Method and installation for the oxidative dehydrogenation of ethane

Abstract

The invention relates to a method (100, 200, 300) for the oxidative dehydrogenation of ethane, wherein a first component mixture comprising steam, ethane, and oxygen is subjected to one or more reaction steps (10) in order to obtain a second component mixture comprising ethane, ethene, oxygen, ethyne, acetic acid, water, carbon monoxide, and carbon dioxide; the one or more reaction steps (10) involve(s) the oxidative dehydrogenation of ethane; the second component mixture or a part thereof is used to form a third component mixture comprising ethane, ethene, ethyne, oxygen, carbon monoxide, and carbon dioxide; the third component mixture is subjected to a raw gas treatment (50); and oxygen and ethyne in the third component mixture are reacted during the raw gas treatment (50). According to the invention, the raw gas treatment (50) is advantageously carried out using one or more fixed-bed reactors, the content of oxygen and carbon monoxide in the third component mixture is adjusted in that one or more recycled fourth component mixtures and / or oxygen is / are used in the formation of the third component mixture, and in the third component mixture, the volume fraction of oxygen corresponds to 3 times the volume fraction of ethyne and / or the molar reaction stoichiometric ratio of carbon monoxide to oxygen is at least 0.5. The invention also relates to a corresponding installation.

Description

[0001] December 9, 2025 - Dr. Schwarz

[0002] 1

[0003] Description

[0004] Process and plant for the oxidative dehydrogenation of ethane

[0005] The present disclosure relates to a process and a plant for the oxidative dehydrogenation of ethane.

[0006] background

[0007] The oxidative dehydrogenation (ODH) of alkanes with two to four carbon atoms is a well-known process. In oxidative dehydrogenation, these alkanes react with oxygen to form, among other things, the respective alkenes and water. Byproducts such as carbon monoxide, carbon dioxide, alkynes, and higher hydrocarbons can be formed, and a residue of unreacted alkanes and oxygen may remain in the product mixture. Typically, the corresponding (saturated and possibly unsaturated) carboxylic acid associated with the alkane used is also formed as a coproduct. Alkynes and oxygen, in particular, must be removed from the product mixture for the reasons explained below.

[0008] The present disclosure relates to the oxidative dehydrogenation of ethane to ethene, also known as ODHE, although in some places reference should be made more generally to the oxidative dehydrogenation without specifically mentioning ethane as the starting material.

[0009] It is important to improve relevant processes, particularly with regard to the removal of unwanted by-products.

[0010] Overview

[0011] Against this background, a process and a plant for the oxidative dehydrogenation of ethane with the features of the independent claims are proposed. Embodiments are the subject of the dependent claims and the following description. 09.12.2025 - Dr. Schwarz

[0012] 2

[0013] The proposed process for the oxidative dehydrogenation of ethane comprises subjecting a first component mixture to one or more conversion steps to obtain a second component mixture, wherein the one or more conversion steps in the proposed process comprise the oxidative dehydrogenation of ethane.

[0014] In the proposed process, the second component mixture, or a portion thereof, is used to form a third component mixture, which is then subjected to a raw gas treatment. During this treatment, oxygen and ethyne in the third component mixture are partially or substantially completely reacted and thereby removed.

[0015] The proposed method involves raw gas treatment using one or more fixed-bed reactors, particularly those operated adiabatically, and adjusting the oxygen and / or carbon monoxide and / or acetylene content in the third-component mixture by using one or more recycled fourth-component mixtures and / or oxygen in the formation of the third-component mixture. Adjusting the content of these components typically also changes their ratios to one another, resulting in advantageous oxygen-to-acetylene and / or carbon monoxide-to-oxygen ratios for raw gas treatment operation, as detailed below.

[0016] As detailed below, the proposed method and its embodiments enable particularly advantageous control of the reaction conditions in raw gas treatment, especially the reaction temperature and / or the temperature rise, and thereby further, in particular, a reduction in the loss of valuable products and the formation of undesirable byproducts such as higher hydrocarbons. The proposed method and its embodiments comprise a control concept that overcomes a number of limitations of known methods and enables particularly effective and efficient operation of raw gas treatment. (December 9, 2025 - Dr. Schwarz)

[0017] 3

[0018] enabling very extensive or essentially complete removal of unwanted components of the type described.

[0019] In the proposed process and its embodiments, the first component mixture comprises, in particular, vapor, ethane, and oxygen. The second component mixture comprises, in particular, a portion of the ethane from the first component mixture that was not reacted in one or more reaction steps, as well as ethene, ethyne, oxygen, carbon monoxide, and carbon dioxide. The third component mixture comprises at least a portion of the ethane, ethene, and ethyne, as well as the oxygen, carbon monoxide, and carbon dioxide from the second component mixture. The second component mixture is, in particular, a product mixture of the oxidative dehydrogenation, which also includes the coupling products or byproducts water and acetic acid formed in the oxidative dehydrogenation. The formation of a third component mixture using the second component mixture or a portion thereof occurs by condensation of water and acetic acid, or...This includes the third component mixture. Therefore, compared to the second component mixture, the third component mixture is depleted of water and acetic acid, or essentially free of these substances. Thus, the term "depleted" also includes depletion to zero.

[0020] In the proposed process, the second and third component mixtures comprise, in particular, mainly ethene and ethyne as product and by-product, but this does not exclude the presence of higher alkanes, alkenes and alkynes, since such compounds can also be formed as by-products.

[0021] The proposed process and its embodiments may provide for one or more partial streams of one or more material streams formed in or downstream of the raw gas treatment to be used as one or more fourth component mixtures. A material stream formed "in the raw gas treatment" may be a material stream flowing from a reactor stage (especially an adiabatic one) of a multi-stage raw gas treatment to a downstream reactor stage (also especially an adiabatic one).

[0022] Downstream of the raw gas treatment, material streams suitable for the aforementioned purpose can be any processed, compressed, separated, or otherwise formed material streams. The selection of such material streams can be determined by Dr. Schwarz (December 9, 2025).

[0023] 4

[0024] in particular based on the levels of certain components, for example carbon monoxide, whereby, for example, an adjustment of the level of oxygen and / or carbon monoxide or a ratio of these components in relation to each other or to the ethyne in the third component mixture can be made particularly advantageously.

[0025] In the proposed method and its embodiments, one or more fourth component mixtures can be recycled in a total quantity that is less than 10, 5, 3, or 1 times the quantity of a portion of the third component mixture not formed by the one or more fourth component mixtures. The use of such comparatively small recycling quantities makes it possible, in particular, to continue using existing equipment without expansion or to dimension the necessary equipment accordingly. These small recycling quantities can be used especially when the corresponding fourth component mixtures have sufficient concentrations of the components required to adjust the oxygen and / or carbon monoxide content.

[0026] In the proposed method and its embodiments, the fourth component mixture, or at least one of the several fourth component mixtures, can be compressed together with, or separately from, the second component mixture or the portion thereof used to form the third component mixture. Since the raw gas treatment is advantageously carried out at a higher pressure level than downstream steps, appropriate compression can be provided in such a case. Depending on the pressure conditions upstream of the raw gas treatment, compression of the second component mixture, or the portion thereof used to provide the third component mixture, may also be necessary. In this case, the aforementioned joint compression can be performed. If not, the aforementioned separate compression in the recirculation circuit by a so-called recirculation compressor can also be advantageous.

[0027] In the proposed process and its embodiments, the fourth component mixture, or at least one of the several fourth component mixtures, can be formed using a light gas fraction. 09.12.2025 - Dr. Schwarz

[0028] 5

[0029] This light gas fraction is provided using a demethanization step carried out downstream of the raw gas treatment. It comprises methane and compounds with lower boiling points than methane, including, in particular, carbon monoxide. This light gas fraction is therefore particularly suitable for adjusting the carbon monoxide content of the third component mixture, and thus indirectly also the oxygen content, or more specifically, the carbon monoxide to oxygen ratio and the aforementioned ratios. Other recirculation streams can also be used alongside or as an alternative to this light gas fraction.These are in particular a material stream diverted downstream of the raw gas treatment or downstream of an adiabatic fixed-bed reactor associated with the raw gas treatment, a material stream diverted downstream of a carbon dioxide removal, a material stream diverted downstream of a dryer, a material stream diverted downstream of a deethanizer, or an eth fraction stream from an ethane recycling of a C2 splitter or from a side draw-off of a C2 splitter.

[0030] In the proposed process and its embodiments, oxygen can be adjustable and metered at suitable points during the formation of the third component mixture, either as an alternative or in addition to the aforementioned recirculation of one or more fourth component mixtures. This allows for particularly advantageous and targeted control of the oxygen content, since typically no oxygen is present downstream of the raw gas treatment and therefore cannot be supplied via corresponding recirculation streams.

[0031] The proposed method and its embodiments may provide for the adjustment of one or more quantities of the fourth component mixture or of the oxygen used in the formation of the third component mixture based on a measurement of the concentration of oxygen, carbon monoxide, and / or acetylene upstream of the raw gas treatment and / or based on a measurement of an adiabatic temperature rise in the raw gas treatment. In this way, the conditions present in the raw gas treatment can advantageously be maintained at the desired values ​​or within the desired ranges. 09.12.2025 - Dr. Schwarz

[0032] 6

[0033] The proposed method and its embodiments may provide for the fourth component mixture, or at least one of the several fourth component mixtures, the third component mixture, and / or at least one further component mixture to be temperature-controlled downstream of the raw gas treatment using one or more heat exchangers. In this way, targeted temperature adjustment can be achieved.

[0034] In the proposed process and its embodiments, the oxygen and carbon monoxide content in the third component mixture can be adjusted such that the volume fraction of oxygen is at least 3, 5, 10, 20, or 25 times the volume fraction of ethyne. The ratio of carbon monoxide to oxygen (defined as the molar stoichiometric ratio of one molecule of carbon monoxide to one atom of oxygen) can be at least 0.5, at least 0.7, at least 0.9, at least 1.1, or at least 1.25, and at most 3.2 or at most 3.0. If a regular molecule-based ratio of one molecule of carbon monoxide to one molecule of oxygen is used instead of the molar stoichiometric ratio, the resulting values ​​are doubled.

[0035] The proposed method and its embodiments may further provide for the third component mixture to be fed into the raw gas treatment at a minimum temperature of 160, 180, 200, or 230 °C, where this is the start-of-run (SOR) temperature. A maximum temperature in the raw gas treatment may be, in particular, 370, 360, or 350 °C, and / or the raw gas treatment may be operated by the proposed measures in such a way that a temperature increase in the raw gas treatment of 40 to 150, 60 to 140, or 70 to 120 K occurs.

[0036] The proposed method and its embodiments may also provide for the raw gas treatment to take place at an absolute pressure of 5 to 50 bar, 15 to 40 bar, 20 to 35 bar or 25 to 35 bar and / or with an hourly gas space velocity of 1,000 to 15,000, 2,000 to 12,000 or 4,000 to 10,000 h′. 1is operated. 09.12.2025 - Dr. Schwarz

[0037] 7

[0038] Finally, the proposed method and its embodiments may provide that the third component mixture contains 25 to 80 vol%, 30 to 70 vol%, or 40 to 60 vol% ethene and / or that the raw gas treatment is carried out such that the maximum ethene loss during raw gas treatment is less than 2%, less than 1.5%, less than 1%, or less than 0.5%. In particular, the raw gas treatment may be carried out such that the target ethyne content is below 1,000, 500, or 250 vol. ppp (parts per billion by volume) ethyne, especially 300 vol. ppb ethyne, and the oxygen content is below 100, 50, 20, or 10 vol. ppm (parts per million by volume), especially 10 vol. ppm.

[0039] The aforementioned levels of oxygen and carbon monoxide, as well as the other levels and parameters mentioned, enable the realization of particularly advantageous conditions in raw gas treatment with particularly low losses of valuable products and low formation of by-products.

[0040] In the proposed method and its embodiments, an oxygen and / or ethyne measurement can be carried out at an outlet of the raw gas treatment and, on this basis, a quantity of one or at least one of the several recycled fourth component mixtures can be adjusted.

[0041] In the proposed process and its embodiments, the raw gas treatment can be carried out using a catalyst containing at least one of the elements copper, manganese and ruthenium.

[0042] The corresponding catalysts are particularly well characterized and allow for advantageous influence in the manner mentioned.

[0043] The proposed plant for the oxidative dehydrogenation of ethane is designed to subject a first component mixture to one or more reaction steps, yielding a second component mixture. The one or more reaction steps comprise the oxidative dehydrogenation of ethane. The plant is further designed to use the second component mixture, or a portion thereof, to form a third component mixture, to subject the third component mixture to raw gas treatment, and, during the raw gas treatment, to react oxygen and ethyne in the third component mixture. 09.12.2025 - Dr. Schwarz

[0044] 8

[0045] The proposed plant provides one or more fixed-bed reactors designed for adiabatic operation for raw gas treatment, and provides means designed to adjust the oxygen and carbon monoxide content in the third component mixture by using one or more recycled fourth component mixtures and / or oxygen in the formation of the third component mixture.

[0046] Advantages and features described regarding the proposed process and its configurations also apply to the proposed plant, and vice versa. These are therefore described only once, and reference can be made to the respective explanations.

[0047] Drawings

[0048] Aspects proposed within the scope of this disclosure are explained in more detail with reference to the accompanying drawing. This drawing shows

[0049] Figure 1 shows a process for the oxidative dehydrogenation of ethane, which can form the basis of the embodiments proposed here;

[0050] Figure 2 shows an adiabatic temperature increase as a function of the oxygen content at the inlet of a raw gas treatment;

[0051] Figure 3 Oxygen and ethicone conversions as a function of temperature at the inlet of a raw gas treatment;

[0052] Figures 4a and 4b show ethene losses and the formation of by-products as a function of temperature at the inlet of a raw gas treatment;

[0053] Figure 5 shows a partial view of a proposed design; and

[0054] Figure 6 shows a partial view of a proposed design. 09.12.2025 - Dr. Schwarz

[0055] 9

[0056] Designs

[0057] The embodiments described below are provided solely to assist the reader in understanding the claimed and previously explained features. They represent only representative examples and are not intended to be considered exhaustive or limiting with regard to the features of the invention. It is understood that the advantages, embodiments, functions, features, structures, and / or other aspects described above and below are not to be considered limitations of equivalents to the claims, and that other embodiments may be used and modifications made without deviating from the scope of the claimed invention.

[0058] Different embodiments of the invention may include, feature, consist of, or essentially consist of further advantageous combinations of the described elements, components, features, parts, steps, means, etc., even if such combinations are not specifically described herein. Furthermore, the disclosure may include other inventions that are not currently claimed but may be claimed in the future, particularly if they are within the scope of the independent claims.

[0059] Explanations relating to devices, apparatus, arrangements, systems, etc., according to embodiments of the present invention may also apply to methods, processes, procedures, etc., according to embodiments of the present invention, and vice versa. Identical, functionally equivalent, structurally identical, or comparably constructed elements, process steps, etc., may be indicated by identical reference numerals.

[0060] The following explanations and definitions, which relate to some fundamental aspects of the invention, may apply to all or part of the embodiments presented herein, and the explanation of certain aspects relating to only one part or one of the embodiments should not be understood to mean that these aspects cannot also be realized with other or all embodiments, insofar as technically possible and reasonable. 09.12.2025 - Dr. Schwarz

[0061] 10

[0062] All percentages used here may refer to molar, quantity, or volume fractions. Unless otherwise stated, pressure values ​​in bar are to be understood as absolute pressures.

[0063] The conjunction "and / or," when used before the last item in a list, should be understood to mean that all the items in the list can be combined in any way. In other words, "A, B and / or C" means "A and / or B and / or C" or "at least one of the items A, B, C in any combination."

[0064] When it is stated that, for example, a material stream or component mixture is "formed" using another material stream or component mixture, or a part of that other material stream or component mixture, this can include any steps such as diverting partial quantities or partial streams, combining with other component mixtures or material streams, chemically or physically reacting at least some components, heating, cooling, evaporating, condensing, compressing, expanding, etc. A "part" of a component mixture or material stream can be formed in this way, and it is understood that "forming" a material stream or component mixture using another material stream or component mixture can include using yet another material stream or component mixture, or a pure component.

[0065] The terms used in this disclosure have the meanings generally accepted in the scientific community. For definitions of the terms used here, please refer to the specialist literature cited at the beginning.

[0066] As mentioned at the outset, the proposed embodiments here relate to the oxidative dehydrogenation of ethane. The oxidative dehydrogenation of ethane can be advantageous compared to more established methods for the production of alkenes, such as steam cracking or catalytic dehydrogenation. Due to the exothermic nature of the reactions involved and the practically irreversible formation of water, there is no thermodynamic equilibrium limitation. The oxidative dehydrogenation of ethane can be carried out at comparatively low reaction temperatures. 09.12.2025 - Dr. Schwarz

[0067] 11

[0068] This process is carried out. Finally, in contrast to steam cracking, smaller quantities of worthless byproducts such as coke are formed.

[0069] For further details regarding oxidative dehydrogenation, please refer to relevant specialist literature, for example Ivars, F. and Lopez Nieto, JM, Light Alkanes Oxidation: Targets Reached and Current Challenges, in: Duprez, D. and Cavani, F. (eds.), Handbook of Advanced Methods and Processes in Oxidation Catalysis: From Laboratory to Industry, London 2014: Imperial College Press, pages 767-834, or Gärtner, CA et al., Oxidative Dehydrogenation of Ethane: Common Principles and Mechanistic Aspects, ChemCatChem, Vol. 5, No. 11, 2013, pages 3196 to 3217, as well as X. Li, E. Iglesia, Kinetics and Mechanism of Ethane Oxidation to Acetic Acid on Catalysts Based on Mo-V-Nb Oxides, J. Phys. Chem. C, 2008, 112, 15001-15008. In particular, MoVNb- or MoVTeNb-based catalyst systems have proven promising for oxidative dehydrogenation.In oxidative dehydrogenation, particularly when using such catalysts under industrially relevant reaction conditions, significant amounts of the respective carboxylic acids of the alkanes used are formed as byproducts.

[0070] Figure 1 illustrates a process 100 for the oxidative dehydrogenation of ethane, which can form the basis of embodiments proposed here, but which can itself represent an embodiment proposed here.

[0071] In process 100, ethane (C₂H₆), oxygen (O₂), and (in particular) superheated steam (H₂O) are provided as feedstocks or feed streams and are mixed in a suitable manner to form a reaction input stream 101, as disclosed, for example, in EP 4321 242 A1, to which express reference is made here and below, and whose content, to the extent permitted, is incorporated in full into the present disclosure. The reaction input stream is the component mixture referred to above and below as the "first component mixture," and the terms "reaction input stream" and "first component mixture" are used synonymously.

[0072] In particular, to form the first component mixture, i.e., the reaction inlet stream 101, ethane (C₂He) and vapor (H₂O) can first be mixed, and only then can oxygen (O₂) be introduced. The ethane (C₂He) can be... 09.12.2025 - Dr. Schwarz

[0073] 12

[0074] The vapor (H₂O) is preheated by feed / effluent heat exchangers before being mixed with it. The oxygen (O₂) is typically not preheated, or only very slightly, i.e., just enough to prevent oxyhydrogen combustion but to avoid condensation of the vapor (H₂O). This minimizes the risk of explosion and avoids direct contact between pure ethane (C₂He) and oxygen (O₂). As described, for example, in WO 2022 / 194793 A1, pure or substantially pure oxygen with a content of at least 95% by volume, in particular at least 97%, 99%, or 99.5% by volume, is used. The oxygen can be supplied, in particular, from an air separation plant.However, other oxygen sources, such as pressure swing adsorption, as well as the use of air or air enriched with oxygen to a certain extent, are also possible in appropriate configurations.

[0075] Before entering reaction step 10, which includes oxidative dehydrogenation, the first component mixture, i.e., the reaction inlet stream 101, and / or the partial streams from which it is formed, are heated as needed, as just mentioned. Heat exchangers known to those skilled in the art, and in particular so-called feed-effluent heat exchangers, as well as suitable control concepts, can be used for this purpose. This heating can also be carried out in multiple stages and include separate heating of the feed materials or corresponding mixtures before and after the respective injection points. Condensation of water must be avoided. In particular, in certain embodiments, (cold or moderately heated) oxygen is injected as close as possible to reaction step 10 or to a corresponding reactor for carrying it out.

[0076] The conversion step 10 can be carried out, for example, using MoVNbOx or MoVNbTeOx catalysts, in particular using a tube bundle reactor with molten salt cooling. Suitable internals and / or distribution systems, as also described, for example, in EP 4321 242 A1, can be used to introduce the reaction inlet stream 101, in order to ensure the most uniform distribution possible across all tubes of the tube bundle reactor. The molten salt can be cooled in the same or 09.12.2025 - Dr. Schwarz

[0077] 13

[0078] The flow is directed countercurrently to the direction of the reaction inlet stream 101, particularly in countercurrent flow, since the heat removed from the later reaction zones can be utilized in the front reaction zones. Depending on the respective temperature range of the reaction, thermal oils or, in particular, molten salts are used as coolants. To cool the molten salt, i.e., to remove the heat of reaction from the molten salt, steam, especially saturated or high-pressure steam, can be generated to counteract the heating caused by the heat of reaction of the oxidative dehydrogenation reaction.

[0079] Depending on the plant capacity, several tube bundle reactors can be used in parallel to carry out reaction step 10. In the inlet zone of a tube bundle reactor, where the reaction tubes are usually filled with an inert material, the final heating of the reaction inlet stream 101 to the desired inlet temperature into the actual reaction zone takes place. This subsequent reaction zone can be divided into sections that may differ, in particular, in the activity of the catalyst used. Corresponding configurations are described, for example, in WO 2019 / 243480 A1.

[0080] The product distribution can be influenced, in particular, by selecting the process conditions, such as residence time, linear velocity, space velocity, inlet pressure, and partial pressure of the reactants. However, adjusting the water content in the reaction inlet stream 101, especially the water partial pressure in the hot (i.e., before condensation) reactor outlet stream, allows for precise control of the ratio of the reaction products ethene and acetic acid, as described, for example, in WO 2018 / 115416 A1. A certain minimum water content in the inlet stream is helpful or even necessary to ensure stable catalyst activity. Further details are provided, for example, in WO 2018 / 115418 A1. Catalysts and process conditions are described, for example, in WO 2022 / 194793 A1.

[0081] The oxidative dehydrogenation in the tube bundle reactor typically takes place in a temperature range between 240 °C and 500 °C, particularly between 280 °C and 450 °C or 300 °C and 400 °C, and at a total pressure of the reaction feed stream 101 at the inlet of the 09.12.2025 - Dr. Schwarz

[0082] 14

[0083] Tube bundle reactor in a range between 1 bar and 10 bar, in particular between 2 bar and 6 bar absolute pressure.

[0084] Typical ethane conversions in reaction step 10 range from 25% to 75%, particularly from 40% to 60%. The ratio of the reaction products ethene and acetic acid in an outlet stream 102 of reaction step 10, depending on the exact reaction and process conditions, ranges from 98:1 to 70:30, particularly from 95:2 to 80:20 and from 95:5 to 90:10.

[0085] While the oxidative dehydrogenation of ethane is typically operated with a certain oxygen content at the reactor outlet, on the other hand the oxygen content at the reactor outlet, i.e. in the outlet stream 102, and especially before entering a subsequent decomposition section, should not exceed a certain limit in order to avoid burdening the following process steps with excessively high oxygen concentrations, and in particular to avoid excessive oxygen enrichment and thus the possible formation of an explosive atmosphere.

[0086] The outlet stream 102 can represent the component mixture referred to previously and subsequently as the "second component mixture", and the terms "outlet stream" and "second component mixture" can also be used synonymously herein.

[0087] The residual oxygen content in the outlet stream 102 can be as low as a few percent. In contrast, the ethyne content in the product stream 102 downstream of reaction step 10, i.e., also in the still moist, acetic acid-containing process gas, is typically less than one percent. The carbon monoxide and carbon dioxide concentrations in the product stream 102 downstream of reaction step 10 are, independently of each other, a few percent.

[0088] In the aforementioned condensate separation step 20, the outlet stream 102, i.e., the second component mixture, is first cooled. This causes a portion of the outlet stream 102 to condense, followed by the separation and removal of condensate 202, which, in addition to condensed steam and the in09.12.2025 - Dr. Schwarz

[0089] 15

[0090] The water formed in reaction step 10 contains, in particular, acetic acid as a co-product of the oxidative dehydrogenation. After the separation of the condensate 202, a gaseous stream remains as the aforementioned subsequent stream 201, which consists essentially of unreacted ethane, the reaction product ethene, and the byproducts carbon monoxide and carbon dioxide.

[0091] The follower stream 201, as well as a subsequently defined follower stream 401, can represent the component mixture referred to previously and subsequently as the "third component mixture", and the terms "follower stream" and "third component mixture" can also be used synonymously here.

[0092] Residual oxygen and other light trace components, such as ethyne, may also be present in this subsequent stream 201. Optionally, a washing column, as described in WO 2018 / 115414 A1, can be used in the condensate separation step 20. Further embodiments may include a first condensate separation step using only a separator upstream of a multi-stage compression unit 40 (see below) (main separation), followed by further condensate separation steps after each compressor stage or a portion of the compressor stages.

[0093] In particular, if the acetic acid is to be used as a valuable product in its own right, the condensate 202 is fed to an optional acetic acid purification unit 30. Such an acetic acid purification unit 30 utilizes process steps known to those skilled in the art, which may include, in particular, extraction and rectification, and obtain acetic acid of the desired purity, for example, more than 95%, more than 97%, or more than 99%. Furthermore, the water H₂O obtained in an acetic acid purification unit 30 can again be used, in part, to generate the aforementioned steam for the formation of the reaction inlet stream 101, as illustrated by a dashed arrow in Figure 1.

[0094] The gaseous stream 201 is fed to the aforementioned compression unit 40. The compression unit 40 is typically carried out in several stages (usually three or four to six stages) and may include appropriate intermediate cooling and condensate separation to remove substances generated during the compression unit 40. 09.12.2025 - Dr. Schwarz

[0095] 16

[0096] Condensate fractions, which are collectively referred to here as common condensate fraction 402, are included. A process gas compressor used in the compression stage 40 can be driven electrically by an electric motor or by steam via a suitable steam turbine. A process stream 401 is obtained from the compression stage 40 at an elevated pressure level, the composition of which results from the inlet stream 201 after removal of the condensate fraction 402.

[0097] Process stream 401 can also be understood as the component mixture previously and subsequently referred to as the "third component mixture", since its composition typically does not differ, or only slightly in water and acetic acid content, from the subsequent stream 201.

[0098] The material streams 201 and 401, or more generally the third component mixture, contain, in addition to ethane, ethene, carbon monoxide, and carbon dioxide, oxygen corresponding to the residual oxygen content in the outlet stream 102 of reaction step 10 in the oxidative dehydrogenation, i.e., the second component mixture, as well as ethyne formed as a trace component. Due to the prior separation of the condensates 202 and 402, respectively, ethane, ethene, carbon monoxide, carbon dioxide, oxygen, and ethyne are enriched in material streams 201 and 401 compared to outlet stream 102.

[0099] With regard to potential further enrichment in downstream process steps of Process 100, oxygen removal from the process gas is necessary for safety reasons (more details below). Furthermore, the target product, ethene, must also have a very low oxygen concentration, typically a few parts per million (ppb) by volume, thus requiring strict oxygen removal. Similarly, an ethyne specification must be met in the ethene product. This is typically below 2 ppm by volume (parts per million by volume), and in particular below 1 ppm by volume. Therefore, suitable ethyne removal must be provided within the framework of Process 100.

[0100] According to the state of the art, various approaches are known for this.

[0101] For example, US 8,519,210 B2 describes a downstream or also in a 09.12.2025 - Dr. Schwarz

[0102] 17

[0103] The reactor or the reaction step includes integrated catalytic oxygen removal, although only a very general "oxygen elimination catalyst" is specified. According to WO 2017 / 144584 A1, an oxygen removal catalyst is also preferably used in the reactor downstream of the main reaction zone. Neither document addresses the aspect of ethyne removal.

[0104] Only WO 2020 / 187572 A1 and WO2018 / 153831 A1 describe an approach in which a combined removal of both oxygen and acetylene takes place, which is also referred to here as raw gas treatment 50. In this process, oxygen is also reacted with carbon monoxide to produce carbon dioxide. According to the prior art, and as described in WO 2020 / 187572 A1, catalysts containing at least one of the elements copper, manganese, or ruthenium are used. The raw gas treatment 50 can be arranged before or after the compression stage 40. However, it is particularly advantageous, for example according to WO 2020 / 187572 A1, to arrange the raw gas treatment 50 of oxygen and acetylene after the compression stage 40 or at least after a compressor stage associated with the compression stage 40.As mentioned, the removal of oxygen can lead to a reaction with carbon monoxide and acetylene, forming carbon dioxide and water, which correspondingly increases the carbon dioxide content in the process gas stream. Therefore, regardless of the exact arrangement and sequence of compression 40 and raw gas treatment 50, a stream depleted of oxygen and acetylene, and possibly a stream enriched with carbon dioxide, is formed.

[0105] WO 2023 / 104962 discloses the integration of an oxidative dehydrogenation of ethane to ethene into a steam cracker, wherein oxygen and ethyne are removed from the product stream of an oxidative dehydrogenation and subsequently carbon dioxide is introduced into the product stream of the steam cracker downstream of the selective hydrogenation and upstream of the demathanization.

[0106] This stream 501 is subjected to carbon dioxide removal 60, resulting in a carbon dioxide-depleted subsequent stream 601. Carbon dioxide is conventionally removed, in particular by absorption, for example, by regenerable amine scrubbing and non-regenerable caustic scrubbing. Due to its high interaction with suitable 09.12.2025 - Dr. Schwarz

[0107] 18

[0108] Carbon dioxide can be removed relatively easily from the product mixture using solvents or washing liquids. In the embodiments proposed here, known methods for carbon dioxide removal, in particular appropriate washing processes such as amine washing, can be employed. In amine washing, the loaded detergent is then regenerated in a separate column, releasing essentially pure carbon dioxide through desorption. As not specifically illustrated, this relatively pure stream is available for further potential use. Further purification and reduction of the carbon dioxide content is possible through an (optional, downstream) caustic washing process.

[0109] The carbon dioxide-depleted subsequent stream 601 is then subjected to drying 70 to prevent the formation of hydrates and / or ice in the following process steps. Drying agents known to those skilled in the art, such as molecular sieves or zeolites, are used in drying 70. The use of special materials that enable the removal of residual carbon dioxide or trace compounds such as oxygenates is also generally known.

[0110] The drying stage 70 is followed by a so-called "cold section," which may include, in particular, a demethanization stage 80 and a separation and / or removal 90 of hydrocarbons with two carbon atoms from each other and from three carbon atoms. In the demethanization stage 80, carbon monoxide and other low-boiling components are separated as the overhead stream 801. The separation and / or removal 90 includes, in particular, a separator for the separation of ethane and ethene to obtain the target product ethene (stream 921) in the required and specified purity. If necessary, a deethaneizer may also be provided, which yields a stream 923, which may contain predominantly three-carbon hydrocarbons and heavier components, as a bottom fraction from a stream that contains predominantly two-carbon hydrocarbons, i.e., ethane and / or ethene.The arrangement of the splitter and deethanizer can be carried out in a suitable manner, as is generally known from the prior art.

[0111] A plant for carrying out one of the processes 100 also includes the necessary auxiliary systems, such as, in particular, steam and condensate systems. 09.12.2025 - Dr. Schwarz

[0112] 19

[0113] Boiler feedwater system, regeneration system, blowdown and flare system, cooling water system, propylene and optional ethene refrigeration system, nitrogen system, compressed air system, slop and wastewater system, lye treatment, chemical and inhibitor dosing system, fire extinguishing water system, and tank and storage facilities for feedstocks, intermediates, and products.

[0114] The process 100 illustrated in Figure 1 and other processes, as explained, include oxygen or trace removal, in particular of ethyne, also referred to here as raw gas treatment 50, from the process gas of the oxidative dehydrogenation. As previously stated, a minimum oxygen content at the reactor outlet of a reactor used in reaction step 10 must be ensured for the oxidative dehydrogenation. However, this residual oxygen should be removed from the process gas stream 102 in accordance with specifications, at least for the reasons explained below, both for subsequent process steps of process 100 and for downstream processes.

[0115] One economic reason lies in the fact that the presence of oxygen leads to faster aging or decomposition of the detergent (amines) used in the carbon dioxide scrubbing process. Removing oxygen during the raw gas treatment upstream of the (regenerative) carbon dioxide removal process thus results in minimal detergent consumption / replacement.

[0116] One safety (and economic) reason is that the oxygen remaining in the process gas 102 becomes highly concentrated during cryogenic product separation, particularly in the overhead stream of the demethanizer 80. This can lead to critical and potentially flammable mixtures of hydrocarbons, carbon monoxide, and oxygen in the overhead stream of the demethanizer 80. Consequently, the demethanizer 80 would need to be designed for very high process pressures, which would either result in very high or even excessive investment costs, or push the limits of feasibility for such a pressure range.

[0117] Ethyne removal from the process gas is necessary to ensure the purity of the ethene product. Ethyne acts particularly as a catalyst poison in downstream processes where the product is further processed. 09.12.2025 - Dr. Schwarz

[0118] 20

[0119] Particularly relevant in corresponding processes 100 are aspects relating to the oxygen and ethyne content in the product stream 102 of an oxidative dehydrogenation, especially of ethane, as previously explained. Suitable catalysts and raw gas treatment arrangements 50 are described elsewhere. Examples are briefly explained below.

[0120] WO 2020 / 187572 A1 specifically provides for the injection of hydrogen for a raw gas treatment 50 as an essential element. A different embodiment of a raw gas treatment 50 is described in WO 2018 / 153831 A1.

[0121] WO 2014 / 134703 A1 specifically considers a chemical complex with an ethane cracker and shard, complemented by the oxidative dehydrogenation of ethane. Similar to US 8,519,210 B2, this document discloses, among other things, oxygen removal as a so-called afterburner immediately downstream of a reactor for the oxidative dehydrogenation of ethane. This oxygen removal is typically intended to take place at temperatures significantly below the temperature of the actual oxidative dehydrogenation reaction of ethane. Mixtures of Mn₂Oa and CuMn₂O₄ or others are used as catalysts, with reference to US 6,747,066 A and US 6,992,112 A. This step is explicitly described as "oxygen scavenging," particularly using a low-temperature reactor in the range of 100 °C to 400 °C. Here, methane, hydrogen, or carbon monoxide are oxidatively reacted.These compounds can also be added to process stream 102 as needed. This is known to those skilled in the art and is typical for the listed catalysts. Typical residual oxygen contents of less than 1000 ppm by volume are reported after this process step.

[0122] A very similar embodiment, only partly using different catalysts, is also disclosed in US 2022 / 380277 A1. US 11,447,434 B2 describes, among other things, a separate oxidation of carbon monoxide for oxygen removal and, in particular, a separate ethyne removal using a catalyst that employs a metal from Group 11 of the periodic table and a promoter (CeÜ2 and ZrÜ2) on a SiO2 support. 09.12.2025 - Dr. Schwarz

[0123] 21

[0124] US 8,519,210 B2 describes a downstream or integrated catalytic oxygen removal process for the oxidative dehydrogenation of ethane, although it only mentions an oxygen removal catalyst in general terms. This catalyst can include, in particular, oxidation catalysts, combustion catalysts, and hydrogenation catalysts. The descriptive section of this document describes the oxygen removal process as involving the combustion of carbon monoxide and, optionally, hydrocarbons with two or fewer carbon atoms, which can lead to a corresponding loss of yield. According to this document, a material independent of and different from the actual catalyst for the oxidative dehydrogenation of ethane can be used, and the underlying reaction is a conversion to carbon monoxide and / or carbon dioxide and water.

[0125] However, none of the documents show a solution for a particularly advantageous control and operating concept for oxygen or trace removal 50 in the context of an overall process such as the described process 100, but are essentially limited to the position within an overall process or the selection of suitable catalysts and general operating conditions.

[0126] The conversion step 10 is normally operated in such a way that the required minimum oxygen concentration is reliably maintained. According to the state of the art, the aim is to exceed the minimum oxygen concentration just enough to ensure safe and stable operation with regard to catalyst damage, even considering possible, but typically only minor, operational fluctuations. Therefore, the oxygen discharge concentration in the discharge stream 102 of conversion step 10, or in the subsequent stream 201 after acetic acid separation 20, is considered a key operational and safety parameter and thus generally defines the composition of the inlet stream to the raw gas treatment 50.

[0127] A flexible adjustment of the reactor operation or the conversion step to the requirements of the raw gas treatment 50 is therefore not usually provided for or technically or economically feasible. Nevertheless, short-term or longer-lasting significant deviations in the oxygen concentration upwards or downwards can occur during the operation of an overall process 100. 09.12.2025 - Dr. Schwarz

[0128] 22

[0129] These can occur, for example, due to (unforeseen) operational disruptions or deviations from the reactor's normal operation, but also due to adjustments during ongoing operation. When starting up a plant for carrying out process 100, the goal is also to achieve stable operation of the entire plant as quickly as possible and to produce products that meet specifications (here, ethene with regard to the proportion of oxygen and ethyne). These requirements necessitate a rapid and reliable adjustment of the operation of the raw gas treatment 50.

[0130] It must be ensured that in the raw gas treatment 50, as explained for example in relation to process 100, the tasks specified below are solved or the framework conditions are met.

[0131] Oxygen and ethyne must be removed to such an extent that oxygen enrichment is reliably prevented in subsequent process steps (prevention of the formation of ignitable or explosive mixtures) and required specifications in value products (here especially ethene, e.g. especially "PE-grade") are reliably met.

[0132] The reactions in the raw gas treatment 50 are oxidative and strongly exothermic. The corresponding heat input from catalytic conversion favors non-selective reactions, which can lead to losses of ethene and ethane. Simultaneously, an optimal temperature must be maintained in the raw gas treatment 50, particularly at the reactor inlet and when using a fundamentally known adiabatic fixed-bed reactor. Thermal runaway of the raw gas treatment must be avoided.In the present case, due to the limited oxygen concentration in the inlet stream of the raw gas treatment 50, a complete classical run-through is often initially self-limiting. However, with complete oxygen conversion, an undesirably strong reaction can occur close to the reactor inlet, which in turn can lead to the aforementioned non-selective reactions in this area, as well as catalyst damage due to temperature spikes. The loss of ethene and the formation of carbon monoxide and carbon dioxide have an additional negative impact here. 09.12.2025 - Dr. Schwarz.

[0133] 23

[0134] According to the state of the art, the oxidative dehydrogenation of ethane must, for these reasons as well, be operated in such a way that the oxygen concentration at the inlet of the raw gas treatment 50 is minimized as much as technically possible under the described circumstances and then kept as constant as possible. In particular, upward deviations in the oxygen content must be avoided, as these promote the effects described above and, in extreme cases (i.e., excessively high oxygen concentrations), can even lead to thermal runaway. However, downward deviations in the oxygen concentration can also lead to coking or alteration of the catalytically active species, thus reducing the efficiency and / or shortening the service life of the catalyst in the raw gas treatment 50, which may necessitate premature regeneration or even replacement of the catalyst.These scenarios are usually addressed by shutting down the raw gas treatment unit 50, which in turn leads to a production failure of the entire plant for the oxidative dehydrogenation of ethane.

[0135] According to the state of the art for highly exothermic reactions, 50 suitable fixed-bed reactors can generally be used for raw gas treatment. While a cooled tube bundle reactor can be used for effective heat removal and temperature control, it represents a considerable investment in equipment for the reactor itself, as well as for the required cooling circuit and the associated control technology. In addition, the comparatively high effort involved in filling and emptying the catalyst must be considered.

[0136] However, adiabatic fixed-bed reactors are also known and suitable in principle.

[0137] However, certain framework conditions and restrictions apply specifically to this type of reactor, which are explained below.

[0138] The strongly exothermic reaction leads to a pronounced temperature profile across the reactor, and in the case of an adiabatic fixed-bed reactor, in particular to a (very) high adiabatic temperature rise. This is illustrated by way of example in Figure 2 for typical product gas from the oxidative dehydrogenation of ethane, consisting of ethane, ethene, carbon monoxide, carbon dioxide, and ethyne. In Figure 1, an oxygen inlet concentration in mol% on the horizontal axis is shown in relation to an adiabatic temperature rise in K on the horizontal axis. (09.12.2025 - Dr. Schwarz)

[0139] 24

[0140] The vertical axis is illustrated. The calculation of the expected adiabatic temperature rise is possible from considering the complete conversion of the residual oxygen and the ethyne according to the reaction equations (1) and (2) given below.

[0141] C2H2+ 2.5 O22 CO2+ H2O (1) CO + 0.5 O2CO2(2)

[0142] Heat dissipation can essentially only occur in downstream heat exchangers. At the same time, overreaction or reactor runaway must be prevented. Minimizing the temperature profile across the reactor can be achieved by using a dilution medium; however, this usually leads to an increase in reactor volume, since a larger volume or...

[0143] Mass flow must be enforced.

[0144] The discharge stream from the raw gas treatment process can typically be used as a dilution medium. However, achieving such recycling requires additional equipment (recompression to the inlet pressure level), especially at higher recycling rates. Simultaneously, there is a risk of the undesirable conversion of valuable products (in this case, for example, the oxidation of ethene) during the recycling process. In practice, such recycling streams are usually implemented and operated with a very high recycling rate (see definition below). Furthermore, a minimum recycling rate is typically specified to ensure safe and controlled operation. Part-load operation or adaptation to operating fluctuations, in particular, necessitates design for a wide operating range, resulting in additional requirements for the equipment and control technology.

[0145] In practice, however, the requirements of implementation step 10, i.e., oxidative dehydrogenation, and raw gas treatment 50 also present partially conflicting requirements, as explained below. 09.12.2025 - Dr. Schwarz

[0146] 25

[0147] In principle, the conversion step 10 can be operated in such a way that an advantageous ratio of oxygen to ethyne and of carbon monoxide to oxygen is maintained at the inlet of the raw gas treatment 50.

[0148] However, oxidative dehydrogenation is easier to operate and control if a higher oxygen concentration is maintained at the outlet of reaction step 10, i.e., in mass stream 102 or the second component mixture. This has a positive effect on the catalyst for oxidative dehydrogenation and its service life, and simplifies operational adjustments. Furthermore, optimal adjustment of the selectivity for the valuable products ethene and acetic acid is possible with a higher oxygen outlet concentration, or when the oxygen outlet concentration remains as a degree of freedom. At the same time, misdistributions or irregularities in the catalyst bed of individual tubes within a tube bundle reactor with tens of thousands of tubes can be tolerated.

[0149] On the other hand, for selectivity in raw gas treatment 50, it is advantageous to keep the carbon monoxide to oxygen ratio as high as possible in order to minimize ethene losses in raw gas treatment 50. According to the prior art, this results in an upper limit for the oxygen content at the outlet of the reactor for oxidative dehydrogenation or of reaction step 10 with regard to advantageous and efficient operation of the overall plant.

[0150] At the same time, with regard to the oxygen content at the inlet of the raw gas treatment 50, there is also a lower limit or a minimum oxygen content for its operation in accordance with specifications, i.e. in particular the removal of ethyne in accordance with specifications.

[0151] Starting from a minimum oxygen inlet concentration at the raw gas treatment inlet 50, the expected adiabatic temperature rise is at least approximately 40 K (for an oxygen inlet concentration of 0.47 mol%, see Figure 2) if the raw gas treatment proceeds via the reactions described above (oxidation / combustion of the ethyne with oxygen and reaction of the remaining oxygen with carbon monoxide, i.e., in particular without ethene loss). A significantly lower adiabatic temperature rise corresponding to the oxygen inlet concentration (cf. Figure 2) therefore indicates a reduced or 09.12.2025 - Dr. Schwarz

[0152] 26

[0153] This indicates a failure in the raw gas treatment (insufficient oxygen and / or ethene removal). A significantly excessive adiabatic temperature rise, corresponding to the inlet oxygen concentration, suggests excessive ethene loss through combustion according to reaction equation 3. This reaction is considerably more exothermic than the reaction according to reaction equation 2 above.

[0154] C2H4 + 3 O22 CO2 + 2 H2O (3)

[0155] As shown in Figure 3, complete removal of oxygen and ethyne can be achieved at temperatures of approximately 170 °C and above at the reactor inlet of a raw gas treatment unit 50. Figure 3 shows an inlet temperature in °C on the horizontal axis versus a conversion rate in mol% on the vertical axis. Values ​​for oxygen conversion are represented by circles, and values ​​for ethyne conversion by triangles. A horizontal line at 100% indicates the maximum achievable total conversion of oxygen or ethyne, respectively. The results illustrated in Figure 2 were obtained using a CuO / MnO-based catalyst under oxidative conditions. The reaction conditions included a reaction pressure of 21 bar and an hourly gas space velocity of 3,700 h⁻¹. 1 , an inlet temperature, as illustrated, of 120 to 170 °C, and an oxygen content in use of 0.47 vol%.

[0156] The removal of ethyne only, in accordance with specifications, can be achieved earlier, at approximately...

[0157] Temperatures of 140 °C are reached. According to Figure 2, a temperature increase occurs in an adiabatic reactor for raw gas treatment 50, which depends in particular on the oxygen inlet concentration. Both parameters, the reactor inlet temperature and the adiabatic temperature rise, therefore have an effect on the degree of removal of oxygen and ethyne.

[0158] Although Figure 3 shows that almost complete removal of ethyne and oxygen can be achieved at approximately 170 °C, the catalyst did not exhibit stable performance at this temperature. This applies particularly to oxygen removal, which can be attributed to relatively rapid catalyst deactivation. Stable long-term performance was achieved at catalyst bed inlet temperatures above 200 °C, and especially at least 230 °C. These values ​​apply particularly to start-of-run (SOR) conditions. 09.12.2025 - Dr. Schwarz

[0159] 27

[0160] immediately after regeneration of the catalyst and can then shift upwards during operation over time.

[0161] The minimum temperature for stable operation is therefore at least 200 °C, preferably at least 230 °C. An excessively high catalyst bed temperature or an excessively high outlet temperature for an adiabatic reactor leads to significantly increased ethene losses on the one hand and the formation of undesirable byproducts (especially higher aliphatic and non-aliphatic hydrocarbons) on the other, which negatively impacts the economic viability of the overall process. In this context, a maximum permissible temperature of approximately 400 °C, and particularly approximately 370 °C, has proven to be sufficient.

[0162] Figures 4a and 4b illustrate maximum temperatures in °C on the horizontal axis versus ethene loss in % on the vertical axis (Figure 4a) and formation of byproducts in the form of hydrocarbons with three to six carbon atoms in wt ppm, respectively. The bars on the left, representing maximum temperatures of 339, 374, and 400 °C, show results obtained at a constant oxygen concentration of 1.5 vol% by varying the reaction inlet temperature (230, 270, and 300 °C). The bars on the right, however, show results obtained by varying the oxygen concentration (1.43, 1.92, and 2.39 vol%) at a constant catalyst bed inlet temperature of 232 °C. The remaining reaction conditions included a carbon monoxide to oxygen ratio of 1.2 and an hourly gas space velocity of 6,000 IT. 1 and a catalyst bed length of 15 cm.

[0163] While the previously cited documents describe suitable catalysts for oxygen and ethyne removal and the position of such removal in an overall process, the present invention aims to provide an optimized operating and control concept for raw gas treatment 50 within an overall process, particularly with regard to the aspects summarized below.

[0164] An advantageous solution should in particular allow for rapid and reliable adaptation to fluctuations in the oxygen content at the outlet of conversion step 10 (short-09.12.2025 - Dr. Schwarz).

[0165] 28

[0166] and in the long term). Furthermore, simple controllability and decoupling of the operation or adjustment of conversion step 10 and the raw gas treatment 50 should be possible. Another important aspect is ensuring the specification-compliant removal of oxygen and ethyne in the overall process 100 with the lowest possible ethene losses of less than 2%, less than 1.5%, less than 1% and especially less than 0.5% in a single pass, as well as only minimal by-product formation (especially concerning higher hydrocarbons) totaling less than 1000 ppm by weight.

[0167] An important aspect is the reliable avoidance of critical oxygen concentrations. This is achieved in particular through enrichment in the decomposition section of the overall process 100 (e.g., in the overhead stream of a demethanizer 80). This also enables optimized operation of the amine scrubbing for CO2 removal (no oxidation of the scrubbing agent by oxygen and thus only minimal replacement of amine is necessary). Furthermore, a necessary minimum temperature or a necessary minimum temperature rise in the raw gas treatment 50 should be possible. Limiting the maximum catalyst bed or outlet temperature and limiting the maximum adiabatic temperature rise to limit ethene loss or byproduct formation is possible (outlet temperature and simultaneously maximum temperature between 300 and 400 °C, especially between 330 and 370 °C).

[0168] The solutions proposed here include carrying out the raw gas treatment 50 using a single- or multi-stage adiabatic fixed-bed reactor. In particular, a single-stage design can be provided. In the case of a multi-stage design, temperature adjustment (cooling) can be provided before each subsequent stage.

[0169] The raw gas treatment stage 50 within an overall process 100 can, in principle, be positioned after an acetic acid separation step 20, i.e., without further pressure increase. However, the raw gas treatment stage 50 can also be positioned at a pressure increased compared to the conversion step 10 (5 to 50 bara, 15 to 40 bara, 20 to 35 bara, 25 to 35 bara). Proposed embodiments advantageously utilize existing elements of the overall process 100 by preferably positioning the raw gas treatment stage 50 after the compression stage 40 or a compressor stage associated with the compression stage 40. 09.12.2025 - Dr. Schwarz

[0170] 29

[0171] A suitable partial flow from the overall process 100 can be used as a recirculation flow upstream of the compression stage, or in particular upstream of a compressor stage in the raw gas treatment stage 50. This avoids high pressure differentials and the additional effort required for separate compression of a recirculation flow.

[0172] If the raw gas treatment is arranged upstream of at least one compressor stage, this at least one compressor stage can be used analogously to equalize the pressure difference. Alternatively, a separate recirculating compressor can also be provided for the recirculation flow.

[0173] In principle, various recirculation streams are possible, for example, a stream diverted downstream of the raw gas treatment 50 or a stream diverted after an adiabatic fixed-bed reactor used in the raw gas treatment 50. Further examples, which can be used in combination or as alternatives, include one or more streams provided downstream of the carbon dioxide removal, the drying and cooling 70, the demethanization 80, a deethanization in the form of a partial stream from an ethane recycling process, or downstream of an ethane / ethene splitter (in particular the bottom fraction, which consists of or is rich in ethane, or from a side draw-off). In the case of demethanization 80, the light gas separated overhead can be used, which has the additional advantage of allowing adjustment of the carbon monoxide to oxygen ratio.

[0174] The amount of the recirculated stream can be between 0 and 10 relative to the inlet stream of the raw gas treatment 50, in particular between 0 and 5, between 0 and 2.5, or between 0 and 1, defined as the ratio of the mass of the recirculated stream to the mass of the input stream. The measures proposed here are also based on the understanding that ethyne is always sufficiently removed if enough oxygen is present at the inlet of a raw gas treatment 50.

[0175] To achieve sufficient or complete ethyne removal, an excess of oxygen compared to ethyne is necessary in the raw gas treatment. In particular, the volume fraction of oxygen must correspond at least to the value specified in the document dated 3-09.12.2025 - Dr. Schwarz.

[0176] 30

[0177] multiplied by at least 5 times, at least 10 times, preferably at least 20 times and particularly preferably at least 25 times the volume fraction of ethyne.

[0178] In the raw gas treatment 50, any oxygen not consumed by the oxidative conversion of ethyne then reacts further with carbon monoxide and, if applicable, other hydrocarbons. In this way, oxygen can always be reduced to the necessary target value after the raw gas treatment 50. The primary reaction product of these exothermic reactions is always carbon dioxide.

[0179] The carbon dioxide is removed in a downstream carbon dioxide removal unit. For reasons related to reaction kinetics, the oxygen initially reacts preferentially with the carbon monoxide present in the process gas before potentially attacking hydrocarbons, which then leads to a loss of the valuable product (ethene loss). Therefore, a minimum ratio of carbon monoxide to oxygen should be present or established to minimize this loss of the valuable product. Advantageous molar stoichiometric ratios (see above) of carbon monoxide to oxygen are, in particular, at least 0.5, at least 0.7, at least 0.9, or at least 1.1, for example, at least 1.25. Advantageous ratios of carbon monoxide to oxygen are at most 3.2, in particular at most 3.0.

[0180] To prevent a reaction of oxygen with ethene, which leads to a loss of this valuable product, an advantageous temperature range exists for the raw gas treatment 50, whereby it is particularly important not to exceed a maximum temperature. Advantageous operation of the raw gas treatment 50 takes place at inlet temperatures (see Figure 3) above 160 °C, preferably above 180 °C, preferably above 200 °C, and particularly preferably above 230 °C. (As mentioned above, these are in particular the SOR values, i.e., an increase is possible during operation.) This results in an adiabatic temperature rise, as shown in Figure 2, which is selected such that the temperature rise is 40 to 150 K, 60 to 140 K, and particularly 70 to 120 K.The inlet temperature, the temperature rise, and the outlet temperature can serve as suitable control variables for both oxygen dosing and the adjustment of the recycle stream, with an overall maximum catalyst bed temperature (corresponding to the following for an adiabatic reactor: 09.12.2025 - Dr. Schwarz).

[0181] 31

[0182] The outlet temperature should not exceed 370 °C, in particular 360 °C and further, in particular, 350 °C, in order to limit both ethene loss and the formation of by-products.

[0183] Other process-relevant conditions include, in particular, the gaseous hourly space velocity (GHSV), expressed as the total gas volume flow rate of the feed gas under standard conditions of 0 °C, 1.013 bara per catalyst volume in the standard units (Nm³). 3 / h)gas / m 3 Cat or h -1) as well as the process pressure. The hourly gas space velocity is particularly between 1,000 and 15,000 h′. 1 , especially between 2,000 and 12,000 hours -1 and, for example, between 4,000 and 10,000 hours 1 The pressure can be between 5 and 50 bara, in particular between 15 and 40 bara, further in particular between 20 and 35 bara, and for example between 25 and 35 bara.

[0184] An oxygen injection point proposed here can be located at a suitable position within the overall process 100. An injection point immediately before the raw gas treatment stage 50 can be advantageous. This can be located before or after the device for recirculating a recycled stream and is then independent of the recycled stream's control, which can also be switched off. A position downstream of the condensate separator 20, i.e., upstream of the compressor 40 or a compressor stage associated with the compressor 40, is also possible. This is advantageous if oxygen can only be supplied at a reduced pressure level (as required, for example, for conversion step 10), but may have potential disadvantages regarding fouling effects in the compressor stages. A reduced pressure level is understood here to be a pressure level below the pressure at which the raw gas treatment 50 takes place.As already mentioned, the use of a separate 45-liter circulating compressor is also possible as an alternative.

[0185] From an operational perspective, online measurement of both the oxygen content (e.g., in the form of electrochemical oxygen measurement, paramagnetic oxygen measurement, or Raman spectroscopy, especially using a so-called quantum cascade laser) and the ethane content (e.g., using gas chromatography or infrared spectroscopy, especially FTIR spectroscopy) can be implemented relatively easily and reliably and integrated into the process control system. 09.12.2025 - Dr. Schwarz

[0186] 32

[0187] can be integrated. Additionally, the ethyne and / or carbon monoxide concentration can be measured (e.g., using gas chromatography, IR / Raman spectroscopy, or quantum cascade lasers). These measurements (individually or in combination), as well as the oxygen-to-ethyne and / or carbon monoxide-to-oxygen ratio derived from the measured values, can be advantageously used as a control parameter for oxygen injection. Furthermore, the oxygen measurement, in particular, can be used to adjust a recycle stream, which can be regulated between 0 and a maximum value. Additionally, the carbon monoxide-to-oxygen ratio can be used to control the recirculation of a carbon monoxide-rich partial stream from the head of a Demethanizer 80.

[0188] Possible positions for these measurements are located upstream of the raw gas treatment unit 50, in particular upstream of the return of a recycled stream and / or downstream of the return of a recycled stream. Here, the effective concentrations at the inlet to a fixed-bed reactor of the raw gas treatment unit 50 are measured, which is particularly advantageous due to the direct correlation.

[0189] To monitor and ensure proper operation, the O2 concentration (d / s) of the raw gas treatment unit 50 can also be measured. If necessary, the oxygen concentration determined here can also be used as a further parameter for controlling the recirculation rate. Measuring the ethyne concentration at this point is also optional.

[0190] The proposed configurations are illustrated in Figures 5 and 6 and labelled 200 and 300, respectively. Their integration into an overall process 100, as illustrated in Figure 1, is achieved through the identical designation of at least some of the material streams, such as 401 and 501, or the compaction step 40 shown.

[0191] In embodiment 200 according to Figure 5, the raw gas treatment 50 is arranged after a compression unit 40 or an associated compressor stage and comprises a first raw gas treatment step 51 using a corresponding reactor and optionally a second raw gas treatment step 52. In the example of Figure 5 or embodiment 200, a return flow upstream of the compression unit 40 or any associated compressor stage is shown. Before entering the raw gas treatment 5009.12.2025 - Dr. Schwarz

[0192] 33

[0193] In the example, as denoted by M, a measurement of the oxygen, carbon monoxide and / or ethyne content in stream 401 is carried out.

[0194] If the oxygen-to-acetylene ratio or the oxygen content is too low for optimal operation of the raw gas treatment unit 50, the oxygen dosing is activated or increased. Unlike temperature adjustment, this measure acts immediately and can, in particular, compensate for fluctuations in the oxygen content of the inlet stream 401 of the raw gas treatment unit 50, i.e., the third component mixture (especially those resulting from fluctuations in the upstream streams 102 and 201). Conversely, if the oxygen content is too high, the oxygen dosing can be reduced or even switched off. In this embodiment, the inlet stream 401 already includes a potential recirculation stream 511.

[0195] If the oxygen concentration in the inlet stream 401 of the raw gas treatment 50 remains too high and no further reduction of the oxygen feed is possible (because the dosing is already deactivated and / or an optimal ratio of oxygen to ethyne has already been reached), activation or

[0196] Increasing the recycling stream 511 reduces the oxygen content at the inlet of the raw gas treatment 50. This recycling stream can be formed as a partial stream 514a from the outlet stream 512 of the first raw gas treatment step 51, as a partial stream 514b from the outlet stream 513 of a subsequent stage (shown here as an example of the second raw gas treatment step 52), or as stream 515, as mentioned above, as a partial stream from a process step downstream of the raw gas treatment 50. In particular, the carbon monoxide to oxygen ratio can also be adjusted by targeted adaptation of the carbon monoxide-rich recirculation stream 802, which is formed as a partial stream of the overhead stream 801 of a demethanization stage 80.

[0197] If a partial stream 514a is recycled after a first crude treatment step 51, a subsequent (optional) crude treatment step 52 can also serve for fine purification. The recycled stream 511 can also be formed from a suitable combination of the partial streams 514a, 514b, 515 and / or 802. Conversely, a reduction in the oxygen content in stream 401 can be addressed by reducing / deactivating the recycled stream 511 and activating / increasing the O2 injection. 09.12.2025 - Dr. Schwarz

[0198] 34

[0199] The ratio of oxygen to acetylene can be increased to the minimum ratio required for optimal effect. Similarly, the ratio of carbon monoxide to oxygen can be specifically adjusted, particularly by adjusting the flow 802. Necessary heat exchanges before and after the raw gas treatment 50, or in the recirculation flows or between the raw gas treatment steps 51 and 52, are not shown in this example and can be implemented in a manner known to those skilled in the art.

[0200] Regarding Figure 6 and embodiment 300, only the deviations from Figure 5 and embodiment 200, respectively, are explained. If a separate circulating compressor 45 is used, or if the raw gas treatment 50 is followed by a further compressor stage (not shown), the recirculation of a stream 512 can take place directly before the raw gas treatment 50, in particular before or after a measurement of oxygen, carbon monoxide, and / or ethyne, as well as before or after a device according to the invention for supplying oxygen. The stream 512 is formed from the stream 511 by increasing the pressure.

[0201] In this case, current 401 does not include any components from a recirculating flow; rather, current 402 is formed from the combination of currents 401 and 512 as the direct input flow for raw gas treatment 50. In principle, the use of several recirculating compressors for different partial flows 514a, 514b, 515, and / or 802 is also conceivable, but hardly relevant in practice. Therefore, preferably, in this embodiment, only one recirculating compressor 45 is used, or a compressor stage 42 following the raw gas treatment 50 takes over the function of the recirculating compressor 45.

Claims

December 9, 2025 - Dr. Schwarz 35 Patent claims 1. A process (100, 200, 300) for the oxidative dehydrogenation of ethane, wherein a first component mixture comprising vapor, ethane and oxygen is subjected to one or more reaction steps (10) to obtain a second component mixture, wherein the one or more reaction steps (10) comprise(s) the oxidative dehydrogenation, wherein the second component mixture, comprising a portion of the ethane from the first component mixture that was not reacted in the one or more reaction steps (10), ethene, oxygen, ethyne, acetic acid, water, carbon monoxide and carbon dioxide, or a portion thereof, is used to form a third component mixture comprising at least a portion of the ethane, ethene and ethyne, as well as the oxygen, carbon monoxide and carbon dioxide from the second component mixture, wherein the third component mixture is subjected to a raw gas treatment (50).and wherein in the raw gas treatment (50) oxygen and ethyne are reacted in the third component mixture, characterized in that the raw gas treatment (50) is carried out using one or more fixed-bed reactors and that the oxygen and carbon monoxide content in the third component mixture is adjusted by using one or more recycled fourth component mixtures, for which one or more partial streams of one or more material streams formed in or downstream of the raw gas treatment (50) are used, and / or by using oxygen in the formation of the third component mixture, wherein the oxygen and carbon monoxide content in the third component mixture is adjusted such that a volume fraction of oxygen is at least 3 times a volume fraction of ethyne and / or wherein the molar reaction stoichiometric ratio of carbon monoxide to oxygen is at least 0.

5.

2. Method (100, 200, 300) according to claim 1, wherein the third component mixture is depleted of acetic acid and water compared to the second component mixture.

3. Method (100, 200, 300) according to one of the preceding claims, wherein one or more fourth component mixtures in a total quantity 09.12.2025 - Dr. Schwarz 36 is or are recycled, which is less than 10 times, 5 times, 3 times or 1 time the amount of a proportion of the third component mixture not formed by one or more fourth component mixtures.

4. Method (100, 200, 300) according to one of the preceding claims, wherein the fourth component mixture or at least one of the several fourth component mixtures is or are compressed together with or separately from the second component mixture or the part thereof used to form the third component mixture.

5. Method (100, 200, 300) according to any one of the preceding claims, wherein the fourth component mixture or at least one of the several fourth component mixtures is formed using a light gas fraction provided by means of a demethanization step (80) carried out downstream of the raw gas treatment (50), using a material stream diverted downstream of the raw gas treatment (50) or downstream of an adiabatic fixed-bed reactor associated with the raw gas treatment (50), using a material stream diverted downstream of a carbon dioxide removal, using a material stream diverted downstream of a dryer, using a material stream diverted downstream of a deethanizer, and / or an eth fraction stream of an ethane recycle of a C2 splitter or from a side draw of a C2 splitter.

6. Method (100, 200, 300) according to one of the preceding claims, wherein the oxygen used in the formation of the third component mixture is adjustableally dosed during the formation of the third component mixture.

7. Method (100, 200, 300) according to any one of the preceding claims, wherein one or more quantities of the fourth component mixture used in the formation of the third component mixture and / or of the oxygen used in the formation of the third component mixture are adjusted based on a measurement of a concentration of oxygen, carbon monoxide and / or ethyne upstream of the raw gas treatment (50) and / or based on a measurement of an adiabatic temperature rise in the raw gas treatment (50). 09.12.2025 - Dr. Schwarz 37 8. Method (100, 200, 300) according to one of the preceding claims, wherein the fourth component mixture or at least one of the several fourth component mixtures, the third component mixture, and / or at least one further component mixture is tempered downstream of the raw gas treatment (50) using one or more heat exchangers.

9. Method (100, 200, 300) according to one of the preceding claims, wherein the third component mixture is supplied to the raw gas treatment (50) at a minimum temperature of 160 °C and / or the raw gas treatment (50) is operated at a maximum temperature of 370 °C and / or the raw gas treatment (50) is operated in such a way that a temperature increase in the raw gas treatment (50) of 40 to 150 K occurs.

10. Method (100, 200, 300) according to one of the preceding claims, wherein the raw gas treatment (50) is carried out at an absolute pressure of 5 to 50 bar and / or with an hourly gas space velocity of 1,000 to 15,000 tr 1 is operated and / or wherein the third component mixture contains 25 to 80 vol%, 30-70 vol% or 40-60 vol% ethene and / or the raw gas treatment (50) is carried out such that a maximum ethene loss in the raw gas treatment (50) is less than 2%, less than 1.5%, less than 1% or less than <0.5% and / or the fourth component mixture contains less than 1,000 vol. ppb ethyne and / or less than Contains 100 vol. ppm oxygen.

11. Method (100, 200, 300) according to one of the preceding claims, wherein an oxygen and / or ethyne measurement is carried out at an outlet of the raw gas treatment (50) and on this basis a quantity of one or at least one of the several recycled fourth component mixtures is adjusted.

12. Method (100, 200, 300) according to one of the preceding claims, wherein the raw gas treatment (50) is carried out using a catalyst containing at least one of the elements copper, manganese or ruthenium.

13. Method (100, 200, 300) according to one of the preceding claims, wherein a compression (40) and / or 09.12.2025 - Dr. Schwarz 38 Condensate separation (20) is carried out and / or a gas mixture taken from the raw gas treatment (50) is subjected to carbon dioxide removal (60) and / or drying (70) and / or a dried gas mixture is subjected to demethanization (80) and / or separation (90) of hydrocarbons.

14. Plant for the oxidative dehydrogenation of ethane, which is configured to subject a first component mixture to one or more reaction steps (10) to obtain a second component mixture, wherein the one or more reaction steps (10) comprise or comprise the oxidative dehydrogenation of ethane, using the second component mixture or a part thereof to form a third component mixture, subjecting the third component mixture to a raw gas treatment (50), and reacting oxygen and ethyne in the third component mixture in the raw gas treatment (50), characterized in that one or more fixed-bed reactors are provided for the raw gas treatment (50) and that means are provided which are configured to adjust the oxygen and carbon monoxide content in the third component mixture.by using one or more recycled fourth component mixtures and / or oxygen in the formation of the third component mixture.

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