FROM SOUR GAS

GOVERNMENT FUNDING

This invention was made with government support under grant number DE-FG02-12ER16362 awarded by the United States Department of Energy, Office of Basic Energy Sciences,

Divisional of Chemical Sciences, Geosciences and Biosciences. The government has certain rights in the invention.

PRIORITY

This application claims priority to United States Provisional Application Number 62/235,870 filed on October 1, 2015 entitled Methods of Selectively Removing Hydrogen Sulfide from Sour Gas, the entire disclosure of which is incorporated herein by reference thereto.

BACKGROUND

In recent years, discovery of shale gas and the advancement in fracking technologies have led to a large increase in the North American natural gas production. However, even today, a significant fraction of the global gas reserves continue to remain untapped, due to the sour nature of these wells with hydrogen sulfide (H2S) concentrations high enough to deem the conventional amine-based absorptive separation uneconomical. Finding innovative and cost-effective solutions for this sweetening step in natural gas processing could have far-reaching economic and environmental implications. SUMMARY

Disclosed herein are materials and methods for selectively removing hydrogen sulfide versus one or more hydrocarbons, water, carbon dioxide, nitrogen, or combinations thereof from sour natural gas, the method including using one or more zeolites or zeotypes selected from framework types ACO, AEL, AET, AFS, AFY, AHT, APC, APD, ATV, AWO, BIK, CAS, CZP, DFT, EDI, EPI, GIS, ITH, ITW, IWV, JBW, TNT, JSN, JST, LOV, LTL, MEL, MER, MFI, MON, PAU, PHI, RHO, RRO, RSN, RWR, SBN, SEW, SFF, STW, THO, TON, UEI, VFI, VNI, and WEI.

Also disclosed are materials and methods for selectively removing hydrogen sulfide versus at least methane, ethane, water, carbon dioxide, nitrogen, or any combination thereof from sour natural gas, the method including using one or more zeolites and zeotypes selected from all-silica forms of ACO, AEL, AET, AFS, AFY, AHT, APC, APD, ATV, AWO, BIK, CAS, CZP, DFT, EDI, EPI, GIS, ITH, ITW, IWV, JBW, JNT, JSN, JST, LOV, LTL, MEL, MER, MFI, MON, PAU, PHI, RHO, RRO, RSN, RWR, SBN, SEW, SFF, STW, THO, TON, UEI, VFI, VNI, and WEI.

Also disclosed are materials and methods for selectively removing hydrogen sulfide versus at least methane, ethane, water, carbon dioxide, nitrogen, or any combination thereof from sour natural gas, the method including using one or more zeolites and zeotypes selected from high silicon/aluminum forms of ACO, AEL, AET, AFS, AFY, AHT, APC, APD, ATV, AWO, BIK, CAS, CZP, DFT, EDI, EPI, GIS, ITH, ITW, IWV, JBW, TNT, JSN, JST, LOV, LTL, MEL, MER, MFI, MON, PAU, PHI, RHO, RRO, RSN, RWR, SBN, SEW, SFF, STW, THO, TON, UEI, VFI, VNI, and WEI. [07] Also disclosed are materials and methods for selectively removing hydrogen sulfide versus at least methane, ethane, water, carbon dioxide, nitrogen, or any combination thereof from sour natural gas, the method including using one or more zeolites and zeotypes selected from aluminum/phosphate balanced forms of ACO, AEL, AET, AFS, AFY, AHT, APC, APD, ATV, AWO, BIK, CAS, CZP, DFT, EDI, EPI, GIS, ITH, ITW, IWV, JBW, TNT, JSN, JST, LOV, LTL, MEL, MER, MFI, MON, PAU, PHI, RHO, RRO, RSN, RWR, SBN, SEW, SFF, STW, THO, TON, UEI, VFI, VNI, and WEI.

[08] Also disclosed are materials and methods for selectively removing hydrogen sulfide versus at least methane or ethane from sour natural gas, the method including using one or more zeolites and zeotypes selected from all-silica forms of ACO, AEL, AET, AFS, AFY, AHT, APC, APD, ATV, AWO, BIK, CAS, CZP, DFT, EDI, EPI, GIS, ITH, ITW, IWV, JBW, TNT, JSN, JST, LOV, LTL, MEL, MER, MFI, MON, PAU, PHI, RHO, RRO, RSN, RWR, SBN, SEW, SFF, STW, THO, TON, UEI, VFI, VNI, and WEI.

[09] Also disclosed are materials and methods for selectively removing hydrogen sulfide versus at least methane or ethane from sour natural gas, the method including using one or more zeolites and zeotypes selected from high silicon/aluminum forms ACO, AEL, AET, AFS, AFY, AHT, APC, APD, ATV, AWO, BIK, CAS, CZP, DFT, EDI, EPI, GIS, ITH, ITW, IWV, JBW, TNT, JSN, JST, LOV, LTL, MEL, MER, MFI, MON, PAU, PHI, RHO, RRO, RSN, RWR, SBN, SEW, SFF, STW, THO, TON, UEI, VFI, VNI, and WEI.

[010] The above summary of the present disclosure is not intended to describe each disclosed

embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples can be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list.

BRIEF DESCRIPTION OF THE FIGURES

[Oi l] FIGs. 1A, IB, and 1C show H2S/CH4 binary adsorption at different feed concentrations of H2S, y? = 0.50 [FIG. 1A], 0.30 [FIG. IB], and 0.10 [FIG. 1C] and at an overall pressure, p = 50 bar and temperature, T= 343 K. Circles represent the property P s. Yellow circles show data points where S s < 10 while framework types with S s > 10 are highlighted using cyan. Triangles represent the total mass of zeolite required to achieve a final concentration of 90 mole % or more H2S in the adsorbed phase and for removing 10 mmol of H2S from the feed. Black up triangles show framework types that can achieve this purity in a single stage, while magenta down triangles show frameworks that can achieve this purity in 2 stages.

[012] FIG. 2 shows the H2S/CH4 binary adsorption atj/F = 0.50 vs. y? = 0.10 and at an overall pressure, p = 50 bar and temperature, T= 343 K.

[013] FIG. 3 shows the H2S/CH4 binary adsorption at_yF = 0.30 vs. y? = 0.10 and at an overall pressure, p = 50 bar and temperature, T= 343 K.

[014] FIG. 4 shows the H2S/CH4 binary adsorption atj/F = 0.50 vs. y? = 0.30 and at an overall pressure, p = 50 bar and temperature, T= 343 K.

[015] FIG. 5 shows the H2S/CH4 binary adsorption atp = 50 bar and T= 343 K vs. p = 10 bar and T = 298 K.

[016] FIGs. 6A, 6B and 6C show H2S/C2H6 binary adsorption at different feed concentrations of H2S, yF = 0.50 [FIG. 6A], 0.30 [FIG. 6B], and 0.10 [FIG. 6C] and at an overall pressure, p = 50 bar and temperature, T= 343 K. Circles represent the property P s. Yellow circles show data points where S s < 10 while framework types with S s > 10 are highlighted using cyan. Triangles represent the total mass of zeolite required to achieve a final concentration of 90 mole % or more H2S in the adsorbed phase and for removing 10 mmol of H2S from the feed. Black up triangles show framework types that can achieve this purity in a single stage, while magenta down triangles show frameworks that can achieve this purity in two stages.

[017] FIG. 7 shows the H2S/C2H6 binary adsorption atj/F = 0.50 vs. y? = 0.10 and at an overall

pressure, * = 50 bar and temperature, T= 343 K.

[018] FIG. 8 shows the H2S/C2H6 binary adsorption atj/F = 0.30 vs. y? = 0.10 and at an overall

pressure, * = 50 bar and temperature, T= 343 K.

[019] FIG. 9 shows the H2S/C2H6 binary adsorption atj/F = 0.50 vs. y? = 0.30 and at an overall

pressure, * = 50 bar and temperature, T= 343 K.

[020] FIG. 10 shows the H2S/C2H6 binary adsorption atp = 50 bar and T= 343 K vs. p = 10 bar and T = 298 K.

[021] FIG. 11 shows selectivity (left axis) and AH _ac j _s (right axis) in top-performing zeolite structures atyp = 0.50, T = 343 K, and p = 50 bar. Selectivity vs. methane: cyan triangles, Selectivity vs. ethane: magenta squares, and A/J _ac j _s (for the H2S/CH4 mixture): green bars.

[022] FIG. 12 shows five-component adsorption at T= 343 K and p = 50 bar usingis jja

H2S:C02:CH4:C2Hg:N2 feed composition with molar ratio of 25: 10:50: 10:5. Equilibrium mole fractions in the gas phase (top) and in the adsorbed phase (bottom) for 16 high-performing zeolite structures.

[023] FIG. 13 shows four-component adsorption at T= 343 K and p = 24 bar usingis jja

H2S:C02:CH4:C2Hg feed composition with molar ratio of 16: 10:70:4. This mixture is representative of the Lacq gas reservoir and is less sour than the five-component mixture.

Equilibrium mole fractions in the gas phase (top) and in the adsorbed phase (bottom) for 16 high- performing zeolite structures.

[024] The figures are not necessarily to scale. Like numbers used in the figures refer to like

components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

DETAILED DESCRIPTION

[025] Disclosed herein are methods of selectively removing hydrogen sulfide (H2S) from sour gases, in some embodiments highly sour gases, using particular zeolites or zeotypes. The phrases

"zeolites or zeotypes" and "zeolites and zeotypes" as used herein denote porous and fully crosslinked framework structures consisting of corner-sharing T0 ₄ tetrahedra. This group includes but is not limited to silicates, aluminosilicates, aluminophosphates, and silico- aluminophosphates. Zeolites and zeotypes may be used interchangeably throughout this application and either or both can refer to "zeolites and zeotypes". The term "cation" is used to denote exchangeable and non-exchangeable metal cations, and non-metallic cations that are not part of the T0 ₄ tetrahedra. Particular zeolites referred to herein also include those zeolites that contain defects due to methods of making them, use of the zeolites, or other factors.

[026] Zeolites can be described as a three-dimensional framework of tetrahedrally coordinated T-atoms (linked together by bridging oxygen atoms) that form cavities or channels with the smallest opening larger than six T-atoms. The "T-atoms" include silicon (Si), aluminum (Al), phosphorus (P), arsenic (As), gallium (Ga), germanium (Ge), boron (B), beryllium (Be), as well as others. The connectivity of the tetrahedra in a zeolite controls the channel and pore openings.

[027] Zeolites and zeotypes are commonly described using a zeolite framework type that is assigned by the International Zeolite Association (IZA). There are numerous framework type codes. The framework type codes represent an abbreviated name and a full name of the particular material or structure. For example, the framework code LTL represents the abbreviated name Linde Type L, whose full name is Zeolite L (Linde Division, Union Carbide). A code does not describe an actual material, but instead describes and defines the framework.

[028] In some embodiments, zeolites and zeotypes that can be utilized herein can have a high silicon to aluminum ratio (Si/Al). The silicon and aluminum in such zeolites and zeotypes make up the T atoms. The high Si/Al ratio may provide high adsorption selectivities for FhS over water and over light hydrocarbons such as methane (CFh) and ethane (C2H6). In some embodiments, zeolites and zeotypes having Si/Al ratios of not less than (or greater than) 50 can be utilized. In some embodiments, zeolites and zeotypes having Si/Al ratios of not less than (or greater than) 100 can be utilized. In some embodiments, where dry natural gas mixtures are to be separated, zeolites with Si/Al of not less than (or greater than) 50 can be useful. Zeolites or zeotypes can also be described by the T atom/cation ratio. In some embodiments, the T atom/cation ratio of not less than (or greater than) 100 can be utilized. In some embodiments, the T atom/cation ratio of not less than(or greater than) 50 can be used.

[029] In some embodiments, zeolites and zeotypes that can be utilized herein can be all silica zeolites and zeotypes. In such zeolites and zeotypes, all of the T atoms are silicon atoms. The high level of silicon may provide high adsorption selectivities for FhS over water and over some light hydrocarbons such as methane (CH4) and ethane (C2H6). [030] In some embodiments, zeolites and zeotypes that can be utilized herein can have a balanced aluminum to phosphorus ratio (Al/P). Zeolites and zeotypes with a balanced Al/P ratio contain only a minimal quantity of polar cations or protons and are therefore extremely hydrophobic. This may reduce the ability of water to occupy the adsorption sites, thereby allowing H2S those sites.

[031] Disclosed herein are methods of selectively separating H2S from light hydrocarbons, such as CH ₄ , and C2H6 for example from natural gas, e.g., sour natural gas using particular zeolites or zeotypes having particular frameworks. Sour natural gas typically includes relatively high levels of water (H2O). H2O and H2S will compete for the strong adsorption sites, and water is more likely to win because of water's inherently larger dipole moment and higher affinity for the formation of hydrogen bonds. For this reason, siliceous zeolites, those with a high Si/Al ratio, or aluminophosphates with a balanced Al/P ratio, which both contain only minute quantities of polar cations or protons and are therefore extremely hydrophobic, were investigated herein. In some embodiments, zeolites or zeotypes with only silicon (instead of some other atoms at T positions, e.g. Al) were also investigated herein and can be utilized herein.

[032] In some embodiments, disclosed herein are all-silica (all T are Si) forms of zeolite frameworks that can be utilized to selectively remove H2S versus light hydrocarbons from sour natural gas.

[033] In some embodiments, a zeolite having any of a ACO*, AFY*, AHT*, or SBN* framework can be utilized. As noted by the *, these structures until now have only been synthesized in aluminophosphate or germanate forms. Although all-silica (all T are Si) forms of ACO*, AFY*, AHT*, or SBN* were determined by computational screening to be effective to selectively separate H2S from light hydrocarbons such as CH4, the all-silica ACO*, AFY*, AHT*, or SBN* zeolites themselves may perform slightly different than the idealized structures reported by the IZA. However, in some embodiments, all-silica ACO*, AFY*, AHT*, or SBN* framework zeolites can be utilized herein.

[034] In some embodiments, zeolites having any of AFY-0, APC-1, ACO-0, SBN-0, AHT-1, VFI-1, JST-0, AFS-1, GIS-5, AFS-0, PAU-0, IWV-1, RHO-0, APD-0, LTL-2, DFT-0, PHI-1, GIS-1, AWO-0, JSN-1, EPI-1, UEI-0, or MEL-1 frameworks may be utilized. Framework types in this list that are represented by XXX-0 were idealized into their all-silica forms and DFT (density functional theory)-optimized to overcome unreasonably high energy structures. Framework types in this list that are represented by XXX-(l-6) were not DFT-optimized but instead the Al or P atoms were physically replaced by Si atoms (in the computational screenings) at the same position without any energy minimization. Although all-silica (all T are Si) forms of AFY-0, APC-1, ACO-0, SBN-0, AHT-1, VFI-1, JST-0, AFS-1, GIS-5, AFS-0, PAU-0, IWV-1, RHO-0, APD-0, LTL-2, DFT-0, PHI-1, GIS-1, AWO-0, JSN-1, EPI-1, UEI-0, or MEL-1 were determined by computational screening to be effective to selectively separate H2S from light hydrocarbons such as CH ₄ , the all-silica AFY-0, APC-1, ACO-0, SBN-0, AHT-1, VFI-1, JST-0, AFS-1, GIS-5, AFS-0, PAU-0, IWV-1, RHO-0, APD-0, LTL-2, DFT-0, PHI-1, GIS-1, AWO-0, JSN-1, EPI-1, UEI-0, or MEL-1 zeolites themselves may perform slightly different than the idealized structures. However, in some embodiments, all-silica AFY-0, APC-1, ACO-0, SBN-0, AHT-1, VFI-1, JST-0, AFS-1, GIS-5, AFS-0, PAU-0, IWV-1, RHO-0, APD-0, LTL-2, DFT-0, PHI-1, GIS-1, AWO-0, JSN-1, EPI-1, UEI-0, or MEL-1 framework zeolites can be utilized herein.

[035] In some embodiments, zeolites having any of AEL, AET, BIK, ITH, MER, MFI, MON, SEW, SFF, STW, THO, and WEI frameworks may be effective to selectively separate H2S from light hydrocarbons such as CH ₄ . [036] In some embodiments, a zeolite having any of a ACO*, APC*, APD*, or SBN* frameworks can be utilized. As noted by the *, these structures presently only exist in aluminophosphate or germanate forms. Although all-silica (all T are Si) forms of ACO*, AFY*, AHT*, or SBN* were determined by computational screening to be effective to selectively separate H2S from light hydrocarbons such as C2H6, the all-silica ACO*, AFY*, AHT*, or SBN* zeolites themselves may perform slightly different than the idealized structures. However, in some embodiments, all- silica ACO*, AFY*, AHT*, or SBN* framework zeolites can be utilized herein.

[037] In some embodiments, zeolites having any of SBN-0, APC-1, ACO-0, APD-0, DFT-0, APC-2, AHT-1, ATV-1, CAS-0, AWO-0, ATV-0, GIS-1, APC-0, CZP-0, EDI-1, JBW-0, RWR-0, LOV-

0, JNT-0, ITW-0, VNI-0, RSN-0, and RRO-0 frameworks may be utilized. Framework types in this list that are represented by XXX-0 were idealized into their all-silica forms and DFT

(density functional theory)-optimized to overcome unreasonably high energy structures.

Framework types in this list that are represented by XXX-(l-6) were not DFT-optimized but instead the Al or P atoms were physically replaced by Si atoms (in the computational screenings) at the same position without any energy minimization. Although all-silica (all T are Si) forms of SBN-0, APC-1, ACO-0, APD-0, DFT-0, APC-2, AHT-1, ATV-1, CAS-0, AWO-0, ATV-0, GIS-

1, APC-0, CZP-0, EDI-1, JBW-0, RWR-0, LOV-0, JNT-0, ITW-0, VNI-0, RSN-0, and RRO-0 were determined by computation screening to be effective to selectively separate H2S from light hydrocarbons such as C ₂ H ₆ , the all-silica SBN-0, APC-1, ACO-0, APD-0, DFT-0, APC-2, AHT- 1, ATV-1, CAS-0, AWO-0, ATV-0, GIS-1, APC-0, CZP-0, EDI-1, JBW-0, RWR-0, LOV-0, JNT-0, ITW-0, VNI-0, RSN-0, and RRO-0 zeolites themselves may perform slightly different than the idealized structures. However, in some embodiments, all-silica SBN-0, APC-1, ACO-0, APD-0, DFT-0, APC-2, AHT-1, ATV-1, CAS-0, AWO-0, ATV-0, GIS-1, APC-0, CZP-0, EDI- 1, JBW-0, RWR-0, LOV-0, JNT-0, ITW-0, VNI-0, RSN-0, and RRO-0 framework zeolites can be utilized herein.

[038] In some embodiments, zeolites having any of APC-1, ACO-0, SBN-0, AHT-1, APD-0, DFT-0, GIS-1, and AWO-0 frameworks may be utilized. Framework types in this list that are represented by XXX-0 were idealized into their all-silica forms and DFT (density functional theory)-optimized to overcome unreasonably high energy structures. Framework types in this list that are represented by XXX-(l-6) were not DFT-optimized but instead the Al or P atoms were physically replaced by Si atoms (in the computational screenings) at the same position without any energy minimization. Although all-silica (all T are Si) forms of APC-1, ACO-0, SBN-0, AHT-1, APD-0, DFT-0, GIS-1, and AWO-0 were determined by computation screening to be effective to selectively separate H2S from light hydrocarbons such as CH ₄ and C2H5, the all-silica APC-1, ACO-0, SBN-0, AHT-1, APD-0, DFT-0, GIS-1, and AWO-0 zeolites themselves may perform slightly different than the idealized structures in selectively separating both CH ₄ and C2H6 from H2S. However, in some embodiments, all-silica APC-1, ACO-0, SBN-0, AHT-1, APD-0, DFT-0, GIS-1, and AWO-0 framework zeolites can be utilized herein.

[039] In some embodiments, zeolites having any of AEL, AET, BIK, ITH, MER, MFI, MON, SEW, SFF, STW, THO, and WEI frameworks may be effective to selectively separate H2S from light hydrocarbons such as C2H5.

[040] Disclosed zeolites and zeotypes can be utilized in various methods and process schemes for selectively separating H2S from light hydrocarbons, water, or combinations thereof. Zeolites and zeotypes that may be utilized herein can be utilized in any form, including for example powders, pellets, membrane forms, or otherwise. It should also be noted that various amounts of one or more zeolites or zeotypes could be utilized in various methods, depending on a number of process considerations, for example.

[041] EXAMPLES

[042] The particular zeolites used herein were determined by computational screening of many

zeolites. Large-scale computational screening is an extremely useful tool; specially, when it comes to systems involving very hazardous and lethal chemicals like hydrogen sulfide. The focus of this work was to develop zeolite-based adsorptive solutions for sweetening of sour gas mixtures by a computational screening of over 200 known zeolite framework types. Sour gas mixtures may contain not only CH ₄ and H2S, but also C2H6 and higher hydrocarbons that are valuable. The particular zeolites utilized herein were chosen because they are not only selective towards H2S in a mixture with CH ₄ , but also perform well to selectively adsorb H2S from H2S/C2H6 mixtures.

[043] One of the big challenges for selective removal of H2S from sour gas streams is the presence of water vapor. Unless one is seeking to react the two, which is inherently an energy-intensive separation, H2O and H2S will compete for the strong adsorption sites, and H2O is more likely to win simply because of water's inherently larger dipole moment and higher affinity for the formation of hydrogen bonds. However, disclosed zeolites, e.g. siliceous zeolites (high Si/Al ratio) contain only minute quantities of polar cations, which makes the zeolite extremely hydrophobic, offering an opportunity to selectively capture H2S over methane and water.

[044] Natural gas reserves vary significantly in compositions, temperatures, and pressures from one geographical location to another. A temperature of 343 K and an overall pressure of 50 bar were assumed for the computational screening of 385 unique zeolite adsorbents. Specifically, seven different compositions are examined for each of the two binary mixtures (H2S/CH4 and H2S/C2H6) to fit to a smooth adsorption isotherm, which can then be used to estimate the performance at any specific composition of H2S in the gas phase.

[045] For any adsorptive separation process, if one assumes that the material cost per ton of the

adsorbent for the various adsorbents is similar and reasonable, there are two prime attributes of the adsorbent that will determine whether that adsorbent and also the overall adsorption process will be cost-effective or not: (i) Loading of desired sorbate molecule at pre-specified adsorption conditions, (qms) and (ii) Selectivity towards the desired component, (Sms). As a first-order approximation, the cost for an adsorption step would be inversely proportional to the loading. Contrary to this, if the target separation factor is 1000, an adsorbent with a selectivity of 1000 would achieve this separation in a single step, while adsorbents with a selectivity of 100 and 10 would require 2 and 3 steps, respectively. Hence, for selectivity, (InSms) ^-1 would be a better representative of the cost of separation. Hence, for each of the binary mixtures investigated in this work, we define the performance criteria, ms, as the product of qms and ln(SH2s). This performance metric is quite general and is not a function of any particular means of operating an adsorption process. We go a step further and calculate the number of adsorption stages that it would take to achieve a target purity of 90 mole % H2S in the zeolite, if one started with different feed compositions of H2S, _yF = 0.10, 0.30, and 0.50, with increasingly high sourness quotient. In addition to the number of stages, we also compute the total quantity of a particular zeolite that would be needed for the required «-stage adsorption (this is not simply a product of qms and n because loading can vary considerably with composition). The target purity of 90 mole % is sufficient to allow for subsequent condensation of the retentate at or above a temperature of 343 K if a liquid waste stream is desirable.

[046] Materials and Methods [047] Molecular models Non-bonded interactions are modeled using a pairwise-additive potential consisting of Lennard-Jones (LJ) 12-6 and Coulomb terms: where ry, £ij , σ _¾ , qi, q are the site-site separation, LJ well depth, LJ diameter, and partial charges on beads i and j, respectively. The Transferable Potentials for Phase Equilibria (TraPPE) force field is used for the zeolites, H ₂ S, CH ₄ , and C2H6. In the TraPPE-zeo force field, LJ interaction sites and partial charges are placed on both silicon and oxygen atoms. H2S is represented by the recently developed 4-site TraPPE model where LJ sites are placed on the S and H nuclei and partial charges are placed on H nuclei and an off-atom site. For the methane molecule, the 5-site TraPPE-EH model where LJ interaction sites are located at the carbon atom nucleus and the four C-H bond centers is used. As far as ethane is considered, the 2-site TraPPE-UA model where LJ interaction sites are located at the carbon atom nucleus, is used to gain a factor of order 16 in efficiency with some compromise in the accuracy compared to the 8-site TraPPE-EH version of ethane. The standard Lorentz-Berthelot combining rules:

and

are used to determine the LJ parameters for all unlike interactions.

[048] Simulation details Configurational-bias Monte Carlo simulations in the isobaric-isothermal {NpT) version of the Gibbs ensemble are used to compute the binary (H2S/CH4 and H2S/C2H6) adsorption isotherms in all-silica frameworks at 343 K and 50 bar and at 298 K and 10 bar. At 343 K and 50 bar, seven different compositions have been simulated for each zeolite. A variable system size, that is proportional to the mass of the simulated supercell of the zeolite, is used for the gas phase. The zeolite framework is treated to be rigid during the course of the simulation, with Si and O atoms fixed at their crystallographically-determined positions. Only those frameworks in the ISA-SC database that have no net charge remaining in a unit cell after removing any bound ions or solvent molecules are used for the purpose of this work. Only frameworks that contain Si, O, P, and Al atoms are used for this study. The force field parameters for P and Al are taken to be same as that for Si; this approximation can be justified to some extent because Al and P are immediate neighbors of Si in the same row of the periodic table, and are likely to have very similar strength of dispersive interactions.

As far as the repulsive-dispersive interactions are concerned, the LJ term is truncated at 14 A and analytical tail corrections are applied. For the zeolite phase, the number of unit cells in each dimension is chosen to allow for a 14 A cutoff and the cutoff interactions in the vapor-phase is set to approximately 40% of box length. The Ewald summation method with screening parameter of K = 3.2/rcut and Kmax = int(Klbox)+l for the upper bound of the reciprocal space summation is used for the calculation of first-order electrostatics. In order to improve the efficiency of simulation, all sorbate-sorbent interactions are pre-tabulated with a grid spacing of 0.02 nm and interpolated during the simulation for any position of the guest species in the zeolite phase. Four kinds of Monte Carlo moves, translational, rotational, volume exchange, and particle transfer moves, are used to sample the phase space. The coupled-decoupled configurational-bias Monte Carlo algorithm is used to enhance the acceptance rate for particle transfer moves. The probabilities for volume and transfer moves are adjusted to have approximately one accepted move per Monte Carlo cycle (MCC), where an MCC consists of a number of randomly selected moves that is equal to the number of total molecules in the system. In case of binary simulations, the probability to choose a molecule type for transfer move is set proportional to its overall mole fraction for the 2-box simulation. The remaining moves are divided equally between translations and rotations. An equilibration period of at least 25000 MCCs is used for each simulation trajectory, which is followed by a production period between 100,000 to 150,000 MCCs.

[050] Results

[051] H2S/CH4 separation FIG. 1 (H2S/CH4 binary adsorption at different feed concentrations of H2S, yF = 0.50 [A], 0.30 [B], and 0.10 [C] and at an overall pressure, p = 50 bar and temperature, T = 343 K. Circles represent the property PH2S. Yellow circles show data points where SH2S < 10 while framework types with SH2S > 10 are highlighted using cyan (upside down triangles). Triangles (right side up) represent the total mass of zeolite required to achieve a final

concentration of 90 mole % or more H2S in the adsorbed phase and for removing 10 mmol of H2S from the feed. Black up triangles show framework types that can achieve this purity in a single stage, while magenta down triangles show frameworks that can achieve this purity in 2 stages) shows the binary H2S/CH4 adsorption in the different zeolite frameworks that have S s > 1 and qaisiy?) > 1 mmol/g. The zeolites are sorted by the performance criteria, P s, at_yF = 0.50. As can be seen from FIG. 1, the number of zeolites that meet S s > 1 and qHisiyF) > 1 mmol/g decreases from 353 out of 385 at 50 mole % to 350 at 30 mole %, but to only 232 at 10 mole %. Similarly, zeolites with S s > 10 and qaisiy?) > 1 mmol/g drop quickly with the numbers being 180, 158, and 106 at 50, 30, and 10 mole % H2S, respectively. The number of good zeolite structures drop at lower concentrations, however, their ranking by P s does not change significantly. There is a good correlation between performance at 50 mole % and that at 10 mole % (FIG. 2 - H2S/CH4 binary adsorption at yF = 0.50 vs. yF = 0.10 and at an overall pressure, p = 50 bar and temperature, T = 343 K); the correlation is even better between 30 and 10 mole % (FIG. 3 - H2S/CH4 binary adsorption atyp = 0.30 vs. _yF = 0.10 and at an overall pressure, * = 50 bar and temperature, T= 343 K) and between 50 and 30 mole % (FIG. 4 - H2S/CH4 binary adsorption at yF = 0.50 vs. yF = 0.30 and at an overall pressure, p = 50 bar and temperature, T = 343 K). Additionally, we also carried out simulation of the same system in the Gibbs ensemble at 298 K and 10 bar for a 50:50 starting composition. We find that there is a very good correlation between data at 343 K and at 298 K and that the P s is generally higher at 298 K and 10 bar for all zeolites (FIG. 5 - H2S/CH4 binary adsorption at p = 50 bar and T = 343 K vs. p = 10 bar and T = 298 K. In each case, a gas mixture with 50 mole % H2S was contacted with a zeolite, such that the number of total gas molecules equals the number of silicon atoms in the simulated supercell of the zeolite). In each case, a gas mixture with 50 mole % H2S was contacted with a zeolite, such that the number of total gas molecules equals the number of silicon atoms in the simulated supercell of the zeolite. This gives additional confidence that the screening carried out here at 343 K and 50 bar is sufficient to find good candidate zeolites at varied temperature and pressure conditions.

The number of adsorption stages leads to a proportional increase in the operating costs, because each time one would have to spend energy to desorb similar amounts in each stage and hence a similar heat duty for temperature swing adsorption (TSA) or cost of compression-expansion for pressure swing adsorption (PSA), and hence, it is not economically feasible to use more and more adsorption stages to achieve the desired purity. Shown also in FIG. 1 are data for those zeolites that can achieve the target purity of H2S in the adsorbed phase in at most two adsorption stages. Atj/F = 0.50, most zeolites (332 out of 385) can accomplish the target purity in 2 stages, while only 25 can achieve the target in a single stage. Once again, it can be seen from FIG. 1 how the number of zeolites that can accomplish the target in 1 and 2 steps drops significantly at lower feed compositions. These is due to two factors: (i) decrease in the selectivity at lower concentrations, and (ii) the enrichment that needs to be met from a low concentration feed to the target is higher than that needs to be achieved for a high concentration feed. The number of better performing zeolites is a function of the target purity and will increase as one relaxes the target.

[053] With the performance criteria, P s, the top 4 structures at each composition yield a total of 5 structures (ACO*, AFY*, AHT*, APC*, and SBN*) because of significant overlap of the best structures at all compositions. These structures presently exist only in their aluminophosphate or germanate forms (as indicated by * after the framework code). In reality, these

aluminophosphates may perform slightly differently than the idealized structures that contain only silicon and oxygen atoms. The top structures for H2S/CH4 separation include AFY-0, APC- 1, ACO-0, SBN-0, AHT-1, VFI-1, JST-0, AFS-1, GIS-5, AFS-0, PAU-0, IWV-1, RHO-0, APD- 0, LTL-2, DFT-0, PHI-1, GIS-1, AWO-0, JSN-1, EPI-1, UEI-0, and MEL-1. XXX-0 represent framework types that have been idealized into their all-silica form and DFT-optimized to overcome unreasonably high energy structure. The XXX-(l-6) stand for structures that are not DFT-optimized but, the Al or P atoms are physically replaced by a Si atom at the same position without any energy minimization.

[054] H2S/C2H6 separation Separating H2S from C2H6 is more challenging than separating H2S from CH4 because H2S and C2H6 have critical temperatures that differ by only a factor of 1.2 and hence, similar strength of interactions overall. FIGs. 6A, 6B and 6C (H2S/C2H6 binary adsorption at different feed concentrations of H2S, yF = 0.50 [A], 0.30 [B], and 0.10 [C] and at an overall pressure, p = 50 bar and temperature, T = 343 K. Symbol styles and colors same as in FIG. 1) shows the binary H2S/C2H6 adsorption in the different zeolite frameworks that have S s > 1 and qHisi F) > 1 mmol/g, but sorted in the same order as that for methane in FIGs. 1A, IB and 1C. Similar to the observation for mixture with methane, the performance of most zeolites declines with a decrease in the feed concentration. Only 23 out of the 385 zeolites have a selectivity towards H2S of 10 or more atyp = 0.50, 20 of which make it atyp = 0.30 as well, and only 12 of these have a selectivity over 10 atyp = 0.10. For the H2S/C2H6 system, there is an even better correlation between data at low and high compositions (FIGs. 7, 8 and 9). FIG. 7 shows H2S/C2H6 binary adsorption atyp = 0.50 vs. yp = 0.10 and at an overall pressure, * = 50 bar and temperature, T= 343 K. FIG. 8 shows H2S/C2H6 binary adsorption at yF = 0.30 vs. yF = 0.10 and at an overall pressure, p = 50 bar and temperature, T = 343 K. FIG. 9 shows H2S/C2H6 binary adsorption at yF = 0.50 vs. yF = 0.30 and at an overall pressure, p = 50 bar and temperature, T = 343 K. Similar to mixture with methane, there is also a very good correlation between data at 343 K and 50 bar and that at 298 K and 10 bar (FIG. 10 - H2S/C2H6 binary adsorption at p = 50 bar and T = 343 K vs. p = 10 bar and T = 298 K. In each case, a gas mixture with 50 mole % H2S was contacted with a zeolite, such that the number of total gas molecules equals the number of silicon atoms in the simulated supercell of the zeolite). The better performing zeolite structures for H2S/C2H6 separation range from ones that perform very well in a mixture with methane to those that do not offer very high performance in mixtures with methane. Most of these high selectivity structures achieve the target purity in either one or two adsorption steps.

Beyond high selectivity and reasonable loading, enthalpy of adsorption, which will in turn determine the cost of regeneration of the adsorption bed during every adsorption-desorption cycle, is an important property (FIG. 11- Selectivity (left axis) and AHads (right axis) in top- performing zeolite structures at yF = 0.50, T = 343 K, and p = 50 bar. Selectivity vs. methane: cyan triangles, Selectivity vs. ethane: magenta squares, and AHads (for the H2S/CH4 mixture): green bars).

[056] Real sour gas mixtures may contain several impurities in addition to H2S. Also disclosed herein is an investigation of an extremely sour five-component mixture and a four-component mixture representative of the Lacq gas field were (FIGs. 12 and 13) showing that the top-performing framework types perform the H2S separation for complex mixtures containing impurities beyond alkanes, such as CO2 and N2. FIG. 12 shows five-component adsorption at T= 343 K and p =

50 bar usingis pja H2S:C02:CH4:C2Hg:N2 feed composition with molar ratio of 25 : 10:50: 10:5.

Equilibrium mole fractions in the gas phase (top) and in the adsorbed phase (bottom) for 16 high- performing zeolite structures (the bars are presented in the order given in the legend: H2S, CO2,

CH ₄ , C2H6, N2) FIG. 13 shows four-component adsorption at T = 343 K and p = 24 bar usingis jja

H2S:C02:CH4:C2H ₆ feed composition with molar ratio of 16: 10:70:4. This mixture is

representative of the Lacq gas reservoir and is less sour than the five-component mixture.

Equilibrium mole fractions in the gas phase (top) and in the adsorbed phase (bottom) for 16 high- performing zeolite structures (the bars are presented in the order given in the legend: H2S, CO2, CH ₄ , C ₂ H ₆ ).

[057] With the performance criteria, P s, top 4 structures at each composition are the same (ACO*, APC*, APD*, and SBN*), just a different ordering at different compositions. Unlike for the H2S/CH4 mixture, very few framework types perform well for the separation of H2S/C2H6. The ones that have Sm$ > 10 include SBN-0, APC-1, ACO-0, APD-0, DFT-0, APC-2, AHT-1, ATV- 1, CAS-0, AWO-0, ATV-0, GIS-1, APC-0, CZP-0, EDI-1, JBW-0, RWR-0, LOV-0, JNT-0, ITW-0, VNI-0, RSN-0, and RRO-0. The most interesting structures are the ones that perform well for both the mixtures investigated in this work and these include APC-1, ACO-0, SBN-0, AHT-1, APD-0, DFT-0, GIS-1, and AWO-0.

[058] Further information can be found in M. S. Shah, M. Tsapatsis, and J. I. Siepmann, 'Identifying Optimal Zeolitic Sorbents for Sweetening of Highly Sour Natural Gas,' Angew. Chem. Intl. Ed.2016, 55, 5938; the disclosure of which is incorporated herein by reference thereto.

[059] One skilled in the art will appreciate that the methods described herein can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation. One will also understand that components of the methods depicted and described with regard to the figures and embodiments herein may be

interchangeable.

[060] All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.

[061] As used in this specification and the appended claims, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise.

[062] As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise. The term "and/or" means one or all of the listed elements or a combination of any two or more of the listed elements.

[063] As used herein, "have", "having", "include", "including", "comprise", "comprising" or the like are used in their open ended sense, and generally mean "including, but not limited to". It will be understood that "consisting essentially of, "consisting of, and the like are subsumed in "comprising" and the like. For example, a conductive trace that "comprises" silver may be a conductive trace that "consists of silver or that "consists essentially of silver.

[064] As used herein, "consisting essentially of," as it relates to a composition, apparatus, system, method or the like, means that the components of the composition, apparatus, system, method or the like are limited to the enumerated components and any other components that do not materially affect the basic and novel characteristic(s) of the composition, apparatus, system, method or the like.

[065] The words "preferred" and "preferably" refer to embodiments that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure, including the claims.

[066] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc. or 10 or less includes 10, 9.4, 7.6, 5, 4.3, 2.9, 1.62, 0.3, etc.). Where a range of values is "up to" a particular value, that value is included within the range.

[067] Use of "first," "second," etc. in the description above and the claims that follow is not intended to necessarily indicate that the enumerated number of objects are present. For example, a "second" substrate is merely intended to differentiate from another infusion device (such as a "first" substrate). Use of "first," "second," etc. in the description above and the claims that follow is also not necessarily intended to indicate that one comes earlier in time than the other.