Oxygen removal from ethane ODH product streams using ethanol.

Abstract

A method and system for converting ethane to ethylene is provided. An exemplary method includes feeding a feed stream comprising ethane and oxygen to an oxidative dehydrogenation reactor, and converting at least a portion of the ethane to ethylene in the oxidative dehydrogenation reactor to provide a reactor effluent stream comprising ethane, ethylene, and oxygen, acetylene, or both. The method includes cooling the reactor effluent stream to form a cooled effluent stream, and feeding the cooled effluent stream to an oxygen removal reactor comprising an ODH catalyst bed. A deoxygenated stream comprising water and alcohol is fed to the oxygen removal reactor to form a deoxygenated effluent.

Description

[Technical field]

[0001] The present invention relates generally to the oxidative dehydrogenation of ethane to ethylene (ODH). More specifically, the present invention relates to an ODH process that includes multiple reactors in series for removing oxygen, acetylene, or both from a product stream. [Background technology]

[0002] Olefins, such as ethylene, propylene, and butylene, are the basic building blocks of a variety of commercially valuable polymers. Because naturally occurring sources of olefins do not exist in commercial quantities, polymer producers rely on methods to convert the more abundant lower alkanes into olefins. The method of choice for commercial-scale producers today is steam cracking. Steam cracking is an endothermic process in which alkanes diluted with steam are exposed to temperatures of up to about 900 °C for very brief periods. The fuel demand to generate the required temperatures, and the need for equipment that can withstand those temperatures, significantly increase overall costs. In addition, high temperatures promote coke formation, which builds up in the system, necessitating costly periodic reactor shutdowns for maintenance and coke removal.

[0003] The oxidative dehydrogenation (ODH) process is an alternative to steam cracking that is exothermic and produces little or no coke. In ODH, lower alkanes such as ethane are mixed with oxygen in the presence of a catalyst and optionally an inert diluent (such as carbon dioxide, nitrogen, or steam) at temperatures as low as 300° C. to produce the corresponding alkenes. A variety of other oxidation products may be produced in this process, including, but not limited to, carbon dioxide and acetic acid.

[0004] It is beneficial to operate an ODH reactor with at least a small amount of oxygen remaining in the reactor product stream to protect the ODH catalyst from permanent damage or deactivation caused by exposure to a high temperature, oxygen-free, reducing environment.

[0005] In the case of fixed bed ODH reactors, another reason for operating the reactor with at least a small amount of oxygen is to ensure that the entire ODH catalyst bed is utilized in the reaction, rather than only the upstream region of the catalyst bed being utilized, which can occur when the O2 concentration in the ODH product stream is less than 1 ppm.

[0006] However, the presence of oxygen in the ODH product gas stream creates significant safety and operational problems in downstream equipment, primarily the first compression stage and downstream of an ODH plant. As a result, there is a need to remove oxygen to very low to undetectable levels prior to compressing the product gas.

[0007] The patent and open literature disclose a number of different approaches, focusing on catalytically combusting a small portion of the ODH product gas to completely consume the residual oxygen. Although this approach is viable, it is highly undesirable because it increases the overall oxygen consumption in the ODH process and reduces the overall process selectivity to ethylene. Summary of the Invention

[0008] An embodiment described in the Examples herein provides a method for converting ethane to ethylene. The method includes feeding a feed stream comprising ethane and oxygen to an oxidative dehydrogenation reactor, and converting at least a portion of the ethane to ethylene in the oxidative dehydrogenation reactor to provide a reactor effluent stream comprising ethane, ethylene, and oxygen, acetylene, or both. The method includes cooling the reactor effluent stream to form a cooled effluent stream, and feeding the cooled effluent stream to an oxygen removal reactor comprising an ODH catalyst bed. A deoxygenation stream comprising water and alcohol is fed to the oxygen removal reactor to form a deoxygenated effluent.

[0009] Another embodiment described in the Examples herein provides a system for producing ethane from ethylene, the system including an oxidative dehydrogenation (ODH) reactor, a first heat exchanger for cooling an ODH effluent from the ODH reactor, and an oxygen removal reactor including an ODH catalyst. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a simplified block diagram of an oxidative dehydrogenation (ODH) process unit. [Diagram 2] FIG. 1 is a simplified block diagram of a process unit for removing oxygen and acetylene in an oxygen removal reactor. [Diagram 3] FIG. 1 is a process flow diagram of a process for converting ethane to ethylene and removing oxygen from the effluent. [Figure 4] FIG. 1 is a flow diagram of components in a simulation of an oxygen removal reactor including an ODH catalyst. [Diagram 5] FIG. 1 is a flow diagram of components in a simulation of an oxygen removal reactor containing a Cu / Zn oxide catalyst. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Ethane undergoes oxidative dehydrogenation at temperatures between about 300 °C and about 450 °C to produce ethylene and other by-products such as steam, acetic acid, CO2, and CO. The catalysts used for this are usually MoVNbTeO x The oxygen content of the gas stream leaving the reactor is therefore maintained at about 0.1 mole %, or 1000 ppm, on a dry basis, to avoid catalyst deactivation.

[0012] However, unreacted oxygen in the reactor effluent stream can be problematic for the operation of downstream equipment, such as amine towers, where the presence of oxygen can cause decomposition of the amine. Additionally, unreacted oxygen can cause fouling in downstream product gas compressors. Additionally, unreacted oxygen can cause undesirable reactions, such as the formation of peroxides, among other reactions. Therefore, it is desirable to remove all or most of the unreacted oxygen from the ODH product gas as much as possible to minimize the above-mentioned problems.

[0013] Additionally, acetylene in the product stream can be problematic for downstream users: for example, acetylene can be a catalyst poison in some polymerization processes.

[0014] The embodiments described in the Examples herein provide methods and systems for removing unreacted oxygen and acetylene from an ODH product gas. The product stream from the primary ODH reactor can be cooled to a temperature lower than the reaction temperature, for example, from about 140° C. to about 170° C., from about 145° C. to about 165° C., from about 150° C. to about 160° C., or from about 150° C. to about 152° C. This stream is then fed to another reactor, referred to herein as the oxygen removal reactor. The oxygen removal reactor contains an ODH catalyst, and a mixture of ethanol and water is either combined with the product stream or injected into the bed of the oxygen removal reactor.

[0015] The ODH catalyst used in the oxygen removal reactor may be the same as the ODH catalyst present in the main ODH reactor catalyst bed, or a different ODH catalyst may be used. The amount of ethanol injected depends on the desired results, for example, the amount may be in excess of the stoichiometric amount used to completely react with the unreacted oxygen, or it may be an amount that leaves some unreacted oxygen in the product gas, for example, for use in a subsequent reaction.

[0016] The deoxygenated stream from the oxygen removal reactor is passed through a scrubber, for example, to remove acetic acid. The process gas from the scrubber may be fed through a purification unit to remove acetylene. In some embodiments, the purification unit is a second oxygen removal reactor. For example, in some embodiments, the process gas is compressed and fed to a heat exchanger to raise its temperature to 150° C., which is the operating temperature of the catalyst used in the second oxygen removal reactor. For example, the catalyst may include a Cu / Zn oxide catalyst, among many other catalysts described herein. Chemisorbed oxygen on the Cu / Zn oxide catalyst selectively oxidizes CO and acetylene in the product stream to CO2. The depleted bed then initiates a chemical reaction to remove traces of unreacted oxygen and acetylene remaining in the gas stream, forming a polished gas stream. The purified gas stream may be passed through an amine column or a caustic column to remove CO2.

[0017] Except in the operating examples or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, and the like used in the specification and claims should be understood to be modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed at least in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0018] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible, however, any numerical values ​​inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0019] It should also be understood that any numerical range described herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges therebetween, including the stated minimum of 1 and the stated maximum of 10, i.e., the minimum is equal to or greater than 1 and the maximum is equal to or less than 10. The disclosed numerical ranges are continuous, and therefore include all values ​​between the minimum and maximum. Unless otherwise indicated, the various numerical ranges specified in this application are approximations.

[0020] <Definition> As used herein, the term "diluent" refers to a gas that forms a non-flammable mixture with a hydrocarbon or oxidizing gas. In some examples, a diluent may be selected that participates in an ODH reaction in the presence of an ODH catalyst, such as carbon dioxide. Additionally, a diluent may be used to remove heat. In some embodiments, a diluent may also be used to ensure that the mixture of ethane and oxygen is outside the flammable limits.

[0021] As used herein, the term "essentially oxygen-free" means that the amount of oxygen remaining in the process streams described herein, if any, is sufficiently low so as not to pose a flammable or explosive risk to downstream process streams or equipment. The amount of oxygen present is preferably less than 10 ppm, more preferably less than 5 ppm, and most preferably less than 1 ppm.

[0022] As used herein, the term "fixed bed reactor" refers to one or more reactors in series or parallel, often containing cylindrical tubes packed with catalyst pellets in which reactants flow through the beds and are converted to products. The catalyst within the reactor can have several configurations, including, but not limited to, one large bed, several horizontal beds, several parallel packed tubes, and multiple beds within their own shell.

[0023] As used herein, the term "fluidized bed reactor" refers to one or more reactors in series or parallel that contain a fluid (gas or liquid) passing through a solid, particulate catalyst, often in the form of small spheres (typically smaller than 200 μm), at a velocity sufficient to suspend the solids and cause them to behave as if they were a fluid.

[0024] As used herein, the term "linear velocity" often refers to the linear velocity of the gas stream (m / s) and refers to the flow rate of the gas stream / cross-sectional area of ​​the reactor / void fraction of the catalyst bed. Often, the flow rate refers to the sum of the flow rates of all gases entering the ODH reactor, measured where the oxygen and ethane first contact the ODH catalyst at that temperature and pressure. The cross-sectional area of ​​the reactor is also measured at the inlet of the ODH catalyst bed. The "void fraction" of the catalyst bed refers to the volume of voids in the catalyst bed / total volume of the catalyst bed. The "void volume" refers to the voids between the catalyst particles, not including the volume of the pores inside the catalyst particles. Often, linear velocities range from 5 cm / s to 1500 cm / s, and sometimes from 10 cm / s to 500 cm / s.

[0025] As used herein, the term "MoVOx catalyst" refers to a catalyst having an empirical formula of Mo 6.5-7.0 V3O d where d is a number that satisfies at least the valence of the metals; 6.25-7.25 V3O d where d is a number that satisfies the valence of the metals, or combinations thereof.

[0026] As used herein, the term "oxidative dehydrogenation" or "ODH" refers to a process that combines the endothermic dehydrogenation of ethane with the strongly exothermic oxidation of hydrogen, as further described herein.

[0027] As used herein, the term "substantially oxygen-free" means that the amount of acetylene remaining in the process streams described herein, if any, is undetectable or zero ppmv using the analytical techniques described herein.

[0028] <ODHプロセスユニット> FIG. 1 is a simplified block diagram of an ODH process unit 100. The ODH process unit may be constructed as an independent chemical complex or may be part of a larger chemical complex such as a refinery or polymerization plant. In some embodiments, the chemical complex, one embodiment of which is shown diagrammatically in FIG. 1, comprises an ODH reactor 102, a heat exchanger 104, an oxygen removal reactor 106, a quench tower or acetic acid scrubber 108, a purification unit 110, an amine wash tower 112, a dryer 114, and a distillation tower 116 in a coordinated arrangement. The ODH reactor 102 includes at least one ODH catalyst capable of catalyzing the oxidative dehydrogenation of ethane introduced via an ethane line 122 in the presence of oxygen, which may be introduced via an oxygen line 120. The purification unit 110, which may be a second oxygen removal reactor or an acetylene adsorption bed, is shown immediately after the quench tower or acetic acid scrubber 108, but may be located further downstream as described with respect to FIG. 2. In many cases, a process configuration can be more energy efficient if the purification unit 110 is located after the input stream has been compressed.

[0029] In various embodiments, the ODH process for the oxidative dehydrogenation of ethane is carried out in the ODH reactor 102 at a temperature between about 300° C. and about 500° C., or between about 300° C. and about 450° C., or between about 330° C. and about 425° C. In various embodiments, the ODH reactor 102 is operated at a pressure between about 0.5 psig and about 100 psig (between about 3.447 kPag and about 689.47 kPag), or between about 15 psig and about 50 psig (between about 103.4 kPag and about 344.73 kPag). In various embodiments, the residence time of ethane in the ODH reactor 102 is between about 0.12 seconds and about 9 seconds, or between about 1 second and about 3.6 seconds.

[0030] In some embodiments, the process has a selectivity for the corresponding alkene (e.g., ethylene in the case of ODH of ethane) of greater than about 85%, or greater than about 90%, or greater than 95%, or greater than about 98%. In various embodiments, the gas hourly space velocity (GHSV) is greater than about 400 h-1 and about 30,000h -1 or about 1000 hours -1 and about 30,000h -1 In some embodiments, the gas velocity can be described in terms of weight hourly space velocity (WHSV). In various embodiments, the WHSV is between about 0.4 h -1 and about 30 hours -1 In some embodiments, the gas velocity can be described in terms of linear velocity, for example, between about 5 cm / sec and about 500 cm / sec. In some embodiments, the space-time yield (productivity) of the corresponding alkene in g / hr per kg of catalyst can be at least about 50, or at least about 1500, or at least about 3000, or at least about 3500 at temperatures in the ODH reactor 102 between about 330 and 500° C., depending on the temperature profile of the catalyst bed. In some embodiments, the productivity of the catalyst will increase with increasing temperature until selectivity decreases.

[0031] The ODH reaction may also occur in the presence of a diluent, such as carbon dioxide, nitrogen, or steam, which is added to ensure that the mixture of oxygen and hydrocarbon is outside the flammability limits. As described herein, the diluent may or may not participate in the ODH reaction (e.g., carbon dioxide or steam) or may not (e.g., nitrogen). It is within the knowledge of one of ordinary skill in the art to determine whether a mixture is outside the flammability limits for a given temperature and pressure.

[0032] The ODH reaction and the oxygen removal reaction using an ODH catalyst can be carried out using any number of ODH catalysts. As noted herein, the catalysts used for the ODH reaction and the oxygen removal reaction can be the same or different. Non-limiting examples of suitable oxidative dehydrogenation catalysts include those containing one or more mixed metal oxides selected from the following: i) a catalyst of the formula: Mo a V b Te c Nb d Pd eO f (wherein a, b, c, d, e, and f are the relative atomic weights of the elements Mo, V, Te, Nb, Pd, and O, respectively; a=1, b=0.01-1.0, c=0.01-1.0, d=0.01-1.0, 0.00≦e≦0.10, and f is a number that at least satisfies the valence state of the metal in the catalyst); ii) a catalyst of the formula: Ni g A h B i D j O f (In the formula, g is a number of 0.1 to 0.9, often 0.3 to 0.9, in other cases 0.5 to 0.85, and sometimes 0.6 to 0.8; h is a number of 0.04 to 0.9; i is a number of 0 to 0.5; j is a number of 0 to 0.5; f is a number that satisfies at least the valence state of the catalyst; A is Ti, Ta, V, Nb, Hf, W, Y, Zn, Zr, Si, and Al, or any of them. B is selected from La, Ce, Pr, Nd, Sm, Sb, Sn, Bi, Pb, Tl, In, Te, Cr, Mn, Mo, Fe, Co, Cu, Ru, Rh, Pd, Pt, Ag, Cd, Os, Ir, Au, Hg, and mixtures thereof; D is selected from Ca, K, Mg, Li, Na, Sr, Ba, Cs, Rb, and mixtures thereof; O is oxygen; iii) a catalyst of the formula: Mo a E k G l O f (wherein E is selected from Ba, Ca, Cr, Mn, Nb, Ta, Ti, Te, V, W, and mixtures thereof; G is selected from Bi, Ce, Co, Cu, Fe, K, Mg, V, Ni, P, Pb, Sb, Si, Sn, Ti, U, and mixtures thereof; a=1; k is 0-2; l=0-2, with the proviso that the sum of l for Co, Ni, Fe, and mixtures thereof is less than 0.5; and f is a number that at least satisfies the valence states of the metals in the catalyst); iv) a catalyst of the formula: V m Mo n Nb o Tep Me q O f (wherein Me is selected from Ta, Ti, W, Hf, Zr, Sb and mixtures thereof; m is 0.1 to 3; n is 0.5 to 1.5; o is 0.001 to 3; p is 0.001 to 5; q is 0 to 2; and f is a number that at least satisfies the valence state of the metal in the catalyst); v) a catalyst of the formula: Mo a V r X s Y t Z u M v O f (wherein X is at least one of Nb and Ta; Y is at least one of Sb and Ni; Z is at least one of Te, Ga, Pd, W, Bi and Al; M is at least one of Fe, Co, Cu, Cr, Ti, Ce, Zr, Mn, Pb, Mg, Sn, Pt, Si, La, K, Ag and In; a=1.0 (normalized); r=0.05-1.0; s=0.001-1.0; t=0.001-1.0; u=0.001-0.5; v=0.001-0.3; f is a number that satisfies at least the valence state of the metal of the catalyst). vi) A mixed metal oxide having the empirical formula: Mo 6.5-7.0 V3O d (wherein d is a number that at least satisfies the valence of the metal in the catalyst); vii) A mixed metal oxide having the empirical formula: Mo 6.25-7.25 V3O d (where d is a number that at least satisfies the valence of the metal in the catalyst).

[0033] In some embodiments, the catalyst may be supported / agglomerated with a binder. Some binders include acidic, basic, or neutral binder slurries of TiO2, ZrO2, Al2O3, AlO(OH) and mixtures thereof. Another useful binder includes Nb2O5. The agglomerated catalyst may be extruded into suitable shapes (rings, spheres, saddles, etc.) of sizes typically used in fixed bed reactors. When extruding the catalyst, various extrusion aids known in the art may be used. In some cases, the resulting support has a cumulative surface area of ​​35 m2 or more as measured by BET. 2 / g, in some cases 20m 2 / g, otherwise 3m 2 / g, and the cumulative pore volume is 0.05 to 0.50 cm 3 / g.

[0034] The ODH reactor 102 may be a fixed bed reactor or a fluidized bed reactor. In some embodiments, the ODH reactor is a fixed bed reactor. In a fixed bed reactor, reactants are introduced into the reactor at one end, flow through an immobilized catalyst, and products are formed and exit the reactor at the other end. In some embodiments, the fixed bed reactor is a shell-and-tube reactor. The design of a fixed bed reactor suitable for the methods disclosed herein can follow known techniques for this type of reactor.

[0035] Additional embodiments include the use of a fluidized bed reactor, where the catalyst bed can be supported by a porous structure, or distribution plate, located near the bottom end of the reactor, and the reactants flow at a velocity sufficient to fluidize the bed (e.g., the catalyst rises and begins to swirl fluidly). The reactants are converted to products upon contact with the fluidized catalyst, and the reactants are then removed from the top of the reactor. Design considerations that one skilled in the art can modify and optimize include, but are not limited to, reactor geometry, distribution plate shape and size, input temperature, output temperature, and reactor temperature and pressure controls.

[0036] Embodiments of the present disclosure include using a combination of both fixed bed and fluidized bed reactors, with each reactor having the same or different ODH catalyst. For example, in one embodiment, oxygen removal reactor 106 has a similar size and configuration as ODH reactor 102, allowing the two reactors to be interchangeable.

[0037] The ODH reaction occurring in ODH reactor 102 may also produce a variety of other products, which may include carbon dioxide, carbon monoxide, oxygenates, and water, depending on the catalyst and the conditions prevailing in ODH reactor 102. These products, along with unreacted ethane, ethylene, residual oxygen, carbon monoxide, and diluent, if added, exit ODH reactor 102 via ODH reactor product line 124.

[0038] The ODH reactor product line 124 is directed to a heat exchanger 104 where the reactor effluent is cooled, for example, from above 300° C. to below 180° C. In some embodiments, the reactor effluent is between about 350° C. and 450° C., between about 375° C. and 425° C., or about 400° C. The cooled effluent stream exits the heat exchanger 104 through a cooled effluent line 126. The cooled effluent stream is between about 140° C. and about 180° C., or between about 150° C. and about 160° C., or between about 151° C. and 155° C.

[0039] A cooled effluent line 126 directs the cooled effluent stream to the oxygen removal reactor 106. An ethanol line 128 adds a mixture of water and ethanol to the oxygen removal reactor 106. In various embodiments, the mixture of water and ethanol may be added to the ODH product line 124 prior to the heat exchanger 104. In various embodiments, the mixture of ethanol and water may be added to the cooled effluent stream prior to the oxygen removal reactor 106. Oxygen Removal

[0040] In various embodiments, the ethanol solution comprises ethanol at a concentration of about 0.1% to about 50% by volume, or about 1% to about 35% by volume, or about 10% to about 20% by volume. In one embodiment, the ethanol is at a concentration of about 13.5% by volume in water.

[0041] In the oxygen removal reactor 106, ethanol reacts with oxygen to at least partially remove the oxygen to form a deoxygenated stream having reduced oxygen levels, as described in more detail below. The oxygen removal reactor may be a fixed bed reactor.

[0042] In various embodiments, oxygen removal in oxygen removal reactor 106 is carried out at a temperature in oxygen removal reactor 106 between about 140° C. and about 180° C., or between about 150° C. and about 160° C., or between about 151° C. and about 155° C. In various embodiments, oxygen removal reactor 106 is operated at a pressure between about 0.5 psig and about 100 psig (between about 3.447 kPag and about 689.47 kPag), or between about 15 psig and about 50 psig (between about 103.4 kPag and about 344.73 kPag). In various embodiments, the residence time of the product stream in oxygen removal reactor 106 is between about 0.12 seconds and about 9 seconds, or between about 1 second and about 3.6 seconds.

[0043] The deoxygenated stream is directed by deoxygenated effluent line 130 to a quench tower or acetic acid scrubber 108 to quench the product from the deoxygenated effluent line 130 and facilitate removal of acetic acid and water via quench tower bottom outlet 132. The deoxygenated stream may be cooled prior to entering the quench tower or acetic acid scrubber 108 or the deoxygenated stream may be cooled in the quench tower by contact with a quenching agent such as water. Unconverted ethane, ethylene, unreacted oxygen, carbon dioxide, carbon monoxide, and inert diluent added to the quench tower or acetic acid scrubber 108 exit through quench tower overhead line 134 and are directed to the purification unit 110.

[0044] In various embodiments, purification unit 110 is a second removal reactor using a catalyst system including, for example, copper and zinc, and in other embodiments that can catalyze the removal of acetylene and oxygen, purification unit 110 is an acetylene adsorption bed including, for example, a copper or silver based adsorbent. The adsorbent or catalyst can include any number of copper or silver compounds with different activities. In various embodiments, the catalyst can include CuZnZr, AgCe, CuMn, CuCe, MnCe, and CrCe, among others. These catalysts can be supported on silica.

[0045] In various embodiments, purification unit 110 is operated at a temperature between 60° C. and about 200° C., or between about 70° C. and about 150° C., or between about 80° C. and about 120° C. In various embodiments, purification unit 110 is operated at a pressure between about 0.5 psig and about 100 psig (between about 3.447 kPag and about 689.47 kPag), or between about 15 psig and about 50 psig (between about 103.4 kPag and about 344.73 kPag). In various embodiments, the residence time of the product stream in purification unit 110 is between about 0.12 seconds and about 9 seconds, or between about 1 second and about 3.6 seconds.

[0046] In embodiments where the purification unit 110 is a second oxygen removal reactor, the second reactor contains a catalyst comprising a Group 11 metal with any promoter and any support as described herein. The purification unit may be a fixed bed reactor. The catalyst reacts unreacted oxygen or surface metal oxide with carbon monoxide to produce carbon dioxide. In some embodiments, acetylene is removed by reaction with the unreacted oxygen or surface metal oxide. In the second reactor, most or all of the unreacted oxygen and acetylene remaining after the oxygen removal reactor 106 is consumed. All or a portion of the carbon dioxide in the second reactor can be recycled back to the ODH reactor 102 via recycle lines 136 and 138 as described above to act as an oxidant, a diluent, or both. The remaining unconverted ethane, ethylene, unreacted oxygen (if any), all or a portion of the carbon dioxide, carbon monoxide (if any), and inert diluent are conveyed to the amine scrubber 112 via scrubber feed line 140.

[0047] Any carbon dioxide present in the feed stream from scrubber feed line 140 is captured in the amine scrubber 112 and removed via carbon dioxide bottom outlet 142 and can be sold or alternatively recycled back to the ODH reactor 102 as described above. Components other than carbon dioxide introduced into the amine scrubber 112 via scrubber feed line 140 exit the amine scrubber 112 via amine scrubber overhead line 144 and pass through dryer 114 before being directed via dry feed line 146 to the distillation column 116 where cryogenic distillation is performed to isolate the C2 / C2+ hydrocarbons and remove them via C2 / C2+ hydrocarbon bottom outlet 148. The remainder, comprising primarily C1 hydrocarbons along with residual inert diluent and carbon monoxide (if any), exits the distillation column 116 via overhead stream 150. This overhead stream 150 may be flared and combusted to generate heat (e.g., in a gas-fired furnace) or may be directed to an oxygen separation module as described in U.S. Pat. No. 10,343,957 (assignee NOVA Chemicals (International) SA).

[0048] The C2 / C2+ hydrocarbons removed from the bottom outlet 148 may be directed to a splitter for separating ethylene from ethane. In one embodiment, the distillation column 116 may separate the C2 / C2+ hydrocarbon fraction into an ethane fraction and an ethylene fraction, with the ethylene being removed from a side outlet (not shown) of the distillation column and the ethane being removed from the bottom outlet 148 of the distillation column. The ethane fraction obtained from the splitter or distillation column capable of separating ethane from ethylene may be recycled back to the reactor and the ethylene fraction may be used in additional processes (e.g., the production of ethylene oxide) or may be used to produce polyethylene.

[0049] In some embodiments, a concern in the ODH process is mixing the hydrocarbon with oxygen. Under certain conditions, the mixture may become unstable and cause an explosion. The mixer can be used to mix the hydrocarbon-containing gas with the oxygen-containing gas in an open flooded mixing vessel. By mixing in this manner, pockets of unstable composition are surrounded by non-flammable liquid, so that even if an ignition event occurs, it is quickly extinguished. The result is a non-flammable, homogenous mixture of the hydrocarbon gas and the oxygen gas fed to the ODH reactor. Examples of gas mixers suitable for use in the methods and systems described herein can be found in PCT patent applications WO2018 / 007912 and WO2021 / 019347 (assignee NOVA Chemicals (International) SA).

[0050] In some embodiments, a flooded gas mixer is placed upstream of the ODH reactor 102. In this example, an oxygen line 120 and an ethane line 122 feed into the flooded gas mixer. A homogeneous mixture of hydrocarbons and oxygen, and optionally a diluent, can be introduced from the flooded gas mixer through the mixture line into the ODH reactor 102. The oxygen-rich stream from the oxygen separation module can be fed directly to the flooded gas mixer or can be combined with the oxygen line 120 and fed into the flooded gas mixer.

[0051] Figure 2 is a simplified block diagram of a process unit 200 for removing oxygen and acetylene in an oxygen removal reactor. Like numbered items are the same as those described with respect to Figure 1. With reference to Figure 2, process unit 200, similar to process unit 100, generally includes an ODH reactor 202, a heat exchanger 204, an oxygen removal reactor 206, and a quench tower or acetic acid scrubber 208. Process unit 200, similar to process unit 100, can also include downstream separation components including an amine wash tower, a dryer, a distillation tower, and an optional oxygen separation module, which are not shown in Figure 2 for simplicity.

[0052] ODH reactor 202 includes at least one ODH catalyst capable of catalyzing in the presence of oxygen, which may be introduced via oxygen line 220, the oxidative dehydrogenation of ethane, introduced via ethane line 222, to produce a product stream including unconverted ethane, ethylene, unconverted oxygen, acetic acid, water, and possibly acetylene. As described herein, the ODH product stream is conveyed from ODH reactor 202 to heat exchanger 204 via ODH reactor product line 224. In some embodiments, the product stream is cooled to a temperature below the reaction temperature, for example, between about 140° C. to about 170° C., about 145° C. to about 165° C., about 150° C. to about 160° C., or about 150° C. to about 152° C. This stream is then fed to oxygen removal reactor 206 via cooled effluent line 226.

[0053] The oxygen removal reactor 206 contains an ODH catalyst bed, and the ethanol / water stream is injected into the ODH catalyst bed via ethanol line 228. Alternatively, the ethanol / water mixture may be mixed with the product stream either before or after heat exchanger 204. The ODH catalyst may be the same as that in the ODH reactor, or may be selected to optimize the oxygen removal reaction. The amount of ethanol injected depends on the desired results. For example, the amount injected may exceed the stoichiometric amount required to completely remove the unreacted oxygen. A lower amount may be injected to leave the unreacted oxygen in the process gas. The injected ethanol may be converted to acetic acid by reaction with oxygen, or, in the absence of oxygen, the excess ethanol may be dehydrated to produce ethylene. An alternative alcohol, such as propanol, may be used in place of ethanol. However, it should be noted that the use of propanol will likely result in the production of propanoic acid (if there is residual oxygen) or propylene (if there is no residual oxygen).

[0054] In this embodiment, the effluent of the oxygen removal reactor 206 is fed by deoxygenated effluent line 230 to a cooler 252 where the temperature of the effluent is reduced below the dew point of the acetic acid and water. As a result, a significant amount of the acetic acid and water in the stream condenses. A flash drum 254 is used to separate a liquid stream from the gas stream. The liquid stream may be removed as a bottoms stream 256, which may be further processed in an acetic acid separation system (not shown) to separate the acetic acid from the water.

[0055] The gas stream from the flash drum 254 is fed to a scrubber 208 where traces of acetic acid are removed by countercurrent flow of water added through a water line 256. The remaining gas, including unconverted ethane, ethylene, unreacted oxygen, carbon dioxide, carbon monoxide, and inert diluent added to the scrubber 208, exits through a quench tower overhead line 234 and is compressed in a compressor 260. The compressed process gas may be processed based on acetylene content. If the acetylene gas content is high enough to make downstream hydrogenation economical (e.g., greater than about 5%, greater than about 10%, or more), a bypass line 262 may be used to bypass the purification step. If the acetylene is too low to economically perform separation, the compressed process gas may be fed to a purification unit to remove traces of acetylene and oxygen. In the embodiment shown in FIG. 2, the purification unit is a second oxygen removal reactor 222. The compressed process gas is fed to a heat exchanger 264 to raise its temperature to between about 80° C. and about 250° C., or to about 150° C., which is the operating temperature of the catalyst bed containing the Cu / Zn oxide catalyst in the second oxygen removal reactor 210. The chemisorbed oxygen on the Cu / Zn oxide catalyst selectively oxidizes the CO in the product stream to CO2. The depleted bed then initiates a chemical reaction to remove traces of unreacted oxygen and acetylene remaining in the gas phase. Alternatively, if all unreacted oxygen from the ODH reactor 202 is removed in the oxygen removal reactor 206 and a Cu / Zn oxide catalyst is used for acetylene removal by combustion in the second bed, oxygen must be fed to the second bed, for example, through an oxygen line (not shown). As described herein, the second oxygen removal reactor 210 in the purification unit may be replaced with an acetylene adsorption bed containing an adsorbent containing, for example, Cu, Ag, or both. In this case, due to acetylene's high affinity for the adsorbent, the acetylene in the product stream is adsorbed onto the adsorbent bed, which can be periodically taken out of service for regeneration.

[0056] The purified gas (or bypass gas) may be compressed again in a second compressor 232 before being fed to downstream separation systems including an amine scrubber, dryer, and distillation column. Final processing produces an ethylene stream 248, which can be used to make polyethylene or other ethylene-derived products. The C1 hydrocarbons can be flared, used to heat a furnace, or passed through an oxygen separation module, as described above. Recaptured ethane can be recycled and added to the ODH reactor 202.

[0057] 3 is a process flow diagram of a method 300 for converting ethane to ethylene and removing oxygen from the effluent. The method 300 begins at block 302 by feeding a feed stream comprising ethane and oxygen to an oxidative dehydrogenation reactor. At least a portion of the ethane is converted to ethylene in the oxidative dehydrogenation reactor at block 304 to provide a reactor effluent stream comprising ethane, ethylene, and oxygen, acetylene, or both oxygen and acetylene. At block 306, the reactor effluent stream is cooled to form a cooled effluent stream. At block 308, the cooled effluent stream is fed to an oxygen removal reactor comprising an ODH catalyst bed. At block 310, a deoxygenated stream comprising water and alcohol is fed to the oxygen removal reactor to form a deoxygenated effluent.

[0058] The present disclosure also contemplates the use of various tools commonly used in chemical reactors, including flow meters, compressors, valves, and sensors for measuring parameters such as temperature and pressure. It is expected that one of ordinary skill in the art would include these components as deemed necessary for operation or as required to comply with legal obligations related to safety regulations. EXAMPLES

[0059] The following examples are non-limiting and are intended only to demonstrate the removal or reduction of oxygen and acetylene in an ethane ODH product stream by physical experiments combined with computer modeling. Those skilled in the art will understand that variations of the described components may achieve similar results in reducing oxygen and acetylene levels in an ethane ODH product stream.

[0060] <Preparation of ODH Test Catalyst> The general composition Mo1V in 600 mL of distilled water 0.30-0.40 Te 0.10-0.20 Nb 0.10-0.20 )O 4-14 The ODH catalyst having was prepared as follows: A solution of (NH4)6Mo7O 24 ·4H2O (44.20 g, 35.77 mmol, white solid) was prepared in a 2 L round-bottom flask equipped with a magnetic stir bar. A solution of VOSO4·3.46H2O (14.07 g, 62.95 mmol, light blue solid) in 600 mL of distilled water was prepared in a 1 L beaker equipped with a magnetic stir bar. The two solutions were stirred in a 60 °C water bath until homogeneous. Then, the blue vanadium solution was added to the colorless transparent molybdenum solution. This resulted in a dark purple solution containing a fine suspension. Sodium dodecyl sulfate (SDS) (13.57 g, 47.06 mmol, white solid) was added to the reaction mixture. The purple slurry was stirred at 60 °C for 1 hour.

[0061] The total volume measured after transferring the reaction mixture to a glass liner and rinsing was approximately 1380 mL. The liner was loaded into a 2 L pressure reactor (Parr Instrument Company, Moline, IL) and the gap was filled with distilled water. The reactor was sealed and the headspace was evacuated and backfilled with nitrogen gas 10 times. The headspace was left under 15 psig nitrogen gas and sealed. The reactor was transferred to a programmable oven and heated at 230°C for 24 hours (1 hour ramp to 230°C and 24 hours cool to room temperature). Once cooled to room temperature, the reactor was evacuated and the contents were filtered using a Buchner funnel and four sheets of metered filter paper. The oily mother liquor was decanted off and the filter paper was replaced. The filter cake was rinsed with 1250 mL of distilled water. The filtrate was a deep blue color and the product was a charcoal / gray purple color.

[0062] The filter cake was dried overnight in a 90°C oven to recover 15.29g of product (estimated yield 37%). The uncalcined catalyst was crushed with a spatula and loaded into a programmable muffle furnace. The furnace was programmed to ramp to 280°C over 1 hour, hold at that temperature for 9 hours, and then naturally cool to room temperature. The air-treated product was crushed with a mortar and pestle and submitted for CHN analysis. Carbon and nitrogen contents were found to be less than 1% by weight. The material was loaded into a quartz boat and placed in the center of the quartz tube of a QRU furnace. The quartz tube was purged with nitrogen (400sccm) for 8 hours, after which the nitrogen was passed through an oxygen scrubbing bed to further purify the nitrogen to less than 0.25ppmv oxygen. The ultra-high purity (UHP) nitrogen was purged through the quartz tube overnight. The next morning the furnace was turned on and heated to 400°C over 4 hours. The catalyst was calcined at 400° C. for 2 hours and then allowed to cool naturally to ambient temperature.

[0063] A Cu / Zn oxide catalyst, i.e., a reduced form of an oxide precursor composition containing 70 wt.% CuO, 20 wt.% ZnO, and 10 wt.% ZrO2, was prepared as follows: A Cu-Zn-Zr nitrate solution (metal content 15.2 wt.%, Cu:Zn:Zr ratio corresponds to CuO:ZnO:ZrO2 weight ratio of 7:2:1) was precipitated with ammonium hydroxide solution (28-30 wt.% ammonia) at pH 6.5 and 70°C. After precipitation was complete, the suspension was stirred for an additional 120 min at pH 6.5 and 70°C. The solution was then filtered and the filter cake was washed with demineralized water to remove nitrates and dried at 120°C. The dried powder was calcined in a forced air oven at 300°C for 240 min.

[0064] [Example 1] Removal of residual O2 using ethanol The removal of residual oxygen from an ODH product stream was demonstrated using a fixed bed reactor unit (FBRU) consisting of two fixed bed reactors arranged in series. Each reactor was constructed of 1 inch outer diameter, 34 ft long SS316L stainless steel tubing and was water / steam jacketed for temperature control. Both reactors were loaded with ODH test catalyst and operated as oxygen removal beds at temperatures between about 151 °C and about 153 °C. The reactors were fed a simulated mixture of ODH process effluent containing ethylene, ethane, oxygen, and acetylene along with a mixture of ethanol and water. The combined feed composition (Table 1A), both on a dry and liquid basis, was run for 648 h. -1 The gas was added at a gas hourly space velocity (GHSV) of 1000 g / m.

[0065] In the FBRU experiments, a GC analyzer was used to identify the gas and liquid product effluents. The typical detection limit of the GC analyzer was 0.01%, and it was calibrated at least once a month to ensure the accuracy of the data. In experiments where the detected compounds were close to the detection limit (<0.1), the corresponding GC chromatograms were manually analyzed to determine whether the chromatograms reflected a noise pattern or a distinct peak pattern. Only if a peak pattern was observed, the value was accepted, otherwise it was considered to be zero. The reaction continued for 29 hours and 45 minutes. The product gas composition after the three intervals is shown in Table 1B. The O2 content dropped to zero. The liquid composition, evaluated in the condensed fraction downstream of the fixed-bed reactor, was measured at the end of the experimental time frame.

[0066] [Table 1A]

[0067] [Table 1B]

[0068] Table 2 shows the activity of the ODH catalyst for the conversion of ethanol to ethylene and acetic acid, as determined from the average product gas composition (vol %) over three intervals and the final liquid composition (vol %). It can be seen that the CO2 content in the feed stream and the CO2 content in the product stream are essentially unchanged.

[0069] [Table 2]

[0070] In these experiments, the baseline activity of the catalyst under typical ODH reaction conditions was tested both before and after ethanol injection experiments. ODH conditions were defined as a GHSV of 825 h -1 , WHSV is 1.02h -1The reactor inlet pressure was 18.3 psig, and the feed contained 82% by volume of ethane and 18% by volume of oxygen, respectively. Injection of ethanol vapor for deoxygenation was found not to deactivate the catalyst, as shown in Table 3.

[0071] [Table 3]

[0072] ASPEN simulations were performed to determine the amount of ethanol required to reduce the oxygen concentration to about 10 ppm dry basis at a commercial scale. The simulations were developed using ASPEN Plus® V10 software. The PENG-ROB equation of state was used for the simulations. The vapor properties were obtained using STEAMNBS. The reactor was modeled using the RSTOIC model. The outlet stream composition after the ODH reaction was obtained from the gPROMS® model and fed into ASPEN Plus. The reaction was carried out at 152° C., similar to the FBRU conditions. The two reactions considered for ethanol conversion are: TIFF2024532448000006.tif18133

[0073] The modules and equations used in ASPEN simulations are known in the art. As used herein, PENG-ROB is the Peng-Robinson equation of state, which expresses fluid properties in terms of the various critical properties and acentric factors involved. STEAMNBS is the steam table used to calculate steam properties in ASPEN Plus. RSTOIC is the stoichiometric reactor model used in ASPEN Plus. This model is used when reaction kinetics are unknown or unimportant, but the stoichiometry and molar amounts or conversions of each reaction are known. gPROMS is a software module from Process System Enterprise, Inc., used to build, validate, and run steady-state and dynamic process models.

[0074] The fractional conversion of each reaction step is based on the yields shown in Table 3. The total conversion of ethanol is 87%. Based on the simulation, purification of a process gas stream containing 47.4 kg / hr of oxygen requires 241.8 kg / hr of ethanol. The components of model 400 are shown in FIG. 4 and include an oxygen removal reactor 406 and a heat exchanger 404. Product stream A is mixed with ethanol / water stream B to form mixed stream C, which passes through heat exchanger 404 to form a cooled effluent stream D, which flows into the oxygen removal reactor where a deoxygenated effluent E is formed. The composition of the components at points A-E as well as the mass and heat balances are shown in Table 4. The reactor heat duty was -0.43 GJ / hr.

[0075] [Table 4]

[0076] [Example 2] Removal of oxygen / acetylene using Cu / Zn oxide catalyst The removal of residual oxygen and acetylene using a Cu / Zn oxide catalyst was demonstrated using a laboratory-scale oxidative dehydrogenation reactor called a Microreactor Unit (MRU). The MRU reactor was constructed from a 0.5 inch outer diameter stainless steel tube and was packed with 2 g of ODH test catalyst. A feed containing oxygen, ethane, and nitrogen in a weight ratio of 18% / 36% / 46% by volume, respectively, was passed through the catalyst bed at 8.4 psig, a gas flow rate of 32.8 sccm, and a temperature of 327°C. The effluent from the MRU reactor was passed through a condenser to remove an aqueous solution containing 18.5 wt% acetic acid. The condensed gaseous fraction, minus the acetic acid, was passed through an oxygen removal reactor at 14 psig.

[0077] The oxygen scavenging reactor, a 1 / 4 inch OD tube, was loaded with 1 g of dried, calcined Cu / Zn / Zr oxide catalyst (in powder form) and placed in a temperature controlled oven. The catalyst powder and effluent gas were contacted at 150° C. using a flow rate of 32.8 sccm at a pressure range of 8.4 psig to 4 psig. The effluent exited the oxygen scavenging reactor at ambient pressure and was evaluated using an Agilent® 6890N Gas Chromatograph and ChromPerfect® Analysis, version 6.1.10 software for data evaluation at several temperature and time intervals. The results are shown in Table 5. The feed composition was measured at two different time points to ensure consistency of the GC measurements of the feed.

[0078] [Table 5]

[0079] The data in Table 5 show that the dried, calcined powder catalyst removes O2, CO, and acetylene at temperatures above 120° C. It is also evident from the data in Table 5 that not all of the compounds are chemisorbed but are reacting with oxygen from the catalyst or with oxygen in the gas stream. The constant presence of oxygen in the feed stream was sufficient to oxidize all of the acetylene, and acetylene and O2 continued to be removed even after the chemisorbed oxygen on the catalyst surface was depleted from the catalyst material (as indicated by CO returning to its original feed concentration).

[0080] [Example 3] Aspen simulation of Cu / Zn oxide A second ASPEN Plus simulation was performed to determine the requirements for operating a purification unit for acetylene removal in a commercial plant in isothermal or adiabatic mode. The simulation was developed using ASPEN Plus V10. The PENG-ROB equation of state was used for the simulation. Vapor properties were obtained using STEAMNBS. The reactor was modeled using the RSTOIC model. The two reactions considered for catalytic conversion are: TIFF2024532448000009.tif17133 5 includes an oxygen removal reactor 510 with a Cu / Zn oxide catalyst, a first heat exchanger 564, a pump 566, and a second heat exchanger 568. From this model 500, cooling water surrounding the oxygen removal reactor was modeled to control the heat of the oxygen removal reactor 510 in conjunction with a second heat exchanger 568.

[0081] <Adiabatic operation of reactor> Modeling the adiabatic mode of oxygen-removed water involves passing effluent A (FIG. 5), similar to the deoxygenated effluent formed in the first oxygen removal reactor, through heat exchanger 562 to form heated effluent B, which is introduced into oxygen removal reactor 510 to form polished gas stream C. The composition and material and heat balances at points A, B, and C are shown in Table 6. By operating the reactor adiabatically, the required reaction temperature of 150° C. in the reactor (represented by the temperature of the purified gas stream leaving the oxygen removal reactor) was achieved at a heated effluent B temperature of 141° C. It should be apparent to one skilled in the art that adiabatic operation similar to that shown in this example can be achieved by routinely optimizing the temperature, pressure, and flow rate of effluent A. This includes various setups for compression, heating, and cooling downstream of the quench tower or scrubber. The results in Table 6 show that there is no oxygen or acetylene in the purified gas stream.

[0082] [Table 6]

[0083] <Isothermal operation of reactor> A simulation using model 500 to demonstrate isothermal mode oxygen removal with cooling water circulation around the oxygen removal reactor includes increasing the pressure of cooling water D with pump 566 to form pressurized cooling water E, which cools water returning from the cooling jacket of oxygen removal reactor 510 (double arrow) via heat exchanger 568 to form heated cooling water F, along with effluent A from the adiabatic mode, heated effluent B, and purified gas C. The composition and material and heat balances at each of points A-F are shown in Table 7. The results show that heated effluent B can enter oxygen removal reactor 510 at a temperature of 150° C. if the cooling water flow rate, temperature, and pressure are capable of removing 0.77 GJ / hr of reactor heat load. In this example, the cooling water D conditions in Table 7 were sufficient to remove the heat required for isothermal operation. One skilled in the art would understand that the pressure, temperature, and flow rate can be adjusted to achieve similar isothermal operation as shown in this example.

[0084] [Table 7]

[0085] <Embodiment> An embodiment described in the Examples herein provides a method for converting ethane to ethylene. The method includes feeding a feed stream comprising ethane and oxygen to an oxidative dehydrogenation reactor, and converting at least a portion of the ethane to ethylene in the oxidative dehydrogenation reactor to provide a reactor effluent stream comprising ethane, ethylene, and oxygen, acetylene, or both. The method includes cooling the reactor effluent stream to form a cooled effluent stream, and feeding the cooled effluent stream to an oxygen removal reactor comprising an ODH catalyst bed. A deoxygenated stream comprising water and alcohol is fed to the oxygen removal reactor to form a deoxygenated effluent.

[0086] In one embodiment, the method includes feeding the deoxygenated effluent to an acetylene adsorption column.

[0087] In one embodiment, the method includes cooling the deoxygenated effluent to form a mixed effluent. In one embodiment, the mixed effluent is separated into a gas stream and a liquid stream. In one embodiment, the gas stream is passed through a scrubber to remove acetic acid. In one embodiment, the gas stream is compressed and fed to a cryogenic separation system to form a purified alkene stream.

[0088] In one embodiment, the gas stream is compressed, heated and then fed to a second oxygen removal reactor to form a polished gas stream. In one embodiment, the purified gas stream is compressed and fed to a cryogenic separation system to form a purified alkene stream.

[0089] In one embodiment, the gas stream is passed through a catalyst bed comprising copper, zinc, silver, chromium, cerium, or any combination thereof in a second oxygen removal reactor to form a purified gas stream.

[0090] In one embodiment, the method includes compressing a gas stream, heating the gas stream, and feeding the gas stream to an acetylene adsorption column to form a purified gas stream. In one embodiment, the method includes compressing the purified gas stream and feeding the purified gas stream to a cryogenic separation system to form a purified alkene stream.

[0091] In one embodiment, the gas stream is passed through an adsorbent bed containing copper, silver, or both in an acetylene adsorption column to form a purified gas stream.

[0092] Another embodiment described in the Examples herein provides a system for producing ethylene from ethane, the system including an oxidative dehydrogenation (ODH) reactor, a first heat exchanger for cooling an ODH effluent from the ODH reactor, and an oxygen removal reactor including an ODH catalyst.

[0093] In one embodiment, the system includes a second heat exchanger for cooling the oxygen reduced effluent from the oxygen removal reactor and a flash drum for separating the oxygen reduced effluent into a gas stream and a liquid stream. In one embodiment, the system includes an acetic acid separation system on the liquid stream from the flash drum, the acetic acid separation system separating the liquid stream into an acetic acid stream and a water stream. In one embodiment, the system includes a scrubber with a water inlet for removing acetic acid from the gas stream in countercurrent flow. In one embodiment, the system includes a first compressor on the gas stream from the scrubber. In one embodiment, the system includes a third heat exchanger for heating the gas stream from the compressor.

[0094] In one embodiment, the system comprises a polishing unit coupled to the third heat exchanger, hi one embodiment, the polishing unit comprises a catalyst comprising copper, silver, zinc, cerium, or any combination thereof.

[0095] In one embodiment, the purification unit comprises an acetylene adsorption column comprising an absorption bed comprising copper, silver, zinc, or any combination thereof. In one embodiment, the system comprises a second compressor on the gas stream from the first compressor. In one embodiment, the system comprises a cryogenic separation system coupled to the second compressor to form an alkene outlet stream.

[0096] Although the present disclosure includes many specific embodiment details, these should not be construed as limitations on the scope of the subject matter or the scope of the claims, but rather as descriptions of features specific to particular embodiments. Certain features described in the present disclosure in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable subcombination. Furthermore, although the features described above may be described as functioning in a particular combination and may initially be claimed as such, in some cases one or more features may be deleted from the claimed combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0097] Specific embodiments of the subject matter have been described. Other embodiments, modifications, and permutations of the described embodiments will be apparent to those skilled in the art and are within the scope of the claims. Although operations may be shown in a particular order in the drawings or claims, this should not be understood as requiring that such operations be performed in the particular order shown, or in sequential order, or that all of the illustrated operations (some operations may be considered optional) be performed to achieve desirable results.

[0098] Accordingly, the foregoing exemplary embodiments do not define or limit the disclosure. Other changes, substitutions, and alterations are possible without departing from the spirit and scope of the disclosure.

[0099] Other implementations are within the scope of the following claims. [Industrial Applicability]

[0100] This disclosure relates to the oxidative dehydrogenation of ethane to ethylene. More specifically, this disclosure relates to the removal of oxygen from an ethane ODH product stream using ethanol.

Claims

1. 1. A process for converting ethane to ethylene, comprising: providing a feed stream comprising ethane and oxygen to an oxidative dehydrogenation reactor; converting at least a portion of the ethane to ethylene in an oxidative dehydrogenation reactor to provide a reactor effluent stream comprising ethane, ethylene, and one or both of oxygen and acetylene; cooling the reactor effluent stream in a heat exchanger to form a cooled effluent stream; feeding the cooled effluent stream to an oxygen removal reactor containing an ODH catalyst bed; feeding the deoxygenated stream comprising water and ethanol to an oxygen removal reactor to form a deoxygenated effluent; The above method, comprising:

2. 10. The method of claim 1, comprising feeding the deoxygenated effluent to an acetylene adsorption column.

3. The method of claim 1 , including cooling the deoxygenated effluent to form a mixed effluent.

4. 4. The method of claim 3, comprising separating the mixed effluent into a gas stream and a liquid stream, and optionally further comprising one of the following options (i) to (iv): (i) passing said gas stream through a scrubber to remove acetic acid; (ii) compressing the gas stream; feeding said gas stream into a cryogenic separation system to form a purified alkene stream; (iii) compressing the gas stream; heating the gas stream; feeding the gas stream to a second oxygen removal reactor to form a purified gas stream; or (iv) compressing the gas stream; heating the gas stream; feeding the gas stream to an acetylene adsorption column to form a purified gas stream.

5. 5. The method of claim 4, comprising option (iii): compressing the purified gas stream; feeding the purified gas stream to a cryogenic separation system to form a purified alkene stream; Including, Optionally, the method further comprises passing the gas stream through a catalyst bed comprising copper, zinc, silver, chromium, cerium, or any combination thereof in the second oxygen removal reactor to form the purified gas stream.

6. 5. The method of claim 4, comprising option (iv): compressing the purified gas stream; feeding the purified gas stream to a cryogenic separation system to form a purified alkene stream; Including, Optionally, the method further comprises passing the gas stream through an adsorbent bed comprising copper, silver, or both in the acetylene adsorption column to form the purified gas stream.

7. 1. A system for producing ethylene from ethane, comprising: an oxidative dehydrogenation (ODH) reactor; a first heat exchanger for cooling the ODH effluent from the ODH reactor; an oxygen removal reactor containing an ODH catalyst; The above system.

8. a second heat exchanger for cooling the oxygen-depleted effluent from the oxygen removal reactor; a flash drum for separating the oxygen-depleted effluent into a gas stream and a liquid stream; The system of claim 7, comprising:

9. 10. The system of claim 8, further comprising an acetic acid separation system on the liquid stream from the flash drum that separates the liquid stream into an acetic acid stream and a water stream.

10. 10. The system of claim 8, comprising a scrubber comprising a water inlet for removing acetic acid from the gas stream in a countercurrent flow.

11. The system of claim 10 further comprising a first compressor on the gas flow from the scrubber.

12. The system of claim 11 including a third heat exchanger for heating the gas stream from the compressor.

13. 13. The system of claim 12, comprising a purification unit coupled to the third heat exchanger, optionally comprising: comprising a catalyst comprising copper, silver, zinc, cerium, or any combination thereof; or The above system comprising an acetylene adsorption column comprising an adsorption bed comprising copper, silver, zinc, or any combination thereof.

14. The system of claim 11 including a second compressor on the gas flow from the first compressor.

15. 15. The system of claim 14, comprising a cryogenic separation system coupled to the second compressor to form an alkene outlet stream.

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