Methods and systems for converting carbon oxides to olefins

Abstract

This invention provides a method for converting carbon oxides into olefins. The method may include directing a renewable hydrogen feed stream and a carbon oxide feed stream to a methanation reactor to produce a methane oxidative coupling (OCM) feed stream containing methane. The OCM feed stream and an oxygen-containing oxidant feed stream are then directed to an OCM reactor containing an OCM catalyst to produce an OCM effluent containing ethylene. A system for converting carbon oxides into olefins is also provided. The method and system produce olefins containing ethylene with negative carbon emissions.

Description

Technical Field

[0001] This invention relates to a method and system for converting carbon oxides into olefins. More specifically, this invention relates to a method and system for converting carbon oxides into ethylene with negative carbon emissions. Prior Technology

[0002] The production of olefins generally results in the release of extremely large amounts of carbon dioxide (CO2) into the atmosphere. In fact, the steam cracking of saturated hydrocarbons to produce olefins is one of the most energy-intensive processes in the chemical industry. It has been reported that the production of one ton of olefins (i.e., a mixture of ethylene and propylene) results in the emission of nearly one ton of CO2. Global pressure to reduce greenhouse gas emissions (more specifically, CO2 emissions) is mounting.

[0003] Several methods have been proposed for the production of ethylene (C₂H₄) from CO₂. In one method, the first step is to convert CO₂ to methane (CH₄) using a Sabatier methanation reaction. The next step is steam reforming of CH₄ to produce syngas (i.e., CO and H₂). In a subsequent step, the syngas is used to produce methanol (CH₃OH). Finally, CH₃OH is converted to light olefins (e.g., C₂H₄) and water using a zeolite catalyst. This particular method for producing C₂H₄ involves numerous steps and is costly to construct such a plant to perform the process. Another problem with this particular method involves the source of hydrogen (H₂) used for methanation. Because steam reforming of methane is the primary source of H₂, this particular method produces more CO₂ than it consumes.

[0004] Another method for producing C2H4 from CO2 involves performing methanol synthesis and the conversion of the synthesized CH3OH to olefins in the same reactor, bypassing the steam reforming step and reducing plant costs (Gao et al., Catalysis Science and Technology (2017), Vol. 23, 5602-5607). This method involves using a methanol synthesis catalyst that directly converts CO2 and H2 to CH3OH in the upper catalyst bed of one reactor, and a methanol-to-olefins catalyst (e.g., SAPO-34) that converts CH3OH to light olefins and water in the lower catalyst bed of one reactor.

[0005] In addition, one electrochemical technique for converting CO2 to C2H4 has been proposed (see Qin et al., Int. J. Electrochem. Sci. (2018), Vol. 13, 10101-10112). Another electrochemical technique involves using a catalyst made of carbon, copper, and nitrogen to convert CO2 to ethanol (https: / / www.energy.gov / articles / scientists-accidentally-turned-co2-ethanol). Ethanol can then be converted to C2H4 via a dehydration reaction.

[0006] Thermochemical cycles have also been proposed as a method for converting CO2 into useful products. U.S. Patent No. 9,464,010 discloses the use of a copper-chlorine (Cu-Cl) thermochemical cycle as a method for generating H2 required to capture CO2 and convert it into useful products.

[0007] Although several procedures for converting CO2 into olefins have been proposed, these procedures are generally too expensive to be practical or are still many years away from commercialization. In addition, some of these procedures produce more CO2 than they consume, and some procedures involving CH3OH as an intermediate do not utilize the O2 produced. Summary of the Invention

[0008] This paper discloses methods and systems for converting carbon oxides into olefins (specifically, ethylene), which utilize renewable hydrogen and reduce greenhouse gas emissions. Furthermore, the methods and systems for converting carbon oxides into olefins exhibit high carbon efficiency and achieve negative carbon emissions.

[0009] According to the present invention, a method for converting carbon oxides into olefins comprising ethylene (C₂H₄) is provided. The method comprises guiding a renewable hydrogen (H₂) feed stream and a carbon oxide feed stream comprising carbon dioxide (CO₂), carbon monoxide (CO), or both CO₂ and CO into a methanation reactor to produce a methane oxidative coupling (OCM) feed stream comprising methane (CH₄). The OCM feed stream and an oxidant feed stream comprising oxygen (O₂) are guided into an OCM reactor comprising an OCM catalyst. An OCM reaction is performed to produce an OCM effluent comprising (i) a C₂⁺ compound comprising C₂H₄ and ethane (C₂H₆) and (ii) a non-C₂⁺ impurity comprising one or more of CO, CO₂, H₂, and CH₄. The method produces olefins comprising C₂H₄ with negative carbon emissions.

[0010] According to the present invention, a method for converting CO2 into olefins comprising C2H4 is provided. The method comprises directing a natural gas stream containing CO2 to a gas processing unit to generate a CO2 feed stream and a substantially CO2-free natural gas stream. The CO2 feed stream and a renewable H2 feed stream are directed to a methanation reactor to generate an OCM feed stream comprising CH4. The OCM feed stream and an oxidant feed stream comprising oxygen O2 are directed to an OCM reactor comprising an OCM catalyst. An OCM reaction is performed to produce an OCM effluent comprising (i) C2+ compounds comprising C2H4 and C2H6 and (ii) non-C2+ impurities comprising one or more of CO, CO2, H2, and CH4. The method produces olefins comprising C2H4 with negative carbon emissions.

[0011] According to the present invention, a system for converting carbon oxides into olefins comprising C₂H₄ is ​​provided. The system comprises a renewable hydrogen (H₂) subsystem configured to produce a renewable H₂ feed stream. A methanation subsystem is located downstream of and fluidly coupled to the renewable H₂ subsystem. The methanation subsystem is configured to receive the renewable H₂ feed stream and a carbon oxide feed stream comprising CO₂, CO, or both CO₂ and CO, and to produce an OCM feed stream comprising methane (CH₄). An OCM subsystem is located downstream of and fluidly coupled to the methanation subsystem. The OCM subsystem is configured to receive the OCM feed stream and an oxidant feed stream including O2 and produce an OCM effluent comprising (i) C2+ compounds including C2H4 and C2H6 and (ii) non-C2+ impurities including one or more of CO, CO2, H2, and CH4. The system also includes a downstream separation subsystem fluidly coupled to the OCM subsystem. This separation subsystem is configured to receive the OCM effluent and separate it into at least (i) a first stream including one of COx, H2, and CH4 and (ii) a second stream including one of C2+ compounds including C2H4 and C2H6. The system is configured to operate to produce olefins containing C2H4 with negative carbon emissions.

[0012] According to the present invention, a method for converting CO2 into olefins containing ethylene (C2H4) is provided. The method includes directing a feed stream containing CO2 to a CO2 electrolysis unit to generate a first regenerable electrolytic stream containing CO and a second regenerable electrolytic stream containing O2. A regenerable H2 feed stream and the first regenerable electrolytic stream are directed to a methanation reactor to generate an OCM feed stream containing CH4. The OCM feed stream and an oxidant feed stream containing the second regenerable electrolytic stream are directed to an OCM reactor containing an OCM catalyst. An OCM reaction is performed to produce an OCM effluent containing (i) a C2+ compound containing C2H4 and ethane (C2H6) and (ii) a non-C2+ impurity containing one or more of CO, CO2, H2, and CH4. The method produces olefins containing C2H4 with negative carbon emissions.

[0013] According to the present invention, a method for converting CO2 into olefins containing ethylene (C2H4) is provided. The method includes directing a first feed stream containing CO2 and a second feed stream containing water (H2O) to a co-electrolysis unit to generate a renewable syngas stream containing CO and H2 and a renewable oxidant stream containing O2. The renewable syngas stream is then directed to a methanation reactor to generate an OCM feed stream containing CH4. The OCM feed stream and the renewable oxidant stream are then directed to an OCM reactor containing an OCM catalyst. An OCM reaction is performed to produce an OCM effluent containing (i) C2+ compounds containing C2H4 and C2H6 and (ii) non-C2+ impurities containing one or more of CO, CO2, H2, and CH4. The method produces olefins containing C2H4 with negative carbon emissions.

[0014] According to the present invention, a system for converting CO2 into an olefin comprising C2H4 is provided. The system comprises: a renewable hydrogen (H2) subsystem configured to generate a renewable H2 feed stream; and a CO2 electrolysis unit configured to receive a feed stream comprising CO2 and generate a first renewable electrolysis stream comprising CO and a second renewable electrolysis stream comprising O2. A methanation subsystem is located downstream of the renewable H2 subsystem and the CO2 electrolysis unit and is fluidly coupled to both. The methanation subsystem is configured to receive the renewable H2 feed stream and the first renewable electrolysis stream and generate an OCM feed stream comprising methane (CH4). An OCM subsystem is located downstream of the methanation subsystem and the CO2 electrolysis unit and is fluidly coupled to both. The OCM subsystem is configured to: receive the OCM feed stream and an oxidant feed stream including a second regenerable oxidant stream; and produce an OCM effluent comprising (i) C2+ compounds containing C2H4 and C2H6 and (ii) non-C2+ impurities including one or more of CO, CO2, H2, and CH4. The system also includes a downstream separation subsystem fluidly coupled to the OCM subsystem. This separation subsystem is configured to receive the OCM effluent and separate it into at least (i) a first stream including one of COx, H2, and CH4 and (ii) a second stream including one of C2+ compounds containing C2H4 and C2H6. The system is configured to operate such that it produces olefins containing C2H4 with negative carbon emissions.

[0015] According to the present invention, a system for converting CO2 into an olefin comprising C2H4 is provided. The system includes a co-electrolysis unit configured to receive a first feed stream comprising CO2 and a second feed stream comprising H2O, and to generate a renewable syngas stream comprising CO and H2 and a renewable oxidant stream comprising O2. A methanation subsystem is located downstream of the co-electrolysis unit and fluidly coupled to the co-electrolysis unit. The methanation subsystem is configured to receive the renewable syngas stream and to generate an OCM feed stream comprising methane (CH4). An OCM subsystem is located downstream of the methanation subsystem and the co-electrolysis unit and fluidly coupled to both the methanation subsystem and the co-electrolysis unit. The OCM subsystem is configured to receive the OCM feed stream and the renewable oxidant stream and produce an OCM effluent comprising (i) C2+ compounds containing C2H4 and C2H6 and (ii) non-C2+ impurities including one or more of CO, CO2, H2, and CH4. The system also includes a downstream separation subsystem fluidly coupled to the OCM subsystem. This separation subsystem is configured to receive the OCM effluent and separate it into at least (i) a first stream containing one of COx, H2, and CH4 and (ii) a second stream containing one of C2+ compounds containing C2H4 and C2H6. The system is configured to operate to produce olefins containing C2H4 with negative carbon emissions.

[0016] Other aspects and advantages of the present invention will become apparent from the following description. Simple Explanation of the Diagram

[0017] Figure 1 illustrates a block flow diagram of a system for generating olefins (such as ethylene) from a carbon oxide feed stream according to the present invention;

[0018] Figure 2 illustrates a block flow diagram of a system for generating olefins (such as ethylene) from a carbon oxide feed stream according to the present invention;

[0019] Figure 3 illustrates a block flow diagram of a gas processing unit for generating a carbon dioxide feed stream according to the present invention;

[0020] Figure 4 illustrates a block flow diagram of a system for generating olefins (such as ethylene) from a carbon oxide feed stream according to the present invention;

[0021] Figure 5 illustrates a block flow diagram of a system for generating olefins (such as ethylene) from a carbon oxide feed stream according to the present invention; and

[0022] Figure 6 illustrates a block flow diagram of one of the systems for generating olefins (such as ethylene) from a carbon oxide feed stream according to the present invention. Implementation

[0023] This document describes methods and systems for converting carbon oxides into olefins. According to the invention, a carbon oxide feed stream is supplied to one of the primary or sole carbon sources in a process or system, together with a renewable hydrogen (H₂) feed stream and an oxidant feed stream including oxygen (O₂) to produce olefins containing ethylene (C₂H₄). The olefins are produced via a methane oxidative coupling (OCM) reaction. According to the invention, the methods and systems for converting carbon oxides into olefins can: (i) reduce or eliminate greenhouse gas emissions associated with olefin production; (ii) operate at a high carbon efficiency (i.e., greater than 90%); and / or (iii) produce olefins with negative carbon emissions.

[0024] As used herein, the term "OCM reaction" generally refers to an oxidative coupling reaction or process of methane to produce ethylene (C₂H₄). An OCM reaction may involve the oxidation of methane to hydrocarbons and water and is an exothermic reaction. In an OCM reaction, methane may be partially oxidized to one or more C₂+ compounds, such as ethylene. In one example, an OCM reaction is 2CH₄ + O₂ → C₂H₄ + 2H₂O. An OCM reaction can produce C₂+ compounds. An OCM reaction may be promoted by an OCM catalyst (such as a heterocatalyst). Other byproducts of an OCM reaction may include CO, CO₂, and H₂. In an OCM reaction, ethane may also react with an OCM catalyst to form ethylene.

[0025] As used herein, the terms "C2+" and "C2+ compound" generally refer to compounds comprising one of two or more carbon atoms, such as C2, C3, etc. C2+ compounds include (but are not limited to) alkanes, alkenes, alkynes, aldehydes, ketones, aromatic esters, and carboxylic acids containing two or more carbon atoms. Examples of C2+ compounds include ethane, ethylene, acetylene, propane, propylene, propyne, etc. Similarly, as used herein, the terms "C3+" and "C3+ compound" generally refer to compounds comprising one of three or more carbon atoms, such as C3, C4, C5, etc. C3+ compounds include (but are not limited to) alkanes, alkenes, alkynes, aldehydes, ketones, aromatic esters, and carboxylic acids containing two or more carbon atoms. Examples of C3+ compounds include propane, propylene, propyne, butane, butene, etc.

[0026] As used herein, the term "non-C2+ impurity" generally refers to material that does not contain C2+ compounds. Examples of non-C2+ impurities that can be found in certain OCM reaction product streams include (but are not limited to) nitrogen (N2), oxygen (O2), water (H2O), argon (Ar), hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4).

[0027] As used herein, the term "carbon efficiency" generally refers to the ratio of the moles of carbon present in all process input streams (in some cases, including all hydrocarbon feedstocks, such as, for example, natural gas and ethane and fuel streams) to the moles of carbon present in all commercially (or industrially) available or marketable products of the process. These products may include hydrocarbons (such as petrochemicals) suitable for various downstream uses or used as commercial chemicals. These products may exclude CO and CO2. Process products may be marketable products, such as C2+ hydrocarbon products containing at least about 99% C2+ hydrocarbons and all marketable or pipeline gas products containing at least about 90% methane. Process input streams may include input streams that power the operation of the process. In some cases, at least a portion of the power for the operation of the process may be provided by the heat released from an OCM reaction.

[0028] As used herein, the term "CO x" refers to carbon monoxide (where x=1), carbon dioxide (where x=2), or both carbon monoxide and carbon dioxide.

[0029] As used herein, the term "unit" generally refers to a unit operation. A unit operation can be one or more basic operations in a process. A unit can have one or more subunits (or subsystems). A unit operation can involve a physical change or chemical transformation, such as separation, crystallization, evaporation, filtration, polymerization, isomerization, other reactions, or combinations thereof. A unit can contain one or more individual components. For example, a separation unit can contain one or more separation columns, or an amine unit can contain one or more amine columns.

[0030] The terms "olefin" and "alkene" are used interchangeably in this document and generally refer to hydrocarbons containing one or more double bonds.

[0031] The term "insulation" or "insulation process" generally refers to a process in which the pressure of a gas is allowed to increase without significant heat loss to the surrounding environment. An insulation unit or element may allow virtually no heat transfer between units or elements, such as (for example) less than 15%, 10%, 5%, 4%, 3%, 2%, or 1% heat transfer (e.g., measured by the total heat input and heat output of the unit).

[0032] As used herein, the term "substantially CO2-free" generally refers to a CO2 mole percentage of less than 1% (including less than 0.5%, less than 0.25%, less than 0.1%, less than 0.05%, and also including 0%).

[0033] According to the present invention, it has been found that olefins comprising C₂H₄ can be produced by methods and systems that utilize a carbon oxide feed stream as one of the main or sole carbon sources supplied to a process or system, together with a renewable H₂ feed stream and an oxidant feed stream comprising O₂. The methods and systems disclosed herein also utilize methanation and oxidative coupling (OCM) reactions to produce olefins. The methods and systems of the present invention have several advantages over known OCM methods and systems, including reducing or eliminating greenhouse gas emissions (e.g., CO₂), the ability to operate with high carbon efficiency, and the ability to produce C₂H₄-containing olefins with negative carbon emissions.

[0034] The method and system of the present invention will now be further described with reference to the accompanying drawings. It should be understood that the drawings and components therein are not necessarily drawn to scale. In the drawings, the direction of fluid flow between units is indicated by arrows. Fluid can be guided from one unit to another by means of valves and a fluid flow system. As those skilled in the art will understand, such fluid flow systems may include compressors and / or pumps, as well as a control system for regulating fluid flow.

[0035] Referring now to FIG1, a block flow diagram of a system 100 for performing a method of converting carbon oxides into olefins (comprising C2H4) according to the present invention is shown. System 100 includes a methanation subsystem 101, a renewable H2 subsystem 102, and an OCM subsystem 103. The methanation subsystem 101 is fluidly coupled to the renewable H2 subsystem 102 and configured to receive a carbon oxide feed stream 104 and a renewable H2 feed stream 106 generated by the renewable H2 subsystem 102 to produce an OCM feed stream 107 comprising CH4. OCM subsystem 103 is located downstream of methanation subsystem 101 and is fluidly coupled to methanation subsystem 101 and configured to receive OCM feed stream 107 and oxidant feed stream 108 including O2 to produce an OCM effluent 109, which includes C2+ compounds including C2H4 and C2H6 and non-C2+ impurities including one or more of CO, CO2, H2 and CH4.

[0036] Methanation subsystem 101 may include one or more methanation reactors containing a methanation catalyst (e.g., a nickel-based catalyst) for carrying out the methanation reaction. Typical operating conditions for the methanation reactor may be a pressure of about 3 bar to about 50 bar and a temperature of about 150°C to about 400°C. In methanation subsystem 101, carbon oxides (e.g., CO2, CO, or both) in carbon oxide feed stream 104 react with H2 from renewable H2 feed stream 106 to produce CH4 via the following reactions: i) CO2 + 4H2 → CH4 + 2H2O and ii) CO + 3H2 → CH4 + H2O. The CH4 produced in methanation subsystem 101 is directed to OCM subsystem 103 as OCM feed stream 107.

[0037] According to the method and system of the present invention, the carbon oxide feed stream 104 includes CO2, CO, or both CO2 and CO. According to the method and system of the present invention, the carbon oxide feed stream 104 is supplied to one of the main or sole carbon sources in system 100 or the process. According to some embodiments of the method and system of the present invention, the carbon oxide feed stream 104 includes captured CO2. The captured CO2 may be CO2 captured from industrial facilities including (but not limited to) steel / metal production facilities, cement production facilities, coal-fired power plants, coal gasification, and biomass gasification. The captured CO2 may also contain a certain amount of CO. According to some embodiments of the method and system of the present invention, the carbon oxide feed stream 104 includes a CO2 feed stream generated by removing CO2 from a natural gas stream containing CO2. According to some embodiments of the method and system of the present invention, the carbon oxide feed stream 104 includes captured CO2 (e.g., CO2 captured from an industrial facility), which may contain a certain amount of CO, and CO2 generated by removing CO2 from a natural gas stream containing CO2.

[0038] The renewable H2 feed stream 106, directed to the methanation subsystem 101, is generated by the renewable H2 subsystem 102. According to the method and system of the present invention, the renewable H2 subsystem 102 may be based on one or more technologies for generating renewable H2. These technologies include (but are not limited to) water electrolysis, biogasification, ammonia cracking, and hydrogen sulfide decomposition. The energy required to power the renewable H2 subsystem 102 to generate the renewable H2 feed stream 106 may be provided by one or more renewable energy sources. Exemplary renewable energy sources that can be used according to the method and system of the present invention include (but are not limited to) wind power, solar power, biomass energy, geothermal energy, hydropower, and nuclear power.

[0039] As shown in Figure 1, an H2 carrier stream 105 is directed to a regenerative H2 subsystem 102 to produce a regenerative H2 feed stream 106 directed to a methanation subsystem 101. According to the method and system of the present invention, the H2 carrier stream 105 comprises an H2 carrier. The H2 carrier can be any compound or substance that can be processed (e.g., reacted, decomposed) to produce H2 gas. Examples of suitable H2 carriers for use in the method and system of the present invention include (but are not limited to) water, biomass, ammonia, and hydrogen sulfide.

[0040] Referring again to Figure 1, the OCM feed stream 107 generated by the methanation subsystem 101, together with the oxidant feed stream 108, is directed to the OCM subsystem 103 to produce the OCM effluent 109. As will be described in more detail herein, the OCM effluent 109 may be directed to downstream units and / or a separation subsystem for additional treatment of the OCM effluent 109. The oxidant feed stream 108 supplied to the OCM subsystem 103 can be provided by any suitable O2 source. According to some embodiments of the invention, the OCM feed stream 107 and the oxidant feed stream 108 may be heated before being injected into the OCM subsystem 103. Although Figure 1 illustrates the OCM feed stream 107 and the oxidant feed stream 108 as separate flows directed to the OCM subsystem 103, it is considered that the OCM feed stream 107 and the oxidant feed stream 108 may be combined and mixed to form a single stream directed to the OCM subsystem 103. According to some embodiments of the invention, the oxidant feed stream 108 may be generated by an air stream or an air separation unit, or provided by an O2 stream generated by a renewable H2 subsystem 102, a CO2 electrolysis unit, or a co-electrolysis unit as described below.

[0041] According to the methods and systems of the present invention, the OCM subsystem 103 may include one or more OCM reactors connected in series and / or parallel. The OCM reactor includes one or more OCM catalysts for promoting an OCM reaction to produce OCM effluent 109, which includes C2+ compounds comprising C2H4 and C2H6 and non-C2+ impurities comprising one or more of CO, CO2, H2, and CH4. The OCM reactor can be operated under isothermal or adiabatic conditions to carry out the OCM reaction. In some embodiments of the methods and systems of the present invention, an inlet temperature of one of the OCM reactors may be from about 400°C to about 600°C, and an outlet temperature of one of the OCM reactors may be from about 700°C to about 900°C. In some embodiments of the methods and systems of the present invention, an inlet pressure of one of the OCM reactors is from about 15 pounds per square inch (psig) to about 150 psig. The OCM catalyst may be any known OCM catalyst, such as an OCM catalyst designed to operate at low temperatures (i.e., from about 400°C to about 600°C), as described in, for example, U.S. Patent Nos. 8,921,256, 8,962,517 and 9,718,054, the entire disclosure of which is incorporated herein by reference.

[0042] According to the method and system of the present invention, the OCM subsystem 103 may include a column-type cracking (PBC) unit for the production of olefins (e.g., C2H4) from alkanes (e.g., C2H6, C3H8). The PBC unit may be located downstream of the OCM reactor, specifically downstream of the OCM catalyst contained in the OCM reactor. The PBC unit may be a separate reactor, or it may be a section of the OCM reactor (e.g., an OCM catalyst bed located upstream of the PBC unit in the same reactor vessel). Since the OCM reaction is exothermic and generates heat, the heat generated by the OCM reaction can be used to crack alkanes (e.g., C2H6) into olefins (e.g., C2H4). The PBC unit can perform the cracking at a temperature of about 600°C to about 1,000°C (including a temperature of about 800°C to about 950°C).

[0043] According to the method and system of the present invention, the PBC unit can be used to pyrolyze additional external alkanes (e.g., C2H6, C3H8) in addition to the alkanes contained in the OCM effluent 109. The heat capacity of the OCM effluent 109 is sufficient to pyrolyze a certain amount of the additional external alkanes. The additional external alkanes can be provided from a circulating stream in the process or from a completely independent alkane source. The external alkanes can be heated before being injected into the PBC unit. The external alkanes can be heated by, for example, heat exchange with the OCM reactor and / or the OCM effluent 109.

[0044] Referring now to FIG2, a block flow diagram of a system 200 for performing a method of converting carbon oxides into olefins (including C2H4) according to the present invention is shown. System 200 includes a methanation subsystem 201, a renewable H2 subsystem 202, an OCM subsystem 204, and a separation subsystem 206. The methanation subsystem 201 is fluidly coupled to the renewable H2 subsystem 202 and configured to receive a carbon oxide feed stream 210 and a renewable H2 feed stream 212 generated by the renewable H2 subsystem 202, and to generate an OCM feed stream 213 including CH4. OCM subsystem 204 is located downstream of methanation subsystem 201 and fluidly coupled to methanation subsystem 201. It is configured to receive OCM feed stream 213 and oxidant feed stream 214 containing O2 to produce an OCM effluent 215, which includes C2+ compounds comprising C2H4 and C2H6, and non-C2+ impurities comprising one or more of CO, CO2, H2, and CH4. Separation subsystem 206 is located downstream of OCM subsystem 204 and fluidly coupled to OCM subsystem 204. It is configured to receive OCM effluent 215 and separate OCM effluent 215 into at least one first stream 217 comprising COx, H2, and CH4, and a second stream comprising one of C2+ compounds comprising C2H4 and C2H6. The second stream can be further separated in the separation subsystem 206 to produce a third stream 218 containing one of C2H4 and a fourth stream 219 containing one of C2H6.

[0045] In the system 200 shown in Figure 2, the methanation subsystem 201, the renewable H2 subsystem 202, and the OCM subsystem 204 may be the same configuration as the methanation subsystem 101, the renewable H2 subsystem 102, and the OCM subsystem 103 previously described with reference to Figure 1.

[0046] As shown in Figure 2, the carbon oxide feed stream 210, together with a renewable H2 feed stream 212 generated by the renewable H2 subsystem 202, is directed to the methanation subsystem 201. According to the method and system of the present invention, the carbon oxide feed stream 210 includes CO2, CO, or both CO2 and CO. According to the method and system of the present invention, the carbon oxide feed stream 210 is supplied to one of the main or sole carbon sources in system 200 or the process. In some embodiments of the method and system of the present invention, the carbon oxide feed stream 210 includes captured CO2. The captured CO2 may be CO2 captured from industrial facilities including (but not limited to) steel / metal production facilities, cement production facilities, coal-fired power plants, coal gasification, and biogasification. The captured CO2 may also contain a certain amount of CO.

[0047] Referring now to Figures 2 and 3, in some embodiments of the method and system according to the present invention, the carbon oxide feed stream 210 may include a CO2 feed stream 310 generated by removing CO2 from a CO2-containing natural gas stream 301. As shown in Figure 3, the CO2-containing natural gas stream is directed to a gas processing unit 300 configured to remove CO2 from the natural gas and thereby generate a CO2 feed stream and a substantially CO2-free natural gas stream 302. In some embodiments of the present invention, the substantially CO2-free natural gas stream 302 may be output to a natural gas pipeline (e.g., sold as a sales gas to a natural gas infrastructure). In some embodiments of the method and system according to the present invention, at least a portion of the substantially CO2-free natural gas stream 302 may be directed to the OCM subsystem 204 as a supplementary stream 221 including CH4.

[0048] Natural gas stream 301 may contain CO2 of any concentration. In some embodiments of the method and system of the present invention, natural gas stream 301 may contain up to 50% by weight of CO2, including 1% to 50% by weight, 5% to 50% by weight, 10% to 50% by weight, 15% to 50% by weight, 20% to 50% by weight, 25% to 50% by weight, 30% to 50% by weight, 35% to 50% by weight, 40% to 50% by weight, and also 45% to 50% by weight of CO2. In some embodiments of the method and system of the present invention, CO2 feed stream 310 includes at least a portion of carbon oxide feed stream 210 directed to methanation subsystem 201, and the remainder is supplied by captured CO2, as described above. According to some embodiments of the method and system of the present invention, the carbon oxide feed stream 210 guided to the methanation subsystem 201 consists of the CO 2 feed stream 310 generated by the gas processing unit 300.

[0049] The gas processing unit 300 may include any known conventional system or method for removing CO2 from natural gas. For example, in some embodiments of the methods and systems of the present invention, the gas processing unit 300 may be a natural gas processing plant or part thereof. In other embodiments of the methods and systems of the present invention, the gas processing unit 300 may be a conventional amine absorber system. In some embodiments of the methods and systems of the present invention, the gas processing unit 300 is fluidly coupled to a methanation subsystem (e.g., 101, 201). In some embodiments of the methods and systems of the present invention, the gas processing unit 300 is fluidly coupled to a methanation subsystem (e.g., 101, 201) and an OCM subsystem (e.g., 103, 204).

[0050] Referring again to Figure 2, system 200 includes a renewable H2 subsystem 202 configured to generate a renewable H2 feed stream 212. In system 200 illustrated in Figure 2, the renewable H2 subsystem 202 includes an electrolysis unit powered by electricity generated from a renewable energy source (such as wind, solar, biomass, geothermal, hydropower, nuclear power, and combinations thereof). The electrolysis unit is located upstream of and fluidly coupled to the methanation subsystem 201 and the OCM subsystem 204. The electrolysis unit receives a water stream 211 and converts the water into H2 gas and O2 gas via a given water electrolysis reaction from 2H2O → 2H2 + O2. The H2 gas generated by the electrolysis reaction is directed to the methanation subsystem 201 as the renewable H2 feed stream. Similarly, the O2 gas generated by the electrolysis reaction is directed to the OCM subsystem 204 as at least a portion of the oxidant feed stream 214. In some embodiments of the method and system of the present invention, the oxidant feed stream 214 directed to the OCM subsystem 204 consists of renewable O2 gas generated by the electrolysis reaction. Therefore, the electrolysis unit can renewably supply all the oxygen required for the oxidant feed stream 214 directed to the OCM subsystem 204. This embodiment is particularly advantageous because it eliminates the need to supply oxygen to one of the air separation units (ASUs) of the OCM subsystem 204 (which are expensive and energy-intensive).

[0051] In the methanation subsystem 201, carbon oxides (i.e., CO2, CO, or both) in the carbon oxide feed stream 210 react with H2 from the renewable H2 feed stream 212 to produce CH4 via the following reactions: i) CO2 + 4H2 → CH4 + 2H2O and ii) CO + 3H2 → CH4 + H2O. The CH4 produced in the methanation subsystem 201 is directed to the OCM subsystem 204 as an OCM feed stream 213.

[0052] As can be understood from the methanation reactions listed above, these reactions can produce water, which can be present in the OCM feed stream 213 exiting the methanation subsystem 201. Therefore, in some embodiments of the method and system of the present invention, at least a portion of the H₂O present in the OCM feed stream 213 can be removed before it is directed to the OCM subsystem 204. For example, the OCM feed stream 213 can be directed to a dehydration unit 203 to remove H₂O from the OCM feed stream 213. The dehydration unit 203 can be a liquid-gas separator that removes H₂O from the OCM feed stream 213 by cooling it, or any other separation unit capable of removing H₂O from the OCM feed stream 213. In some embodiments of the method and system of the present invention, the H₂O removed from the OCM feed stream 213 can be recycled to the electrolysis unit via stream 222. On the other hand, if the OCM catalyst present in the OCM subsystem 204 is resistant to the presence of vapor, the dehydration unit 203 can be omitted.

[0053] Referring again to Figure 2, the OCM feed stream 213, together with the oxidant feed stream 214, is directed to the OCM subsystem 204 to produce an OCM effluent 215 containing C2+ compounds of C2H4 and C2H6, and non-C2+ impurities including one or more of CO, CO2, H2, and CH4. The OCM effluent 215 can be directed to a separation subsystem 206 to separate the OCM effluent 215 into at least one first stream 217 containing COx, H2, and CH4, and a second stream containing one of the C2+ compounds of C2H4 and C2H6. As shown in Figure 2, the first stream 217, containing COx, H2, and CH4 or a portion thereof, can be recycled to the methanation subsystem 201 to promote the generation of the methanated OCM feed stream 213. According to some embodiments of the method and system of the present invention, at least a portion of the first stream 217 may be purged to prevent the accumulation of inert components (e.g., N₂) in the system. Additionally, the separation subsystem 206 may separate the second stream, comprising C₂⁺ compounds, into a third stream 218 comprising C₂H₄ products and a fourth stream 219 comprising C₂H₆ products. As shown in FIG. 2, the fourth stream 219 comprising C₂H₆ may be directed to the OCM subsystem 204 (e.g., to the OCM reactor or to the PBC unit) to generate additional C₂H₄ by pyrolyzing C₂H₆. According to some embodiments of the method and system of the present invention, the electrolysis unit is fluidly coupled to the separation subsystem 206 and receives a stream 220 comprising H₂O (connection not shown), which is separated or otherwise removed by the separation subsystem 206 from the OCM effluent 215.

[0054] Separation subsystem 206 may include any number of separation units or any combination of separation techniques suitable for separating the products of an OCM reaction. For example, separation subsystem 206 may separate OCM effluent 215 by means of cryogenic separation, pressure swing adsorption, temperature swing adsorption, membrane separation, adsorbents, and combinations thereof. Examples of separation subsystems suitable for implementation in the methods and systems of the present invention are described, for example, in WO 2014 / 011646 A1, WO 2013 / 106771 A2, WO 2015 / 106023 A1, WO 2017 / 065947 A1 and WO 2018 / 118105 A1, the entire disclosure of which is incorporated herein by reference.

[0055] As shown in Figure 2, according to some embodiments of the method and system of the present invention, system 200 includes a CO2 removal unit 205 fluidly coupled to one of the OCM subsystem 204, methanation subsystem 201, and separation subsystem 206. CO2 removal unit 205 is configured to remove CO2 from OCM effluent 215, guide at least a portion of the removed CO2 to methanation subsystem 201 via flow 216, and guide substantially CO2-free OCM effluent to separation subsystem 206. According to some embodiments of the method and system of the present invention, all CO2 removed by CO2 removal unit 205 is guided to methanation subsystem 201 via flow 216. CO2 removal unit 205 may include any known technique suitable for removing CO2 from a programmed flow. Examples of suitable CO2 removal techniques include (but are not limited to) amine absorber systems, pressure swing adsorption, temperature swing adsorption, membrane separation, solvent separation, and cryogenic separation.

[0056] Although Figure 2 illustrates a CO2 removal unit 205 located downstream of OCM subsystem 204 and upstream of separation subsystem 206, considering that CO2 contained in OCM effluent 215 can be removed via separation subsystem 206, CO2 removal unit 205 is unnecessary. This configuration would be particularly suitable for systems in which separation subsystem 206 is based on adsorption technology.

[0057] As described above, the system 200 illustrated in Figure 2, used to perform a method for converting carbon oxides into olefins, utilizes a carbon oxide feed stream 210 as the primary or sole carbon source supplied to the system 200, along with a renewable hydrogen (H2) feed stream generated by an electrolysis unit powered by a renewable energy source and a renewable oxidant feed stream. The main reactions occurring throughout the process shown in Figure 2 are as follows: Methanation: CO₂ + 4H₂ → CH₄ + 2H₂O Water electrolysis: 2H₂O → 2H₂ + O₂ OCM: 2CH₄ + O₂ → C₂H₄ + 2H₂O

[0058] As can be seen from the above reaction equations, the electrolysis unit will obviously produce H2 and O2 in a molar ratio of 2:1 (i.e., 2H2:O2). Based on the methanation and OCM reactions, each molar of CO2 supplied to the system (i.e., CO2 via stream 210) will consume 4 molars of H2 and 0.5 molars of O2. Therefore, the process consumes much more H2 than O2, and thus it is necessary to remove excess O2 from the process. In some versions of the method and system of the present invention, excess O2 can be removed from the process / system and stored for later use or sale.

[0059] To balance the OCM reaction occurring in OCM subsystem 204 with the 2:1 ratio of H₂ to O₂ produced by the electrolysis unit, a supplementary stream 221, including CH₄, can be directed to OCM subsystem 204. It has been determined that increasing the molar ratio of CH₄ to CO₂ supplied to the system will reduce the molar ratio of H₂ to O₂ consumption in the process. Estimates of these molar ratios are shown in Table 1. [surface] [1] [What is supplied] [CH] 4 [:CO] 2 [The amount consumed by the comparison with Morse] [H] 2 [:O] 2 [The Influence of Morby] The molar ratio of CH4:CO2 supplied The molar ratio of H2:O2 consumed 0:1 5.3:1 0.3:1 4.25:1 1:1 3:1 2.33:1 2.05:1

[0060] As can be seen from the data shown in Table 1, compared to CO2, the higher the proportion of CH4 introduced into the system, the lower the molar ratio of H2:O2 consumption. In fact, the 2.33:1 molar ratio of CH4 to CO2 introduced into system 200 results in a molar ratio of approximately 2:1 of H2 to O2 consumed in system 200, which is approximately the same as the molar ratio of H2 to O2 produced by the electrolysis unit. Therefore, in some embodiments of the system and method of the present invention, a supplementary CH4 stream 221 can be directed to the OCM subsystem 204, and the molar ratio (i.e., CH4:CO2) of CH4 in the supplementary stream to CO2 in the oxide feed stream 210 is 0.01:1 to 5:1, including a molar ratio of 0.1:1 to 4:1, 0.5:1 to 3.5:1, 0.75:1 to 3:1, and also including a molar ratio of 1:1 to 2.5:1. Furthermore, in cases where the supply of oxides to the system 200 via the oxide feed stream 210 is fluctuating or intermittent, the ability to provide a CH4 source to the system 200 (e.g., via the supplementary stream 221) provides flexibility to the operating system 200.

[0061] As mentioned above, when no CH4 is supplied to system 200, excess O2 needs to be removed from the system, but there is no need to emit CO2 or other carbon emission sources from system 200. However, since CH4 is supplied to system 200 in an increased amount via supplementary stream 221 (i.e., relative to the CO2 supplied to system 200), a certain amount of CO2 may need to be removed from system 200 (e.g., via a purified stream flowing out of gravity stream 217). This CO2 will accumulate in system 200 unless, in addition to removing inert components such as N2, it is supplied to the system as a small amount of impurity (e.g., via oxidant feed stream 214 and / or optional supplementary stream 221). Generally, the amount of CO2 that needs to be removed from the system of the present invention is less than the amount of CO2 supplied to the system. Furthermore, the use of H2 and O2 in the method and system of the present invention does not result in the generation of renewable energy sources and resources that produce CO2 emissions. Therefore, the system and method of the present invention advantageously consume more CO2 than it emits and thereby produce olefins (such as C2H4 and C3H6) with negative carbon emissions (specifically, negative CO2 emissions).

[0062] Another advantage of the system and method of the present invention is that the system and method can be adjusted to achieve a desired carbon efficiency. In some embodiments of the system and method of the present invention, the system and method operate with a carbon efficiency of at least 90%, including at least 92%, at least 94%, at least 96%, at least 98%, and also including at least 99% carbon efficiency. In some embodiments of the system and method of the present invention, the system and method operate with a carbon efficiency of 92% to 100%, including 92% to 99.9% carbon efficiency, 93% to 99.9% carbon efficiency, 94% to 99.9% carbon efficiency, 95% to 99.9% carbon efficiency, 96% to 99.9% carbon efficiency, 97% to 99.9% carbon efficiency, and also including 99% to 99% carbon efficiency. In OCM reactions, carbon efficiency is typically determined based on the amount of carbon supplied in the process of converting CH4 to C2+ compounds. However, in the system and method of the present invention, the carbon oxide feed stream (i.e., a feed stream including CO2, CO, or both) is used as the primary or sole carbon source supplied to the system, and therefore, the carbon efficiency based on the amount of carbon supplied to the process from CH4 will always be greater than 100%. For example, if the system 200 shown in FIG2 includes a supplementary stream 221 including CH4 and a carbon oxide feed stream 210 including CO2 as feed, and the molar ratio of CH4 in the supplementary stream to CO2 in the carbon oxide feed stream 210 (i.e., CH4:CO2) is 2.33:1, then the system 200 will produce 3.33 moles of carbon as a C2+ compound. Therefore, the system 200 will produce 3.33 moles of carbon as a C2+ compound based on only 2.33 moles of carbon supplied as CH4, which translates to a carbon efficiency of approximately 143%.

[0063] Referring now to FIG4, a block flow diagram of another embodiment of a system 400 for performing a method of converting carbon oxides into olefins (comprising C2H4) according to the present invention is shown. Similar to system 200 illustrated in FIG2, system 400 includes a methanation subsystem 401, a renewable H2 subsystem 402, an OCM subsystem 403, and a separation subsystem (unnumbered). The methanation subsystem 401 is fluidly coupled to the renewable H2 subsystem 402 and configured to receive a carbon oxide feed stream 410 and a renewable H2 feed stream 412 generated by the renewable H2 subsystem 402, and to generate an OCM feed stream 413 comprising CH4. OCM subsystem 403 is located downstream of methanation subsystem 401 and fluidly coupled to methanation subsystem 401 and configured to receive OCM feed stream 413 and oxidant feed stream 414 including O2 to produce an OCM effluent 415 comprising C2+ compounds including C2H4 and C2H6 and non-C2+ impurities including one or more of CO, CO2, H2 and CH4.

[0064] In the system 400 illustrated in Figure 4, the methanation subsystem 401, the renewable H2 subsystem 402, and the OCM subsystem 403 may be configured similarly to the methanation subsystems 101, 201, the renewable H2 subsystems 102, 202, and the OCM subsystems 103, 204 previously described with reference to Figures 1 and 2. For example, the renewable H2 subsystem 402 includes an electrolysis unit powered by electricity generated from a renewable energy source (such as wind, solar, biomass, geothermal, hydropower, nuclear power, and combinations thereof). The electrolysis unit is located upstream of and fluidly coupled to the methanation subsystems 401 and 403. The electrolysis unit receives a water flow 411 and converts the water into H2 gas and O2 gas via a given water electrolysis reaction from 2H2O → 2H2 + O2. The H2 gas produced by the electrolysis reaction is directed to the methanation subsystem 401 as a renewable H2 feed stream. Similarly, the O2 gas produced by the electrolysis reaction is directed to the OCM subsystem 403 as at least a portion of the oxidant feed stream 414. In some embodiments of the method and system of the present invention, the oxidant feed stream 414 directed to the OCM subsystem 403 consists of renewable O2 gas produced by the electrolysis reaction. Therefore, the electrolysis unit can regenerately supply all the oxygen required for the oxidant feed stream 414 directed to the OCM subsystem 403. This embodiment is particularly advantageous because it eliminates the need to supply oxygen to an air separation unit (ASU) of the OCM subsystem 403 (which is expensive and energy-intensive). Furthermore, as described above with reference to FIG. 2, an optional supplementary stream 421 including CH4 can be directed to the OCM subsystem 403 in the system 400 illustrated in FIG. 4.

[0065] OCM effluent 415 may be directed to one or more heat exchangers 404 to transfer heat from OCM effluent 415 to a process flow and thereby cool OCM effluent 415. In some embodiments, one or more heat exchangers may be a heat recovery steam generator (HRSG) that generates steam that can be used for heating, generating electricity via a gas turbine, or for other processes.

[0066] Referring again to Figure 4, after passing through one or more heat exchangers 404, the OCM effluent 415 may be directed to a programmable gas compressor 405 to increase the pressure of the OCM effluent 415 to a desired or suitable pressure, such as at least about 100 psig (690 kPa), at least about 150 psig (1035 kPa), at least about 200 psig (1380 kPa), at least about 250 psig (1725 kPa), or at least about 300 psig (2070 kPa). The compressed OCM effluent 415 may be directed to a CO2 removal unit 406 to remove CO2 from the OCM effluent 415. At least a portion of the removed CO2 may be directed to the methanation subsystem via stream 416. According to some embodiments of the method and system of the present invention, all CO2 removed by the CO2 removal unit 406 is directed to the methanation subsystem 401 via stream 416. CO2 removal unit 406 may be configured similarly to CO2 removal unit 205 described above. The substantially CO2-free OCM effluent 415 may be directed to a programmable gas dryer 407 to remove H2O from the substantially CO2-free OCM effluent 415. The programmable gas dryer 407 may be one or more molecular sieve dryers or separator containers used for condensing and separating H2O from the substantially CO2-free OCM effluent 415.

[0067] Although Figure 4 illustrates a CO2 removal unit 406 located downstream of the OCM subsystem 403 and upstream of the separation subsystem, considering that the CO2 contained in the OCM effluent 415 can be removed via the separation subsystem, the CO2 removal unit 406 is unnecessary. This configuration is suitable for systems where the separation subsystem is based on adsorption technology.

[0068] Referring again to Figure 4, after exiting the program gas dryer 407, the dried, substantially CO2-free OCM effluent 415 can be directed to a separation subsystem downstream of and fluidly coupled to the OCM subsystem 403, which includes at least one demethanizer unit 408 and a C2 purification unit 409. The demethanizer unit 408 is fluidly coupled to the methanation system 401 and the C2 purification unit 409, as illustrated in Figure 4. The demethanizer unit 408 is configured to receive the OCM effluent 415 to separate it into a first stream 417 comprising COx, H2, and CH4, and a second stream 418 comprising C2+ compounds including C2H4 and C2H6. At least a portion of the first stream 417 is directed from the demethanizer unit 408 to the methanation subsystem 401 to facilitate the generation of the methanated OCM feed stream 413. According to some embodiments of the method and system of the present invention, all first streams 417 are recycled from the demethanizer unit 408 to the methanation subsystem to facilitate the generation of the OCM feed stream 410 via methanation. According to some embodiments of the method and system of the present invention, at least a portion of the first stream 417 is purged to prevent the accumulation of inert components (e.g., N2) in the system 400.

[0069] As shown in Figure 4, a second stream 418 comprising C2+ compounds including C2H4 and C2H6 can be directed to a C2 purification unit 409. The C2 purification unit 409 is fluidly coupled to an OCM subsystem 403 and configured to receive the second stream 418 and separate it into at least one third stream 419 comprising C2H4 and one fourth stream 420 comprising C2H6. The third stream 419 comprising C2H4 can be collected or directed to a downstream process utilizing C2H4 as a feedstock. As seen in Figure 4, the fourth stream 420 comprising C2H6 can be recycled to the OCM subsystem 403 (e.g., to an OCM reactor or to a PBC unit) to generate additional C2H4 by pyrolyzing C2H6. In some embodiments of the methods and systems of the present invention, the C2 purification unit 409 may include a deethanizer unit (not shown) capable of separating C2 compounds (e.g., ethane and ethylene) from C3+ compounds (e.g., propane, propylene, butane, butene). The separated C3+ compounds can exit the deethanizer unit along stream 422 and undergo additional downstream processing. The C2 compounds from the deethanizer unit can be directed to a C2 separator (not shown) which can separate C2H6 from C2H4. The C2 separator may be a distillation column.

[0070] Referring now to FIG5, a block flow diagram of a system 500 for performing a method of converting carbon dioxide into olefins (including C2H4) according to the present invention is shown. System 500 includes a methanation subsystem 501, a renewable H2 subsystem 502, an OCM subsystem 504, a separation subsystem 506, and a CO2 electrolysis unit 507. The CO2 electrolysis unit 507 is configured to receive a feed stream 510 including CO2 and generate a first renewable electrolysis stream 511 including CO and a second renewable electrolysis stream 512 including O2. The methanation subsystem 501 is fluidly coupled to the renewable H2 subsystem 502 and the CO2 electrolysis unit 507 and is configured to receive the first renewable electrolysis stream 511 and a renewable H2 feed stream 514 generated by the renewable H2 subsystem 502 and generate an OCM feed stream 515 including CH4. OCM subsystem 504 is located downstream of and fluidly coupled to the methanation subsystem 501 and the CO2 electrolysis unit 507. It is configured to receive the OCM feed stream 515 and the oxidant feed stream 517, including a second regenerable electrolysis stream 512, and to produce an OCM effluent 518, which includes C2+ compounds comprising C2H4 and C2H6, and non-C2+ impurities comprising one or more of CO, CO2, H2, and CH4. Separation subsystem 506 is located downstream of and fluidly coupled to the OCM subsystem 504. It is configured to receive the OCM effluent 518 and separate it into at least one first stream 520 comprising COx, H2, and CH4, and a second stream comprising one of the C2+ compounds comprising C2H4 and C2H6. The second stream can be further separated in the separation subsystem 506 to produce a third stream 521 containing one of C2H4 and a fourth stream 522 containing one of C2H6.

[0071] In the system 500 illustrated in Figure 5, the methanation subsystem 501, the renewable H2 subsystem 502, and the OCM subsystem 504 may have a configuration similar to or identical to that of the methanation subsystem 101, renewable H2 subsystem 102, and OCM subsystem 103 previously described herein with reference to Figure 1 and include similar or identical components. For example, the methanation subsystem 501 may include one or more methanation reactors containing a methanation catalyst. The renewable H2 subsystem 502 may include, for example, a water electrolysis unit powered by a renewable energy source. The OCM subsystem 504 may include, for example, one or more OCM reactors containing one or more OCM catalysts for promoting an OCM reaction to produce OCM effluent 518. The OCM subsystem 504 may also include a PBC unit.

[0072] As shown in Figure 5, a feed stream 510 containing CO2 is directed to a CO2 electrolysis unit 507. According to the method and system of the present invention, the feed stream 510 containing CO2 is supplied to a primary or sole carbon source in system 500 or the process. In some embodiments of the method and system of the present invention, the feed stream 510 includes captured CO2. The captured CO2 may be CO2 captured from industrial facilities including (but not limited to) steel / metal production facilities, cement production facilities, coal-fired power plants, coal gasification, and biogasification. The captured CO2 may also contain a certain amount of CO. In some embodiments of the method and system of the present invention, the feed stream 510 may include CO2 generated by removing CO2 from a natural gas stream, as previously described with respect to Figure 3. According to some embodiments of the present invention, as described above with respect to FIG3, at least a portion of a substantially CO2-free natural gas stream generated by a gas processing unit may be directed to the OCM subsystem 504 as a supplementary stream 524 including CH4.

[0073] As mentioned above, the CO2 electrolysis unit 507 is configured to receive a feed stream 510 containing CO2 and generate a first regenerable electrolytic stream 511 containing CO and a second regenerable electrolytic stream 512 containing O2. The CO2 electrolysis unit 507 is operable to convert CO2 gas into CO gas and O2 gas. For example, in some configurations, the CO2 electrolysis unit can convert CO2 gas into CO gas and O2 gas according to the reaction: CO2 → CO + ½O2. The CO2 electrolysis unit 507 can be based on any technology that can electrochemically convert CO2 into CO and O2. Such technologies include (but are not limited to) solid oxide electrolysis, molten carbonate electrolysis, and cryogenic electrolysis (e.g., a hydrogen cell electrode or a gas diffusion electrode). For example, techniques for the electrochemical conversion of CO2 to CO and O2 are described in WO 2014 / 154253 A1 and U.S. Patent No. 9,624,589 B2, the entire contents of which are incorporated herein by reference. In some embodiments of the methods and systems of the present invention, CO2 electrolysis unit 507 includes a solid oxide electrolytic cell (SOEC). The SOEC can operate at temperatures from 500°C to 1,200°C. The SOEC may include an electrolyte material comprising (but not limited to) stabilized zirconium oxide (such as yttrium-stabilized zirconium oxide (a solid solution of YSZ, Y2O3, and ZrO2) or scandium-stabilized zirconium oxide (ScSZ)) and doped cerium oxide (such as zirconium-doped cerium oxide (CGO) or samarium-doped cerium oxide). Additionally, the SOEC may include a cathode material comprising (but not limited to) a composite of nickel and either YSZ or CGO. Furthermore, the SOEC may include an anode material comprising (but not limited to) lanthanide and transition metal-doped perovskites, such as Sr-doped LaMnO3 (LSM), Sr-doped La(Fe,Co)O3 (LSCF), or Sr-doped SmCoO3 (SSC). The energy required to power the CO2 electrolysis unit 507 to generate the first renewable electrolytic flow 511 and the second renewable electrolytic flow 512 may be provided by one or more renewable energy sources. Exemplary renewable energy sources that can be used in the method and system according to the invention include (but are not limited to) wind power, solar power, biomass power, geothermal power, hydropower, and nuclear power.

[0074] As shown in Figure 5, a first renewable electrolysis stream 511, together with a renewable H2 feed stream 514 generated by the renewable H2 subsystem 502, is guided to the methanation subsystem 501. In the system 500 illustrated in Figure 5, the renewable H2 subsystem 502 includes a water electrolysis unit powered by electricity generated from renewable energy sources (such as wind, solar, biomass, geothermal, hydropower, nuclear power, and combinations thereof). The water electrolysis unit is located upstream of and fluidly coupled to the methanation subsystem 501 and the OCM subsystem 504. The water electrolysis unit receives a water stream 513 and converts the water into H2 gas and O2 gas via a given water electrolysis reaction from 2H2O → 2H2 + O2. The H2 gas generated by the water electrolysis reaction is guided to the methanation subsystem 501 as the renewable H2 feed stream 514. Similarly, the O2 gas generated by the water electrolysis reaction is guided via stream 516 to the OCM subsystem 504 to form at least a portion of the oxidant feed stream 517. As shown in FIG. 5, the O2-containing stream 516 formed by the water electrolysis reaction can be combined with the second regenerable electrolysis stream 512 to form the oxidant feed stream 517. In some embodiments of the method and system of the present invention, the oxidant feed stream 517 guided to the OCM subsystem 504 consists of: i) the regenerable O2 stream 516 generated by the water electrolysis unit; and ii) the second regenerable electrolysis stream 512. Thus, the water electrolysis unit and the CO2 electrolysis unit can regenerately supply all the oxygen required for the oxidant feed stream 517 guided to the OCM subsystem 504. This embodiment is particularly advantageous because it eliminates the need to supply oxygen to one of the air separation units (ASUs) of the OCM subsystem 504 (which is expensive and energy-intensive).

[0075] In the methanation subsystem 501, carbon oxides (i.e., CO, CO2, or both) in the first regenerable electrolysis stream 511 react with H2 from the regenerable H2 feed stream 514 to produce CH4 via the following reactions: i) CO2 + 4H2 → CH4 + 2H2O and ii) CO + 3H2 → CH4 + H2O. By providing a larger proportion of CO instead of CO2 to the methanation subsystem 501 (as can be achieved using the CO2 electrolysis unit 507), the methanation reaction requires less H2 and produces less H2O. Furthermore, a higher concentration of CO in the feed to the methanation subsystem 501 reduces the size of the methanation reactor and the amount of methanation catalyst required to perform the methanation reaction. The CH4 produced in the methanation subsystem 501 is directed to the OCM subsystem 504 as the OCM feed stream 515.

[0076] As can be understood from the methanation reactions listed above, these reactions can produce water, which can be present in the OCM feed stream 515 exiting the methanation subsystem 501. Therefore, in some embodiments of the method and system of the present invention, at least a portion of the H₂O present in the OCM feed stream 515 can be removed before the OCM feed stream 515 is directed to the OCM subsystem 504. For example, the OCM feed stream 515 can be directed to a dehydration unit 503 to remove H₂O from the OCM feed stream 515. The dehydration unit 503 can be a liquid-gas separator that removes H₂O from the OCM feed stream 515 by cooling it, or any other separation unit capable of removing H₂O from the OCM feed stream 515. In some embodiments of the method and system of the present invention, the H₂O removed from the OCM feed stream 515 can be recycled to the water electrolysis unit via stream 525. On the other hand, if the OCM catalyst present in the OCM subsystem 504 is resistant to the presence of vapor, the dehydration unit 503 can be omitted.

[0077] Referring again to Figure 5, the OCM feed stream 515, together with the oxidant feed stream 517 including the second regenerable electrolytic stream 512, is directed to the OCM subsystem 504 to produce an OCM effluent 518, which includes C2+ compounds comprising C2H4 and C2H6 and non-C2+ impurities comprising one or more of CO, CO2, H2, and CH4. The OCM effluent 518 can be directed to a separation subsystem 506 to separate the OCM effluent 518 into at least one first stream 520 comprising COx, H2, and CH4, and a second stream comprising one of the C2+ compounds comprising C2H4 and C2H6. As shown in Figure 5, the first stream 520, comprising COx, H2, and CH4 or a portion thereof, can be recycled to the methanation subsystem 501 to promote the generation of the methanated OCM feed stream 515. According to some embodiments of the method and system of the present invention, at least a portion of the first stream 520 may be purged to prevent the accumulation of inert components (e.g., N₂) in the system. Additionally, the separation subsystem 506 may separate the second stream, comprising C₂⁺ compounds, into a third stream 521 comprising C₂H₄ products and a fourth stream 522 comprising C₂H₆ products. As shown in FIG. 5, the fourth stream 522 comprising C₂H₆ may be directed to the OCM subsystem 504 (e.g., to the OCM reactor or to the PBC unit) to generate additional C₂H₄ by pyrolyzing C₂H₆. According to some embodiments of the method and system of the present invention, the water electrolysis unit is fluidly coupled to the separation subsystem 506 and receives a stream 523 comprising H₂O (connection not shown), which is separated or otherwise removed from the OCM effluent 518 by the separation subsystem 506.

[0078] Separation subsystem 506 may include any number of separation units or any combination of separation techniques suitable for separating the products of an OCM reaction. For example, separation subsystem 506 may separate OCM effluent 518 by means of cryogenic separation, pressure swing adsorption, temperature swing adsorption, membrane separation, adsorbents, and combinations thereof. Examples of separation subsystems suitable for implementation in the methods and systems of the present invention are described in WO 2014 / 011646 A1, WO 2013 / 106771 A2, WO 2015 / 106023 A1, WO 2017 / 065947 A1 and WO 2018 / 118105 A1, the entire disclosure of which is incorporated herein by reference.

[0079] As shown in Figure 5, according to some embodiments of the method and system of the present invention, system 500 includes a CO2 removal unit 505 fluidly coupled to an OCM subsystem 504, a CO2 electrolysis unit 507, and a separation subsystem 506. The CO2 removal unit 505 is configured to remove CO2 from the OCM effluent 518, guide at least a portion of the removed CO2 to the CO2 electrolysis unit 507 via a flow 519, and guide substantially CO2-free OCM effluent to the separation subsystem 506. According to some embodiments of the method and system of the present invention, all CO2 removed by the CO2 removal unit 505 is guided to the CO2 electrolysis unit 507 via a flow 519. The CO2 removal unit 505 may include any known technique suitable for removing CO2 from a programmed flow. Examples of suitable CO2 removal techniques include (but are not limited to) amine absorber systems, pressure swing adsorption, temperature swing adsorption, membrane separation, solvent separation, and cryogenic separation.

[0080] Although Figure 5 illustrates a CO2 removal unit 505 located downstream of the OCM subsystem 504 and upstream of the separation subsystem 506, considering that the CO2 contained in the OCM effluent 518 can be removed via the separation subsystem 506, the CO2 removal unit 505 is unnecessary. This configuration would be suitable for systems where the separation subsystem 506 is based on adsorption technology.

[0081] Referring now to FIG6, a block flow diagram of a system 600 for performing a method of converting carbon dioxide into olefins (including C₂H₄) according to the present invention is shown. System 600 includes a methanation subsystem 601, a co-electrolysis unit 602, an OCM subsystem 604, and a separation subsystem 606. The co-electrolysis unit 602 is configured to receive a first feed stream 610 including CO₂ and a second feed stream including H₂O, and to generate a renewable syngas stream 612 including CO and H₂ and a renewable oxidant stream 614 including O₂. The methanation subsystem 601 is fluidly coupled to the co-electrolysis unit 602 and is configured to receive the renewable syngas stream 612 and to generate an OCM feed stream 613 including CH₄. OCM subsystem 604 is located downstream of and fluidly coupled to methanation subsystem 601 and co-electrolysis unit 602, and is configured to receive OCM feed stream 613 and regenerable oxidant stream 614 and produce an OCM effluent 615, which includes C2+ compounds comprising C2H4 and C2H6 and non-C2+ impurities comprising one or more of CO, CO2, H2 and CH4. Separation subsystem 606 is located downstream of OCM subsystem 604, fluidly coupled to and configured to receive OCM effluent 615, and separates OCM effluent 615 into at least one first stream 617 comprising COx, H2 and CH4 and a second stream comprising one of C2+ compounds comprising C2H4 and C2H6. The second stream can be further separated in the separation subsystem 606 to produce a third stream 618 containing one of C2H4 and a fourth stream 619 containing one of C2H6.

[0082] In the system 600 illustrated in Figure 6, the methanation subsystem 601 and the OCM subsystem 604 may have a configuration similar to or identical to that of the methanation subsystem 101 and the OCM subsystem 103 previously described herein with reference to Figure 1, and include components similar to or identical thereto. For example, the methanation subsystem 601 may include one or more methanation reactors containing a methanation catalyst. The OCM subsystem 604 may include, for example, one or more OCM reactors containing one or more OCM catalysts for promoting an OCM reaction to produce OCM effluent 615. The OCM subsystem 604 may also include a PBC unit.

[0083] As shown in Figure 6, a first feed stream 610 containing CO2 and a second feed stream 611 containing H2O are directed to the co-electrolysis unit 602. According to the method and system of the present invention, the first feed stream 610 containing CO2 is supplied to one of the main or sole carbon sources of the system 600 or process. In some embodiments of the method and system of the present invention, the first feed stream 610 includes captured CO2. The captured CO2 may be CO2 captured from industrial facilities including (but not limited to) steel / metal production facilities, cement production facilities, coal-fired power plants, coal gasification, and biomass gasification. The captured CO2 may also contain a certain amount of CO. In some embodiments of the method and system of the present invention, the first feed stream 610 may include CO2 generated by removing CO2 from a natural gas stream, as previously described with respect to Figure 3. According to some embodiments of the invention, as described above with respect to FIG3, at least a portion of a substantially CO2-free natural gas stream generated by a gas processing unit may be directed to the OCM subsystem 604 as a supplementary stream 621 including CH4. According to some embodiments of the method and system of the invention, the second feed stream 611 contains vapor.

[0084] As mentioned above, the co-electrolysis unit 602 is configured to receive a first feed stream 610 and a second feed stream 611 and generate a renewable synthesis gas stream 612 comprising CO and H2 and a renewable oxidant stream 614 comprising O2. In some configurations, the renewable oxidant stream 614 comprising O2 is the sole source of O2 supplied to the OCM subsystem 604. Therefore, the co-electrolysis unit 602 can renewably supply all the oxygen required to perform an OCM reaction in the OCM subsystem 604. This configuration is particularly advantageous because it eliminates the need to supply oxygen to an air separation unit (ASU) in the OCM subsystem 604 (which is expensive and energy-intensive). The co-electrolysis unit 602 is operable to convert CO2 and water or vapor into CO, H2, and O2. For example, in some embodiments, co-electrolysis unit 602 can convert CO2 and water or vapor into CO, H2, and O2 gases according to the following reaction: CO2 → CO + ½O2 and H2O → H2 + ½O2. Co-electrolysis unit 602 can be based on any technology that can electrochemically convert CO2 and water or vapor into syngas components CO, H2, and O2. One example of this technology is solid oxide electrolysis. Exemplary technologies applicable to the co-electrolysis unit 602 of the present invention are described in U.S. Patent Nos. 7,951,283 B2, 8,366,902 B2, and 9,631,284, the entire contents of which are incorporated herein by reference. In some embodiments of the methods and systems of the present invention, co-electrolysis unit 602 includes a solid oxide electrolytic cell (SOEC). The SOEC can operate at temperatures from 500°C to 1,200°C. SOEC may include an electrolyte material comprising (but not limited to) yttrium-stabilized zirconia electrolyte, scandium-stabilized zirconia electrolyte, lanthanum gallate electrolyte (LSGM), ytterbium-stabilized zirconia electrolyte, and cerium oxide (CeO₂) electrolyte. SOEC may include cathode materials conventionally used in solid oxide electrolyzers, such as (but not limited to) a nickel-zirconia cermet material. SOEC may include anode materials conventionally used in solid oxide electrolyzers, such as (but not limited to) lanthanum strontium manganese oxide or strontium-doped lanthanum manganate. In some embodiments of the methods and systems of the present invention, in addition to CO, H₂, and O₂, co-electrolysis unit 602 also generates CH₄. The energy required to power co-electrolysis unit 602 to generate the renewable synthesis gas stream 612 and the renewable oxidant stream 614 may be provided by one or more renewable energy sources. Exemplary renewable energy sources that can be used in the methods and systems of the present invention include (but are not limited to) wind power, solar power, biomass power, geothermal power, hydropower and nuclear power.

[0085] As shown in Figure 6, the renewable syngas stream 612 is directed to the methanation subsystem 601. In the methanation subsystem 601, the carbon oxides (i.e., CO, CO2, or both) and H2 in the renewable syngas stream 612 react to produce CH4 via the following reactions: i) CO2 + 4H2 → CH4 + 2H2O and ii) CO + 3H2 → CH4 + H2O. By providing a larger proportion of CO instead of CO2 to the methanation subsystem 601 (as can be achieved using the co-electrolysis unit 602), the methanation reaction requires less H2 and produces less H2O. Furthermore, a higher concentration of CO in the feed to the methanation subsystem 601 reduces the size of the methanation reactor and the amount of methanation catalyst required to perform the methanation reaction. In addition, the H2 produced by the co-electrolysis unit 602 eliminates the need for a separate renewable H2 subsystem. The CH4 produced in the methanation subsystem 601 is guided to the OCM subsystem 604 as an OCM feed stream 613.

[0086] As can be understood from the methanation reactions listed above, these reactions can produce water, which can be present in the OCM feed stream 613 exiting the methanation subsystem 601. Therefore, in some embodiments of the method and system of the present invention, at least a portion of the H₂O present in the OCM feed stream 613 can be removed before the OCM feed stream 613 is directed to the OCM subsystem 604. For example, the OCM feed stream 613 can be directed to a dehydration unit 603 to remove H₂O from the OCM feed stream 613. The dehydration unit 603 can be a liquid-gas separator that removes H₂O from the OCM feed stream 613 by cooling it, or any other separation unit capable of removing H₂O from the OCM feed stream 613. In some embodiments of the method and system of the present invention, the H₂O removed from the OCM feed stream 613 can be recycled to the co-electrolysis unit 602 via stream 622. On the other hand, if the OCM catalyst present in the OCM subsystem 604 is resistant to the presence of vapor, the dehydration unit 603 can be omitted.

[0087] Referring again to Figure 6, the OCM feed stream 613, together with the regenerable oxidant stream 614, is directed to the OCM subsystem 604 to produce an OCM effluent 615, which includes C2+ compounds comprising C2H4 and C2H6 and non-C2+ impurities comprising one or more of CO, CO2, H2, and CH4. The OCM effluent 615 can be directed to a separation subsystem 606 to separate the OCM effluent 615 into at least one first stream 617 comprising COx, H2, and CH4, and a second stream comprising one of the C2+ compounds comprising C2H4 and C2H6. As shown in Figure 6, the first stream 617, comprising COx, H2, and CH4 or a portion thereof, can be recycled to the methanation subsystem 601 to facilitate the generation of the methanated OCM feed stream 613. According to some embodiments of the method and system of the present invention, at least a portion of the first stream 617 may be purged to prevent the accumulation of inert components (e.g., N₂) in the system. Additionally, the separation subsystem 606 may separate the second stream, comprising C₂⁺ compounds, into a third stream 618 comprising C₂H₄ products and a fourth stream 619 comprising C₂H₆ products. As shown in FIG. 6, the fourth stream 619 comprising C₂H₆ may be directed to the OCM subsystem 604 (e.g., to the OCM reactor or to the PBC unit) to generate additional C₂H₄ by pyrolyzing C₂H₆. According to some embodiments of the method and system of the present invention, the co-electrolysis unit is fluidly coupled to the separation subsystem 606 and receives a stream 620 comprising H₂O (connection not shown), which is separated or otherwise removed by the separation subsystem 606 from the OCM effluent 615.

[0088] Separation subsystem 606 may include any number of separation units or any combination of separation techniques suitable for separating the products of an OCM reaction. For example, separation subsystem 606 may separate OCM effluent 615 by means of cryogenic separation, pressure swing adsorption, temperature swing adsorption, membrane separation, adsorbents, and combinations thereof. Examples of separation subsystems suitable for implementation in the methods and systems of the present invention are described, for example, in WO 2014 / 011646 A1, WO 2013 / 106771 A2, WO 2015 / 106023 A1, WO 2017 / 065947 A1 and WO 2018 / 118105 A1, the entire disclosure of which is incorporated herein by reference.

[0089] As shown in Figure 6, according to some embodiments of the method and system of the present invention, system 600 includes a CO2 removal unit 605 fluidly coupled to an OCM subsystem 604, a co-electrolysis unit 602, and a separation subsystem 606. The CO2 removal unit 605 is configured to remove CO2 from the OCM effluent 615, guide at least a portion of the removed CO2 to the co-electrolysis unit 602 via flow 616, and guide substantially CO2-free OCM effluent to the separation subsystem 606. According to some embodiments of the method and system of the present invention, all CO2 removed by the CO2 removal unit 605 is guided to the CO2 electrolysis unit 507 via flow 519. The CO2 removal unit 605 may include any known technique suitable for removing CO2 from a programmed flow. Examples of suitable CO2 removal techniques include (but are not limited to) amine absorber systems, pressure swing adsorption, temperature swing adsorption, membrane separation, solvent separation, and cryogenic separation.

[0090] Although Figure 6 shows a CO2 removal unit 605 located downstream of the OCM subsystem 604 and upstream of the separation subsystem 606, considering that the CO2 contained in the OCM effluent 615 can be removed via the separation subsystem 606, the CO2 removal unit 605 is unnecessary. This configuration would be suitable for systems in which the separation subsystem 606 is based on adsorption technology.

[0091] Although the diagram can illustrate various streams introduced into a unit individually, it is considered that two or more streams introduced into a unit may be combined or mixed into a single stream before being introduced into the unit. For example, the carbon oxide feed stream 410 and the CO2-containing stream 416 shown in Figure 4 may be combined and supplied as a single stream to the methanation subsystem 401.

[0092] All references to the singular characteristics or limitations of this invention shall include the corresponding plural characteristics or limitations, and vice versa, unless otherwise indicated or expressly implied in the text to which the reference is made.

[0093] All combinations of methods or procedures used herein may be performed in any order unless otherwise indicated or expressly implied in the text when making the referenced combination.

[0094] All ranges and parameters disclosed herein (including, but not limited to, percentages, fractions, and ratios) should be understood to encompass any and all subranges assumed and generalized therein, and every number between the endpoints. For example, a specified range of "1 to 10" should be considered to include any and all subranges between (and including) the minimum value of 1 and the maximum value of 10; that is, all subranges begin with a minimum value of 1 or greater (e.g., 1 to 6.1) and end with a maximum value of 10 or less (e.g., 2.3 to 9.4, 3 to 8, 4 to 7), and end at each of the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 contained within the range.

[0095] The methods and systems of the present invention may include, consist of, or substantially consist of the essential elements and limitations of the disclosures as described herein, and any additional or optional components or features described herein or otherwise known for hydrocarbon or petrochemical processing applications (including methane oxidative coupling applications).

[0096] With regard to the term "include, includes, or including" as used in the specification or claims, it is intended to include in a manner similar to the term "comprising," as the term is interpreted when used as a transitional word in a technical solution. Furthermore, with regard to the use of the term "or" (e.g., A or B), it is intended to mean "A or B or both A and B." The term "A or B only but not both" will be used when the applicant intends to indicate "only A or B but not both." Therefore, the use of the term "or" herein is inclusive rather than exclusive. Furthermore, the phrase "at least one of A, B, and C" should be interpreted as "only A or only B or only C or any combination thereof." In this invention, the use of "a" or "an" will be considered to include both the singular and the plural. Conversely, where appropriate, any reference to a plural item should include the singular.

[0097] According to the present invention, various inventive concepts can be utilized in combination. Furthermore, any particular feature relating to a specific disclosure of the method and system of the present invention should be interpreted as usable with all disclosures of the method and system of the present invention, unless the incorporation of such a feature would contradict the express terms of the disclosed disclosure. Additional advantages and modifications will be readily apparent to those skilled in the art. Therefore, the present invention, in its broader forms, is not limited to the specific details, representative devices, or illustrative examples shown and described therein. Thus, deviations from such details may be made without departing from the spirit or scope of the general inventive concept.

[0098] The scope of the general inventive concept presented herein is not intended to be limited to the specific illustrative forms shown and described herein. Based on the given disclosure, those skilled in the art will not only understand the general inventive concept and its associated advantages, but will also discover obvious variations and modifications to the disclosed apparatus, systems, and methods. Therefore, it is sought to encompass all such variations and modifications and any equivalents that fall within the spirit and scope of the general inventive concept described and / or claimed herein.

[0099] 100: System 101: Methanation Subsystem 102: Renewable H2 Subsystem 103: OCM Subsystem 104: Carbon oxide feed flow 105:H 2 carrier flow 106: Renewable H2 feed stream 107: OCM feed flow 108: Oxidant feed flow 109: OCM effluent 200: System 201: Methanation Subsystem 202: Renewable H2 Subsystem 203: Dehydration Unit 204: OCM Subsystem 205: CO2 Removal Unit 206: Separation Subsystem 210: Carbon oxide feed flow 211: Water Flow 212: Renewable H2 feed stream 213: OCM feed flow 214: Oxidant feed flow 215: OCM effluent 216: Flow 217: First-class 218: Third-rate 219: Fourth Stream 220: Flow 221: Supplementary Flow 222: Flow 300: Gas processing unit 301: Natural Gas Flow 302: Natural Gas Flow 310: CO2 feed stream 400: System 401: Methanation Subsystem 402: Renewable H2 Subsystem 403: OCM Subsystem 404: Heat exchanger 405: Programmable Gas Compressor 406: CO2 Removal Unit 407: Programmable Gas Dryer 408: Demethanizer Unit 409:C 2 Purification Unit 410: Carbon oxide feed flow 411: Water Flow 412: Renewable H2 feed stream 413: OCM feed flow 414: Oxidant feed flow 415: OCM effluent 416: Flow 417: First-class 418: Second-rate 419: Third-rate 420: Fourth Stream 421: Supplementary Flow 422: Flow 500: System 501: Methanation Subsystem 502: Renewable H2 Subsystem 503: Dehydration Unit 504: OCM Subsystem 505: CO2 Removal Unit 506: Separation Subsystem 507: CO2 Electrolysis Unit 510: Feed Flow 511: First Renewable Electrolysis Current 512: Second Renewable Electrolysis Current 513: Water Flow 514: Renewable H2 feed stream 515: OCM feed flow 516: Renewable O2 airflow 517: Oxidant Feed Flow 518: OCM effluent 519: Flow 520: First-class 521: Third-rate 522: Fourth Stream 523: Flow 524: Supplementary Flow 525: Flow 600: System 601: Methanation Subsystem 602: Co-electrolysis unit 603: Dehydration Unit 604: OCM Subsystem 605: CO2 Removal Unit 606: Separation Subsystem 610: First feed stream 611: Second feed flow 612: Renewable Synthetic Gas Stream 613: OCM feed flow 614: Renewable Oxidant Flow 615: OCM effluent 616: Flow 617: First-class 618: Third-rate 619: Fourth Stream 620: Flow 621: Supplementary Flow 622: Flow

Claims

1. A method for converting carbon oxides into olefins containing ethylene (C2H4), the method comprising: (a) A renewable hydrogen (H2) feed stream and a carbon oxide feed stream comprising carbon dioxide (CO2), carbon monoxide (CO), or both CO2 and CO are directed to a methanation reactor to produce a methane oxidative coupling (OCM) feed stream comprising methane (CH4); and (b) the OCM feed stream and an oxidant feed stream comprising oxygen (O2) are directed to an OCM reactor comprising an OCM catalyst and an OCM reaction is performed to produce an OCM effluent comprising (i) a C2+ compound comprising C2H4 and ethane (C2H6), and (ii) a non-C2+ impurity comprising one or more of CO, CO2, H2 and CH4, wherein the carbon oxide feed stream is one of the sole carbon sources used in the method, wherein the method produces olefins comprising C2H4 with negative carbon emissions; and wherein the method achieves a carbon efficiency greater than 100%, the carbon efficiency being based on the amount of carbon supplied from CH4 to the process.

2. The method of claim 1, wherein the renewable H2 feed stream is generated by at least one of: (i) water electrolysis; (ii) biogasification; (iii) ammonia cracking; or (iv) hydrogen sulfide decomposition.

3. The method of claim 2, wherein the renewable H2 feed stream is generated by water electrolysis, and wherein the water electrolysis generates renewable O2 which is used as at least a portion of the oxidant feed stream.

4. The method of claim 3 further includes removing water from the OCM feed stream and directing the water to an electrolysis unit for performing the water electrolysis.

5. The method of claim 1 further includes separating the OCM effluent into at least (i) a first stream comprising one of COx, H2 and CH4, and (ii) a second stream comprising one of C2+ compounds comprising C2H4 and C2H6; and directing at least a portion of the first stream to the methanation reactor.

6. The method of claim 1 further includes removing CO2 from the OCM effluent and directing at least a portion of the removed CO2 to the methanation reactor.

7. The method of claim 5 further includes separating the second stream to produce a third stream including C2H4 and a fourth stream including C2H6; and directing the fourth stream to a post-bed cracking unit downstream of the OCM catalyst.

8. The method of claim 1, further comprising directing a supplementary stream comprising CH4 to the OCM reactor, wherein the molar ratio of CH4 in the supplementary stream to CO2 in the carbon oxide feed stream is 0.01:1 to 5:

1.

9. The method of claim 1, wherein the carbon oxide feed stream includes captured CO2.

10. A method for converting carbon dioxide into an olefin comprising ethylene (C2H4), the method comprising: (a) directing a natural gas stream containing carbon dioxide (CO2) to a gas processing unit to generate a CO2 feed stream and a substantially CO2-free natural gas stream; (b) directing a renewable hydrogen (H2) feed stream and the CO2 feed stream to a methanation reactor to generate a methane oxidative coupling (OCM) feed stream including methane (CH4); and (c) directing the OCM feed stream and an oxidant feed stream including oxygen (O2) to an OCM reactor including an OCM catalyst and performing an OCM reaction to generate an OCM effluent comprising (i) a C2+ compound including C2H4 and ethane (C2H6), and (ii) a non-C2+ impurity including one or more of CO, CO2, H2 and CH4, wherein the method produces an olefin containing C2H4 with negative carbon emissions, wherein the CO2 feed stream is one of the sole carbon sources used in the method.

11. The method of claim 10, wherein the renewable H2 feed stream is generated by at least one of: (i) water electrolysis; (ii) biogasification; (iii) ammonia cracking; or (iv) hydrogen sulfide decomposition.

12. The method of claim 11, wherein the renewable H2 feed stream is generated by water electrolysis, and wherein the water electrolysis generates renewable O2 which is used as at least a portion of the oxidant feed stream.

13. The method of claim 12 further includes removing water from the OCM feed stream and directing the water to an electrolysis unit for performing the water electrolysis.

14. The method of claim 10 further includes separating the OCM effluent into at least (i) a first stream comprising COx, H2 and CH4, and (ii) a second stream comprising C2+ compounds comprising C2H4 and C2H6; and directing at least a portion of the first stream to the methanation reactor.

15. The method of claim 10 further includes removing CO2 from the OCM effluent and directing at least a portion of the removed CO2 to the methanation reactor.

16. The method of claim 14 further includes separating the second stream to produce a third stream comprising C2H4 and a fourth stream comprising C2H6; and directing the fourth stream to a columnar cracking unit downstream of the OCM catalyst.

17. The method of claim 10 further includes directing a supplementary stream comprising at least a portion of the substantially CO2-free natural gas stream to the OCM reactor, wherein the molar ratio of CH4 in the supplementary stream to CO2 in the CO2 feed stream is 0.01:1 to 5:

1.

18. The method of claim 10 further includes adding a captured CO2 source to the CO2 feed stream.

19. A method for converting carbon oxides into olefins including ethylene (C2H4), the method comprising: (a) a renewable hydrogen (H2) feed stream and a carbon oxide feed stream including carbon dioxide (CO2), carbon monoxide (CO), or both CO2 and CO are directed to a methanation reactor to produce a methane oxidative coupling (OCM) feed stream including methane (CH4); and (b) the OCM feed stream and an oxidant feed stream including oxygen (O2) are directed to an OCM reactor including an OCM catalyst and an OCM reaction is performed to produce an OCM effluent comprising (i) a C2+ compound including C2H4 and ethane (C2H6), and (ii) a non-C2+ impurity including one or more of CO, CO2, H2 and CH4, wherein the method produces an olefin containing C2H4 with negative carbon emissions, and wherein the carbon oxide feed stream is one of the sole carbon sources used in the method.

Images