Separation of hydrocarbons using n-doped activated carbon adsorbents

Abstract

Disclosed embodiments may include a method for separating methane from a hydrocarbon gas mixture comprising methane along with at least one of C2 and heavier hydrocarbons. The method may include the steps of: i) providing an N-doped activated carbon adsorbent having a BET Surface Area (SBET) of at least about 1000 m2 / g and a nitrogen content of at least 1 at%; ii) contacting the hydrocarbon gas mixture with the N-doped activated carbon adsorbent to at least partially remove the C2 and / or heavier hydrocarbons from the hydrocarbon gas mixture to produce a methane-rich product stream and a C2 and / or heavier hydrocarbon-loaded adsorbent; and iii) recovering at least part of the C2 and / or heavier hydrocarbons from the C2 and / or heavier hydrocarbon-loaded adsorbent to produce a C2 and / or heavier hydrocarbon-rich stream and an at least partially regenerated adsorbent.

Description

Attorney Docket No.: 243981.000115 SEPARATION OF HYDROCARBONS USING N-DOPED ACTIVATED CARBON ADSORBENTS CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 594,098 filed on October 30, 2023, titled SEPARATION OF HYDROCARBONS USING N- DOPED ACTIVATED CARBON ADSORBENTS, the contents of which are incorporated herein by reference in its entirety. FIELD

[0002] The present application relates to methods for separating hydrocarbons using N-doped activated carbons with tunable capacity and selectivity as adsorbents. Said adsorbents may be regenerated by steam replacement in the alternative or in addition to a pressure swing and / or a temperature swing process. BACKGROUND

[0003] Many sources of hydrocarbons such as natural gas include mixtures of paraffins (e.g., methane, ethane, propane, butane, etc.) along with a variety of heavier hydrocarbons and other gases. There are many reasons to separate the higher alkanes known as natural gas liquids (NGLs) and other non-methane contaminants to provide a methane rich natural gas stream, for instance in order to meet pipeline specifications, or liquefied natural gas (LNG) specification, or any other end use specification. NGL components such as ethane, propane, and butane can have higher sales values than pipeline gas, which is largely comprised of methane. Among others, NGLs may be used as petrochemical feedstocks where they have a higher value as compared to their value as a fuel gas component. For instance, ethane is a valuable chemical feedstock, and propane and butane can be blended to form liquefied petroleum gas (LPG) which is a valuable residential fuel. Therefore, NGLs are oftentimes extracted and fractionated in gas processing plants in accordance with the specific requirements of the regional markets and customers. Generally, commercial NGL specifications require less than about 0.5% by liquid volume of methane and less than 500 ppm of 1 303581687v1Attorney Docket No.: 243981.000115 CO2 by volume in liquid. Generally, pipeline specifications indicate that there should be less than about 4.0 mol. % of other non-hydrocarbon gases (for example N2+CO2) in the natural gas, less than about 10 mol. % ethane in the natural gas, and the specific energy content of the natural gas should not exceed about 1,100 British thermal unit per standard cubic foot of natural gas (BTU / SCF).

[0004] Hydraulic fracturing sources of natural gas as well as other sources possess high levels of natural gas liquids (NGLs) compared with traditional sources of natural gas. This high NGLs result in higher BTU content causing devices (e.g., generators, compressors, etc.) that use natural gas as a fuel source to operate outside of their design parameters. This causes such devices to have higher operating temperatures, increased pollution levels, and more maintenance. Hydrocarbon gas co- produced with oil has similar issues. The higher NGLs content also causes storage and transport issues as they require higher pressure and lower temperatures to transport when present. In addition, NGL is more valuable as liquid products: unrecovered propane and butane in a sales gas stream will be sold at a discount in the sales gas (methane).

[0005] Cryogenic separation is commonly used to extract NGLs from hydrocarbon mixtures. This process generally involves cooling a natural gas stream to temperatures below around -85 °C (- 120° Fahrenheit). These low temperature requirements have high associated energy consumption costs in traditional sources of natural gas and has become even more energy intensive with respect to the new sources with higher NGL content.

[0006] Other separation processes include Liquid Sub-cooled Process (LSP), Vapor Enrichment process (VEP), Gas sub-cooled Process (GSP), Cold residue-recycle (CRR), Split Flow Reflux (SFR), Recycle Split Vapor (RSV), Flashed Vapor Reflux (FVR), and Enhance NGL recovery (IPSI). See Park et al., Techno-economic evaluation of a novel NGL recovery scheme with nine patented schemes for offshore applications, Journal of Natural Gas Science and Engineering, Volume 27, Part 1, 2015, Pages 2-17, incorporated herein by reference in its entirety. The use of a stripper and heat exchanger to remove light components form an ethylene stream has also been considered. See U.S. Patent No.10,101,083, incorporated herein by reference in its entirety.

[0007] Carbonaceous adsorbents have also been described for use in the purification of hydrogen and the removal of water, methane, sulfur, carbon dioxide, nitrogen oxides and halocarbons from 2 303581687v1Attorney Docket No.: 243981.000115 various fluid mixtures. See for example: U.S. Patent No. 5,059,578, U.S. Patent No. 5,217,505, U.S. Patent. No.5,972,834 and U.S. Published Patent Application No.2013 / 0220935, Cavenati et al., Methane Purification by PSA from Natural Gas Sources, 2nd Mercosure Congress on Chemical Engineering, each of which is incorporated herein by reference in their entirety. Carbonaceous adsorbents are carbonized forms of carbon compounds such as coal, coke, peat, wood charcoal, nut shell char, fruit nut char, coconut shell char, bone char, phenol resins, furan resins, and vinylidene chloride copolymers, see for example U.S. Patent No.5,300,468 and U.S. Patent No. 5,972,834, each of which are incorporated herein by reference in their entirety.

[0008] An overview of various adsorbents and their use in gas separations is provided in: Tagliabue, et al., Natural Gas Treating by Selective Adsorption: Material Science and Chemical Engineering Interplay, Chemical Engineering Journal 155 (2009) 553-566, which is incorporated herein by reference in its entirety. A variety of adsorbents have been used in gas separations and include aluminas, hydrotalcites, silicates, silica gels and clinoptilotics (U.S. Patent No.5,993,516, which is incorporated herein by reference in its entirety), organosilica media (U.S. Patent No. 10,081,775, which is incorporated herein by reference in its entirety), metal organic frameworks (Zhang et al., Selective Adsorption Performances of UiO-67 for Separation of Light Hydrocarbons C1, C2, and C3, Ind. Eng. Chem. Res. 2017, 56, 30, 8689–8696 (July 7, 2017), which is incorporated herein by reference in its entirety), partially pyrolized macroporous polymer (U.S. Published Patent Application No.2016 / 0122671, which is incorporated herein by reference in its entirety), silica gel, alumina, silica-alumina, zeolites, activated carbon, polymer supported silver chloride, copper-containing resins, porous cross-linked polymeric adsorbents, pyrolized macroporous polymers, porous cross-linked polymeric adsorbents, pyrolized macroporous polymers (U.S. Published Patent Application No.2016 / 0340595, which is incorporated herein by reference in its entirety); silica gels; activated aluminas, zeolite imidazole frameworks (ZIFs); metal organic frameworks (MOFs), other zeolites (U.S. Published Patent Application No. 2019 / 0134556, which is incorporated herein by reference in its entirety); asphalt-based activated carbon (Liang et al., Novel Asphalt-based Carbon Adsorbents with Super-high Adsorption Capacity and Excellent Selectivity for Separation for Light Hydrocarbons, Separation and Purification Technology 190, 60-67 (2018), which is incorporated herein by reference in its 3 303581687v1Attorney Docket No.: 243981.000115 entirety); and N-doped activated carbons (Yuan et al., Unprecedented performance of N-doped activated hydrothermal carbon towards C2H6 / CH4, CO2 / CH4, and CO2 / H2 separation, J. Mater. Chem. A, 4 (2016) 2263-2276), which is incorporated herein by reference in its entirety).

[0009] Gas separation is important in various industries and can typically be accomplished by flowing a mixture of gases over an adsorbent that preferentially adsorbs a more readily adsorbed component relative to a less readily adsorbed com ponent of the mixture. Gas separation by swing adsorption, such as pressure swing adsorption (PSA), temperature swing adsorption (TSA), partial pressure swing or displacement purge adsorption (PPSA), and pressure temperature swing adsorption (PTSA) is achieved when a first gas component is more readily adsorbed on an adsorbent material compared to other gas components in the gas mixture. In many important swing adsorption applications, described as “equilibrium-controlled processes”, the adsorptive selectivity is primarily based upon differential equilibrium uptake of first and second components. For two- component (binary) adsorption, the common metric that is used to study the preferential adsorption of one component over another is referred to as selectivity α12 and defined as α12= (x1 / y1) / ( x2 / y2), where component “1” is the preferred component over “2”. x and y aremole fractions of adsorbed phase and bulk phase, respectively.

[0010] PSA employs multiple fixed bed adsorption columns for continuous adsorption and regeneration purposes. In PSA processes, a target gaseous component is separated from a gas mixture by use of cyclic variations of pressure coordinated with cyclic flows of the gas mixture, component product streams, and / or purge streams contacting a bed comprised of adsorbent material in an adsorber vessel. In the case of TSA or PPSA processes, cyclic variations of temperature and / or partial pressure of the gas components may be coordinated with gas flow through a flow path to perform a separation. The process in any specific PSA application operates at a cyclic frequency characterized by its period, and over a pressure envelope between a first relatively higher pressure and a second relatively lower pressure. PSA processes rely on the fact that under pressure gases tend to be adsorbed within the pore structure of microporous adsorbent materials or within the free volume of polymeric materials. The higher the pressure, the more gas is adsorbed. When the pressure is reduced, the adsorbed gas is released, or desorbed. PSA processes can be used to separate gases from a mixture of gases because different gases tend to 4 303581687v1Attorney Docket No.: 243981.000115 adsorb in the micropores or free volume of the adsorbent to different extents. For example, if a gas mixture such as natural gas is passed under pressure through a vessel containing polymeric or microporous adsorbent that fills with more NGL than it does methane, part or all of the NGL will stay in the sorbent bed, and the gas coming out of the vessel will be enriched in methane. When the bed reaches the end of its capacity to adsorb NGL, it can be regenerated by reducing the pressure, thereby releasing the adsorbed NGL. It is then ready for another cycle. When the desorption step is performed at sub-ambient pressures the process is referred to as vacuum pressure swing adsorption (VPSA).

[0011] Another important gas separation technique is temperature swing adsorption (TSA). TSA processes also rely on the fact that under pressure gases tend to be adsorbed within the pore structure of the microporous adsorbent materials. When the temperature of the adsorbent is increased, the gas is released, or desorbed. By cyclically swinging the temperature of adsorbent beds, TSA processes can be used to separate gases in a mixture when used with an adsorbent that selectively adsorbs one or more of the components in the gas mixture relative to another. Combined PSA / TSA (also referred to as PTSA) processes may also be utilized in the art for adsorption processes. In such combined PSA / TSA processes the pressure is decreased while the temperature is also increased during a desorption step in order to facilitate desorption of the components adsorbed in the adsorbent material. A purge gas may also be utilized during the desorption step or in an adjoining purge step to further facilitate removal of the adsorbed components by lowering the partial pressure of the adsorbed components, raising the temperature of the adsorbent material (e.g., by utilizing a heated purge gas), or a combination thereof. In order to achieve separation performance objectives (i.e., product gas purity, recovery and productivity), process parameters and operating conditions are designed to achieve a sufficiently high adsorptive selectivity of at least the first and second components in the adsorbent material, at the cyclic frequency and within the pressure envelope.

[0012] Separation of olefins and paraffins is one of the key seven separation needs of the modern world. The main type of olefin and paraffin separation is attributed to the purification and isolation of ethylene from ethane and propylene from propane. Ethylene and propylene are the precursors or monomers of two most important polymeric plastics of modern society, polyethylene and 5 303581687v1Attorney Docket No.: 243981.000115 polypropylene. Owing to the very close physicochemical properties of light olefins, such as boiling points, with their corresponding paraffins, it is very difficult to separate them. The current state- of-the-art separation process of ethylene from ethane and propylene from propane involves cryogenic distillation that harnesses a small difference in boiling points between ethylene / ethane and propylene / propane in the cryogenic range. To obtain a high quality and polymer grade olefins, the distillation must be operated at the extreme conditions of temperature and pressure. The capital cost of installing cryogenic separation unit of ethylene is around twenty million dollars with the utility costs more than one million dollar every year (http: / / seperationtechnology.com / separation- of-ethylene-from-ethane).

[0013] It would be desirable to have a regenerable adsorbent and associated method that is efficiently capable of generating a methane rich stream by removing C2 and / or heavier hydrocarbons from gas mixtures, e.g., by separating methane from natural gas liquids (NGLs) in natural gas streams, and regenerating the adsorbent in an economic manner. It would also be desirable to have an adsorbent with high adsorption capacity along with the above-mentioned benefits. SUMMARY

[0014] The various embodiments of the disclosure relate generally to processes, methods, and systems for adsorbing C2 and / or heavier hydrocarbons from a hydrocarbon gas mixture, e.g., from a natural gas stream, on N-doped activated carbon adsorbents, and at least partially regenerating the loaded adsorbent by desorbing at least part of the C2 and / or heavier hydrocarbons.

[0015] A first embodiment may include a method for separating methane from a hydrocarbon gas mixture including methane along with at least one of C2 and heavier hydrocarbons. The method includes the steps of: i) providing an N-doped activated carbon adsorbent having a BET SurfaceArea (SBET) of at least about 1000 m2 / g and a nitrogen content of at least 1 at%, ii) contacting thehydrocarbon gas mixture with the N-doped activated carbon adsorbent to at least partially remove the C2 and / or hydrocarbons from the hydrocarbon gas mixture to produce a methane-rich product stream and a C2 and / or heavier hydrocarbon-loaded adsorbent, and iii) recovering at least part of the C2 and / or heavier hydrocarbons from the C2 and / or heavier hydrocarbon-loaded 6 303581687v1Attorney Docket No.: 243981.000115 adsorbent to produce a C2 and / or heavier hydrocarbon-rich stream and an at least partially regenerated adsorbent.

[0016] A second embodiment may include a method for regenerating a N-doped activated carbon adsorbent loaded with one or more hydrocarbon gases that includes treating the loaded adsorbent with steam.

[0017] These and other features and attributes of the present disclosure and their advantageous applications and / or uses will be apparent from the detailed description which follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, wherein:

[0019] FIG. 1A illustrates a system for an exemplary adsorption and desorption process, in accordance with certain embodiments of the disclosed technology.

[0020] FIG.1B is a flow chart showing a method of separating hydrocarbons using an adsorbent, in accordance with certain embodiments of the disclosed technology.

[0021] FIG. 2 is a flow chart showing a method of making the adsorbent, in accordance with certain embodiments of the disclosed technology.

[0022] FIG.3 is a chart showing elemental composition of the adsorbents prepared from various amounts of melamine, in accordance with certain embodiments of the disclosed technology.

[0023] FIG. 4 is a chart showing adsorption capacity of ethane, as an example of hydrocarbon, illustrating tunable capacities of N-doped activated carbon adsorbents in accordance with certain embodiments of the disclosed technology.

[0024] FIG. 5A is a chart showing the adsorption capacity of ethylene, as an example of hydrocarbon, illustrating tunable capacities of N-doped activated carbon adsorbents, in accordance with certain embodiments of the disclosed technology.

[0025] FIG.5B is a chart showing the adsorption capacity of ethane versus ethylene on N-doped activated carbon adsorbents, in accordance with certain embodiments of the disclosed technology.

[0026] FIG.6 is a chart showing the methane, ethane, and propane adsorption capacities at 25 °C of an alternative adsorbent compared to SM30, a representative adsorbent according to certain 7 303581687v1Attorney Docket No.: 243981.000115 embodiments of the disclosed technology, which has medium hydrocarbon capacities in the whole series tested.

[0027] FIG. 7 is a chart showing the adsorption capacity of water for the tunable adsorbent material, in accordance with certain embodiments of the disclosed technology.

[0028] FIG.8 is a chart showing the methane, ethane, and propane adsorption capacities at 25 °C of SM30, a representative adsorbent according to certain embodiments of the disclosed technology, which has medium hydrocarbon capacities in the whole series tested.

[0029] FIG.9 is a chart showing the methane, ethane, and propane adsorption capacities at 150 °C of SM30, a representative adsorbent according to certain embodiments of the disclosed technology, which has medium hydrocarbon capacities in the whole series tested. DETAILED DESCRIPTION

[0030] Embodiments of the present invention utilize tunable and selective adsorbents to separate methane from C2 and / or heavier hydrocarbons, e.g., to separate methane from natural gas liquids (NGLs) in a natural gas stream. These adsorbents may also be tuned to be selective for olefins (e.g., ethylene or propylene), paraffins (e.g., methane, ethane, propane, or butane), or for C2 hydrocarbons, C3 hydrocarbons, or C4 hydrocarbons which may include mixtures of both paraffins and olefins. These adsorbents can thus also be used to separate olefins from paraffins, e.g., ethylene from ethane and / or propylene from propane; to separate C2 (and optionally C1) hydrocarbons from heavier (C3+) hydrocarbons, e.g., ethane and optionally methane (if any) from C3+ hydrocarbons; and / or to separate C3 (and optionally C1 and C2) hydrocarbons from heavier hydrocarbons, e.g., propane and optionally ethane and / or methane (if any) from C4+ hydrocarbons. Therefore, while the present focuses on separation of methane from C2 and / or heavier hydrocarbons, the same applies to separation of olefins from paraffins and / or to separation of C2 (and optionally C1) or C3 (and optionally C1 and / or C2) from hydrocarbon gas mixtures containing heavier (C3+ or C4+) hydrocarbons.

[0031] In the present disclosure, C2+ refers broadly to hydrocarbons having two or more carbons. For instance, the C2+ hydrocarbons may be selected from at least one of ethylene, ethane, propylene, propane, 1-butene, n-butane, and heavier hydrocarbons. The hydrocarbon gas mixture 8 303581687v1Attorney Docket No.: 243981.000115 may for instance include methane, ethane, and heavier C3+ paraffins. In some examples, the hydrocarbon gas mixture may include a natural gas stream which typically includes mixtures of methane and C2+ hydrocarbons (also referred to as natural gas liquids (NGLs)). NGLs typically include ethane, propane, butane, and possibly small quantities of pentanes or heavier hydrocarbons. Natural gas is most commonly obtained from oil wells, gas wells and condensate wells. Raw natural gas also often contains impurities such as water or acid gases, for example carbon dioxide, hydrogen sulfide, sulfur dioxide, carbon disulfide, hydrogen cyanide, carbonyl sulfide, and mercaptans. The term “natural gas stream” as used in the present disclosure includes any natural gas source, raw or raw natural gas that has been treated one or more times to remove water and / or other impurities. Natural gas typically contains about 60-100 mol% methane, the balance being primarily heavier alkanes, alkanes of increasing carbon number being normally present in decreasing amounts. Typically, the hydrocarbon gas mixture includes at least methane and possibly ethane in significant concentrations in the feed.

[0032] Embodiments enable the adsorptive separation of hydrocarbons via control of the surface chemistry and pore structure of N-rich, nanoporous activated carbon adsorbents. These adsorbents achieve highly controllable affinity for selective adsorption of hydrocarbons, with capacities tunable by 10x for water and by 7x for hydrocarbons such as ethane and ethylene. The attainable capacities for hydrocarbon adsorption are much larger for these N-functionalized carbons than for other adsorbents.

[0033] Embodiments of the present invention utilize an activated carbon adsorbent that may have adsorption capacities tuned through N-doped functional groups.

[0034] Embodiments of the present invention also include adsorbents with tunable water capacities therefore allowing efficient use of steam displacement for regeneration instead of traditional pressure swing adsorption (PSA) / temperature swing adsorption (TSA) systems. This is especially advantageous to reduce operational cost. In an embodiment, a regeneration process employs steam displacement to at least partially clean the loaded adsorbents, and is not based on pressure swing, vacuum swing, or temperature swing cycling for regeneration. Hence, the process is not subject to some of the energy requirements of the conventional swing cycling. Water vapor is used to desorb the captured hydrocarbon in a concentration swing process. Using steam 9 303581687v1Attorney Docket No.: 243981.000115 displacement could allow an increase in the overall energy efficiency relative to conventional PSA or TSA cycling processes. Generally, as the heats of adsorption are lower than the heat of absorption; thus, the process is internally less energetically demanding than some conventional absorption processes. In a second embodiment, the present disclosure therefore also relates to a method for regenerating a N-doped activated carbon adsorbent loaded with one of more hydrocarbon gases, comprising treating the loaded adsorbent with steam. Said N-doped activated carbon adsorbent loaded with one of more hydrocarbon gases may for instance be the C2 and / or heavier hydrocarbon-loaded adsorbent as defined in the first embodiment. This regeneration method may advantageously be conducted at substantially constant pressure and / or temperature, without using PSA, TSA or PTSA. Through said steam regeneration step, the adsorbent may be loaded with about 1 mmol / g to about 11 mmol / g of water at a temperature of 30˚C and a partial water pressure of less than 0.014 bar.

[0035] The ability of N-rich carbon-based adsorbents to selectively adsorb hydrocarbons from gas mixtures, e.g., to selectively adsorb C2 and / or heavier (C2+) hydrocarbons from a natural gas stream, is possible because, surprisingly, the adsorbent can be tuned through synthetic procedure to maximize equilibrium capacities of C2+hydrocarbons. Even more surprising, these same adsorbents can also be tuned for desorption of said C2+ hydrocarbons with steam in a process characterized as concentration swing desorption.

[0036] Embodiments enable tunable N contents from 1 – 20+ at%. Adjusting the surface chemistry modulates the strength of van der Waals interactions with polarizable adsorbates, while large surface area enables ample adsorption. As a result, the N-doped activated carbon adsorbents of the present disclosure show unique promise in achieving selective adsorption with large working capacities. System and process of the present disclosure

[0037] FIG. 1A shows a system 100 for an exemplary adsorption and desorption process. As shown, a hydrocarbon gas mixture 104 is passed through an adsorption bed 102 containing exemplary N-doped activated carbon adsorbents described herein. The adsorption bed 102 adsorbs C2 and / or heavier hydrocarbons (e.g., NGLs) from the hydrocarbon gas mixture 104 and generates a methane-rich product stream (e.g., NGL Lean stream) 106 that exits adsorption bed 102. 10 303581687v1Attorney Docket No.: 243981.000115 Afterwards, the adsorption bed 102 is regenerated by passing steam 108 through bed 102 to generate a C2 and / or heavier hydrocarbon-rich stream (e.g., NGL Rich stream). In this specific embodiment, no additional heat is needed to regenerate the bed 102. Following regeneration, adsorption bed 102 is placed back into service and hydrocarbon gas mixture 104 is passed through the adsorption bed 102. Switching between the adsorption and desorption steps may be conducted via a series of vales and pipes.

[0038] An embodiment may include a C2+ hydrocarbons (e.g., an NGL) separation system having an adsorbent bed with an adsorption zone and a desorption zone. The adsorbent bed can alternate between the adsorption zone and the desorption zone, via a series of vales and pipes, where it adsorbs C2+ hydrocarbons (e.g., NGLs) from a hydrocarbon gas mixture comprising methane and at least one of C2+ hydrocarbons (e.g., a natural gas stream) in the adsorption zone and desorbs at least part of the C2+ hydrocarbons (e.g., NGLs) loaded on the adsorbent bed in the desorption zone. In addition, a steam stream may be provided to adsorption bed while in desorption zone via the inlet while a C2+ hydrocarbon-rich stream (e.g., an NGL enriched stream) exits via the outlet of the adsorption bed. The system can further include a purge stage after the desorption zone where adsorbent bed is purged with a stripping gas stream.

[0039] The adsorption zone in the C2+ hydrocarbons (e.g., NGL) separation system may operate as concentration swing and adsorptive displacement while the desorption zone may operate as concentration swing and desorption displacement. The adsorbent bed in the adsorption zone may have an adsorption inlet and an adsorption outlet while the adsorbent bed in the desorption zone may have a desorption inlet and a desorption outlet. The adsorption inlet and adsorption outlet may be in opposing positions from the desorption inlet and the desorption outlet, relative to the adsorbent bed.

[0040] FIG.1B shows an exemplary method 150 for separating methane from a hydrocarbon gas mixture including methane along with at least one of C2 and heavier hydrocarbons. Method 150 includes providing 152 an N-doped activated carbon adsorbent (e.g., in an adsorbent bed 102)having a BET surface area (SBET) of at least about 1000 m2 / g and a nitrogen content of at least 1at%. Method 150 also includes contacting 154 the hydrocarbon gas mixture with the N-doped activated carbon adsorbent to a least partially remove the C2 and / or heavier hydrocarbons from 11 303581687v1Attorney Docket No.: 243981.000115 the hydrocarbon gas mixture to produce a methane-rich product steam and a C2 and / or heavier hydrocarbon-loaded adsorbent. In some examples, the methane-rich product stream may include at least 80 wt.%, at least 90 wt.%, or at least 99 wt.% of the methane present in the hydrocarbon gas mixture.

[0041] Method 150 also includes recovering 156 at least part of the C2 and / or heavier hydrocarbons from the C2 and / or heavier hydrocarbon-loaded adsorbent to produce a C2 and / or heavier hydrocarbon-rich stream and an at least partially regenerated adsorbent. Recovering 156 at least part of the C2 and / or heavier hydrocarbons from the C2 and / or heavier hydrocarbon-loaded adsorbent may include exposing the loaded adsorbent to at least one of steam, a different pressure (typically a lower pressure compared to the pressure in the contacting step 154), and a different temperature (typically a higher temperature compared to the temperature in the contacting step 154). For example, recovering 156 at least part of the C2 and / or heavier hydrocarbons from the C2 and / or heavier hydrocarbon-loaded adsorbent may utilize pressure swing adsorption (PSA) at constant temperature, temperature swing adsorption (TSA) at constant pressure, pressure temperature swing adsorption (PTSA), or steam displacement. In some examples, recovering 156 at least part of the C2 and / or heavier hydrocarbons from the C2 and / or heavier hydrocarbon-loaded adsorbent involves passing steam through an adsorbent bed including the loaded adsorbent under substantially constant pressure and temperature without using a pressure swing adsorption (PSA) process or a temperature swing adsorption process (TSA).

[0042] Method 150 may sequentially repeat steps 154 and 156 for at least one cycle, using the at least partially regenerated adsorbent.

[0043] In some examples, the contacting 154 the hydrocarbon gas mixture with the N-doped activated carbon adsorbent occurs in an adsorption chamber and recovering 156 at least part of the C2 and / or heavier hydrocarbons from the C2 and / or heavier hydrocarbon-loaded adsorbent occurs in a desorption chamber. For instance, for a two-bed system (e.g., two adsorbent beds in parallel), there might be one bed in the adsorption stage and another bed in the desorption stage at the same time, then a swap between adsorption and desorption stages. In addition, the C2 and / or heavier hydrocarbons-loaded adsorbent may be continuously transferred from the adsorption chamber to the desorption chamber, and the at least partially regenerated adsorbent may be continuously 12 303581687v1Attorney Docket No.: 243981.000115 transferred from the desorption chamber to the adsorption chamber. In some further examples, the adsorption chamber and desorption chamber may be the same chamber wherein the adsorbent, for instance in the form of an adsorbent bed, can switch states from different modes. In some examples, the adsorbent located in the adsorption chamber may form a packed moving bed. Adsorbent characteristics

[0044] Exemplary N-doped activated carbon adsorbents (exemplary adsorbents) have a BETSurface Area (SBET) of at least about 1000 m2 / g and a nitrogen content, as measured by XPS, ofat least 1 at%.

[0045] Exemplary adsorbents may typically have a nitrogen content (or surface nitrogen content), as measured by XPS, of from about 1 at% to about 20 at%, in particular from about 2 at%, such in excess of 2 at%, to about 15 at%, and more particularly from about 5 at% to about 10 at%. In the exemplary adsorbents, it is especially suitable that at least 60% of the surface nitrogen be comprised of pyridinic (C-N=C) and pyrrolic (C2NH) functionalities, in particular from about 60% to about 85%, and more particularly from about 71 to about 75% (based on N at%).

[0046] Exemplary adsorbents may also have a total (or bulk) nitrogen content, as measured by elemental analysis, of from about 1 at% to about 20 at%, in particular from about 2 at%, such in excess of 2 at%, to about 15 at%, and more particularly from about 5 at% to about 10 at%.

[0047] Exemplary adsorbents may further have a carbon content of about 80 at% to about 95 at%, in particular from about 80 or 85 at% to about 90 at%, as measured by XPS.

[0048] Exemplary adsorbents may further have an oxygen content of about 2 at% to about 15 at%, such as from about 3 at% to about 10 at%, as measured by XPS.

[0049] Exemplary adsorbents may further have a N:C ratio of about 0.01 to about 0.20, such as from about 0.02 to about 0.17, e.g., from about 0.05 to 0.15, as measured by XPS.

[0050] Exemplary adsorbents may have a BET Surface Area (SBET) in a range from about 1000to about 5000 m2 / g, in particular from about 1550 to about 3500 m2 / g, and more particularly fromabout 2000 to about 2800 m2 / g. Exemplary adsorbents may have a Total Pore Volume (Vtot) offrom about 0.70 to about 2.0 cc / g, in particular from about 0.90 to about 1.8 cc / g, and more particularly from about 1.1 to about 1.6 cc / g. Exemplary adsorbents may have a Micropore 13 303581687v1Attorney Docket No.: 243981.000115Volume (Vmicro) of from about 0.30 to 1.0 cc / g, in particular from about 0.40 to about 0.90 cc / g,and more particularly from about 0.50 or 0.60 to about 0.80 cc / g.

[0051] Exemplary adsorbents may have a propane loading capacity at 25 °C of about 15 cm3 / g to about 100 cm3 / g at a pressure of about 1 mmHg to about 175 mmHg. Exemplary adsorbent may have a loading capacity at 25 °C of at least 100 cm3 / g of C3 hydrocarbons at a pressure of 200 mmHg or higher. Exemplary adsorbents may have a loading capacity at 25 °C of about 5 cm3 / g to about 60 cm3 / g of C2 hydrocarbons at a pressure of about 1 mmHg to about 400 mmHg. Exemplary adsorbents may have an ethane loading capacity at 25 °C of about 40 cm3 / g to about 75 cm3 / g at a pressure of about 300 mmHg to about 700 mmHg. Exemplary adsorbents may have a methane loading capacity at 25 °C of about 1 cm3 / g to about 20 cm3 / g at a pressure of about 1 mmHg to about 700 mmHg. Method of Making the Adsorbent

[0052] N-doped activated carbon adsorbents according to the present disclosure can advantageously be synthesized via potassium activation of N-doped carbon precursors derived from polycondensation of sucrose and melamine. Said synthesis process typically includes (i) combining sucrose and melamine in a mixing step to produce a sucrose and melamine mixture, (ii) a carbonization step to produce a N-doped carbon precursor, and (iii) an activation step to produce a N-doped activated carbon adsorbent.

[0053] In mixing step (i) sucrose and melamine can be mixed together by any method known in the art, for instance by grinding or milling.

[0054] Carbonization step (ii), which may also be referred to as a semi-carbonization step in view of the relatively moderate calcination temperature, typically includes heating the sucrose and melamine mixture in air (or oxygen or an oxygen containing gas) to a temperature of about 250 °C to about 650 °C, such as from about 300 °C to about 500 °C, e.g. about 400 °C, for about 1 hour to about 6 hours, e.g., about 2.5 hours. Heating rate is not critical and may vary from about 0.1 °C / min to about 10 °C / min, e.g., about 5 °C / min. As a result of the (semi-)carbonization step, polycondensation of sucrose and melamine occurs, resulting in a N-doped carbon precursor, also referred to as (semi-)carbonized precursor, carbon foam, or N-rich carbon. The N-doped carbon precursor is typically left to cool to room temperature and optionally ground before the next step. 14 303581687v1Attorney Docket No.: 243981.000115 15 303581687v1Attorney Docket No.: 243981.000115

[0055] Activation step (iii) corresponds to a so-called potassium activation step and comprises impregnating the N-doped carbon precursor with potassium followed by pyrolysis of the impregnated compound. Impregnation of the N-doped carbon precursor with potassium includes contacting the precursor with a potassium compound such as at least one of potassium oxalate (K2C2O4), potassium carbonate (K2CO3) or potassium hydroxide (KOH), in particular K2CO3 or K2C2O4, more particularly K2C2O4, advantageously in the form of an aqueous solution. The amount of a potassium compound may be selected to achieve a potassium amount of at least about 0.008, such at least 0.01 mol of potassium per gram of carbon precursor, for instance from 0.01 to 0.05 mol of potassium per gram of carbon precursor, e.g., from 0.015 to 0.02 mol of potassium per gram of carbon precursor or from 0.02 to 0.05 mol of potassium per gram of carbon precursor. After an optional drying step, the impregnated N-doped carbon precursor is activated by pyrolysis, preferably in an inert atmosphere, to a temperature of about 400 °C to about 1200 °C, such as from about 600 °C to about 1000 °C, e.g. about 800 °C, for about 30 minutes to about 3 hours, e.g., about 1 hour. Heating rate is not critical and may vary from about 0.1 °C / min to about 6 or 10 °C / min, e.g., about 3 °C / min. The resulting N-doped activated carbon adsorbent is typically left to cool to room temperature before being washed to remove residual potassium salts, for instance with an acid such as HCl and water.

[0056] FIG. 2 shows an exemplary method 200 for making a tunable N-doped activated carbon adsorbent. Method 200 may include determining 202 a target component and target amount for adsorption. For example, a target component of C2 (or C2+) hydrocarbons may be selected with maximum adsorbent capacity. Method 200 may include selecting 204 a sucrose amount and a melamine amount based on the target component and target amount for adsorption. For example, if C2 (or C2+) hydrocarbons and a maximum adsorption capacity was selected, then 10 wt. % melamine and 90 wt.% sucrose may be selected to maximize the capacity for C2 (C2+) hydrocarbon adsorption as described in more detail below. Method 200 includes creating 206 a mixture of sucrose and melamine on the selected sucrose amount and the melamine amount. Method 200 includes heating 208 the mixture, cooling 210 the heated mixture, grinding 212 the cooled mixture, impregnating 214 the ground mixture with potassium oxalate, drying 216 the impregnated mixture, heating 218 the impregnated mixture to create an activated mixture, cooling 16 303581687v1Attorney Docket No.: 243981.000115 220 the activated mixture, and washing 222 the activated mixture with an acid and water to remove residual potassium salts and create the adsorbent. After acid washing the adsorbent is substantially free of potassium. EXAMPLES Exemplary Synthesis

[0057] A series of N-doped activated carbon adsorbents were synthesized by combining sucrose and melamine and carbonization of the mixtures, resulting in carbonized precursors (or N-doped carbon precursors), followed by potassium activation into activated carbons. The N-doped activated carbon samples were designated “SMx”, where x corresponds to the mass percent of melamine added to sucrose in the synthesis process (e.g., SM10, SM20, etc.). Sucrose and melamine mixtures were prepared with between 10 and 80 % melamine by weight, increasing the melamine content by 10 wt.% between samples (e.g., 10 % by weight melamine, 20% by weight melamine, 30 % by weight melamine, 40% by weight melamine, 50% by weight melamine, 60% by weight melamine, 70% by weight melamine, and 80 % by weight melamine). A reference sample was also prepared in the same conditions but in the absence of melamine (SM0).

[0058] For each of the mixtures approximately 20 g total was combined, ground in a mortar and pestle, and then divided evenly among four 250 mL alumina crucibles. In the carbonization step, the crucibles were covered and heated in air at a rate of about 5 °C / min to about 410 °C, held for about 2.5 hours, then allowed to cool naturally to room temperature. Resulting carbonized materials (or N-doped carbon precursors) were then ground again in a mortar and pestle prior to activation. Before activation, 1.5 g of the carbonized precursors were impregnated with 13.35 mL of 1M K2C2O4.H2O. The impregnation volume was selected to achieve a nominal 1:1.64 mass ratio of carbonized precursor to K2C2O4.H2O, corresponding to 0.0178 mol of potassium per gram of carbonized precursor. After addition of the K2C2O4.H2O, the samples were dried in air at about 110 °C. Impregnated samples were then transferred to covered alumina crucibles (about 20 mL), placed in a tube furnace and pyrolyzed, under flowing Argon (Ar) at 150 sccm, by heating at a rate of about 3 °C / min to a temperature of about 800 °C, and held for about 1 hour before cooling naturally. After activation, samples were washed with about 50 mL of 1M HCl followed by about 17 303581687v1Attorney Docket No.: 243981.000115 2 L of deionized water to remove residual potassium salts. Samples were then dried overnight in air at 110 °C. Physico-chemical Characterization of Activated Carbons

[0059] The physico-chemical properties of the activated carbon samples (SMx) are summarized in Table 1 below.

[0060] Textural properties of the SMx samples were determined with N2adsorption at 77 K with a Quantachrome Autosorb iQ-MP (Anton Paar) after vacuum outgassing at 200 °C for 16 hours. The Brunauer-Emmett-Teller (BET) surface area for each sample was calculated using the IUPAC recommendations for microporous materials in the relevant relative pressure (p / po) range. Pore size distributions, cumulative pore volumes, and micropore volumes were determined using a quenched-solid density functional theory (QSDFT) kernel for N2 adsorption on carbon at 77 K in S a w r s l e a dwith Fourier-transformed infrared spectroscopy (FTIR) in attenuated total reflectance (ATR) mode der was the unt303581687v1Attorney Docket No.: 243981.000115 ent ted %, ing, , , , N elemental analysis agreed with XPS quantifications. N-speciation via deconvolution of high- resolution N 1s XPS spectra, detailed in Table 2 below, showed the activated carbons to have at least 60% of surface nitrogen being comprised of pyridinic N (C-N=C) and pyrrolic N (C2NH) functionalities. Table 1 Samples Oxygen Nitrogen Carbon N / C by N / C bySBETVmicroVtotby XPS by XPS by XPS XPS (mol CHN (mol (m2 / g) (mL / g) (mL / g) (at%) (at%) (at%) ratio) ratio) SM0 16 0 84 0 0 943 0.33 0.42 SM10 9 2 89 0.02 0 2500 0.72 1.15 SM20 6 6 88 0.07 0.07 2740 0.69 1.44 SM30 4 9 87 0.10 0.12 2660 0.64 1.5 SM40 3 12 85 0.14 0.16 2040 0.56 1.15 SM50 4 10 86 0.12 0.18 1580 0.37 0.94 SM60 3 20 77 0.26 0.28 834 0.25 0.49 SM70 6 16 78 0.20 0.36 754 0.22 0.51 SM80 4 20 76 0.26 0.39 670 0.21 0.45 Table 2 Samples  C=N‐C  C2NH  CN3  NOx  (%)  (%)  (%)  (%)  SM10  15  45  22  18  SM20  32  43  15  10  SM30 38  33  15  13 SM40  43  33  17  7  19 303581687v1Attorney Docket No.: 243981.000115 SM50 41  32  16  11 SM60  52  32  11  5  SM70  53  31  12  4  SM80 58  27  12  3

[0065] Adsorption Capacities

[0066] Embodiment of the present invention relate to tunable hydrocarbons capacities by N- doping functional groups on activated carbon, which leads to higher hydrocarbon adsorption capacities compared to commercial activated carbon.

[0067] Referring to FIG.4, ethane adsorption capacities of samples SM10, SM20, SM30, SM50 and SM80 were measured at 25 °C. As shown, the higher amount of melamine (and thereby the higher amount of N-doping functional groups) resulted in lower ethane capacities of the adsorbents. For example, SM10 had a maximum measured capacity of 7.4 mmol / g of ethane at an absolute pressure of 1 bar whereas SM80 had a maximum measured capacity of about 1.3 mmol / g of ethane at an absolute pressure of 1 bar, while SM20, SM30 and SM50 had intermediate capacities between 3.9 and 6.7 mmol / g of ethane at an absolute pressure of 1 bar. Put another way, the ethane capacities can be increased from 1.3 mmol / g to 6.7 or 7.4 mmol / g using SM10 or SM20 rather than SM80. This example clearly demonstrates tunable ethane capacities through surface function group of N and can achieve very high ethane capacities. It is noticeable that SM30 has very similar ethane capacities as SM50 which can be related to a very similar N content, i.e., 9 at% for SM30 and 10 at% for SM50.

[0068] FIG.5A shows the ethylene adsorption capacities of samples SM10, SM20 and SM50 as measured at 25 °C. Similarly to ethane capacities, it can be seen that a higher amount of melamine (and thereby a higher amount of N-doping functional groups) resulted in lower ethylene capacities of the adsorbents. Put another way, the ethylene capacity can be increased from 3.6 mmol / g to 5.5 or 6.2 mmol / g by using SM10 or SM20 rather than SM50 (at an absolute pressure of 1 bar).

[0069] These results indicate that adsorption capacities of paraffins and olefins having the same N-303581687v1Attorney Docket No.: 243981.000115 5B, able ane ol / g ieve ared (W. and ogy that t an ding ight 340;the metal-organic frameworks M-2(dobdc) (M = Mg, Mn, Fe Co, Ni, Zn), Chem. Sci.4 (2013) 2054– 2061; E.D. Bloch et al., Hydrocarbon separations in a metal-organic framework with open iron(II) co- ordination sites, Science 335 (2012) 1606–161; Y. He et al., A robust doubly interpenetrated metal-organic framework constructed from a novel aromatic tri- carboxylate for highly selective separation of small hydrocarbons, Chem. Commun.48 (2012) 6493–6495; S. Meng et al., A facile approach to prepare porphyrinic porous aromatic frameworks for small hydrocarbon separation, J. Mater. Chem. A 2 (2014) 14536–14541; S. Couck et al., Adsorption and separation of small hydrocarbons on the flexible, Vanadium-containing MOF, COMOC-2, Langmuir 31 (2015) 5063– 5070; and B. Yuan et al., Unprecedented performance of N-doped activated hydrothermal carbon towards C2H6 / CH4, CO2 / CH4, and CO2 / H2separation, J. Mater. Chem. A 4 (2016) 2263–2276. Table 3 Adsorbent Methane Ethane Propane Conditions Capacity Capacity Capacity (mmol / g) (mmol / g) (mmol / g) 21 303581687v1Attorney Docket No.: 243981.000115 Flexible Metal Organic 0.45 4.21 6.76 293 K, 1 bar Framework (MFM-202a) Fe2(dobdc) 0.77 5.00 5.67 318 K, 1 bar UTSA-35a 0.43 2.43 2.97 296 K, 1 bar Porphyrin-based porous 0.62 1.85 2.58 298 K, 1.1 bar aromatic frameworks (PAF-40-Fe) Porphyrin-based porous 0.49 2.05 2.51 298 K, 1.1 bar aromatic frameworks (PAF-40-Mn) Vanadium-containing Metal 0.30 1.20 3.00 303 K, 1 bar Organic Framework (COMOC-2) Asphalt-based activated carbon 1.38 7.09 11.34 298 K, 1 bar (1:3 ratio asphalt to KOH) (A-AC-3) Asphalt-based activated carbon 1.18 6.59 11.73 298 K, 1 bar (1:4 ratio asphalt to KOH) (A-AC-4) N-doped activated hydrothermal N / A 3.7 N / A 298K, 100 carbon (NAHA) kPa SM10 of the present disclosure N / A 7.4 N / A 298K, 1 bar SM20 of the present disclosure N / A 6.7 N / A 298K, 1 bar SM30 of the present disclosure N / A 3.9 N / A 298K, 1 bar

[0071] Exemplary adsorbents of the present invention were also compared to microporous alkylene-bridged adsorbents from Dow Global Technologies LLC recommended for separating NGLs from a gas mixture containing NGLs and methane, described in U.S. Patent No.9,908,079, filed January 6, 2016, entitled Separation of Hydrocarbons Using Regenerable Macroporous Alkylene-Bridged Adsorbent, which is hereby incorporated by reference in its entirety. FIG. 6 compares the sorption isotherms for methane, ethane and propane (C1, C2, and C3 hydrocarbons) of SM30 and DowexTMOptiporeTMV493 adsorbent under the conditions defined in Example 1 of U.S. Patent No.9,908,079 and as illustrated in FIG.2 of U.S. Patent No.9,908,079. Unexpectedly, higher capacities and higher selectivity are shown for the N-doped activated carbon adsorbents of the present invention as compared to the macroporous alkylene-bridged adsorbent. For example, SM30 had a loading capacity of about 100 cm3 / g for C3 hydrocarbons at a pressure of about 175 mmHg as compared to about 40 cm3 / g for the macroporous alkylene-bridged adsorbent at a similar pressure. Additionally, SM30 had a loading capacity of about 68 cm3 / g for C2 hydrocarbons at a 22 303581687v1Attorney Docket No.: 243981.000115 pressure of about 600 mmHg as compared to about 32 cm3 / g for the macroporous at a similar pressure. There was actually no pressure at which the macroporous alkylene-bridged adsorbent had a greater loading capacity for C1, C2, or C3 hydrocarbons as compared to SM30. Adsorbents regeneration

[0072] Moreover, the N-doped activated carbon adsorbents of the present invention can be synthesized in such a way as to enable optimum water capacity. This is especially advantageous as it allows energy efficient use of steam to displace the hydrocarbons loaded on the adsorbent therefore regenerating it. An optimized adsorption process may use N-doped activated carbon adsorbent to adsorb C2 and / or heavier hydrocarbons from a hydrocarbon gas mixture, e.g., a natural gas stream, and then use steam to displace the adsorbed C2 and / or heavier hydrocarbons therefore providing a C2 and / or heavier hydrocarbons / water mixture and an at least partially regenerated adsorbent. The hydrocarbons / water mixture (or stream) obtained from the desorbed adsorbent can then be condensed and the hydrocarbons separated from the water. Steam displacement is especially advantageous as it allows regeneration of the hydrocarbon-loaded adsorbent without need of high temperature, allowing cleaning of the adsorbent at lower temperature compared to temperature swing processes. General or conceptual process configurations and contactors are shown above in FIG.1 and are only used as examples and not meant to limit the scope of implementation. The N-doped activated carbon adsorbents of the present invention can allow steam displacement process for C2 and / or heavier hydrocarbons (e.g., NGLs) recovery which in a more energy efficient way than PSA or TSA processes used previously. As shown in FIG.7, there is a factor of 10 in water capacity increase between SM10 and SM80, where SM80 has the higher water loading capacity between the two. For example, SM80 has a water loading capacity of about 11 mmol / g at a temperature of 30 °C and a partial water pressure of about 0.011 bar as compared to a water loading capacity of about 1 mmol / g for SM10 in the same conditions. It is of note that increasing the amount of N-doping in the adsorbent material results in lower C2 capacity but higher water capacity.

[0073] Looking to FIGS.8 and 9, the loading capacity of SM30 for methane, ethane, and propane was compared at 25 °C and 150 °C. The SM30 adsorbent had capacities for propane, ethane, and methane up to about 4.5 mmol / g at 0.2 bar, about 3.2 mmol / g at 0.9 bar, and about 0.6 mmol / g at 23 303581687v1Attorney Docket No.: 243981.000115 0.9 bar, respectively, at 25 °C (see FIG.8) whereas the capacities for propane, ethane, and methane were about 0.7 mmol / g at 0.2 bar, about 0.5 mmol / g at 0.9 bar, and about 0.01 mmol / g at 0.9 bar, respectively, at 150 °C (see FIG.9).

[0074] This shows that the N-doped activated carbon adsorbents of the present invention are also regenerable through temperature swing adsorption. As examples, the swing capacities for propane is over 3.8 mmol / kg, 2.7 mmol / g for ethane, and 0.5 mmol / kg for methane at a temperature swing from 25 to 150 °C.

[0075] By comparing the hydrocarbon and steam capacities in FIGs.7 and 8, it can be found that N-doped activated carbon adsorbents with intermediate N content can have similar loading capacities of water and ethane / propane, while N-doped activated carbon adsorbents with low N content have lower water capacities but high ethane / propane capacities. On the other direction, N-doped activated carbon adsorbents with high N content have higher water capacities but lower ethane / propane capacities. It is therefore possible to match required steam capacities for displacing hydrocarbons in regeneration processes by optimizing the N-content of the activated carbon adsorbents of the present invention.

[0076] In general, fundamental tradeoffs likely exist between achievable selectivity vs. process throughput vs. operating costs. These stem ultimately from the material properties / adsorption behavior of the N-doped activated carbons. For example, a carbon that is highly sensitive to water vapor (steam) might show great selectivity for C2 and / or heavier hydrocarbons separation with relatively low energy requirements. However, after the steam displacement step, water must also be desorbed from the surface of these activated carbon adsorbents. In this way, while enhanced hydrophilicity could increase separation performance of the C2 and / or heavier hydrocarbons, the net operating / energy costs for the process may be negatively impacted. These limitations can be overcome by top-down process design: process modelling could enable identification of optimal adsorbent properties, and the synthetic mechanisms could be adjusted accordingly to achieve a favorable combination of affinity vs. capacity for various adsorbates simultaneously. Therefore, tunable capacities through nitrogen content for N-doped activated carbon adsorbents of the present invention can provide the knob for the optimization of processes while lowering energy cost.

[0077] Additional Embodiments 24 303581687v1Attorney Docket No.: 243981.000115

[0078] Embodiment 1. A method for separating methane from a hydrocarbon gas mixture comprising methane along with at least one of C2 and heavier hydrocarbons, wherein the method comprises the steps of: (i) providing an N-doped activated carbon adsorbent having a BET SurfaceArea (SBET) of at least about 1000 m2 / g and a nitrogen content of at least 1 at%, as measured byXPS; (ii) contacting the hydrocarbon gas mixture with the activated carbon adsorbent toat least partially remove the C2 and / or heavier hydrocarbons from the hydrocarbon gas mixture to produce a methane-rich product stream and a C2 and / or heavier hydrocarbon-loaded adsorbent; and (iii) recovering at least part of the C2 and / or heavier hydrocarbons from the C2 and / or heavier hydrocarbon-loaded adsorbent to produce a C2 and / or heavier hydrocarbon-rich stream and an at least partially regenerated adsorbent.

[0079] Embodiment 2. The method of embodiment 1, further comprising: iv) sequentially repeating steps (ii) and (iii) for at least one cycle, using the at least partially regenerated adsorbent.

[0080] Embodiment 3. The method of embodiment 1 or 2, wherein step (iii) comprises exposing the loaded adsorbent to at least one of steam, a different pressure, and a different temperature.

[0081] Embodiment 4. The method of any one of embodiments 1 to 3, wherein C2 and / or heavier hydrocarbons include at least one of ethylene, ethane, propylene, propane, 1-butene, n-butane, and heavier hydrocarbons.

[0082] Embodiment 5. The method of any one of embodiments 1 to 4, wherein the hydrocarbon gas mixture comprises methane, ethane and heavier paraffins.

[0083] Embodiment 6. The method of any one of embodiments 1 to 5, to separate methane from natural gas liquids (NGLs) in a natural gas stream, preferably wherein the natural gas stream contains about 60 to 100 mol% methane.

[0084] Embodiment 7. The method of any one of embodiments 1 to 6, wherein the methane-rich product stream comprises at least 80 wt% of the methane present in the hydrocarbon gas mixture.

[0085] Embodiment 8. The method of any one of embodiments 1 to 7, wherein the adsorbent has a loading capacity of about 5 cm3 / g to about 75 cm3 / g of the C2 and / or heavier hydrocarbons at a pressure of about 1 mmHg to about 700 mmHg. 25 303581687v1Attorney Docket No.: 243981.000115

[0086] Embodiment 9. The method of any one of embodiments 1 to 8, wherein adsorbent has a loading capacity of about 40 cm3 / g to about 75 cm3 / g of the C2 and / or heavier hydrocarbons at a pressure of about 400 mmHg to about 700 mmHg.

[0087] Embodiment 10. The method of any one of embodiments 1 to 9, wherein the N-dopedactivated carbon adsorbent has a BET Surface Area (SBET) of from about 1000 to about 5000m2 / g, in particular from about 1550 to about 3500 m2 / g, more particularly from about 2000 to about 2800 m2 / g.

[0088] Embodiment 11. The method of any one of embodiments 1 to 10, wherein the N-doped activated carbon adsorbent has a Total Pore Volume (Vtot) of from about 0.70 to about 2.0 cc / g, in particular from about 0.90 to about 1.8 cc / g, more particularly from about 1.1 to about 1.6 cc / g.

[0089] Embodiment 12. The method of any one of embodiments 1 to 11, wherein the N-doped activated carbon adsorbent has a Micropore Volume (Vmicro) of from about 0.30 to 1.0 cc / g, in particular from about 0.40 to about 0.90 cc / g, and more particularly from about 0.50 or 0.60 to about 0.80 cc / g.

[0090] Embodiment 13. The method of any one of embodiments 1 to 12, wherein the N-doped activated carbon adsorbent has a total nitrogen content, as measured by elemental analysis, of from about 1 at% to about 20 at%, in particular from about 2 at%, such in excess of 2 at%, to about 15 at%, more particularly from about 5 at% to about 10 at%.

[0091] Embodiment 14. The method of any one of embodiments 1 to 13, wherein the N-doped activated carbon adsorbent has a surface nitrogen content, as measured by XPS, of from about 1 at% to about 20 at%, in particular from about 2 at%, such in excess of 2 at%, to about 15 at%, more particularly from about 5 at% to about 10 at%.

[0092] Embodiment 15. The method of any one of embodiments 1 to 14, wherein, in the N-doped activated carbon adsorbent, at least about 60% of the surface nitrogen is comprised of pyridinic (C-N=C) and pyrrolic (C2NH) functionalities, in particular from about 60% to about 85%, more particularly from about 71 to about 75%.

[0093] Embodiment 16. The method of any one of embodiments 1 to 15, wherein the N-doped activated carbon adsorbent has a carbon content, as measured by XPS, of about 80 at% to about 95 at%, in particular from about 80 or 85 at% to about 90 at%. 26 303581687v1Attorney Docket No.: 243981.000115

[0094] Embodiment 17. The method of any one of embodiments 1 to 16, wherein the N-doped activated carbon adsorbent has an oxygen content, as measured by XPS, of about 2 at% to about 15 at%, in particular from about 3 at% to about 10 at%.

[0095] Embodiment 18. The method of any one of embodiments 1 to 17, wherein the N-doped activated carbon adsorbent has a N:C ratio, as measured by XPS, of about 0.01 to about 0.20, in particular from about 0.02 to about 0.17, more particularly from about 0.05 to 0.15.

[0096] Embodiment 19. The method of any one of embodiments 1 to 18, wherein the N-doped activated carbon adsorbent is synthesized via potassium activation of a N-doped carbon precursor derived from polycondensation of sucrose and melamine.

[0097] Embodiment 20. The method of embodiment 18, including (i) combining sucrose and melamine in a mixing step to produce a sucrose and melamine mixture, (ii) carbonizing the sucrose and melamine mixture to produce a N-doped carbon precursor, and (iii) activating the N-doped carbon precursor in a potassium activation step to produce a N-doped activated carbon adsorbent.

[0098] Embodiment 21. The method of embodiment 19 or 20, wherein potassium activation comprises impregnating the N-doped carbon precursor with potassium followed by a pyrolysis step.

[0099] Embodiment 22. The method of embodiment 21, wherein impregnation of the N-doped carbon precursor with potassium includes contacting the N-doped carbon precursor with a potassium compound selected from the group consisting of potassium carbonate (K2CO3), potassium oxalate (K2C2O4), potassium hydroxide (KOH) and mixtures thereof, in particular K2CO3 or K2C2O4, more particularly K2C2O4.

[0100] Embodiment 23. The method of any one of embodiments 19 to 22, potassium is used in an amount of at least about 0.008 of K per gram of N-doped carbon precursor, in particular at least 0.01 mol of K per gram of carbon precursor, more particularly from 0.01 to 0.05 mol of K per gram of carbon precursor, most particularly from 0.015 to 0.02 mol of K per gram of carbon precursor.

[0101] Embodiment 24. The method of any one of embodiments 19 to 23, wherein synthesis of the N-doped activated carbon adsorbent further comprises a washing step to remove residual potassium salts. 27 303581687v1Attorney Docket No.: 243981.000115

[0102] Embodiment 25. A method for regenerating a N-doped activated carbon adsorbent loaded with one or more hydrocarbon gases, comprises treating the loaded adsorbent with steam.

[0103] Embodiment 26. The method of embodiment 25, wherein the N-doped activated carbon adsorbent loaded is the C2 and / or heavier hydrocarbon-loaded adsorbent produced in the method of any one of embodiments 1 to 24.

[0104] Embodiment 27. The method of embodiment 25 or 26, wherein the N-doped activated carbon adsorbent is provided in the form of a bed and steam is passed through the adsorbent bed to at least partially displace the one or more hydrocarbon gases from the adsorbent bed to produce a stream comprising water and at least part of the one or more hydrocarbon gases; and separating at least part of the one or more hydrocarbon gases from the water.

[0105] Embodiment 28. The method of any one of embodiments 25 to 27, conducted at substantially constant pressure and / or temperature, preferably conducted at substantially constant pressure and temperature.

[0106] Embodiment 29. The method of any one of embodiments 25 to 28, wherein the adsorbent is loaded with about 1 mmol / g to about 11 mmol / g of water at a temperature of 30˚C and a partial water pressure of less than 0.014 bar.

[0107] Certain features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

[0108] Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.

[0109] The foregoing description of the disclosure illustrates and describes the present methodologies. Additionally, the disclosure shows and describes exemplary methods, but it is to 28 303581687v1

Claims

Attorney Docket No.: 243981.000115 be understood that various other combinations, modifications, and environments may be employed, and the present methods are capable of changes or modifications within the scope of the concept as expressed herein, commensurate with the above teachings and / or the skill or knowledge of the relevant art. 29 303581687v1Attorney Docket No.: 243981.000115 6. The method of Claim 1, wherein the adsorbent has a loading capacity of about 5 cm3 / g to about 75 cm3 / g of the C2 and / or heavier hydrocarbons at a pressure of about 1 mmHg to about 700 mmHg.

7. The method of Claim 1, wherein adsorbent has a loading capacity of about 40 cm3 / g to about 75 cm3 / g of the C2 and / or heavier hydrocarbons at a pressure of about 400 mmHg to about 700 mmHg.

8. The method of Claim 1, wherein the N-doped activated carbon adsorbent has a BETSurface Area (SBET) of from about 1000 to about 5000 m2 / g9. The method of Claim 1, wherein the N-doped activated carbon adsorbent has a Total Pore Volume (Vtot) of from about 0.70 to about 2.0 cc / g.

10. The method of Claim 1, wherein the N-doped activated carbon adsorbent has a Micropore Volume (Vmicro) of from about 0.30 to 1.0 cc / g.

11. The method of Claim 1, wherein the N-doped activated carbon adsorbent has a total nitrogen content, as measured by elemental analysis, of from about 1 at% to about 20 at%.

12. The method of Claim 1, wherein the N-doped activated carbon adsorbent has a surface nitrogen content, as measured by XPS, of from about 1 at% to about 20 at%.

13. The method of Claim 12, wherein, in the N-doped activated carbon adsorbent, at least about 60% of the surface nitrogen is comprised of pyridinic (C-N=C) and pyrrolic (C2NH) functionalities. 31 303581687v1Attorney Docket No.: 243981.000115 14. The method of Claim 1, wherein the N-doped activated carbon adsorbent is synthesized via potassium activation of N-doped carbon precursors derived from polycondensation of sucrose and melamine.

15. The method of Claim 14, wherein potassium activation comprises adding at least one of potassium carbonate (K2CO3), potassium oxalate (K2C2O4) and potassium hydroxide (KOH) to N- doped carbon precursors followed by a pyrolysis step.

16. The method of Claim 15, wherein synthesis of the N-doped activated carbon adsorbent further comprises a washing step to remove residual potassium salts.

17. A method for regenerating a N-doped activated carbon adsorbent loaded with one or more hydrocarbon gases, comprises treating the loaded adsorbent with steam.

18. The method of Claim 17, wherein the N-doped activated carbon adsorbent is provided in the form of a bed and steam is passed through the adsorbent bed to at least partially displace the one or more hydrocarbon gases from the adsorbent bed to produce a stream comprising water and at least part of the one or more hydrocarbon gases; and separating at least part of the one or more hydrocarbon gases from the water.

19. The method of Claim 17, wherein the adsorbent is loaded with about 1 mmol / g to about 11 mmol / g of water at a temperature of 30˚C and a partial water pressure of less than 0.014 bar. 32 303581687v1

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