the circular economy, helps prevent environmental pollution and waste disposal / recycling, and contributes to reducing carbon dioxide emissions and saving energy (compared to the use of conventional fossil feedstocks).

[0057] The basic concepts or embodiments of the present invention can be supplemented with further embodiments involving additional purification steps, depending on the requirements / properties of the pyrolysis oil. Filtration, absorption / washing, extraction methods, and physical and chemical adsorption / selective adsorption are particularly relevant. Fractionation is also an option, especially for separating heavy components (separating the high-boiling end to remove asphaltenes and metals, typically reducing their content in the corresponding pyrolysis oil fraction to below 10% or 5%, or separating components with boiling points above 300°C, especially above 350°C, such as those above 380°C, 390°C, or 400°C, by distillation after hydrotreating to facilitate evaporation of the pyrolysis feedstock in the furnace). These steps can be used alone or in combination, either upstream or downstream of the hydrotreating unit.

[0058] Other specific scenarios include: In the first example, pyrolysis is performed first, followed by distillation, then washing with water to reduce inorganic salts and water-soluble polar compounds, particularly chlorine, then drying, directional hydrogenation, and further purification, for example, by adsorption. A second scenario may include: pyrolysis followed by distillation to remove the heavy end, then preliminary adsorption purification, for example, for chlorine. The latter can then be followed by directional hydrogenation and further purification, for example, by adsorption or distillation.

[0059] Alternatively, hydrogenation can be carried out outside the cracking environment, but at the pyrolysis oil generator or a centralized location, where hydrogenation can be performed on various pyrolysis oils from different sources. Here, the quality of the treated oil also has a positive impact on transport performance, and especially on storage performance before further use as a cracking feedstock.

[0060] In addition to pyrolysis oil, other feedstocks, such as bio-based pyrolysis oil, can also be processed accordingly for use as pyrolysis feedstocks. Utilities and waste streams (wastewater, waste gas) can be integrated with the pyrolysis unit, for example, by recirculating the waste gas stream to a waste gas purification system or flare system, or to a heating gas network.

[0061] Alternatively, additional hydrogen demand can be met by converting the methane or methane-rich fraction of the cracker into hydrogen and carbon dioxide (with optional supplementation by carbon capture). Attached Figure Description

[0062] Embodiments of the present invention will be described below by way of example only and with reference to the accompanying drawings, wherein Figure 1 A method according to an embodiment of the present invention is shown. Figure 2 Several aspects of a method according to embodiments of the present invention are illustrated. Figure 3Several aspects of a method according to embodiments of the present invention are illustrated. Specific Implementation The embodiments described below are only intended to help the reader understand the claimed and previously discussed features. These embodiments are merely representative examples and should not be considered as an exhaustive and / or limiting description of the features of the invention. It goes without saying that the advantages, embodiments, examples, functions, features, structures, and / or other aspects described above and below should not be considered as limiting the scope of the invention as defined by the claims or its equivalents, and other embodiments and modifications may be made without departing from the scope of the claimed invention.

[0064] Different embodiments of the invention may include, have, be constituted by, or substantially consist of further suitable combinations of the described elements, components, features, portions, steps, means, etc., even if such combinations are not specifically described herein. Furthermore, this disclosure may include other inventions not currently claimed but potentially claimable in the future, particularly when included within the scope of the independent claims.

[0065] The descriptions of apparatuses, devices, arrangements, systems, etc., according to embodiments of the present invention are also applicable to procedures, processes, methods, etc., according to embodiments of the present invention, and vice versa. Components, process steps, etc., that are identical, have the same effect, correspond in function, have the same structure, or are structurally similar, may be represented by the same reference numerals.

[0066] exist Figure 1 In this paper, the method according to embodiments of the present invention is shown in a simplified schematic flowchart and is generally designated as 100. This method 100 is described using plastic pyrolysis. As previously stated, the method according to embodiments of the present invention is also applicable to other pyrolytic raw materials.

[0067] In method 100, a pyrolysis feedstock 1 containing or composed of plastic is subjected to pyrolysis 110, in this case, plastic pyrolysis. Any number of separation steps can be assigned to the pyrolysis, thereby enabling the production of pyrolysis oil 2 from the pyrolysis (and separation steps).

[0068] In the example shown, the pyrolysis oil 2 undergoes one or more optional treatment steps 120, which have been explained above. These steps may include, in particular, adsorption or washing. In this way, treated pyrolysis oil 3 is obtained. Optionally, after the treated pyrolysis oil 3 is fed with a circulating hydrogen stream 4, or, particularly in the absence of treatment step 120, after the pyrolysis oil 2 is fed with, the treated pyrolysis oil 3, or the pyrolysis oil 2 in the absence of treatment step 120, may be hydrogenated as a hydrogenation feedstock 5 using a suitable catalyst in a selective hydrogenation manner as described above.

[0069] In hydrogenation 130, hydrogenation product 6 is obtained, which is a mixture of alkanes and olefins (feed olefins). This mixture may also contain other components such as aromatics, but due to the specific nature of hydrogenation, the components with heteroatoms are reduced or removed compared to hydrogenation feedstock 5. The monounsaturated olefin compounds (feed olefins) fed into hydrogenation feedstock 5 in hydrogenation 130 are converted to a very limited extent at most.

[0070] Hydrogen can be separated from hydrogenation product 6 by a separation device not shown separately and recycled to the circulating hydrogen stream. The liquid hydrogenation product is processed as steam cracking feedstock 7 via steam cracking 140. Any other desired feedstock can be used. The separation device associated with steam cracking 140 and some of the products obtained herein are not shown separately. In any case, one or more products, such as olefins 8, can be obtained in this manner. Hydrogen or light gas fractions can be recycled in the form of feed stream 9.

[0071] Figure 2 and Figure 3 The results of comparative experiments using naphtha and olefin-containing pyrolysis oil are shown. The results for naphtha are represented by the symbol 'x', the results for the first pyrolysis oil are represented by hollow rhombuses, and the results for the second pyrolysis oil are represented by solid rhombuses. The results of two parallel experiments are also shown. The main difference between the first and second pyrolysis oils lies in the different raw materials used for pyrolysis, particularly the ratio of polyethylene to polypropylene.

[0072] Figure 2 The graph shows the temperature at the end of the pyrolysis tube (vertical axis, in °C) versus the propylene-ethylene ratio (horizontal axis, in kg / kg). Figure 3 The graph shows the ethylene yield (in wt.%) on the vertical axis and the propylene-ethylene ratio (in kg / kg) on ​​the horizontal axis.

[0073] from Figure 2 and Figure 3 It can be seen that pyrolysis oil with high olefin content and appropriate structure, especially pyrolysis oil with suitable chain length, can be converted with good yield, thus achieving a cracking operation that is both technically and economically satisfactory.

[0074] Contrary to existing technologies, the results obtained in the context of this application unexpectedly show that the influence of double bonds in the feedstock molecule generally decreases with increasing chain length, because the hydrogen-to-carbon ratio and the content of dienes and alkynes play a major role here. This also applies to the tendency to coke.

Claims

1. A method (100) for producing product olefin (8), wherein, A pyrolysis oil (2) is provided, wherein a hydrogenation feedstock (5) is provided using the pyrolysis oil (2) or a portion thereof, wherein the hydrogenation feedstock (5) is hydrogenated (130) to obtain a hydrogenation product (6), wherein a cracking feedstock (7) is provided using the hydrogenation product (6) or a portion thereof, and wherein the cracking feedstock (7) or a portion thereof is subjected to steam cracking (140) to obtain the product olefin (8), wherein the hydrogenation feedstock (5) has alkane compounds, monounsaturated olefin compounds, and other compounds that can be hydrogenated, wherein the hydrogenation (130) is performed as selective hydrogenation of at least one of the other compounds that can be hydrogenated, and wherein the hydrogenation product (6) or a portion thereof used to provide the cracking feedstock (7) is fed to the cracking feedstock (7) without further hydrogenation.

2. The method (100) according to claim 1, wherein, The hydrogenation (130) is carried out using one or more catalysts having one or more transition elements.

3. The method (100) according to claim 2, wherein, One or more of the additional compounds that can be hydrogenated are heteroatom compounds or include heteroatom compounds, wherein the selective hydrogenation includes selective hydrogenation of one or more of the heteroatom compounds.

4. The method (100) according to claim 2 or 3, wherein, The heteroatom compound is a chlorine-containing compound, or the plurality of heteroatom compounds include chlorine-containing compounds, wherein the selective hydrogenation includes selective hydrogenation of the chlorine-containing compound.

5. The method (100) according to any one of claims 2 to 4, wherein, The one or more catalysts include one or more elements from Group VIII and / or Group VI as active components.

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

7. The method (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 unit.

8. The method (100) according to any one of the preceding claims, wherein, Additional selective hydrogenation is performed on polyunsaturated compounds and / or alkynes in the same catalyst bed or in an upstream catalyst bed.

9. The method (100) according to any one of the preceding claims, wherein, 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, Providing the hydrogenation feedstock (5) includes removing impurities.

11. The method (100) according to any one of the preceding claims, wherein, More than 10% of the components of the pyrolysis oil and / or the components formed from the pyrolysis oil in the hydrogenation (130) are used to provide the cracking feedstock (7).

12. The method (100) according to any one of the preceding claims, wherein, The steam pyrolysis (140) is performed using one or more flame-heated and / or at least partially electrically heated pyrolysis furnaces.

13. The method (100) according to any one of the preceding claims, wherein, A hydrogen-containing fraction is separated from the component mixture obtained by the steam cracking (140) and the hydrogen-containing fraction is recycled to the hydrogenation (130).

14. The method (100) according to any one of the preceding claims, wherein, Providing the cracking feedstock (7) includes removing components from the hydrogenation product or a portion thereof used to provide the cracking feedstock (7).

15. An apparatus for producing product olefin (8), the apparatus being designed to: use pyrolysis oil (2) as feedstock, provide hydrogenation feedstock (5) using the pyrolysis oil (2) or a portion thereof, hydrogenate the hydrogenation feedstock (5) (130) to obtain hydrogenated product (6), provide cracking feedstock (7) using the hydrogenated product (6) or a portion thereof, and treat the cracking feedstock (7) or a portion thereof by steam cracking (140) to obtain product olefin (8), wherein, The hydrogenation feedstock (5) has alkane compounds, monounsaturated olefin compounds, and other compounds that can be hydrogenated, and wherein the apparatus is designed to perform the hydrogenation (130) as selective hydrogenation of at least one of the other compounds that can be hydrogenated, and to deliver the hydrogenation product (6) or a portion of the hydrogenation product (6) to the pyrolysis feedstock (7) without further hydrogenation.

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