16T&I0105; 092474.028921 (375U2) PCT

DESCRIPTION

METHOD FOR OXIDATIVE CONVERSION OF METHANE TO ETHYLENE WITH CO

RECYCLE

Technical Field

[0001] The present disclosure relates to the conversion of hydrocarbons to C2 hydrocarbons. More specifically, the disclosure relates to the conversion of methane to C2 hydrocarbons and oxidation products.

Background

[0002] The conversion of methane to longer chain hydrocarbons may be achieved via a number of processes. Traditional methods of converting a lower molecular weight carbon- containing molecule such as methane to higher molecular weights and/or more complex compounds such olefins are numerous. Unsaturated hydrocarbons have been prepared via thermal pyrolysis in the conversion of natural gas condensates and petroleum distillates, which include methane, ethane, and larger hydrocarbons. Historically methane has been converted to longer chain hydrocarbons through steam reforming to yield a synthesis gas (syngas), a mixture of carbon monoxide and hydrogen, which may then be used as a feedstock to a Fischer-Tropsch process to convert the carbon monoxide and hydrogen into liquid hydrocarbons. Still, the Fischer-Tropsch process may be limited in converting methane to shorter chain alkenes such as ethylene.

[0003] An oxidative coupling of methane (OCM) may provide alkene hydrocarbons such as ethylene via an exothermic reaction of methane and oxygen in the presence of one or more catalysts. It is known however that methane oxidative conversion to C2 hydrocarbons, such as ethylene, may also produce what may be considered deep oxidations products such as carbon monoxide and carbon dioxide. These deep oxidation products may be generated because a combustion reaction of methane proceeds along with the oxidative conversion in the same temperature range. Removal of carbon dioxide is performed more readily but separation of the remaining oxidation product, carbon monoxide, from the desired coupling product may be more costly. Often that cost is realized by either performing a separation process to remove the carbon monoxide or by incorporating an additional process step to 16T&I0070; 092474.028920 (375U1) convert the carbon monoxide.

[0004] There remains a need in the art for a methane oxidative conversion process (or an oxidative coupling of methane process) that resolves the problem of the formed carbon monoxide.

Summary

[0005] As described in more detail herein, the present disclosure provides processes, apparatuses, and systems for the production of C2 hydrocarbons. Integrated processes of methane oxidative coupling, separation, and recycling feeds are described herein. Aspects of the present disclosure allow for a generated carbon monoxide and unreacted or unconverted methane from the OCM process to be redirected to the OCM reactant mixture thereby eliminating additional process schemes for carbon monoxide conversion.

[0006] In one aspect, a method may comprise subjecting a hydrocarbon feedstock to an oxidative conversion process to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted hydrocarbon product; separating at least a portion of the carbon dioxide product from the product mixture; isolating at least a portion of the carbon monoxide product and a portion of the unconverted hydrocarbon from the product mixture by separating at least a portion of the ethylene and the ethane from the product mixture; and combining the isolated portion of the carbon monoxide product and isolated portion of the unconverted hydrocarbon product with a hydrocarbon feedstock to undergo the oxidative conversion wherein an oxidative conversion of the isolated portion of carbon monoxide generates heat to facilitate the oxidative conversion of the hydrocarbon feedstock.

Brief Description of the Drawings

[0007] The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become apparent and be better understood by reference to the following description of an aspect of the disclosure in conjunction with the accompanying drawings, wherein:

[0008] FIG. 1 shows a reaction scheme for methane conversion to C2 hydrocarbons integrated with the recycle of generated carbon monoxide and unconverted methane to the OCM reactant mixture.

[0009] FIG. 2 shows a schematic diagram for methane conversion to C2 hydrocarbons integrated with the recycle of a process stream comprising generated carbon monoxide and 16T&I0070; 092474.028920 (375U1) unconverted methane to the OCM reactant mixture.

[0010] FIG. 3 shows a process block diagram for the for methane conversion to C2 hydrocarbons integrated with the recycle of generated carbon monoxide and unconverted methane to the OCM reactant mixture.

[0011] Additional advantages of the disclosure will be set forth in part in the description that follows, and in part will be obvious from the description, or can be learned by practice of the disclosure. The advantages of the disclosure will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

Detailed Description

[0012] C2 hydrocarbons such as ethane and ethylene may be prepared by an oxidative coupling of methane. A hydrocarbon feedstock comprising methane is typically reacted with oxygen in the presence of an appropriate catalyst. The oxidative coupling process may release large amounts of energy (e.g., about 280 kilojoules per mole, kj/mol) and may proceed at higher temperatures greater than 500 °C, typically between about 750 °C to about 950 °C to achieve conversion of the methane. A drawback to oxidative coupling of methane processes is the low per-pass yield of product, usually less than 30 mole percent, and the high yield of carbon oxide byproducts such as carbon monoxide and carbon dioxide. Thus, the resultant product mixture may comprise the desired C2 hydrocarbon in addition to deep oxidation byproducts carbon dioxide and carbon monoxide. Carbon dioxide may be readily removed from the product mixture by processes well known in the art. The carbon monoxide may be formed in the oxidative coupling of methane in a relatively small amount (i.e., less than 5 % conversion).

[0013] Such a small amount of generated carbon monoxide makes it far less likely that the volume of carbon monoxide would be gathered and collected for use as a synthesis gas (syngas) component. Also, as molecular hydrogen is generally not present in the product of the OCM, there is little or no syngas available. Thus, the question becomes what is there to do with such a relatively small amount of carbon monoxide. It is undesirable to leave the carbon dioxide with the desired coupling product (ethane or ethylene) particularly where the ethane or ethylene are collected for downstream processing such as polymerization.

Although the amount of carbon monoxide may be comparatively small, the carbon monoxide may affect formation of a downstream product if allowed to remain with the coupling products of ethane and ethylene. Separation of the carbon monoxide byproduct to isolate the 16T&I0070; 092474.028920 (375U1) desired coupling product however may prove more cumbersome both with respect to time and with respect to associated costs of adding a process to use up the formed carbon monoxide byproduct. The integrated processes of the present disclosure may alleviate concerns related to the presence of carbon monoxide in the OCM product mixture.

[0014] In various aspects, the present disclosure provides an integration of processes for the conversion of a hydrocarbon feedstock comprising methane to C2 hydrocarbons. The integrated processes may combine an oxidative coupling reaction converting a methane feedstock to C2 hydrocarbons and oxidation products (carbon dioxide and carbon monoxide), one or more separation processes to isolate a carbon monoxide byproduct and unconverted methane, and a recycle process of directing the isolated carbon monoxide byproduct and unconverted methane to the initial methane feedstock.

[0015] The oxidative coupling of methane ("OCM") reaction promotes the formation of alkene hydrocarbons such as ethylene using an exothermic reaction of methane and oxygen over one or more catalysts according to the following overall equation (1):

[0016] Methods of the present disclosure describe a separation of at least a portion of the carbon dioxide product from the product mixture. The methods further comprise isolating at least a portion of the carbon monoxide product and a portion of the unconverted hydrocarbon product from the product mixture by separating at least a portion of the coupling products ethylene and the ethane from the product mixture. The isolated portion of carbon monoxide and isolated portion of the unconverted hydrocarbon product may be combined with the methane feedstock and oxidant (or the OCM reactant mixture) to undergo combustion with the oxidant for the oxidative conversion reaction. When subjected to the oxidative conversion process, the recycled, isolated carbon monoxide may generate heat that facilitates the oxidative conversion of the hydrocarbon feedstock.

[0017] As an illustrative example, FIG. 1 presents reaction processes configured to utilize the carbon monoxide byproduct generated during the oxidative coupling of methane. As shown, methane may be reacted with an oxidant, such as molecular oxygen, in the presence of an appropriate catalyst to provide a product mixture comprising at least ethylene, ethane, carbon dioxide, carbon monoxide, and a portion of unreacted or unconverted methane at 100. In one aspect, efficiency of the OCM process may be improved through a series of separation processes configured to isolate at least a portion of the carbon monoxide and unconverted 16T&I0070; 092474.028920 (375U1) methane products. That is, separation processes may be performed on varying components of the product mixture to leave carbon monoxide and unconverted methane remaining as products from the product mixture. At least a portion of carbon monoxide and unconverted methane as remaining components of the product mixture may be recycled to the oxidative conversion process. Carbon dioxide may be separated from the product mixture at 102 and ethylene and ethane may also be separated at 104. Efficiency of the process system may be improved by recycling the carbon monoxide and unconverted methane product throughout the reaction processes back to the oxidative coupling of methane process step at 106.

Oxidative Coupling of Methane

[0018] An oxidative coupling of methane (OCM) reaction is a generally exothermic, catalytic reaction between methane and oxygen to provide a product mixture including longer chain hydrocarbons such as ethane, ethylene and larger hydrocarbons such as propane, propylene, butane, butylene, and the like (i.e., coupling products). Also generated during the reaction are carbon oxides, such as carbon monoxide and carbon dioxide, which are often referred to as deep oxidation products in relation to the OCM reaction. In certain aspects, an OCM product mixture may also include quantities of unreacted oxygen and unconverted or unreacted methane.

[0019] In the reaction, methane (CH4) is activated heterogeneously on the catalyst surface, thereby forming free methyl radicals. The free radicals may then couple in the gas phase to form ethane (C2H6). The ethane may undergo dehydrogenation at the catalyst or in gas phase to form ethylene (C2H4). For example, in a catalyst bed setup, the coupling

reaction of methane to ethane may occur with thermal dehydrogenation of ethane to ethylene and undesired combustion reactions forming in carbon monoxide and carbon dioxide as byproducts take place. Hydrogen may be formed in small amounts from the ethane

dehydrogenation; the amount of hydrogen may vary between 0.5 and 2 % volume depending on the catalyst used. For example, redox system catalysts may provide less than 1 % hydrogen in the product mixture. Reaction yield of the desired C2 products may be reduced by non-selective reactions of methyl radicals with the catalyst surface and with oxygen in the gas phase, which can produce the undesirable carbon monoxide and carbon dioxide by products.

[0020] As provided herein, the overall reaction may proceed according to formula (1) above. More specifically, however, the oxidative conversion of methane to C2 hydrocarbons may 16T&I0070; 092474.028920 (375U1) proceed through stoichiometric reactions of which can be described by the following equations (2-5):

2CH ₄ + O2 = C2H4 + H2O ΔΗ = -34 kcal/mol (2)

2CH4 + ½ O2 = C2H6 + H2O ΔΗ = -21 kcal/mol (3)

CH ₄ +1.502 = CO + 2¾0 ΔΗ = -124 kcal/mol (4)

CH4 + 2Ο2 = CO2 + 2H ₂ 0 ΔΗ = - 192 kcal/mol (5)

[0021] The overall reaction is exothermic (ΔΗ = -67 kilocalories per mole, kcal/mol) and historically has been conducted at very high temperatures of from about 750°C to about 950°C to provide a C2 (ethane + ethylene) yield reported to be in the range of 15%-25%.

[0022] According to methods of the present disclosure, at least a portion of the carbon monoxide product and at least a portion of unconverted methane may be directed, or recycled, back to an OCM reactant mixture. Recycling of at least a portion of the carbon monoxide product and at least a portion of unconverted methane may eliminate additional processes to separate carbon monoxide either from the desired coupling products or from methane. An additional process scheme for utilization of the CO may also be rendered unnecessary. Carbon monoxide recycle to the oxidative conversion portion of the reaction may also reduce or alleviate environmental concerns with respect to the release of carbon monoxide into the atmosphere.

[0023] Moreover, combustion of carbon monoxide is an exothermic reaction as shown the follow stoichiometric reaction:

CO + ½ 02 = CO ΔΗ = -68 kcal/mol (7)

Compared to the energies released for the methane conversion to C2 hydrocarbons (equations 2 and 3 above), the carbon monoxide combustion is more exothermic. Thus, the presence of the recycled carbon monoxide product and unconverted methane with the OCM reactant mixture may facilitate the reaction by providing fuel for the process.

[0024] A conventional OCM reaction comprises a catalytic gas phase reaction of methane and an oxidant, such as oxygen, to provide one or more hydrocarbons having two or more carbon atoms (which may be collectively referred to herein as coupling products). The OCM process may include a methane feedstream or source and an oxidant feedstream provided to one or more reactor vessels equipped for the OCM reaction. 16T&I0070; 092474.028920 (375U1)

[0025] The source of methane may comprise a commercial natural gas source, a natural gas feed from one or more municipal or industrial gas suppliers. In one example, at least a portion of the methane may comprise biogas, i.e., methane that is derived from one or more processes involving the decay of organic substances. Or, at least a portion of the methane may be provided as a byproduct from another co-located process stream or another facility. In further examples, the methane source may comprise a liquefied natural gas ("LNG") or compressed natural gas ("CNG") terminal or storage facility. At least a portion of the methane may comprise wellhead natural gas drawn directly from a naturally occurring or manmade subterranean reservoir or from storage facilities fluidly coupled to the naturally occurring reservoir. The methane source may comprise a gas or mixture of gases containing at least about 5 mole percent (mol%) methane; at least about 10 mol% methane; at least about 20 mol% methane; at least about 30 mol% methane; at least about 40 mol% methane; at least about 50 mol% methane; at least about 60 mol% methane; at least about 70 mol% methane; at least about 80 mol% methane; at least about 90 mol% methane; or at least about 95 mol% methane.

[0026] In some aspects, contaminants from a natural gas methane sources may be removed prior to the OCM reaction. For example, higher molecular weight hydrocarbons (e.g., C3 and above hydrocarbons) present in the natural gas may be partially or completely removed from the natural gas via condensation to form a natural gas liquid ("NGL"). Remaining impurities, such as hydrogen sulfide and other sulfur containing compounds may be removed prior to the OCM process. In a process system, for example, comprising a number of reactors configured to effect the OCM reaction and related processes described herein, contaminants may be removed from a methane feedstream in equipped vessels upstream of the OCM reaction.

[0027] In various aspects of the present disclosure, methane may be reacted with an oxidant in the presence of a catalyst. As an example, a methane feed and an oxidant feed may be combined for contact with the suitable catalyst. An oxidant in the form of purified oxygen, for example may be supplied by an air separation unit ("ASU") equipped to the OCM reactor system. As used herein, the "purified oxygen" may refer to a gas having an oxygen concentration greater than about 21 mol%. In other aspects, at least a portion of the oxidant may comprise air or compressed air. Compressed air may include about 21 mol% oxygen and about 78 mol% nitrogen. In certain aspects, the oxidant may comprise a mixture of air and purified oxygen. Thus, the oxidant may comprise a gas or mixture of gases containing at least about 5 mol% oxygen; at least about 10 mol% oxygen; at least about 20 mol% oxygen; 16T&I0070; 092474.028920 (375U1) at least about 30 mol% oxygen; at least about 40 mol% oxygen; at least about 50 mol% oxygen; at least about 60 mol% oxygen; at least about 70 mol% oxygen; at least about 80 mol% oxygen; at least about 90 mol% oxygen; or at least about 95 mol% oxygen.

[0028] As provided herein, at least a portion of the oxidant may include nitrogen. The oxidant may further include small quantities of inert gases such as argon, particularly where air is used to provide a portion of or all of the oxidant. Nitrogen concentration in the oxidant may be dependent upon the one or more sources used to provide the oxidant, however the nitrogen may be present in the oxidant in an amount no more than about 5 mol%; no more than about 10 mol%; no more than about 20 mol%; no more than about 30 mol%; no more than about 40 mol%; no more than about 50 mol%; no more than about 60 mol%; or no more than about 70 mol%

[0029] Processing conditions for the oxidative coupling of methane may depend upon a number of factors. For example, the net methane-to-oxygen (CH4/O2) ratio may affect conditions. The methane and oxidant may be provided in a specific ratio in the OCM reactant mixture for the OCM process. The methane-to-oxygen stoichiometric ratio may also affect the overall conversion of raw materials to one or more preferred products in the OCM product mixture such as the desired coupling products. Where oxygen as the oxidant is the limiting reagent (i.e., maintaining a stoichiometric ratio for methane molar concentration to oxygen molar concentration of greater than 2: 1) the likelihood of a detonation or deflagration occurring within the one or more reaction vessels may be reduced. In at least some aspects, where the methane is the limiting reagent, the risk of detonation or deflagration within a reaction vessel for the OCM process may increase.

[0030] The methane-to-oxygen stoichiometric ratio may be greater than about 2: 1 ; greater than about 2.25: 1 ; greater than about 2.5: 1 ; greater than about 2.75: 1 ; greater than about 3: 1 ; greater than about 3.5: 1 ; greater than about 4: 1 ; greater than about 4.5: 1 ; greater than about 5: 1 ; greater than about 7.5: 1 ; or greater than about 10: 1. As a specific example, the stoichiometric ratio of methane to oxygen is about 2: 1 or about 2.3: 1.

[0031] The methane feed and oxidant may be combined or introduced concurrently to the catalyst. The composition of the methane feed and oxidant as oxygen mixture may provide an additional variable in controlling the OCM process. The amount of oxygen feed delivered to the oxidative conversion process and present throughout the reaction system may dictate the process yield. The conversion of methane in the OCM process can also be affected or influenced by the overall composition of the methane feed and/or oxygen concentration as 16T&I0070; 092474.028920 (375U1) exposed to the catalyst. In various instances, one or more inert gases such as nitrogen may be present in the methane/oxygen mixture. The presence of inert gases may provide a stable thermal "heat sink" within the methane and oxygen OCM reactant mixture that is capable of absorbing thermal energy and consequently limits the temperature increase experienced by the oxygen, methane and OCM gas present at the catalyst. Thus ratio of methane to oxygen {e.g., the stoichiometric ratio of methane to oxygen) within the methane/oxygen mixture may affect the overall conversion of methane in the OCM reaction.

[0032] As provided herein, the methane and oxidant, which may combine to form the OCM reactant mixture, may include other gases such as longer chain, alkane, alkene, and alkyne hydrocarbons. In at least some instances, the methane source or the oxidant may contain one or more inert gases such as nitrogen. Thus, by controlling the quantity of methane or inert gas present in the methane source and controlling the quantity of oxygen or inert gas present in the oxidant, a methane/oxygen mixture having virtually any composition and methane to oxygen stoichiometric ratio can be provided.

[0033] According to the methods and processes described herein, the oxidative coupling of methane may include the reaction of methane and an oxidant, such as oxygen, in the presence of at least one suitable catalyst. In further aspects the catalyst is an OCM active catalyst. The exact elemental components or morphological form of the catalysts is not critical, provided they may be used in combination with the supports, diluents and/or binders described herein. In this regard, catalysts useful for practice of various embodiments of the invention include any bulk and/or nanostructured catalyst in any combination.

[0034] The conversion of methane and oxygen to one or more hydrocarbons may occur as a gas phase catalytic reaction. Any conventionally produced catalyst may be used to promote the catalytic reaction. In at least one aspect however, the, catalyst may include at least one inorganic catalytic poly crystalline nanowire. Other exemplary catalysts may include heterogeneous catalysts with various elemental components and having activity in a variety of reactions. In certain aspects, the catalyst is an OCM active catalyst. The components or morphological form of the catalysts is not critical, so long as they may be used in

combination with the OCM components described herein or physical reaction systems including supports, diluents and/or binders described herein. Accordingly, catalysts useful for the present disclosure may include any bulk and/or nanostructured catalyst in any combination.

[0035] The catalysts of the present disclosure may comprise a catalytic system in that the 16T&I0070; 092474.028920 (375U1) catalyst may be used in combination with a support, binder and/or diluent material. Diluents may be selected from bulk materials (e.g. commercial grade), nano materials (nanowires, nanorods, nanoparticles, etc.) and combinations thereof. All or at least a portion of the catalyst may be affixed, bonded or otherwise attached to an inert underlying substrate that provides structural strength and form to the catalyst. The substrate may also provide a plurality of gas flow channels. In one example, the substrate may be structured in the form of a hexagonal honeycomb structure or a square "egg-crate" structure. Exemplary catalysts useful in the disclosed processes may include any heterogeneous catalyst. The catalysts may have various elemental components and activity in a variety of reactions. In further aspects, all or at least a portion of the catalyst may react directly without a support structure. For example, the catalyst may be used in the form of a loose catalyst, an agglomerated catalyst, a sintered catalyst, a catalyst pressed or otherwise formed into various shapes such as rings, saddles, spoked wheels, snowflakes, and the like that provide a high ratio of exposed surface area to volume.

[0036] The catalyst may comprise any one of oxides, peroxides, carbonates, phosphates and silicates of elements selected from the group consisting of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs and beryllium Be; peroxides, carbonates, phosphates and silicates of elements selected from the group consisting of strontium Sr and barium Ba; and carbonates, phosphates and silicates of elements selected from the group consisting of lead Pb, tin Sn, germanium Ge, magnesium Mg and calcium Ca.

[0037] In certain aspects, the catalyst may comprise a nanowire catalyst, for example a nanowire comprising a metal oxide, metal hydroxide, metal oxyhydroxide, metal

oxy carbonate, metal carbonate or combinations thereof. In further aspects, the catalyst may comprise an inorganic nanowire comprising one or more metal elements from any of Groups 1 through 7, lanthanides, actinides or combinations thereof and a dopant comprising a metal element, a semi-metal element, a non-metal element or combinations thereof. Nanowires forming the nanowire catalyst may have a surface area of between 0.0001 and 3000 square meters per gram (m ² /g), for example.

[0038] The catalyst may comprise one or more doping elements. For example, the catalyst may comprise one or more doping elements, wherein the doping elements are selected from a metal element, a semi-metal element and a non-metal element, and wherein at least one of the doping elements is potassium K, scandium Sc, titanium Ti, vanadium V, niobium Nb, ruthenium Ru, osmium Os, iridium Ir, cadmium Cd, indium In, thallium Tl, sulfur S, 16T&I0070; 092474.028920 (375U1) selenium Se, polonium Po, praseodymium Pr, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, lutetium Lu or an element selected from any of groups 6, 7, 10, 1 1 , 14, 15 or 17. Other dopant combinations may include, but are not limited to:

europium/sodium Eu/N a, strontium/sodium Sr/Na, sodium/zirconium/europium/calcium Na/Zr/Eu/Ca, magnesium/sodium Mg/Na, strontium/samariuri^liolmium/thulium

Sr/Sm/Ho/Tm, strontium/tungsten Sr/W, magnesium/lanthanum/potassium Mg/La/K, sodium/potassium/magnesium/thulium Na/K/Mg/Tm, sodium/dysprosium/potassium

Na/Dy/K, sodium/lanthanum/dysprosium Na/La/Dy, sodium/lanthanum/europium Na/La/Eu, sodium/lanthanum/europium/indiumNa/La/Eu/In, sodium/lanthanum/potassium Na/La/K, sodiurn/lanthanum/lithium/cesium Na/La/Li/Cs, potassium/lanthanum K/La,

potassium/lanthanum/sulfur K/La/S, potassium/sodium K/Na, lithium/cesium Li/Cs, lithium/cesium/lanthanum Li/Cs/La, lithium/cesium/lanthanum/thulium Li/Cs/La/Tm, lithium/cesium/strontium/thulium Li/Cs/Sr/Tm, lithium/strontium/cesium Li/Sr/Cs, lithium/strontium/zinc/potassium Li/Sr/Zn/K, lithium/gallium/cesium Li/Ga/Cs,

lithium/potassium/strontium/lanthanum Li/K/Sr/La, lithium/sodium Li/Na,

lithium/sodium/rubidium/gallium Li/Na/Rb/Ga, lithium/sodium/strontium Li/Na/Sr, lithium/sodium/strontium/lanthanum Li/Na/Sr/La, lithium/samarium/cesium Li/Sm/Cs, barium/samarium/ytterbium/sulfur Ba/Sm/Yb/S, barium/thulium/potassium/lanthanum Ba/Tm/K/La, barium/thulium/zinc/potassium Ba/Tm/Zn/K, cesium/potassium/lanthanum Cs/K/La, cesium/lanthanum/thulium/sodium Cs/La/Tm/Na,

cesium/lithium/potassium/lanthanum Cs/Li/K/La, samarium/lithium/strontium/cesium Sm/Li/Sr/Cs, strontium/cesium/lanthanum Sr/Cs/La, strontium/thulium/lithium/cesium Sr/Tm/Li/Cs, zinc/potassium Zn/K, zirconium/cesium/potassium/lanthanum Zr/Cs/K/La, rubidium/calcium/indium/nickel Rb/Ca/In/Ni, strontium/holmium/thulium Sr/Ho/Tm, lanthanum/neodymium/sulfur La/Nd/S, lithium/rubidium/calcium Li/Rb/Ca,

lithium/potassium Li/K, thulium/lutetium/tantalum/phosphorous Tm/Lu/Ta/P,

rubidium/calcium/dysprosium/phosphorous Rb/Ca/Dy/P,

magnesium/lanthanum/ytterbium/zinc Mg/La/Yb/Zn, rubidium/strontium/lutetium Rb/Sr/Lu, sodium/strontium/lutetium/niobium Na/Sr/Lu/Nb, sodium/europium/hafnium Na/Eu/Hf, dysprosium/rubidium/gadolinium Dy/Rb/Gd, sodium/platinum/bismuth Na/Pt/Bi, rubidium/haihium Rb/Hf, calcium/cesium Ca/Cs, calcium/magnesium/sodium Ca/Mg/Na, hafnium/bismuth Hf/Bi, strontium/tin Sr/Sn, strontium/tungsten Sr/W, strontium/niobium Sr/Nb, zirconium/tungsten Zr/W, yttrium/tungsten Y/W, sodium/tungsten Na/W, 16T&I0070; 092474.028920 (375U1) bismuth/tungsten Bi/W, bismuth/cesium Bi/Cs, bismuth/calcium Bi/Ca, bismuth/tin Bi/Sn, bismuth/antimony Bi/Sb, germanium/hafnium Ge/Hf, hafnium/samarium Hf/Sm, antimony/silver Sb/Ag, antimony /bismuth Sb/Bi, antimony/gold Sb/Au, antimony/samarium Sb/Sm, antimony /strontium Sb/Sr, antimony/tungsten Sb/W, antimony /hafnium Sb/Hf, antimony/ytterbium Sb/Yb, antimony/tin Sb/Sn, ytterbium/gold Yb/Au, ytterbium/tantalum Yb/Ta, ytterbium/tungsten Yb/W, ytterbium/strontiumYb/Sr, ytterbium/lead Yb/Pb, ytterbium/tungsten Yb/W, ytterbium/silver Yb/Ag, gold/strontium Au Sr,

tungsten/germanium W/Ge, tantalum/hafnium Ta/Hf, tungsten/gold W/Au, calcium/tungsten Ca/W, gold/rhenium Au Re, samarium/lithium Sm/Li, lanthanum/potassium La/K, zinc/cesium Zn/Cs, sodium/potassium/magnesium Na/K/Mg, zirconium/cesium Zr/Cs, calcium/cerium Ca/Ce, sodium/lithium/cesium Na/Li/Cs, lithium/strontium Li/Sr, cesium/zinc Cs/Zn, lanthanum/dysprosium/potassium La/Dy/K, dysprosium/potassium Dy/K, lanthanum/magnesium La/Mg, sodium/neodymium/indium/potassium Na/Nd71n/K, indium/strontium In/Sr, strontium/cesium Sr/Cs, rubidium/gallium/thulium/cesium

Rb/Ga/Tm/Cs, gallium/cesium Ga/Cs, potassium/lanthanum/zirconium/silver K/La/Zr/Ag, lutetium/iron Lu/Fe, strontium/thulium Sr/Tm, lanthanum/dysprosium La/Dy,

samarium/lithium/strontium Sm/Li/Sr, magnesium/potassium Mg/K,

lithium/rubidium/gallium Li/Rb/Ga, lithium/cesium/thulium Li/Cs/Tm, zirconium/potassium Zr/K, lithium/cesium Li/Cs, lithium/potassium/lanthanum Li/K/La,

cerium/zirconium/lanthanum Ce/Zr/La, calcium/aluminum/lanthanum Ca/Al/La,

strontium/zinc/lanthanum Sr/Zn/La, strontium/cesium/zinc Sr/Cs/Zn, samarium/cesium Sm/Cs, indium/potassium In/K, holmiurn/cesiurn/lithium/lanthanum Ho/Cs/Li/La, cesium/lanthanum/sodium Cs/La/Na, lanthanum/sulfur/strontium La/S/Sr,

potassium/lanthanum/zirconium/silver K/La/Zr/Ag, lutetium/titanium Lu/Ti,

praseodymium/zinc Pr/Zn, rubidium/strontium/lanthanum Rb/Sr/La,

sodium/ strontium/ europium/ calcium Na/Sr/Eu/Ca, potassium/ cesium/ strontium/lanthanum K/Cs/Sr/La, sodium/strontium/lutetium Na/Sr/Lu, strontium/europium/dysprosium Sr/Eu/Dy, lutetium/niobium Lu/Nb, lanthanum/dysprosium/gadolinum La/Dy/Gd,

sodium/magnesium/titanium/phosphorus Na/Mg/Ti/P, sodium/platinum

Na/Pt,gadolinium/lithium/potassium Gd/Li/K, rubidium/potassium/lutetium Rb/K/Lu, strontium/lanthanum/dysprosium/lanthanum/sulfur Sr/La/Dy/S, sodium/cerium/cobalt Na/Ce/Co, sodium/cerium Na/Ce, sodium/gallium/gadolinium/aluminum Na/Ga/Gd/Al, barium/rhodium/tantalum Ba/Rh/Ta, barium/tantalum Ba/Ta, sodium/aluminum/bismuth 16T&I0070; 092474.028920 (375U1)

Na/Al/Bi, cesium/europium Cs/Eu/S, samarium/tantalum/ytterbium/iron Sm/Tm/Yb/Fe, samarium/tantalum/ytterbium Sm/Tm/Yb, hafnium/zirconium/tantalum Hf/Zr/Ta, rubidium/ gadolinium/lithium/potats sium Rb/ Gd7Li/K,

gadolinium/holmium/alurninum/phosphorus Gd/Ho/Al/P, sodium/calcium/lutetium

Na/Ca/Lu, copper/tin Cu/Sn, silver/gold Ag/Au, aluminum/bismuth Al/Bi,

aluminum/molybdenum Al/Mo, aluminum/niobium Al/Nb, gold/platinum Au/Pt,

gallium/bismuth Ga/Bi, magnesium/tungsten Mg/W, lead/gold Pb/Au, tin/magnesium Sn/Mg, zinc/bismuth Zn/Bi, gadolinium/holmium Gd/Ho, zirconium/bismuth Zr/Bi,

holmium/strontium Ho/Sr, gadolinium/holmium/strontium Gd/Ho/Sr, calcium/strontium Ca/Sr, calcium/strontium/tungsten Ca/Sr/W, sodium/zirconium/europium/thulium

Na/Zr/Eu/Tm, strontiuri^liolmium/thuliurn/sodium Sr/Ho/Tm/Na, strontium/lead Sr/Pb, strontium/tungsten/lithium Sr/W/Li, calcium/strontium/tungsten Ca/Sr/W, strontium/hafnium Sr/Hf or combinations thereof.

[0039] The catalyst may comprise a lanthanide mixed oxide compound. For example, the catalyst may be a catalytic nanowire comprising a lanthanide and a dopant comprising a metal element, a semi-metal element, a non-metal element or combinations thereof, or a dopant as provided herein. In other aspects, the catalyst may comprise mixed oxide of a rare earth element and a Group 13 element, wherein the catalytic nanowire further comprises one or more Group 2 elements. In some more specific embodiments, the foregoing catalyst is a nanowire catalyst. As an example, the catalyst comprises a lanthanide oxide doped with an alkali metal, an alkaline earth metal or combinations thereof, and at least one other dopant from groups 3-16.

[0040] The catalyst may also comprise a mixed oxide of magnesium and manganese, wherein the catalyst further comprises lithium and boron dopants and at least one doping element from groups 4, 9, 12, 13 or combinations thereof. In other examples, the catalyst comprises an oxide of a rare earth element, wherein the catalyst further comprises at least one doping element from groups 1 -16, lanthanides, actinides or combinations thereof. In still other examples, the catalyst comprises a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4- 6, 8-15, lanthanides or combinations thereof. In yet other aspects, the catalyst comprises a mixed oxide of a lanthanide and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-15, lanthanides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane 16T&I0070; 092474.028920 (375U1) conversion of greater than 10%, 15% or even 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a reactor inlet temperature of 750 °C or less.

[0041] In certain aspects, the catalyst may comprise a combination of an alkaline earth metal salt, a metal salt, and a transition metal oxide. Thus, the reaction may include catalysis of oxidative coupling of methane over a sodium-manganese oxide catalyst. Using this catalyst, the reaction may follow the Rideal-Redox mechanism, involving both homogeneous and heterogeneous reaction steps. Gas phase formation of a CH intermediate is a result of a heterogeneous process (surface reaction) and the formation of C2 and larger hydrocarbons by coupling methyl groups (CH3) is the result of a gas phase homogeneous process. As a specific example, the catalyst may comprise a 6 % sodium, 13 % manganese-silicon dioxide catalyst system at about 830 °C. Such a catalyst system may provide a methane conversion of greater than about 30 % and/or aC2 hydrocarbon selectivity greater than about 50 %.

[0042] As provided herein, where a redox catalyst system is used, smaller amounts of hydrogen may be generated during ethane dehydrogenation to ethylene. Redox catalyst systems may provide hydrogen gas as less than about 1 % of the product mixture. Such a minimal amount of hydrogen limits synthesis gas (hydrogen and carbon monoxide gas) formation in the product mixture. This occurrence emphasizes the need for a process to utilize the generated carbon monoxide product as there may not be a useful amount of syngas in the product mixture to apply to further processing.

[0043] In other aspects, the catalyst may comprise a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 16 or combinations thereof, or a dopant as provided herein. In some other embodiments, the catalyst comprises a rare earth oxide and one or more dopants, wherein the dopant comprises a dopant as provided herein.

[0044] For any of the foregoing catalysts, the catalyst may comprise a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less. In certain aspects, the foregoing catalysts may comprise a C2 selectivity of greater than 50% and a methane conversion of greater than 10%, 15%, 20% or even 25% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.

[0045] A catalyst used according to the processes described herein may provide a C2 (as well 16T&I0070; 092474.028920 (375U1) as compounds with more than two carbons) selectivity of greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, or greater than 75%. The catalysts may provide a methane conversion of greater than 10%, greater than 12%, greater than 15%, greater than 20%, greater than 22%, greater than 25%, and even greater than 30%. In certain aspects, the catalysts may provide selectivity of 50% or greater with conversion of greater than 10%, greater than 15%, greater than 20%, greater than 25%, or greater than 30%.

Likewise, in still further aspects, the catalysts may provide a selectivity of 55% or greater with conversion of greater than 10%, greater than 15%, greater than 20%, greater than 25%, or greater than 30%.

[0046] The catalyst may comprise a single pass methane conversion in an OCM reaction catalyzed by the nanowire is greater than 10%, greater than 15%, greater than 20%, or even greater than 25% for example in some such embodiments the catalyst is a catalytic nanowire. In other embodiments the catalyst comprises a C2 selectivity of greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, or even greater than 60%, in the OCM reaction when the OCM reaction is performed with an oxidant other than air or oxygen.

[0047] Other catalysts useful in the context of the catalytic forms and formulations described herein may be readily apparent to one of ordinary skill in the art.

[0048] As provided herein, the oxidative coupling of methane may proceed in the presence of a catalyst. In one aspect of present disclosure, the oxidative coupling reaction and the separation of carbon oxides take place over two separate zones: a first zone for the oxidative coupling reaction and a second zone for the adsorption and separation of carbon oxide byproducts from the effluent of the first zone. Here, the catalyst for the oxidative coupling reaction in the first zone may not form a stable solid carbonate with the carbon oxide byproducts, or may form only a negligible amount of stable solid carbonate that is insufficient to satisfactorily separate the carbon oxide by-products from the desired products.

Thermal Dehydrogenation

[0049] In various aspects, the oxidative conversion process described herein may comprise a thermal dehydrogenation process to convert ethane, as a coupling product component of the product mixture, to ethylene. Ethane, produced in OCM reaction may undergo catalytic oxidative dehydrogenation in catalyst zone and thermal dehydrogenation as the product mixture stream departs the catalyst. The thermal dehydrogenation process as described 16T&I0070; 092474.028920 (375U1) herein may thus comprise an oxidative or a non-oxidative dehydrogenation process.

Oxidative dehydrogenation may refer to the reaction of a small chain alkane, such as methane, to produce olefins by contacting the small chain alkane with a source of oxygen, either directly or indirectly, in the presence of a catalyst. Via the catalytic process, ethane of the product mixture may generate methyl radicals which may either recombine to reform ethane, or abstract a hydrogen from ethane with production of ethylene and methane.

[0050] The ethane to ethylene thermal dehydrogenation process is generally endothermic (ΔΗ = -144 kJ/mol) and can be described by the following equation:

As an example, in the catalyst bed described herein, with the catalyst bed the coupling reaction of methane to ethane may occur with thermal dehydrogenation of ethane to ethylene. The thermal degradation process may be fueled at least in part by the oxidative conversion reactions described herein.

Separation

[0051] In the presence of a suitable catalyst as provided herein, a methane feed may undergo an oxidative coupling process to form the OCM product mixture comprising a gas stream of at least ethylene, ethane, carbon dioxide, hydrogen, water, and carbon monoxide. In various aspects, one or more separation processes may be employed to isolate gaseous components generated during the methane conversion process. The isolation of gaseous components of the product mixture may also be performed according to a number of gas separation techniques commonly practiced by those skilled in the art. For example, carbon monoxide formed and unreacted methane may be isolated by performing a one or more separation processes.

[0052] To isolate at least a portion of the generated carbon monoxide and the unconverted methane from the OCM product mixture, at least a portion of the generated carbon dioxide product may be separated from the product mixture. In some aspects, carbon dioxide may be removed from the product mixture of gaseous components prior to separation of

hydrocarbons such as ethane and ethylene from the product mixture. The carbon dioxide product may be separated or diverted as a distinct process stream from the product mixture. As provided herein, the separation of CO2 from the product mixture may be achieved by any known methods. In one example, adsorption processes, such as amine adsorption, may be used to separate carbon dioxide from the remaining methane oxidative coupling products. 16T&I0070; 092474.028920 (375U1)

[0053] Amine adsorption may refer to the use of an amine sorbent to capture carbon dioxide gas. Carbon dioxide separated from the product mixture of the present disclosure may be discarded or may be collected and diverted for use different processes. The separated carbon dioxide may be utilized in a number of distinct or integrated processes. As an example and not to be limiting, the separated carbon dioxide may be applied for a methane dry reforming reaction (i.e., methane reacted carbon dioxide), for oxidative methane dry reforming

(methane reacted with carbon dioxide in the presence of oxygen), or for hydrogenation of carbon dioxide to syngas (i.e., carbon dioxide reacted with molecular hydrogen to form syngas).

[0054] To isolate at least a portion of the carbon monoxide product and a portion of the unconverted methane from the product mixture at least a portion of the ethylene and the ethane may be separated from the product mixture. Separation of the ethylene and ethane may proceed after carbon dioxide has been separated from the product mixture. A number of known methods may be used to separate ethylene and ethane from the remaining product mixture. In a specific example, separation of ethylene and ethane may be achieved via cryogenic separation. Cryogenic separation may comprise cold fractionation of liquefied ethylene and ethane from lighter gases methane and carbon monoxide remaining in the product mixture.

[0055] Separation of C2 hydrocarbons, including ethane and ethylene, from the product mixture may also be performed according to a number of gas separation techniques commonly practiced by those skilled in the art. For example, but not to be limiting, the isolation of C2 and unsaturated hydrocarbons may be achieved via a cold box separation, cryogenic processing, membrane separation, or pressure swing absorption. Ethane separated from the product mixture may be recycled back to a post-OCM reaction zone to be converted via thermal dehydrogenation while methane and carbon monoxide may be recycled back to an OCM catalyst zone.

[0056] Separation of at least a portion of the carbon dioxide product and at least a portion of the coupling products (ethylene and ethane), may leave at least a portion of unconverted methane and at least a portion of the carbon dioxide product remaining in the product mixture. At least a portion of the unconverted methane and carbon dioxide product may be recycled back to process streams for the OCM reactant mixture. Thus, the carbon monoxide and the unconverted methane of the OCM product mixture may be used to fuel the conversion of methane in the OCM reactant mixture. Diverting the isolated carbon monoxide 16T&I0070; 092474.028920 (375U1) product and unconverted methane may eliminate the need to include additional process schemes for utilizing the carbon monoxide product.

[0057] In one aspect, the at least a portion of carbon monoxide and unconverted methane for recycle to the oxidative process may comprise at least a portion of one or more remaining products from the product mixture including carbon dioxide, ethylene, ethane. The at least a portion of the one or more remaining products may be a residual amount, for example, less than about 3 %, or less than about 1 %, or less than about 0.5 % of the product mixture. Systems

[0058] Various systems may make use of the integrated processes and methods described herein. A method of converting a methane feedstock or feedstream may comprise subjecting a methane feedstock or feedstream with an oxidant in the presence of a suitable catalyst at a certain temperature and pressure to facilitate an oxidative coupling reaction. The method may further comprises separating at least a portion of products from the OCM product mixture and re-directing a remaining portion of the product mixture to the methane feedstock and oxidant for oxidative conversion.

[0059] In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments. However, one skilled in the art will understand that the disclosure may be practiced without these details. In other instances, well-known structures, standard vessel design details, details concerning the design and construction of pressure vessels, and the like have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the disclosure.

[0060] Instrumentation, such as sensors, transmitters, and the like, and controls, such as single or multi-loop controllers, programmable logic controllers, and distributed control systems, suitable for the measurement and control of gas {e.g., methane, oxygen, nitrogen, ethane, ethylene, etc.) composition and concentration, temperature, pressure are well known in the art are noted, but are not detailed herein for brevity.

[0061] Referring now to FIG. 2, shown therein are certain processes for producing C2 hydrocarbons in accordance with the present disclosure via OCM reaction system 200. The process for an OCM reaction may begin with the introduction of a methane feedstream 20 and an oxidant (oxygen) stream 22 to an oxidative coupling of methane (OCM) reactor 202. The oxidant stream is typically air, but other sources such as purified oxygen are also suitable. As the methane feedstream 20 and oxidant feedstream 22 contact the catalyst, the oxidative coupling of methane reaction is catalyzed and an OCM product mixture gas stream 16T&I0070; 092474.028920 (375U1)

24 comprising at least unreacted methane, ethane, ethylene, and deep oxidation products (carbon monoxide and carbon dioxide) by-products is formed. Hydrogen gas liberated during the conversion of methane to the one or more C2+ hydrocarbons may combine with the oxygen to form water vapor. Oxygen present also combines with at least a portion of the carbon present in the methane to form carbon dioxide in the OCM product mixture stream 24.

[0062] In some aspects, impurities and contaminants may be first removed from the methane feedstream 20. At least a portion of the methane feedstream 20 may be conveyed to a coupling reactor 202 for heating with an oxidant feedstream 22. The coupling reactor 202 may comprise one or more devices and each device may comprise one or more sections or zones. The coupling reactor 202 may comprise a main reaction zone and a secondary reaction zone (not shown) for thermal dehydrogenation of at least a portion of ethane of the product mixture to form additional ethylene. As provided herein, ethane of the product mixture may be subjected to a process of thermal dehydrogenation to form ethylene. Ethane generated from the oxidative coupling reaction may be converted to ethylene using the heat of the reaction produced during the reaction for the oxidative coupling of methane occurring in the coupling reactor. Thus the endothermic conversion of ethane to ethylene may use the energy generated by the exothermic OCM reactor in the reactor. Combining these two reactions in one vessel can increase thermal efficiency while simplifying the process.

[0063] The coupling reactor 202 may be operated at temperatures ranging from about 400 °C. to about 1200 °C and specifically from about 700° C. to about 950° C, pressures ranging from less than about 14 psig to about 400 psig. The OCM product mixture stream 24 may be conveyed to a separator unit 206 to undergo one or more separation processes for isolation of carbon monoxide product and unreacted methane, schematically shown as output stream 30 of the separator unit 206.

[0064] As a methane feedstock and oxygen are contacted with the catalyst, the oxidative coupling of methane may be accompanied by formation of carbon monoxide and carbon dioxide byproducts. Therefore, the OCM product mixture stream 24 from the oxidative coupling reactor contains methane, ethane, ethylene and carbon oxide by-products.

[0065] The OCM reaction may occur within the coupling reactor 202 in a single vessel, in a plurality of serially coupled vessels, in a plurality of parallel vessels, or a combination thereof. The OCM coupling reactor 202 may include one or more vessels comprising a catalyst. In a specific example, the coupling reactor 202 may contain one or more catalysts disposed within a catalyst bed 204. The methane feedstream 20 and an oxidant feedstream 22 16T&I0070; 092474.028920 (375U1) may be either pre-mixed or combined and introduced to the at least one vessel of the coupling reactor or introduced separately to the at least one vessel of the coupling reactor. Within the coupling reactor 202, methane in the methane feedstream 20 and oxygen in the oxidant feedstream 22 react exothermically as they pass through the one or more catalysts disposed in the at least one catalyst bed 204.

[0066] At least a portion of the methane feedstream 20 and oxidant feedstream 22 may react in the presence of one or more catalysts of the catalyst bed 204 to provide the OCM product mixture stream comprising one or more C2 hydrocarbons including at least ethane and ethylene. The overall conversion of methane and oxygen to one or more C2 hydrocarbons is at least dependent upon catalyst composition, reactant concentration, and reaction temperature and pressure within the one or more vessels of the coupling reactor 202 and the thermal profile through the one or more catalysts of the catalyst bed 204, the maximum temperature within the catalyst bed 204, the maximum temperature rise within the one or more catalysts, or combinations thereof.

[0067] In various aspects of the present disclosure, one or more catalysts may be housed in a catalyst bed 204 within one or more vessels of the coupling reactor 202. Reactor vessels may contain one or more catalyst beds and each of the one or more catalyst beds may include one or more layers of catalyst. In certain instances, each of the one or more vessels may contain a single catalyst bed containing a catalyst having a similar chemical composition and physical structure. In other instances, each of the one or more vessels may contain the same or a differing number of catalyst beds and each of the catalyst beds may contain the same or a differing number of layers. The coupling reactor 202 may include one or more catalyst beds 204 located in each of the vessels. The vessels may be, arranged in series, in parallel, or in any combination thereof.

[0068] Control of catalyst loading may be used to adjust one or more preferred properties of the OCM reactor system. Where multiple catalyst beds are arranged in series, either in the same or different vessels, additional methane, oxygen, C2 hydrocarbons, inert gases, or any combination thereof may be added, in some instances at a significantly cooler or warmer temperature than the OCM product mixture exiting a preceding catalyst bed, to adjust the composition and temperature of the methane feed and oxidant prior to its introduction to a subsequent catalyst bed. In some aspects, each catalyst bed may include the same or a differing number of layers, with each layer including a catalytic material, an inert material, or combinations thereof. 16T&I0070; 092474.028920 (375U1)

[0069] The conversion of methane to higher molecular weight hydrocarbons, such as ethane and ethylene may be dependent upon a number of processing conditions including residence time, pressure, temperature, catalyst conditions, and process stream composition. The methane conversion may be dependent upon the residence time of reactants such as methane, ethane, and higher hydrocarbons in the coupling reactor 202. In particular, the ratio of ethane to ethylene may be dependent upon the residence time of reactants such as methane, ethane, and larger hydrocarbons in the coupling reactor 202 at temperatures in excess of about 800°C. The formation of ethylene within the coupling reactor 202 may occur as a secondary reaction that may arise from a steam or thermal cracking process rather than an oxidative coupling process. Thus, the conversion of ethane to ethylene may occur at elevated temperatures of the coupling reaction, either in portions of the coupling reactor 202 or immediately following the coupling reactor 202 where the oxidant feedstream 22

concentration is reduced.

[0070] The rate of the OCM reaction within the one or more vessels of the coupling reactor 202 may be influenced, adjusted, or controlled, at least in part, by the temperature of the methane feedstream 20 and the oxidant feedstream 22 in the coupling reactor 202. The temperature may be controlled by adjusting the temperature of the methane feedstream 20, the oxidant feedstream 22, or both feedstreams 20, 22. In one example, the methane feedstream 20 and the oxidant feedstream 22 comprising the OCM reactant mixture may be passed through one or more thermal transfer devices prior to entering the one or more vessels of the coupling reactor 202. The OCM reactant mixture in the coupling reactor 202 may be at a temperature of less than about 600 °C; less than about 575 °C; less than about 550 °C; less than about 525 °C; less than about 500 °C; less than about 450 °C; or less than about 400°C.

[0071] The yield of the OCM process, typically, although not exclusively measured as the quantity of methane converted to one or more desired products, may be similarly affected by adjusting the catalyst thermal conditions either alone or in tandem. In determining and monitoring the temperature of the methane feedstream and/or oxidant feedstream, one or more thermocouples, resistive thermal devices (RTDs) or similar temperature measuring devices may be used to provide one or more signals indicative of the temperature of the methane source. According to various aspects of the present disclosure, an OCM process may be adiabatic or isothermal. In an adiabatic process, heat generated is not removed during the reaction but is diverted from the reaction by the OCM gas, unreacted reagents, and byproducts. For an isothermal process, a substantial quantity of generated heat is removed 16T&I0070; 092474.028920 (375U1) from the reaction, generally by way of heat transfer media in the coupling reactor 202. Thus, a reaction carried out under adiabatic conditions may experience a greater temperature increase between the input streams and the output streams than would a comparable reaction carried out under isothermal conditions.

[0072] Pressure parameters may also be used to control the OCM process. The pressure of the methane feedstream 20 and oxidant feedstream 22 may be adjusted or controlled by increasing or decreasing the amount of compressive energy delivered to the feedstreams 20, 22 via, for example, one or more gas compressors or by controlling the backpressure through one or more vessels. In determining the pressure of the methane source, one or more pressure transducers or similar pressure measuring devices may be used to provide one or more signals indicative of the pressure of the methane feedstream 20 or the oxidant feedstream 22.

[0073] The flowrate of the methane feedstream 20 and oxidant feedstream 22 to each of the one or more catalyst beds 204 of the coupling reactor 202 may provide another variable that may be used for control of the OCM process. The flowrate may be adjusted or controlled by increasing or decreasing the methane feedstream 20 flowrate, the oxidant feedstream 22 flowrate, or combinations thereof, via, for example, one or more flow control valves. Control of the methane feedstream 20 flow or of the oxidant feedstream 22 flow allows for a methane/oxidant mixture in the coupling reactor at virtually any flowrate to be introduced to the catalyst bed 204 disposed therein. Flow of the methane feedstream 20 and the oxidant feedstream 22 into the coupling reactor may be manually or automatically controlled using one or more final control elements 1 18. Controlling methane and oxygen concentration from the oxidant feedstream within the coupling reactor influence, affect, or control the OCM reaction occurring within the one or more catalysts disposed in the catalyst bed 204. One or more analyzers may be used to determine either or both the methane and the oxygen concentration(s) in the coupling reactor 202. The flowrate may be monitored by one or more mass or volumetric flow meters or similar flow measuring devices. The gas hourly space velocity GHSV for the OCM process described herein may be about 7200 per hour.

[0074] In at least some instances, the rate of the OCM reaction within the one or more vessels of the coupling reactor 202 may be influenced, adjusted, or controlled, by at least in part, the temperature of the methane feedstream 20, or the oxidant feedstream 22, or both feedstreams 20, 22. The temperature of the methane feedstream 20, or the oxidant feedstream 22 may be adjusted using one or more thermal transfer devices capable of transferring thermal energy to methane feedstream 20 and the oxidant feedstream 22. Such 16T&I0070; 092474.028920 (375U1) thermal transfer devices can include, but are not limited to, non-contact combustion type heaters and non-contact thermal fluid heat exchangers.

[0075] The concentrations of the methane feedstream 20 and the oxidant feedstream 22 may affect the conversion of methane in the OCM process. Where methane becomes the limiting reagent {i.e., oxidant in excess) in the coupling reactor 202, the risk of detonation or deflagration within the one or more vessels may increase to an unacceptable level. In at least some circumstances, automatic or manual controls may reduce the methane concentration, the oxygen concentration, or both the methane and the oxygen concentration in the coupling reactor 202. With oxygen (as an oxidant) controlled or otherwise maintained as the limiting reactant, at least a portion of the methane present in the methane feed source remains unconverted by the OCM reaction. As provided herein, the OCM product mixture stream 24, while depleted in oxygen, may contain a quantity of residual unreacted methane. The concentration of unreacted methane within the OCM product mixture stream 24 may vary over time with the aging of the one or more catalysts in the at least one catalyst bed 204. The presence of one or more inert gases such as nitrogen in the methane feedstream and/or oxidant feedstream may provide a stable thermal "heat sink." The heat sink may absorb thermal energy and consequently limit temperature increase experienced by the oxidant and methane in the catalyst bed. The ratio of methane to oxygen {e.g., the stoichiometric ratio of methane to oxygen) may affect the overall conversion of methane in the OCM reaction.

[0076] The reactors, systems and methods of the present disclosure may be useful in carrying out exothermic catalytic reactions such as the catalytic oxidative coupling of methane. The disclosed OCM reactor systems and methods may perform exothermic catalytic reactions at lower temperatures and carry on those reactions within practical operating parameters.

Coupled with the exothermic reactions associated with the OCM process (e.g., in excess of 700°C) reactor systems for carrying out such reactions would be required to withstand temperatures well in excess of 700°C, and even when operated isothermally, e.g., using active external cooling systems, would require operating temperatures that are in excess of any conventionally available cooling systems.

[0077] In addition to the one or more C2+ hydrocarbons (i.e., ethane and ethylene), the OCM product mixture stream 24 proceeding from the coupling reactor 202 may include residual unreacted methane, residual unreacted oxygen, water, and carbon dioxide. The ethane concentration within the OCM product mixture stream 24 may be at least about 5 mol%; at least about 10 mol%; or at least about 15 mol%. The ethylene concentration within the 5 16T&I0070; 092474.028920 (375U1) mol%; at least about 10 mol%; at least about 15 mol%, at least about 20 mol%, at least about 25 mol%, or at least about 30 mol%. Carbon dioxide present in OCM product mixture stream 24 with respect to C2 selectivity in relation to ethylene and ethane may vary within 0.8 to 1.2 (weight ratio CC : combined ethylene and ethane). Carbon monoxide present in OCM product mixture stream 24 may vary between 0.1 and 0.4 (weight ratio CO: combined ethylene and ethane).

[0078] Also presented in FIG. 2, at least a portion of the OCM product mixture stream 24 from the coupling reactor 202 comprising at least ethane, ethylene, carbon monoxide, carbon dioxide, and unconverted methane may be conveyed to a separator unit 206 for separation of the constituent gases. The separator unit 206 may be fluidly connected to the coupling reactor 202 so as to receive the OCM product mixture stream 24 and may comprise any one or more appropriate gas separation methods known to those with skill in the art.

[0079] Carbon dioxide in the OCM product mixture stream 24 may be present as a byproduct formed by the complete combustion of methane and also a catalytic byproduct of the combination of oxygen and carbon in the presence of the one or more catalysts in the at least one catalyst bed 204. In some aspects, the carbon dioxide concentration in the OCM product mixture stream 24 may tend to increase over time with the aging of the one or more catalysts in the at least one catalyst bed 204. The carbon dioxide concentration in the OCM product mixture stream 24 may be less than about 10%; less than about 5 mol%; less than about 4 mol%; less than about 3 mol%; less than about 2 mol%; less than about 1 mol%; or less than about 0.5 mol.

[0080] To isolate carbon monoxide and unreacted methane in the OCM product mixture stream 24, at least a portion of the carbon dioxide product may be removed from the OCM product mixture stream 24 thereby forming a carbon dioxide process stream 28. In the separator unit 206, the carbon dioxide product may be separated from the OCM product mixture stream 24 by any conventional means including, but not limited to, pressure swing absorption, membrane separation, cryogenic processing, and other gas separation techniques practiced by those skilled in the art. The carbon dioxide process stream 28 may be directed for further processing such as in methane dry reforming, in oxidative methane dry reforming, or in carbon dioxide hydrogenation to syngas. The further processing of the carbon dioxide process stream 28 may be integrated with the OCM reaction process described herein or may comprise a distinct reaction system to that of any of the foregoing processes described.

[0081] At least a portion of the ethane and ethylene may be separated from the remaining 16T&I0070; 092474.028920 (375U1)

OCM product mixture stream 24 to isolate the carbon monoxide product and unreacted methane. Separation of at least a portion of the ethane and at least a portion of the ethane may be separated from the OCM product mixture stream 24 in a further separation process in the separator unit 206 of the OCM reaction system 200. To separate ethane and ethylene from the remaining OCM product mixture stream 24, the OCM product mixture stream 24 may be subjected to a cryogenic separation process. For example, the remaining OCM product mixture stream 24 may be cooled so as to liquefy at least a portion of the ethylene and ethane present therein while allowing at least a portion of remaining lighter weight carbon monoxide and unconverted methane to remain in the gas phase. In an example, the OCM product mixture stream 24 may be cooled to a temperature of between about -101 °C to about -62 °C. Cooling may be achieved using refrigerants.

[0082] Separation of the carbon dioxide product and C2 coupling products (ethane and ethylene) from the OCM product mixture stream 24 may allow for isolation of the carbon monoxide product and unconverted methane and is shown schematically as output process stream 30. At least a portion of the carbon monoxide product and unconverted methane provided as output process stream 30 may be directed, or recycled, from the separator unit 206 back to the coupling reactor, or back to an OCM reactant mixture. Recycling of the output process stream may eliminate additional processes to separate carbon monoxide from either the desired coupling products or from methane. An additional, possibly expensive or time consuming process scheme for utilization of the CO is also unnecessary. Moreover, as provided herein, combustion of carbon monoxide is a more exothermic reaction than the oxidative conversion of methane. Thus, the use of CO in the OCM reactant mixture may provide fuel from its combustion for the OCM process.

[0083] In certain aspects, the methods of the present disclosure may be particularly useful in OCM reaction systems including a chlorine catalyst. OCM reaction systems using a chlorine catalyst may lead to significant formation of the carbon monoxide byproduct when compared to the performance of oxide catalysts which provide greater amounts of the carbon dioxide byproduct in the gas phase.

[0084] As provided in FIG. 3, in some aspects, a method of converting a methane feedstream may comprise subjecting a methane feedstream to an oxidative conversion process. The methane feedstream may be combusted with oxygen to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product at 300. The gaseous components of the product mixture may 16T&I0070; 092474.028920 (375U1) be separated to isolate at least a portion of the carbon monoxide product and at least a portion of the unconverted methane from the product mixture at 302. At least a portion of the isolated carbon monoxide product and the unconverted methane may be combined with the methane feedstream thereby facilitating oxidative conversion of the methane feedstream at 304.

[0085] While aspects of the present disclosure can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only and one of skill in the art will understand that each aspect of the present disclosure can be described and claimed in any statutory class. Unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically state in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification.

Examples

[0086] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary and are not intended to limit the disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for.

[0087] There are numerous variations and combinations of reaction conditions, e.g., component concentrations, desired solvents, solvent mixtures, temperatures, pressures and other reaction ranges and conditions that can be used to optimize the product purity and yield obtained from the described process. Only reasonable and routine experimentation will be required to optimize such process conditions.

[0088] Example 1 presents an oxidative conversion of methane to C2 hydrocarbons in the presence of a catalyst comprising 6%Sodium-13%Manganese-Silicon dioxide performed at 830 °C. Example 2 presents an oxidative conversion of methane to C2 hydrocarbons in the presence of a catalyst comprising 6%Na (Sodium)-13% Mn (Manganese)/Si02 (Silicon dioxide). The catalyst system was prepared by impregnation of SiC , then impregnation with 16T&I0070; 092474.028920 (375U1) sodium hydroxide NaOH and manganese(II) nitrate Mn(N03)2. The resulting catalyst was dried at 120 °C for 4 hours. Catalyst after impregnation was calcined at 800 °C for 4 hours.

[0089] The coupling reaction was been carried out in quartz reactor with 10 millimeter (mm) diameter and 15 cm length. The reactor first was heated in air medium to 600 °C. A mixture of methane and air, or a methane-oxygen mixture was then fed to the reactor.

[0090] Example 2 presents an oxidative conversion of methane to C2 hydrocarbons in the presence of a catalyst comprising 6% Na-13%Mn/SiC at 830 °C. . Carbon monoxide is also present as a reagent with the methane. The ratio of methane to oxygen for the conversion reaction is 2: 1 (CH4/O2 =2). The CO concentration in the feed is 1.5%. Example 2 includes catalyst and process conditions provided for Example 1 except that CO was added to the feed.

[0091] In comparing Examples 1 and 2, CO produced in methane oxidative coupling reaction together with methane can be recycled back to the reaction thereby eliminating additional process schemes for CO conversion. The system of example 2 is more efficient. Ethylene selectivity decreased for example 2, methane conversion increased (35 % compared to 31.5%) but selectivity to ethylene decreased. The presence of CO for the oxidative conversion process increases conversion of methane by providing exothermic CO oxidation.

Definitions

[0092] It is to be understood that the terminology used herein is for the purpose of describing 16T&I0070; 092474.028920 (375U1) particular aspects only and is not intended to be limiting. As used in the specification and in the claims, the term "comprising" can include the embodiments "consisting of and

"consisting essentially of." Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined herein.

[0093] As used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural equivalents unless the context clearly dictates otherwise. Thus, for example, reference to "a polycarbonate polymer" includes mixtures of two or more polycarbonate polymers.

[0094] As used herein, the term "combination" is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0095] Ranges can be expressed herein as from one value (first value) to another value (second value). When such a range is expressed, the range includes in some aspects one or both of the first value and the second value. Similarly, when values are expressed as approximations, by use of the antecedent 'about,' it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as "about" that particular value in addition to the value itself. For example, if the value "10" is disclosed, then "about 10" is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 1 1, 12, 13, and 14 are also disclosed.

[0096] As used herein, the terms "about" and "at or about" mean that the amount or value in question can be the designated value, approximately the designated value, or about the same as the designated value. It is generally understood, as used herein, that it is the nominal value indicated ±5% variation unless otherwise indicated or inferred. The term is intended to convey that similar values promote equivalent results or effects recited in the claims. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but can be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. In general, an amount, size, formulation, parameter or other quantity or characteristic is "about" or "approximate" 16T&I0070; 092474.028920 (375U1) whether or not expressly stated to be such. It is understood that where "about" is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.

[0097] Disclosed are the components to be used to prepare the compositions of the disclosure as well as the compositions themselves to be used within the methods disclosed herein.

These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds cannot be explicitly disclosed, each is specifically contemplated and described herein. For example, if a particular compound is disclosed and discussed and a number of modifications that can be made to a number of molecules including the compounds are discussed, specifically contemplated is each and every combination and permutation of the compound and the modifications that are possible unless specifically indicated to the contrary. Thus, if a class of molecules A, B, and C are disclosed as well as a class of molecules D, E, and F and an example of a combination molecule, A-D is disclosed, then even if each is not individually recited each is individually and collectively contemplated meaning combinations, A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are considered disclosed. Likewise, any subset or combination of these is also disclosed. Thus, for example, the sub-group of A-E, B-F, and C- E would be considered disclosed. This concept applies to all aspects of this application including, but not limited to, steps in methods of making and using the compositions of the disclosure. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific aspect or combination of aspects of the methods of the disclosure.

[0098] As used herein, the term "transparent" or "optically clear" means that the level of transmittance for a disclosed composition is greater than 50%. In some embodiments, the transmittance can be at least 60%, 70%, 80%, 85%, 90%, or 95%, or any range of transmittance values derived from the above exemplified values. In the definition of "transparent", the term "transmittance" refers to the amount of incident light that passes through a sample measured in accordance with ASTM D1003 at a thickness of 3.2 millimeters.

[0099] As used herein the term "adiabatic" refers to a system experiencing minimal or ideally no interchange or exchange of thermal energy with the surrounding environment. As used herein "adiabatic" vessels and vessels said to be operating under "adiabatic" conditions refer 16T&I0070; 092474.028920 (375U1) to vessels having no provision specifically for the removal or addition of thermal energy to or from the system. Notwithstanding the foregoing, it will be appreciated that incidental thermal transfer between the vessel and its environment is contemplated within the context of the foregoing definition. Generally, where an adiabatic vessel is used to contain a reaction that releases thermal energy (i.e., an "exothermic" reaction), a positive temperature profile will be maintained between the reactants added to the vessel and the products removed from the vessel. In other words, the products removed from the vessel will generally be at a temperature above the temperature of the reactants introduced to the vessel since the thermal energy liberated by the reaction can only be substantially removed by the products of the reaction.

[00100] As used herein the term "isothermal" refers to a system experiencing an interchange or exchange of thermal energy with the surrounding environment providing a controlled level of increase in thermal energy within the system. As used herein, "isothermal" vessels and vessels, methods, and processes said to be operating under "isothermal" conditions refer to vessels, methods, and processes having specific provisions for the removal and dissipation of thermal energy from the vessel, method or process to the surrounding environment, in addition to any incidental heat transfer with the surrounding environment. Generally, where a vessel used to contain an exothermic reaction is said to be operated under "isothermal" conditions, a more neutral temperature profile as compared to a reactor operated under adiabatic conditions will be maintained across at least a portion of, if not the entire vessel. In other words, the temperature profile across at least a portion of the vessel, e.g., from one position in a catalytic bed to another or downstream position within the catalyst bed, may in some instances be substantially flat or increase at a controlled rate that is less than, and sometimes significantly less than, that which would occur under adiabatic conditions where thermal energy is not removed from the reaction vessel. In some cases, the thermal profile across the entire vessel may in some instances be flat, whereby the products removed from the vessel may be at a temperature substantially equal to the temperature of the reactants introduced to the vessel since the thermal energy liberated by the reaction is removed from the vessel and not by the products of the reaction.

[00101] As used herein the term "stoichiometric ratio" refers to the ratio of one compound to another compound. For example in the OCM reaction, theoretically two moles of methane are required to react with one mole of oxygen, yielding a balanced stoichiometric ratio of 2: 1 . The actual concentration of methane to oxygen may be greater than or less than 16T&I0070; 092474.028920 (375U1)

2: 1 . For example, where the stoichiometric ratio is 1 .5 moles of methane to 1 mole of oxygen (1.5: 1), methane is considered the limiting reagent since an insufficient quantity of methane is present to consume all of the oxygen. Similarly, where the stoichiometric ratio is 3 moles of methane to 1 mole of oxygen (3: 1 ), oxygen can be considered the limiting reagent since an insufficient quantity of oxygen is present to consume all of the methane.

[00102] As used herein the term "temperature profile" or "thermal profile" refers to the temperature as a function of position through a reactor system or portion of a reactor system. A temperature or thermal profile can be either a two-dimensional (e.g., linear function of distance through a catalyst bed) or three dimensions (e.g. linear function of distance through a catalyst bed, to provide a thermal profile as a function of distance through the catalyst bed, and radial function of distance from the center of a catalyst bed, to provide a thermal profile as a function of distance from the center of the catalyst bed).

[00103] As used herein the term "gas hourly space velocity" or the acronym "GHSV" refers to the ratio of reactant gas flow rate (methane source + oxidant) in standard cubic feet per hour or standard cubic meters per hour, divided by the reactor volume (cubic feet or cubic meters). Where diluent gases are added, the GHSV includes the additional volume presented by the diluent gases. As used herein the term "velocity" refers to the superficial or linear velocity of a bulk gas flowing through a defined cross sectional area (e.g. SCFM or ACFM divided by the actual or equivalent cross sectional area in square feet). The resultant ratio has units of inverse hours and is used to relate reactant gas flow rate to reactor volume. The GHSV is one factor considered when scaling a known reactor design to accommodate a lesser or greater reactant flow.

[00104] As used herein the term "higher hydrocarbons" refers to any carbon compound containing at least two carbon atoms and includes alkane, alkene, alkynes, cycloalkanes, and aromatic hydrocarbons.

[00105] Unless otherwise stated to the contrary herein, any test standards described are the most recent standard in effect at the time of filing this application.

Aspects

[00106] The present disclosure comprises at least the following aspects.

[00107] Aspect 1A. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method comprising: subjecting a hydrocarbon feedstock to an oxidative conversion process to form a product mixture comprising at least ethylene, ethane, 16T&I0070; 092474.028920 (375U1) a carbon dioxide product, a carbon monoxide product, and an unconverted hydrocarbon product;

separating at least a portion of the carbon dioxide product from the product mixture;

isolating at least a portion of the carbon monoxide product and a portion of the unconverted hydrocarbon from the product mixture by separating at least a portion of the ethylene and the ethane from the product mixture; and combining the isolated portion of the carbon monoxide product and isolated portion of the unconverted hydrocarbon product with a hydrocarbon feedstock to undergo the oxidative conversion wherein an oxidative conversion of the isolated portion of carbon monoxide generates heat to facilitate the oxidative conversion of the hydrocarbon feedstock.

[00108] Aspect IB. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method consisting essentially of: subjecting a hydrocarbon feedstock to an oxidative conversion process to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted hydrocarbon product;

separating at least a portion of the carbon dioxide product from the product mixture;

isolating at least a portion of the carbon monoxide product and a portion of the unconverted hydrocarbon from the product mixture by separating at least a portion of the ethylene and the ethane from the product mixture; and combining the isolated portion of the carbon monoxide product and isolated portion of the unconverted hydrocarbon product with a hydrocarbon feedstock to undergo the oxidative conversion wherein an oxidative conversion of the isolated portion of carbon monoxide generates heat to facilitate the oxidative conversion of the hydrocarbon feedstock.

[00109] Aspect 1C. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method consisting of: subjecting a hydrocarbon feedstock to an oxidative conversion process to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted hydrocarbon product;

separating at least a portion of the carbon dioxide product from the product mixture;

isolating at least a portion of the carbon monoxide product and a portion of the unconverted hydrocarbon from the product mixture by separating at least a portion of the ethylene and the ethane from the product mixture; and combining the isolated portion of the carbon monoxide product and isolated portion of the unconverted hydrocarbon product with a hydrocarbon 16T&I0070; 092474.028920 (375U1) feedstock to undergo the oxidative conversion wherein an oxidative conversion of the isolated portion of carbon monoxide generates heat to facilitate the oxidative conversion of the hydrocarbon feedstock.

[00110] Aspect 2. The method of aspect 1, wherein the separating the carbon dioxide product from the product mixture comprises an amine adsorption process.

[00111] Aspect 3. The method of any of aspects 1-2, wherein at least a portion of ethane of the product mixture undergoes dehydrogenation to form at least a portion of ethylene of the product mixture.

[00112] Aspect 4. The method of aspect 3, wherein the dehydrogenation is a thermal dehydrogenation.

[00113] Aspect 5. The method of aspect 3, wherein the dehydrogenation is a catalytic dehydrogenation.

[00114] Aspect 6. The method of any of aspects 1-5, wherein the separating the at least a portion of the ethylene and the ethane from the product mixture comprises a cryogenic separation process.

[00115] Aspect 7. The method of any of aspects 1-6, wherein the hydrocarbon feedstock comprises at least methane.

[00116] Aspect 8. The method of any of aspects 1-7, wherein the hydrocarbon feedstock comprises natural gas.

[00117] Aspect 9. The method of any of aspects 1-8, wherein the oxidative conversion process comprises combustion of the hydrocarbon feedstock in the presence of molecular oxygen.

[00118] Aspect 10. The method of any one of aspects 1-9, wherein the oxidative conversion process occurs in the presence of a catalyst.

[00119] Aspect 11. The method of aspect 10, wherein the catalyst comprises any one of oxides, peroxides, carbonates, phosphates and silicates of elements selected from the group consisting of Li, Na, K, Rb, Cs and Be; peroxides, hydroxides, carbonates, phosphates and silicates of elements selected from the group consisting of Sr and Ba; and carbonates, phosphates and silicates of elements selected from the group consisting of Pb, Sn, Ge, Mg and Ca.

[00120] Aspect 12. The method of aspect 10, wherein the catalyst comprises a chlorine compound.

[00121] Aspect 13. The method of aspect 10, wherein the catalyst comprises an oxide. 16T&I0070; 092474.028920 (375U1)

[00122] Aspect 14. The method of any one of aspects 1-13, wherein the oxidative conversion proceeds at a temperature of between about 500 °C and about 900 °C.

[00123] Aspect 15. The method of any one of aspects 1-14, wherein the oxidative conversion comprises an oxidative coupling process.

[00124] Aspect 16. The method of any one of aspectsl-15, wherein the carbon monoxide product is formed in an amount of less than about 10 % based on the amount of the product mixture.

[00125] Aspect 17. The method of any one of aspectsl-16, wherein the carbon monoxide product is formed in an amount of less than about 5 % based on the amount of the product mixture.

[00126] Aspect 18. The method of any one of aspects 1-17, wherein a weight ratio carbon monoxide product to a combined ethane and ethylene in the product mixture is between 0.1 and 0.4.

[00127] Aspect 19. The method of any one of aspects 1-18, wherein the oxidative conversion process has a selectivity for C2 hydrocarbons greater than about 50%.

[00128] Aspect 20 A. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method comprising: reacting a hydrocarbon feedstock with molecular oxygen in the presence of a catalyst to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted hydrocarbon product; isolating at least a portion of the ethylene and the ethane by separating at least a portion of the carbon monoxide product and a portion of the unconverted hydrocarbon from the product mixture; and recycling the isolated portion of the carbon monoxide product and the isolated portion of the unconverted hydrocarbon product to the hydrocarbon feedstock to react with molecular oxygen in the presence of the catalyst, wherein reaction of the isolated portion of the carbon monoxide generates heat energy to facilitate the reacting of the hydrocarbon feedstock with the molecular oxygen.

[00129] Aspect 20B. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method consisting essentially of: reacting a hydrocarbon feedstock with molecular oxygen in the presence of a catalyst to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted hydrocarbon product; isolating at least a portion of the ethylene and the ethane by separating at least a portion of the carbon monoxide product and a portion of the unconverted hydrocarbon from the product mixture; and recycling the isolated portion of the 16T&I0070; 092474.028920 (375U1) carbon monoxide product and the isolated portion of the unconverted hydrocarbon product to the hydrocarbon feedstock to react with molecular oxygen in the presence of the catalyst, wherein reaction of the isolated portion of the carbon monoxide generates heat energy to facilitate the reacting of the hydrocarbon feedstock with the molecular oxygen.

[00130] Aspect 20C. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method consisting of: reacting a hydrocarbon feedstock with molecular oxygen in the presence of a catalyst to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted hydrocarbon product; isolating at least a portion of the ethylene and the ethane by separating at least a portion of the carbon monoxide product and a portion of the unconverted hydrocarbon from the product mixture; and recycling the isolated portion of the carbon monoxide product and the isolated portion of the unconverted hydrocarbon product to the hydrocarbon feedstock to react with molecular oxygen in the presence of the catalyst, wherein reaction of the isolated portion of the carbon monoxide generates heat energy to facilitate the reacting of the hydrocarbon feedstock with the molecular oxygen.

[00131] Aspect 21 A. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method comprising: reacting a methane feedstock with molecular oxygen in the presence of a catalyst to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product; isolating at least a portion of the ethylene and the ethane by separating at least a portion of the carbon monoxide product and a portion of the unconverted methane from the product mixture; and recycling the isolated portion of the carbon monoxide product and the isolated portion of the unconverted methane product to the hydrocarbon feedstock to react with molecular oxygen in the presence of the catalyst, wherein reaction of the isolated portion of the carbon monoxide generates heat energy to facilitate the reacting of the methane feedstock with the molecular oxygen.

[00132] Aspect 21B. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method consisting essentially of: reacting a methane feedstock with molecular oxygen in the presence of a catalyst to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product; isolating at least a portion of the ethylene and the ethane by separating at least a portion of the carbon monoxide product and a portion of the unconverted methane from the product mixture; and recycling the isolated portion of the carbon monoxide 16T&I0070; 092474.028920 (375U1) product and the isolated portion of the unconverted methane product to the hydrocarbon feedstock to react with molecular oxygen in the presence of the catalyst, wherein reaction of the isolated portion of the carbon monoxide generates heat energy to facilitate the reacting of the methane feedstock with the molecular oxygen.

[00133] Aspect 21 C. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method consisting of: reacting a methane feedstock with molecular oxygen in the presence of a catalyst to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product; isolating at least a portion of the ethylene and the ethane by separating at least a portion of the carbon monoxide product and a portion of the unconverted methane from the product mixture; and recycling the isolated portion of the carbon monoxide product and the isolated portion of the unconverted methane product to the hydrocarbon feedstock to react with molecular oxygen in the presence of the catalyst, wherein reaction of the isolated portion of the carbon monoxide generates heat energy to facilitate the reacting of the methane feedstock with the molecular oxygen.

[00134] Aspect 22A. A system for converting methane to ethane and ethylene, the system comprising: a reactor configured to effect an oxidative conversion of a methane feedstream to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product; and

a separator unit configured to effect an isolation of at least a portion of the carbon monoxide product and at least a portion of the unconverted methane product from the product mixture, wherein the isolated portion of the carbon monoxide product and the isolated portion of the unconverted methane product are directed to the reactor and subjected to oxidative conversion.

[00135] Aspect 22B. A system for converting methane to ethane and ethylene, the system consisting essentially of: a reactor configured to effect an oxidative conversion of a methane feedstream to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product; and a separator unit configured to effect an isolation of at least a portion of the carbon monoxide product and at least a portion of the unconverted methane product from the product mixture, wherein the isolated portion of the carbon monoxide product and the isolated portion of the unconverted methane product are directed to the reactor and subjected to oxidative conversion. 16T&I0070; 092474.028920 (375U1)

[00136] Aspect 22C. A system for converting methane to ethane and ethylene, the system consisting of: a reactor configured to effect an oxidative conversion of a methane feedstream to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product; and

a separator unit configured to effect an isolation of at least a portion of the carbon monoxide product and at least a portion of the unconverted methane product from the product mixture, wherein the isolated portion of the carbon monoxide product and the isolated portion of the unconverted methane product are directed to the reactor and subjected to oxidative conversion.

[00137] Aspect 23. The system of aspect 22, wherein the reactor comprises a catalyst or a catalyst system configured to facilitate the reacting of the methane feedstock with molecular oxygen to produce unsaturated C2 hydrocarbons and oxidation compounds.

[00138] Aspect 24. The system of aspect 23, wherein the catalyst is disposed in a catalyst bed.

[00139] Aspect 25. The system of any one of aspects 21-24, wherein the directing the isolated portion of the carbon monoxide product and the isolated portion of the unconverted methane product to the reactor facilitates the oxidative conversion of the methane feedstream.

[00140] Aspect 26A. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method comprising: subjecting a methane feedstock to an oxidative conversion process to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product;

separating at least a portion of the carbon dioxide product from the product mixture;

isolating at least a portion of the carbon monoxide product and a portion of the unconverted methane from the product mixture by separating at least a portion of the ethylene and the ethane from the product mixture; and combining the isolated portion of the carbon monoxide product and isolated portion of the unconverted methane product with a hydrocarbon feedstock to undergo the oxidative conversion wherein an oxidative conversion of the isolated portion of carbon monoxide generates heat to facilitate the oxidative conversion of the methane feedstock.

[00141] Aspect 26B. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method consisting essentially of: subjecting a methane feedstock to an oxidative conversion process to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product; separating at least a portion of the carbon dioxide product from the product mixture; 16T&I0070; 092474.028920 (375U1) isolating at least a portion of the carbon monoxide product and a portion of the unconverted methane from the product mixture by separating at least a portion of the ethylene and the ethane from the product mixture; and combining the isolated portion of the carbon monoxide product and isolated portion of the unconverted methane product with a hydrocarbon feedstock to undergo the oxidative conversion wherein an oxidative conversion of the isolated portion of carbon monoxide generates heat to facilitate the oxidative conversion of the methane feedstock.

[00142] Aspect 26C. A method of producing unsaturated C2 hydrocarbons and oxidation compounds, the method consisting of: subjecting a methane feedstock to an oxidative conversion process to form a product mixture comprising at least ethylene, ethane, a carbon dioxide product, a carbon monoxide product, and an unconverted methane product; separating at least a portion of the carbon dioxide product from the product mixture;

isolating at least a portion of the carbon monoxide product and a portion of the unconverted methane from the product mixture by separating at least a portion of the ethylene and the ethane from the product mixture; and combining the isolated portion of the carbon monoxide product and isolated portion of the unconverted methane product with a hydrocarbon feedstock to undergo the oxidative conversion wherein an oxidative conversion of the isolated portion of carbon monoxide generates heat to facilitate the oxidative conversion of the methane feedstock.