WO2014059132A2

WO2014059132A2 - Membranes including polysiloxane-poly(alkylene oxide) copolymers and methods of using the same

Info

Publication number: WO2014059132A2
Application number: PCT/US2013/064318
Authority: WO
Inventors: Gang Lu; Aaron J. GREINER; Dongchan Ahn; Elizabeth Mcquiston; Kevin A. WIER; Vinita PANDIT; Gary Gibson
Original assignee: Dow Corning Corporation
Priority date: 2012-10-12
Filing date: 2013-10-10
Publication date: 2014-04-17
Also published as: WO2014059132A3

Abstract

The present invention provides membranes including a cured product of a silicone composition. The silicone composition includes a silicone-polyether copolymer having curable silicon-bonded groups. The membrane is either unsupported or supported on a porous substrate. The present invention also provides methods of using the membranes, including methods of using the membranes for separation of gases such as, for example, carbon dioxide from mixtures including carbon dioxide and methane.

Description

MEMBRANES INCLUDING POLYSILOXANE-POLY(ALKYLENE OXIDE) COPOLYMERS AND METHODS OF USING THE SAME

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 61/712,971 entitled "MEMBRANES INCLUDING

POLYSILOXANE-POLY(ALKYLENE OXIDE) COPOLYMERS AND METHODS OF USING THE SAME," filed October 12, 2012, the disclosure of which is incorporated herein in its entirety by reference.

SUMMARY OF THE INVENTION

[0002] The use of membranes to separate gases is an important technique that can be used in many types of procedures. Examples can include recovery of hydrogen gas in ammonia synthesis, recovery of hydrogen in petroleum refining, separation of methane from other components in biogas synthesis, enrichment of air with oxygen for medical or other purposes, removal of water vapor from air or natural gas, removal of carbon dioxide (CO2) from natural gas or biogas, removal of entrained gases from liquids, introduction of water vapor for humidification or moisturization, and carbon-capture applications such as the removal of CO2 from flue gas streams generated by combustion processes.

[0003] In various embodiments, the present invention provides an unsupported membrane. The membrane includes a cured product of a silicone composition. The silicone composition includes a silicone-polyether copolymer. The silicone- polyether copolymer has curable silicon-bonded groups. The unsupported membrane is free-standing.

[0004] In various embodiments, the present invention provides a supported membrane. The membrane includes a cured product of a silicone composition. The silicone composition includes a silicone-polyether copolymer. The silicone- polyether copolymer has curable silicon-bonded groups. The supported membrane includes a porous substrate. The supported membrane is on the porous substrate.

[0005] In various embodiments, the present invention provides a method of separating gas components in a feed gas mixture. The method includes contacting a first side of a membrane with a feed gas mixture. The feed gas mixture includes at least a first gas component and a second gas component. The contacting produces a permeate gas mixture on a second side of the membrane and a retentate gas mixture on the first side of the membrane. The permeate gas mixture is enriched in the first gas component. The retentate gas mixture is depleted in the first gas component. The membrane includes the cured product of a silicone composition. The silicone composition includes a silicone-polyether copolymer having curable silicon-bonded groups.

[0006] Certain embodiments of the present invention have advantages over other membranes and methods of using the same. For example, in some embodiments, the membrane can have a higher selectivity and permeability for particular gas components. For example, the membrane can have a higher CO2/CH4 or CO2/N2 selectivity and a higher CO2 permeability, including as compared to silicone membranes or polyether membranes, including as compared to membranes including non-copolymeric mixtures of silicones and polyethers, and including as compared to membranes including polyether- silicone copolymers not having Si-C linkages. For example, in some embodiments, the membrane can have higher physical strength and a longer lifetime, including as compared to membranes not having chemical crosslinking. For example, in some embodiments, the membrane can have better rheological and oxidative stability. In various embodiments, methods of using the membrane to separate CO2 can separate CO2 with greater efficiency, greater purity, greater speed, or a combination thereof, as compared to methods of separating CO2 using other membranes.

BRIEF DESCRIPTION OF THE FIGURES

[0007] In the drawings, which are not necessarily drawn to scale, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0008] FIG. 1 illustrates ideal selectivity and permeability versus the molar fraction of poly(alkylene oxide)-substituted siloxy-units in various membranes, in accord with various embodiments.

[0009] FIG. 2 illustrates ideal selectivity and permeability versus molar fraction of poly(alkylene oxide)-substituted siloxy-units in various membranes, in accord with various embodiments.

[0010] FIG. 3 illustrates a membrane system, in accord with various embodiments.

[0011] FIG. 4 illustrates a membrane system, in accord with various embodiments. [0012] FIG. 5 illustrates a membrane system including two stages, in accord with various embodiments.

[0013] FIG. 6 illustrates a membrane system including two stages, in accord with various embodiments.

[0014] FIG. 7 illustrates a membrane system including three stages, in accord with various embodiments.

[0015] FIG. 8 illustrates a membrane system including three stages, in accord with various embodiments.

[0016] FIG. 9 illustrates a membrane system including three stages, in accord with various embodiments.

[0017] FIG. 10 illustrates a membrane system including three stages, in accord with various embodiments.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Reference will now be made in detail to certain claims of the disclosed subject matter, examples of which are illustrated in the accompanying drawings. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended to limit the claims to the disclosed subject matter.

[0019] Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of "about 0.1 % to about 5%" or "about 0.1 % to 5%" should be interpreted to include not just about 0.1 % to about 5%, but also the individual values (e.g., 1 %, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1 % to 0.5%, 1 .1 % to 2.2%, 3.3% to 4.4%) within the indicated range.

[0020] In this document, the terms "a," "an," or "the" are used to include one or more than one unless the context clearly dictates otherwise. The term "or" is used to refer to a nonexclusive "or" unless otherwise indicated. In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section. Furthermore, all publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

[0021] In the methods of manufacturing described herein, the steps can be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited.

Furthermore, specified steps can be carried out concurrently unless explicit claim language recites that they be carried out separately. For example, a claimed step of doing X and a claimed step of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.

[0022] The term "about" as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1 % of a stated value or of a stated limit of a range. When a range or a list of sequential values is given, unless otherwise specified any value within the range or any value between the given sequential values is also disclosed. The term "substantially" as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.

[0023] The term "organic group" as used herein refers to but is not limited to any carbon-containing functional group. Examples include acyl, cycloalkyl, aryl, aralkyl, heterocyclyl, heteroaryl, or heteroarylalkyl, linear and/or branched groups such as alkyl groups, fully or partially halogen-substituted haloalkyl groups, alkenyl groups, alkynyl groups, acrylate and methacrylate functional groups; and other organic functional groups such as ether groups, cyanate ester groups, ester groups, carboxylate salt groups, and masked isocyano groups.

[0024] The term "substituted" as used herein refers to an organic group as defined herein or molecule in which one or more hydrogen atoms contained therein are replaced by one or more non-hydrogen atoms. The term "functional group" or "substituent" as used herein refers to a group that can be or is substituted onto a molecule, or onto an organic group. Examples of substituents or functional groups include, but are not limited to, any organic group, a halogen (e.g., F, CI, Br, and I); a sulfur atom in groups such as thiol groups, alkyl and aryl sulfide groups, sulfoxide groups, sulfone groups, sulfonyl groups, and sulfonamide groups; a nitrogen atom in groups such as amines, hydroxylamines, nitriles, nitro groups, N-oxides, hydrazides, azides, and enamines; and other heteroatoms in various other groups.

[0025] The term "alkyl" as used herein refers to straight chain and branched alkyl groups and cycloalkyi groups having from 1 to about 20 carbon atoms, and typically from 1 to 12 carbons or, in some embodiments, from 1 to 8 carbon atoms. Examples of straight chain alkyl groups include those with from 1 to 8 carbon atoms such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n- heptyl, and n-octyl groups. Examples of branched alkyl groups include, but are not limited to, isopropyl, isobutyl, sec-butyl, t-butyl, neopentyl, isopentyl, and 2,2-dimethylpropyl groups. As used herein, the term "alkyl" encompasses all branched chain forms of alkyl. Representative substituted alkyl groups can be substituted one or more times with any functional group, for example, amino, hydroxy, cyano, carboxy, nitro, thio, alkoxy, and halogen groups.

[0026] The term "alkenyl" as used herein refers to straight and branched chain and cyclic alkyl groups as defined herein, except that at least one double bond exists between two carbon atoms. Thus, alkenyl groups have from 2 to about 20 carbon atoms, and typically from 2 to 12 carbons or, in some embodiments, from 2 to 8 carbon atoms. Examples include, but are not limited to

vinyl, -CH=CH(CH₃), -CH=C(CH₃)₂, -C(CH₃)=CH₂, -C(CH₃)=CH(CH₃), -C(CH 2CH₃)=CH2, cyclohexenyl, cyclopentenyl, cyclohexadienyl, butadienyl, pentadienyl, and hexadienyl, among others.

[0027] The term "aryl" as used herein refers to cyclic aromatic hydrocarbons that do not contain heteroatoms in the ring.

[0028] The terms "epoxy-functional" or "epoxy-substituted" as used herein refers to a functional group in which an oxygen atom, the epoxy substituent, is directly attached to two adjacent carbon atoms of a carbon chain or ring system. Examples of epoxy-substituted functional groups include, but are not limited to, 2,3-epoxypropyl, 3,4-epoxybutyl, 4,5-epoxypentyl, 2-glycidoxyethyl, 3- glycidoxypropyl, 4-glycidoxybutyl, 2-(3,4-epoxycylohexyl)ethyl, 3-(3,4- epoxycylohexyl)propyl, 2-(3,4-epoxy-3-methylcylohexyl)-2-methylethyl, 2-(2,3- epoxycylopentyl)ethyl, and 3-(2,3-epoxycylopentyl)propyl.

[0029] The term "hydrocarbyl" or "hydrocarbon" as used herein refers to a functional group or molecule that includes carbon and hydrogen atoms that can be substituted or unsubstituted. The term can also refer to a functional group or molecule that normally includes both carbon and hydrogen atoms but wherein all the hydrogen atoms are substituted with other functional groups. [0030] The term "resin" as used herein refers to polysiloxane material of any viscosity that includes at least one siloxane monomer that is bonded via a Si-O- Si bond to three or four other siloxane monomers. In one example, the polysiloxane material includes T or Q groups, as defined herein.

[0031] The term "number-average molecular weight" as used herein refers to the ordinary arithmetic mean of the molecular weight of individual molecules in a sample. It is defined as the total weight of all molecules in a sample divided by the total number of molecules in the sample. The number average molecular weight (M_n) is equal to∑Mjnj /∑nj, where n; is the number of molecules of molecular weight Mj. The number average molecular weight can be experimentally measured by a variety of well-known methods including gel permeation chromatography, spectroscopic end group analysis, and osmometry. If unspecified, molecular weights of polymers given herein are number-average molecular weights.

[0032] The term "weight-average molecular weight" as used herein refers (M_w), which is equal to IMj^rij /∑Mjnj , where nj is the number of molecules of molecular weight Mj. In various examples, the weight average molecular weight can be determined using light scattering, small angle neutron scattering, X-ray scattering, and sedimentation velocity.

[0033] The term "radiation" as used herein refers to energetic particles travelling through a medium or space. Examples of radiation are visible light, infrared light, microwaves, radio waves, very low frequency waves, extremely low frequency waves, thermal radiation (heat), and black-body radiation.

[0034] The term "cure" as used herein refers to exposing to radiation in any form, heating, or allowing to undergo a physical or chemical reaction that results in hardening or an increase in viscosity.

[0035] The term "pore" as used herein refers to a depression, slit, or hole of any size or shape in a solid object. A pore can run all the way through an object or partially through the object. A pore can intersect other pores.

[0036] The term "free-standing" or "unsupported" as used herein refers to a membrane with the majority of the surface area on each of the two major sides of the membrane not contacting a substrate, whether the substrate is porous or not. In some embodiments, a membrane that is "free-standing" or

"unsupported" can be 100% not supported on both major sides. A membrane that is "free-standing" or "unsupported" can be supported at the edges or at the minority (e.g. less than about 50%) of the surface area on either or both major sides of the membrane.

[0037] The term "supported" as used herein refers to a membrane with the majority of the surface area on at least one of the two major sides contacting a substrate, whether the substrate is porous or not. In some embodiments, a membrane that is "supported" can be 100% supported on at least one side. A membrane that is "supported" can be supported at any suitable location at the majority (e.g. more than about 50%) of the surface area on either or both major sides of the membrane.

[0038] The term "enrich" as used herein refers to increasing in quantity or concentration, such as of a liquid, gas, or solute. For example, a mixture of gases A and B can be enriched in gas A if the concentration or quantity of gas A is increased, for example by selective permeation of gas A through a membrane to add gas A to the mixture, or for example by selective permeation of gas B through a membrane to take gas B away from the mixture. A permeate or retentate on a second side of a membrane can be enriched in a particular gas component as compared to the gas mixture that contacted the first side of the membrane.

[0039] The term "deplete" as used herein refers to decreasing in quantity or concentration, such as of a liquid, gas, or solute. For example, a mixture of gases A and B can be depleted in gas B if the concentration or quantity of gas B is decreased, for example by selective permeation of gas B through a membrane to take gas B away from the mixture, or for example by selective permeation of gas A through a membrane to add gas A to the mixture. A permeate or retentate on a second side of a membrane can be depleted in in a particular gas component as compared to the gas mixture that contacted the first side of the membrane.

[0040] The term "solvent" as used herein refers to a liquid that can dissolve a solid, liquid, or gas. Nonlimiting examples of solvents are silicones, organic compounds, water, alcohols, ionic liquids, and supercritical fluids.

[0041] The term "silicate" as used herein refers to any silicon-containing compound wherein the silicon atom has four bonds to oxygen, wherein at least one of the oxygen atoms bound to the silicon atom is ionic, such as any salt of a silicic acid. The counterion to the oxygen ion can be any other suitable ion or ions. An oxygen atom can be substituted with other silicon atoms, allowing for a polymer structure. One or more oxygen atoms can be double-bonded to the silicon atom; therefore, a silicate molecule can include a silicon atom with 2, 3, or 4 oxygen atoms. Examples of silicates include aluminum silicate. Zeolites are one example of materials that can include aluminum silicate. A silicate can be in the form of a salt, ion, or a neutral compound.

[0042] The term "selectivity" or "ideal selectivity" as used herein refers to the ratio of permeability or permeance of the faster permeating gas over the slower permeating gas, measured at room temperature.

[0043] The term "permeability" as used herein refers to the permeability coefficient (P_x) of substance X through a membrane, where q_mx = P_x ^* A ^* Δρ_χ

^* (1 /δ), where q_mx is the volumetric flow rate of substance X through the membrane, A is the surface area of one major side of the membrane through which substance X flows, Δρ_χ is the pressure difference of the partial pressure of substance X across the membrane, and δ is the thickness of the membrane. P_x can also be expressed as V-5/(A-t-Ap), wherein P_x is the permeability for a gas X in the membrane, V is the volume of gas X which permeates through the membrane, δ is the thickness of the membrane, A is the area of the membrane, t is time, Δρ is the pressure difference of the gas X at the retente and permeate side.

[0044] The term "permeance" as used herein refers to the normalized permeability (M_x) of substance X through a membrane, wherein M_x = Ρ_χ/ δ = V/(A-t-Ap), wherein P_x is the permeability for a gas X in the membrane, V is the volume of gas X which permeates through the membrane, δ is the thickness of the membrane, A is the area of the membrane, t is time, Δρ is the pressure difference of the gas X at the retente and permeate side.

[0045] The term "Barrer" or "Barrers" as used herein refers to a unit of permeability, wherein 1 Barrer = 10^"^ (cm³ gas) cm cm^-2 s^~1 mmHg^"'' , or 10^"

^{1 0} (cm³ gas) cm cm^-2 s^~1 cm Hg^~1 , where "cm³ gas" represents the quantity of the gas that would take up one cubic centimeter at standard temperature and pressure.

[0046] The term "total surface area" as used herein with respect to membranes refers to the total surface area of the side of the membrane exposed to the feed gas mixture.

[0047] The term "air" as used herein refers to a mixture of gases with a composition approximately identical to the native composition of gases taken from the atmosphere, generally at ground level. In some examples, air is taken from the ambient surroundings. Air has a composition that includes approximately 78% nitrogen, 21 % oxygen, 1 % argon, and 0.04% carbon dioxide, as well as small amounts of other gases.

[0048] The term "room temperature" as used herein refers to ambient temperature, which can be, for example, between about 15 °C and about 28 °C.

[0049] The term "coating" as used herein refers to a continuous or

discontinuous layer of material on the coated surface, wherein the layer of material can penetrate the surface and can fill areas such as pores, wherein the layer of material can have any three-dimensional shape, including a flat or curved plane. In one example, a coating can be formed on one or more surfaces, any of which may be porous or nonporous, by immersion in a bath of coating material.

[0050] The term "surface" as used herein refers to a boundary or side of an object, wherein the boundary or side can have any perimeter shape and can have any three-dimensional shape, including flat, curved, or angular, wherein the boundary or side can be continuous or discontinuous. While the term surface generally refers to the outermost boundary of an object with no implied depth, when the term 'pores' is used in reference to a surface, it refers to both the surface opening and the depth to which the pores extend beneath the surface into the substrate.

[0051] The term "mil" as used herein refers to a thousandth of an inch, such that 1 mil = 0.001 inch.

[0052] As used herein, "degree of polymerization" is the number of repeating units in a polymer.

[0053] As used herein, the term "polymer" refers to a molecule having at least one repeating unit. In some embodiments, a terminal repeating unit in a homopolymer can have a functional group at its end bridging back to an interior portion of the unit, but still be considered the same repeating unit as an identical repeating unit not having such a bridge. For example, the functional group 2- (oxiran-2-ylmethoxy)e

can be considered a homopolymer having two ethylene oxide repeating units, one ethylene oxide unit being substituted at the oxygen atom (e.g., the end of the repeating unit) and the carbon atom adjacent thereto (e.g., an interior portion of the unit) by a methylene unit (e.g, bridge), forming an oxirane group.

[0054] The term "copolymer" as used herein refers to a polymer that includes at least two different monomers. A copolymer can include any suitable number of monomers. A copolymer can be, for example, alternating, periodic, graft, statistical, random, or block.

[0055] The term "graft copolymer" as used herein refers to a branched copolymer wherein the side chains are structurally distinct from the main chain.

[0056] The term "block copolymer" as used herein refers to a copolymer wherein each of the different monomers are present at least in part as homopolymers within the copolymer.

[0057] As used herein, "active H, wt%" refers to the weight percent of hydrogen atoms included in Si-H bonds in the molecule.

Silicone Composition

[0058] In various embodiments, the present invention provides a membrane including a cured product of a silicone composition. The silicone composition includes at least one silicone-polyether copolymer having curable silicon- bonded groups. The silicone-polyether copolymer can be present in any suitable wt% in the curable silicone composition, for example, about 1 %, 5%, 1 0%, 20%, 40%, 60%, 80%, 90%, 95%, or about 99 wt%. In addition to the at least one suitable silicone-polyether copolymer, the silicone composition can include any suitable additional ingredients, including any suitable organic or inorganic component, including components that do not include silicon, including components that do not include a polysiloxane structure. In some examples, the cured product of the silicone composition includes a polysiloxane. Silicone-Polyether Copolymer

[0059] The silicone composition includes at least one silicone-polyether copolymer. The copolymer can be any suitable copolymer having siloxane repeating units and alkylene oxide repeating units. The silicone-polyether copolymer has curable silicon-bonded groups. The curable silicon-bonded groups can be any suitable silicon-bonded groups that allow the silicone composition to be cured.

[0060] The silicone-polyether copolymer can be a linear block copolymer. The liner block copolymer can be any suitable linear block copolymer. For example, the linear block copolymer can be a diblock copolymer, a triblock copolymer, a tetrablock copolymer, or have any suitable number of blocks. In some examples, the luinear block copolymer can be the hydrosilylation product of an Si-H terminated polydialkylsiloxane, such as polydimethylsiloxane, and an alkene-terminated polyalkylene oxide, such as allyl-terminated polyethylene glycol. In some examples, the linear block copolymer can have blocks including polydimethylsiloxane and polyethylene oxide. In some examples, the linear block copolymer is terminated in curable silicon-bonded groups, such as Si-H groups, or silicon-bonded epoxide-containing groups.

[0061] In some embodiments, the silicone-polyether copolymer is a linear block copolymer having the formula X[R¹ ₂SiO(R¹ ₂SiO)_mR¹2Si-R²-0(C_nH_2nO)p-R²- ]q(R¹2SiO)_rR¹2SiX. In the preceding formulas, each R¹ is independently C-| - C-| o hydrocarbyl or C-| -C-| Q halogen-substituted hydrocarbyl, such as methyl, ethyl, or isopropyl. Each R² is C-| -C-| Q hydrocarbylene, such as methylene, ethylene, propylene, or butylene, optionally substituted with a C-| -C-|o hydrocarbyl group. Each X is independently a curable silicon-bonded group. Each m is about 0 to 100, or about 0 to 35, or about 0 to 21 . The variable n is about 1 to 8, or about 1 to 6, or about 2 to 4, or about 2 to 3; p is about 1 to 100, 1 to 35, or about 1 to 25, or about 10-25. The variable q is about 1 to 1 000, 1 to 1 00, 2 to 50, or about 4 to 22. The variable r can equal m, or is about 0 to 100, 0 to 35, or about 0 to 21 .

[0062] In some embodiments, the silicone-polyether block copolymer can have any of the following structures, having R = H or CH3 :

[0063] The silicon-polymer copolymer can be a graft copolymer. The graft copolymer can be any suitable graft copolymer. The main and side chains of the graft copolymer can independently be a homopolymer or a copolymer. In some embodiments, the graft copolymer can include homopolymeric side chains including monomer that is not included in the main chain. For example, the graft copolymer can be a hydrosilylation product of a polysiloxane including at least some hydrogenmethylsiloxane groups and an alkene-terminated polyalkylene oxide, such as a polyalkylene oxide-grafted polysiloxane. In some examples, the graft copolymer can have a polysiloxane backbone and polyalkylene oxide side chains. In some embodiments, the polysiloxane- polyether graft copolymer can have Si-H groups or epoxide groups, to allow curing of the copolymer. In some examples, epoxide groups can be terminal epoxide

[0064] In some embodiments, the graft copolymer can include

about 0 to 99, 1 to 66, or about 1 to 32 mol% of siloxy units having the formula I,

R¹2Si02/2- The graft copolymer can include about 1 to 100, 1 to 97, 1 to 95,

14 to 95, or about 15 to 70 mol% of siloxy units having the formula II,

R¹ ESiC>2/2- The graft copolymer can include about 0 to 80, 0 to 60, or about 0 to 40 mol% of siloxy units having the formula III, HR^ SiC>2/2- The graft copolymer can include about 0 to 5, 0 to 10, or about 0 to 66 mol% of siloxy units having the formula IV, RI 3S1O-1 /2. In the preceding formulas, each R^ is independently C-| -C-| Q hydrocarbyl or C-| -C-| Q halogen-substituted hydrocarbyl ; each E is selected from -R²0(C_nH2_nO)pR³ and formula V:

wherein R^ is C-| -C-| Q hydrocarbylene, R^ is selected from R^ , -H, and a curable group that makes E a silicon-bonded curable group, n is about 1 to 8, or about 1 to 6, or about 2 to 4. The variable p is about p is about 1 to 100, 1 to 35, or about 1 to 25, or about 10-25.

[0065] In some examples, the silicone-polyether graft copolymer can have any of the following structures:

having n = about 1 , 2, 4, 6, 8, 10, 12, 15, 20, 25, 50, 75, 100, 200, or 300, such as about 0, p = about 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10, such as about 6.5, and x+y+z = about 50, 100, 150, 200, 250, 300, 350, or 400, such as about 220,

having n = about 1,2, 4, 6,8, 10, 12, 15,20,25,50,75, 100, 200, or 300, such as about 0, p = about 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10, such as about 6.5, and x+y+z = about 50, 100, 150, 200, 250, 300, 350, or 400 such as about 220,

having x = about 1 , 2, 4, 6, 8, 10, 12, 15,20, 25, 50, 75, 100, 200, or 300, such as about 0, and n = y+z = about 50, 100, 150, 200, 250, 300, 350, or 400 such as about 220, or

wherein m and n are polyhydrogenmethylsiloxane rings having m or n number of polysiloxane groups, m and n independently about 3, 4, 5, 6, or 7, a and b = about 0 or greater than about 0, such as 1 , 2, 3, 4, 5, 6, or 7, and p = 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 50, 100, 150, or about 200, or other dumbbell-shaped silicone-polyether graft copolymers as described in WO2004058857, US Patent No. 7,432,338, or WO2003093349. In dumbbell-shaped silicone-polyether graft copolymers such as shown in the above structure, including in the Examples section herein, each polysiloxane ring need not have hydrogen-substituted siloxy units therein, so long as the total active mol% or wt% Si-H is present overall in the molecule; each polysiloxane ring can have about 0 to m or n hydrogen-substituted siloxy units, so long as the specified number or proportion of other types of substituted siloxy units are present (e.g. diakyl-substituted siloxy units or polyether-substituted siloxy units). Curable Silicon-Bonded Groups

[0066] The silicone composition includes a silicone-polyether copolymer having curable silicon-bonded groups. The curable silicon-bonded groups can be any suitable silicon-bonded groups that allow the composition including the silicone- polyether copolymer to be cured via any suitable curing method. For example, curing methods can include hydrosilylation curing, condensation curing, free- radical curing, amine-epoxy curing, radiation curing, cooling, or any combination thereof. For example, the curable silicon-bonded groups can independently be a hydrogen atom, hydroxy group, hydrolysable group, radiation-curable group, free radical-curable group, epoxide-containing group, aliphatic unsaturated carbon-carbon bond-containing group, or a combination thereof. The silicone composition can include a copolymer with properties that allow one curing method, or a copolymer that allows for different curing methods. In some embodiments, the silicone composition can include features that allow it to be cured via one curing method on one copolymer and features that allow it to be curing via the same or different curing methods on a different molecule. For example, the silicone-polymer can have Si-H groups, and another compound can have aliphatic unsaturated carbon-carbon bonds, which can be linked together via hydrosilylation curing. In another example, the silicone-polymer can have epoxy groups, and another compound can have an amine, which can be linked together via amine/epoxy curing. A silicone composition that is curable via a particular method can include other compounds curable via the particular method in addition to silicone-polyether copolymers.

Cross-Linking Agent [0067] In various embodiments, the silicone composition includes a cross- linking agent having an average of at least two aliphatic unsaturated carbon- carbon bonds per molecule. In some examples, the cross-linking agent can be (i) at least one organic compound having an average of at least two aliphatic unsaturated carbon-carbon bonds per molecule. In some examples, the cross- linking agent can be (ii) at least one organosilane having an average of at least two silicon-bonded aliphatic unsaturated carbon-carbon bond-containing groups per molecule. In some examples, the cross-linking agent can be (iii) at least one silicone resin having an average of at least two silicon-bonded aliphatic unsaturated carbon-carbon bond-containing groups per molecule. In some examples, the cross-linking agent can be (iv) at least one organosiloxane having an average of at least two silicon-bonded aliphatic unsaturated carbon- carbon bond-containing groups per molecule. In some examples, the cross- linking agent can be (v) a mixture comprising at least two of (i), (ii), (iii), and (iv). Cross-Linking Agent, (i), Organic Compound

[0068] In some embodiments, the silicone composition can include (i) at least one organic compound having an average of at least two aliphatic unsaturated carbon-carbon bonds per molecule. The aliphatic unsaturated carbon-carbon bonds can be alkenyl groups or alkynyl groups, for example. The organic compound can be a single organic compound or a mixture including two or more different organic compounds.

[0069] The organic compound can be any organic compound containing at least two aliphatic unsaturated carbon-carbon bonds per molecule, provided the compound does not prevent the organohydrogenpolysiloxane of the silicone composition from curing to form a cured product. The organic compound can be a diene, a triene, or a polyene. Also, the unsaturated compound can have a linear, branched, or cyclic structure. Further, in acyclic organic compounds, the unsaturated carbon-carbon bonds can be located at terminal, pendant, or at both terminal and pendant positions. In some examples, the organic compound can include any alkyldiene having terminal unsaturated groups, such as 1 ,4- butadiene, 1 ,6-hexadiene, 1 ,8-octadiene, and internally unsaturated variants thereof.

[0070] The organic compound can have a liquid or solid state at room temperature. The organic compound is typically soluble in the silicone composition. In some embodiments, the organic compound has a normal boiling point greater than the cure temperature of the

organohydrogenpolysiloxane, which can help prevent removal of appreciable amounts of the organic compound via volatilization during cure. The organic compound can have a molecular weight less than 500, or less than 400, or less than 300.

[0071] In one example, the organic compound having an average of at least two aliphatic unsaturated carbon-carbon bonds per molecule is a polyether having at least two aliphatic unsaturated carbon-carbon bonds per molecule. The polyether can be any polyalkylene oxide having at least two aliphatic unsaturated carbon-carbon bonds per molecule, or a halogen-substituted variant thereof.

Cross-Linking Agent, (ii), (iii), and (iv), Silicon-Containing Compound

[0072] In some embodiments, the silicone composition can include (ii) at least one organosilane having an average of at least two silicon-bonded aliphatic unsaturated carbon-carbon bond-containing groups per molecule; (iii) at least one silicone resin having an average of at least two silicon-bonded aliphatic unsaturated carbon-carbon bond-containing groups per molecule; or (iv) at least one organosiloxane having an average of at least two silicon-bonded aliphatic unsaturated carbon-carbon bond-containing groups per molecule.

[0073] The curable silicone composition of the present invention can include an organosilicon compound having an average of at least two aliphatic unsaturated carbon-carbon bonds per molecule. The organosilicon compound can be any suitable organosilicon compound having an average of at least two unsaturated carbon-carbon bonds per molecule, wherein each of the two unsaturated carbon-carbon bonds is independently or together part of a silicon-bonded group. In some embodiments, the organosilicon compound can have an average of at least two or three silicon-bonded aliphatic unsaturated carbon- carbon bond-containing groups per molecule. The organosilicone compound can be present in the uncured silicone composition in an amount sufficient to allow at least partial curing of the silicone composition.

[0074] The organosilicon compound can be an organosilane or an

organosiloxane. The organosilane can have any suitable number of silane groups, and the organosiloxane can be a disiloxane, trisiloxane, or polysiloxane. The structure of the organosilicon compound can be linear, branched, cyclic, or resinous. Cyclosilanes and cyclosiloxanes can have from 3 to 12 silicon atoms, alternatively from 3 to 10 silicon atoms, alternatively from 3 to 5 silicon atoms. In acyclic polysilanes and polysiloxanes, the aliphatic unsaturated carbon- carbon bonds can be located at terminal, pendant, or at both terminal and pendant positions. [0075] Examples of organosilanes suitable for use as component (ii) include, but are not limited to, silanes having the following formulae: Vi4Si, PhSiVi3,

MeSiVi₃, PhMeSiVi₂, Ph₂SiVi₂, and PhSi(CH₂CH=CH₂)3, where Me is methyl, Ph is phenyl, and Vi is vinyl.

[0076] Examples of aliphatic unsaturated carbon-carbon bond-containing groups can include alkenyl groups such as vinyl, allyl, butenyl, and hexenyl; alkynyl groups such as ethynyl, propynyl, and butynyl; or acrylate-functional groups such as acryloyloxyalkyl or methacryloyloxypropyl.

[0077] In some embodiments, Component (iii) or (iv) is an organopolysiloxane of the formula

(e) Ry₃SiO(Ry₂SiO)_a(RyR²SiO)_pSiRy₃,

(f) Ry₂R⁴SiO(Ry₂SiO)_x(RyR⁴SiO)₅SiRy₂R⁴, or combinations thereof.

[0078] In formula (e), a has an average value of 0 to 2000, and β has an average value of 1 to 2000. Each Ry is independently halogen, hydrogen, or an organic group such as acrylate; alkyl; alkoxy; halogenated hydrocarbon; alkenyl; alkynyl; aryl; heteroaryl; and cyanoalkyl. Each R² is independently an unsaturated monovalent aliphatic carbon-carbon bond-containing group, as described herein.

[0079] In formula (f), χ has an average value of 0 to 2000, and δ has an average value of 1 to 2000. Each Ry is independently as defined above, and

R⁴ is independently the same as defined for R² above.

[0080] Examples of organopolysiloxanes having an average of at least two aliphatic unsaturated carbon-carbon bonds per molecule can include compounds having the average unit formula

(R1 R²R3Si0₁ /₂)_a(R⁴R5Si0₂/₂)_b(R6Si0₃/₂)_c(Si04/₂)_d (I) wherein each of R^ , R², R^, R⁴, R5 and R^ is an organic group independently selected from Ry as defined herein, 0<a<0.95, 0<b<1 , 0<c<1 , 0<d<0.95, a+b+c+d=1.

Membrane

[0081 ] In various embodiments, the present invention provides a membrane that includes a cured product of the silicone composition as described herein. In another embodiment, the present invention provides a method of forming a membrane. The membrane can be formed on at least one surface of a substrate. Forming the membrane can include applying the composition that forms the membrane to at least one surface of the substrate, then curing the composition to form the membrane. In some embodiments, the curing process of the composition can begin before, during, or after application of the composition to the surface. The composition that forms the membrane can be applied using conventional coating techniques, for example, immersion coating, spin coating, dipping, spraying, brushing, roll coating, extrusion, screen-printing, pad printing, or inkjet printing. Curing the composition that forms the membrane can include any one or combination of suitable curing method described herein.

[0082] The membrane of the present invention can have any suitable thickness. In some examples, the membrane has a thickness of from about 1 μιτι to about 20 μιτι, about 0.1 μιτι to about 200 μιτι, or about 0.01 μιτι to about 2000 μιτι.

[0083] The membrane of the present invention can be selectively permeable to one substance over another. In some examples, the membrane has a

C0₂/CH₄ selectivity of at least about 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 15, 17, 19, 21 , 23, 25, 27, 29, 31 , 33, 35, 37, or at least about 40. In some

embodiments, the membrane has a CO2 permeation coefficient of at least about 10 Barrers, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 240, 280, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1600, 1800, or at least about 2000 Barrers. In some embodiments, the membrane has a CO2 permeance of at least about 0.01 -4000 GPU, 1000-2000 GPU, 1300-1600 GPU, 0.01 -1000 GPU, 0.1 -100, 1 -30, 2-1 5, or about 4-8 GPU. In some embodiments, the membrane has a CH4 permeation coefficient of at least about 0.001 Barrer,

0.01 , 0.1 , 1 , 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 30, 40, 50, 60, 70, 80, 90, or at least about 100 Barrer. Permeability and permeance can be measured by any suitable method, such as the methods used in the Examples.

[0084] The membrane of the present invention can have any suitable shape. In some examples, the membrane of the present invention is a plate-and-frame membrane, a spiral wound membrane, a tubular membrane, a capillary fiber membrane or a hollow fiber membrane. The membrane can be a continuous or discontinuous layer of material.

[0085] In some embodiments of the present invention, the membrane is supported on a porous or highly permeable non-porous substrate. The substrate can be any suitable substrate, such as a porous or nonporous substrate, a fiber or hollow fiber, a polymer, a water-soluble polymer, and can any suitable size or shape. A supported membrane has the majority of the surface area of at least one of the two major sides of the membrane contacting a porous or highly permeable non-porous substrate. A supported membrane on a porous substrate can be referred to as a composite membrane, where the membrane is a composite of the membrane and the porous substrate. The porous substrate on which the supported membrane is located can allow gases or liquids to pass through the pores and to reach the membrane. The supported membrane can be attached (e.g., adhered) to the porous substrate. The supported membrane can be in contact with the substrate without being adhered. The porous substrate can be partially integrated, fully integrated, or not integrated into the membrane.

[0086] The porous substrate can be any suitable porous material known to one of skill in the art, in any shape. For example, the substrate can be a filter. The porous substrate can be woven or non-woven. The porous substrate can be a frit, a porous sheet, or a porous hollow fiber. The porous substrate can be glass, ceramic, alumina, or a porous polymer. For example, the at least one surface can be flat, curved, or any combination thereof. The surface can have any perimeter shape. The porous substrate can have any number of surfaces, and can be any three-dimensional shape. Examples of three- dimensional shapes include cubes, spheres, cones, and planar sections thereof with any thickness, including variable thicknesses. The porous substrate or highly permeable non-porous substrate can be smooth, be corrugated or patterned, or have any amount of surface roughness. The porous substrate can have any number of pores, and the pores can be of any size, depth, shape, and distribution. In one example, the porous substrate has a pore size of about 0.2 nm to about 500 μιτι. The at least one surface can have any number of pores. In some examples, the pore size distribution may be asymmetric across the thickness of the porous sheet, film or fiber. In some examples, the porous substrate has a thickness of about 0.2 nm to about 500 μιτι, or about 1 -100 μιτι, or about 5-60 μιτι, or about 10-40 μιτι.

[0087] Suitable examples of porous substrates include porous polymeric films, fibers or hollow fibers, or porous polymers or any suitable shape or form. Examples of polymers that can form porous polymers suitable for use as a porous substrate in embodiments of the present invention include those disclosed in U.S. Patent No. 7,858,197. For example, suitable polymers include polyethylene, polypropylene, polysulfones, polyethersulfones, polyamides, polyether ether ketone (PEEK), polyarylates, polyaramides, polyethers, polyarylethers, polyimides, polyetherimides, polyphthalamides, polyesters, polyacrylates, polymethacrylates, cellulose acetate, polycarbonates, polyacrylonitrile, polytetrafluoroethylene and other fluorinated polymers, polyvinylalcohol, polyvinylacetate, syndiotactic or amorphous polystyrene, Kevlar™ and other liquid crystalline polymers, epoxy resins, phenolic resins, polydimethylsiloxane elastomers, silicone resins, fluorosilicone elastomers, fluorosilicone resins, polyurethanes, and copolymers, blends or derivatives thereof. Suitable porous substrates can include, for example, porous glass, various forms and crystal forms of porous metals, ceramics and alloys, including porous alumina, zirconia, titania, and steel.

[0088] In some embodiments of the present invention, the membrane is unsupported, also referred to as free-standing. The majority of the surface area on each of the two major sides of a membrane that is free-standing is not contacting a substrate, whether the substrate is porous or not. In some embodiments, a membrane that is free-standing can be 100% unsupported. A membrane that is free-standing can be supported at the edges or at the minority (e.g., less than 50%) of the surface area on either or both major sides of the membrane. A free-standing membrane can have any suitable shape, regardless of the percent of the free-standing membrane that is supported. Examples of suitable shapes for free-standing membranes include, for example, squares, rectangles, circles, tubes, cubes, spheres, cones, cylinders, and planar sections thereof, with any thickness, including variable thicknesses. The membrane can be a free-standing hollow fiber.

Method of Separating Gas Components

[0089] The present invention also provides a method of separating gas components or water vapor in a feed gas mixture by use of the membrane described herein. The method includes contacting a first side of a membrane with a feed gas mixture to produce a permeate gas mixture on a second side of the membrane and a retentate gas mixture on the first side of the membrane. The permeate gas mixture is enriched in the first gas component. The retentate gas mixture is depleted in the first gas component. The membrane can include any suitable membrane as described herein.

[0090] In some embodiments, the pressure on either side of the membrane can be about the same. In other embodiments, there can be a pressure differential between one side of the membrane and the other side of the membrane. For example, the pressure on the retentate side of the membrane can be higher than the pressure on the permeate side of the membrane. In other examples, the pressure on the permeate side of the membrane can be higher than the pressure on the retentate side of the membrane. [0091] The feed gas mixture can include any mixture of gases. For example, the feed gas mixture can include hydrogen, carbon dioxide, nitrogen, ammonia, methane, water vapor, hydrogen sulfide, or any combination thereof. The feed gas can include any gas known to one of skill in the art. The membrane can be selectively permeable to any one gas in the feed gas, or to any of several gases in the feed gas. The membrane can be selectively permeable to all but any one gas in the feed gas. In some examples, the permeate gas mixture includes carbon dioxide and the feed gas mixture includes at least one of nitrogen and methane. In some examples, the permeate gas mixture includes carbon dioxide and the feed gas mixture includes methane.

[0092] Any number of membranes can be used to accomplish the separation. For example, one membrane can be used. The membranes can be manufactured as flat sheets or as fibers and can be packaged into any suitable variety of modules including hollow fibers, sheets or arrays of hollow fibers or sheets. The module can be a hollow fiber module, a spiral wound module, a plate-and-frame module, a tubular module and a capillary fiber module.

Multiple-Stage Separation

[0093] In various embodiments, the present invention provides a method of separating a gas mixture using a multiple-stage membrane system, wherein at least one of the membranes therein includes a cured product of a silicone composition, wherein the silicone composition includes a silicone-polyether copolymer having curable silicon-bonded groups. The silicone-polyether copolymer can be any silicone-polyether copolymer described herein. The multiple-stage membrane system can have any number of stages, e.g. 2, 3, 4, 5, 6, 7, or more. Each stage can include contacting one or more membranes with at least one of the retentate and the permeate from a previous stage. The multiple-stage membrane system can be arranged in any suitable configuration. The multiple-stage membrane system can be used to separate any suitable gas mixture. The output streams of the system can be used in any suitable way. For example, the output streams can be at least one of sold, stored, liquefied, recycled, burned, and converted into at least one of heat and electrical energy. The multiple-stage membrane separation system can include any combination of feedback and feedforward arrangements, such that any suitable part of any suitable retentate or permeate stream of any stage of the system can be fed back to be recombined with a feed stream for a particular stage or fed forward to be combined with any particular permeate or retentate stream. Such feedback and feedforward arrangements and flow rates can be suitably adjusted to provide a desired composition and flow rate of particular output streams of the system.

[0094] In some examples, the multiple-stage membrane system can be used to separate carbon dioxide from a gas mixture. In some embodiments, the gas mixture can be nitrogen and methane. In some examples, the gas mixture can be natural gas (naturally occurring hydrocarbon gas mixture including at least methane and carbon dioxide) or biogas (e.g. gas produced by the breakdown of organic matter in the substantial absence of oxygen). In some embodiments, the gas mixture can be a mixture including carbon dioxide and methane.

[0095] The multiple-stage separation of a gas mixture including carbon dioxide and methane can generate a methane stream that is predominantly methane and can be about 80% methane, 90%, 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.2%, 99.4%, 99.6%, 99.8%, 99.9%, or about 100% methane, wherein gas stream percent compositions are given in v/v% unless otherwise indicated. In some examples, the methane stream is about 90%- 1 00% methane, or about 95%-99% methane, or about 97%-99% methane, or about 98% methane.

[0096] The multiple-stage membrane separation system can include one or more compressors or vacuum pumps located at suitable locations in the system. The compressors or vacuum pumps can be used to maintain suitable pressure differentials across each of the membranes, which can be configured to obtain the desired mixture of separation speed and efficiency. The pressure differential can be the difference between the total feed pressure and the total permeate pressure, or the difference between the total retentate pressure and the total permeate pressure. The compressor or vacuum pump can be any suitable compressor or vacuum pump. For example, the feed gas mixture can be compressed prior to entering the first stage. In another example, a permeate or retentate stream can be compressed prior to entering a second or third stage. The multi-stage membrane system can include any suitable number and configuration of compressors or vacuum pumps. The compressors or vacuum pumps can maintain a pressure differential across a particular membrane of about 0.1 bar, or about 0.5, 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 50, or about 100 bar. In some examples, the compressors or vacuum pumps maintain a pressure differential across a particular membrane of about 0.1 -1 bar, 1 -10 bar, or about 1 0-50 bar.

[0097] Each membrane stage can independently have any suitable amount of membrane surface area, provided by one membrane or by multiple membranes. For example, the surface area of a stage can be about 1 m², 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 300, 400, 500, 750, 1000, 1500, 2000,

3000, 4000, or about 5000 m².

[0098] The multiple-stage membrane separation system can include one or more valves located at suitable locations in the system. The valves can be used to adjust the flow rate or the pressure, or to stop the flow into a particular stage. For a multiple-stage membrane system that includes mixing various streams, suitable valve arrangements can be used to adjust the composition of the resulting gas mixture. The valve can be any suitable type of valve. For example, the valve can be manually operated or controlled electrically or pneumatically. The valves can be connected to a control system that monitors at least one of the composition and flow rate or pressure of various steams and adjusts the state of the valve accordingly.

[0099] When used to separate a gas mixture including carbon dioxide and methane, in addition to the methane stream, the multiple-stage membrane system also generates one or more additional gas streams. The one or more additional gas streams can be any suitable gas streams. In some examples, one or more of the one or more additional gas streams can form a combustible gas mixture. The combustible gas mixture can be any suitable combustible gas mixture. For example, the combustible gas mixture can be suitable for combustion in a device designed to burn gases. In some examples, the combustible gas mixture can be used in generator, such as a gas turbine generator, for example a gas turbine generator that creates electricity, heat, or a combined heat and power gas turbine generator. The combustible gas mixture can be formed from any suitable combination of output streams and input streams of the multiple-stage membrane system, including in some

embodiments fractions of various output and input streams. The mixture of various streams can be adjusted to maintain a desired gas composition in at least one of the combustible stream and the methane stream. In some examples, the combustible gas mixture includes 20%, 21 %, 22%, 23%, 24%, 25% methane, 26%, 27%, 28%, 29%, 30%, 31 %, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 45%, 50%, 60%, 70%, 80%, 90%, or about 100% methane. In some examples, the combustible gas mixture includes about 20- 1 00% methane, about 20-60% methane, about 20-40% methane, or about 30% methane. In some examples, the combustible gas mixture includes at least about 20% methane, at least about 30%, 35%, 40%, and at least about 45% methane. [00100] The multiple-stage membrane separation system can have low slip, for example low methane slip. For example, when used to separate a feed gas mixture including carbon dioxide and methane, the total amount of

uncombusted methane (e.g. not burned in a gas turbine) that exits the system in streams other than the methane stream can be low, such as less than about 1 0% of the methane present in the feed gas mixture, or less than about 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2.5%, 2%, 1 .8%, 1 .6%, 1 .4%, 1 .2%, 1 %, 0.8%, 0.6%, 0.4%, 0.2%, or less than about 0.1 % of the methane present in the feed gas mixture exits the system in a gas stream other than the methane gas stream and is uncombusted.

[00101 ] In various embodiments, the present invention provides a method of separating gas components in a feed gas mixture. The method includes contacting a first side of a first membrane with a feed gas mixture. The first membrane can be referred to as the first stage of the separation. The feed gas mixture includes at least a first gas component and a second gas component. The membrane includes a cured product of a silicone composition, the silicone composition including a silicone-polyether copolymer having curable silicon- bonded groups, as described herein. The contacting produces a first permeate gas mixture on a second side of the first membrane and a first retentate gas mixture on the first side of the first membrane. The first permeate gas mixture is enriched in the first gas component, and the first retentate gas mixture is depleted in the first gas component, as compared to the feed gas mixture contacted to the first membrane. In some embodiments, the feed gas mixture includes methane and carbon dioxide, the retentate is a methane stream having about 98% methane. In some embodiments, at least part of the feed gas mixture can be combined with the permeate stream to generate a combustible gas stream having at least about 30% methane.

[00102] The membranes of any stage of the separation can be one or more membranes. Each membrane can independently be an unsupported membrane, or a supported membrane. The membrane of any particular stage can be a supported membrane including a porous or nonporous substrate and a membrane on the substrate. Each membrane can independently be an unsupported membrane selected from a plate membrane, a spiral membrane, tubular membrane, and hollow fiber membrane. In some examples, at least part of at least one of the first retentate gas mixture and the first permeate gas mixture is recycled into the feed gas mixture. The feed gas mixture can be compressed before being contacted to the first membrane. In some embodiments, at least part of the feed gas mixture is not contacted to the first membrane. For example, at least part of the feed gas mixture not contacted to the first membrane can be combined with the first retentate gas mixture. In some examples, at least part of least one of the first permeate gas mixture and the first retentate gas mixture is combined with the feed gas mixture.

[00103] In various embodiments, the multiple-stage method can include contacting a first side of a second membrane with at least part of the first retentate gas mixture. The membrane includes a cured product of a silicone composition, wherein the silicone composition includes a silicone-polyether copolymer having curable silicon-bonded groups. The contacting produces a second permeate gas mixture on a second side of the second membrane and a second retentate gas mixture on the first side of the second membrane. The second permeate gas mixture is enriched in the first gas component, and the second retentate gas mixture is depleted in the first gas component, as compared to the at least part of the first retentate gas mixture contacted to the second membrane. In some embodiments, at least part of least one of the second permeate and the second retentate can be combined with at least one of the feed gas mixture, the first retentate, and the first permeate. The at least part of the first retentate gas mixture can be compressed prior to contacting with the second membrane.

[00104] In various embodiments, the multiple-stage method can include contacting a first side of a second membrane with at least part of the first permeate gas mixture. The second membrane can include a cured product of a silicone composition, the silicone composition including a silicone-polyether copolymer having curable silicon-bonded groups. The contacting produces a second permeate gas mixture on a second side of the second membrane and a second retentate gas mixture on the first side of the second membrane. The second permeate gas mixture is enriched in the first gas component, the second retentate gas mixture is depleted in the first gas component, as compared to the at least part of the first permeate gas mixture contacted to the second membrane. In some embodiments, at least part of least one of the second permeate and the second retentate is combined with at least one of the feed gas mixture, the first retentate, and the first permeate. The at least part of the first permeate gas mixture can be compressed prior to contacting with the second membrane.

[00105] In various embodiments, the multiple-stage membrane separation method includes contacting a first side of a third membrane with at least part of the first retentate gas mixture, the first permeate gas mixture, the second permeate gas mixture, the second retentate gas mixture, or a combination of one of at least part of the second permeate gas mixture and at least part of the second retentate gas mixture and one of at least part of the first permeate gas mixture and at least part of the first retentate gas mixture. The third membrane includes a cured product of a silicone composition, wherein the silicone composition includes a silicone-polyether copolymer having curable silicon- bonded groups. The contacting produces a third permeate gas mixture on a second side of the third membrane and a third retentate gas mixture on the first side of the third membrane. The third permeate gas mixture is enriched in the first gas component, and the third retentate gas mixture is depleted in the first gas component, as compared to the gas mixture that is contacted with the first side of the third membrane. In some embodiments, at least part of least one of the third permeate gas mixture or the third retentate gas mixture can be combined with the gas mixture that is contacted to the first side of the third membrane. In some examples, one or more components of the gas mixture that is contacted to the first side of the third membrane can be compressed.

[00106] Figures 3-10 are described herein with relation to an embodiment including separation of a feed gas mixture including carbon dioxide and methane, but it is to be understood that embodiments of the present invention encompass separation of any suitable feed gas mixture. In the embodiments shown in Figures 3-10, at least one output stream has a methane output stream which includes predominantly methane in addition to any other suitable mixture of gases. The remaining one or more output streams can include any suitable content of gases, and can include a stream that has a content of methane along with other gases such as carbon dioxide that allows combustion of the stream, or a stream that has a content of other gases along with a methane content that is too low to allow combustion of the stream (e.g. non-combustible). One or more compressors or valves can be optionally removed or added in any suitable location of the embodiments described in Figures 3-10, as needed to maintain the desired pressure differential across each stage of the membrane and to maintain the desired throughput of the system. Each stage can have one or more membranes in parallel, for example one or more membrane modules each having a plurality of hollow fiber membranes therein.

[00107] Figure 3 illustrates one embodiment of the present invention, membrane separation system 300. Feed gas mixture 301 enters compressor 305 to give compressed feed gas mixture 310. Compressed feed gas mixture 310 enters first stage 315, having first membrane 320. The compressed feed gas mixture 310 contacts the first side 325 of the first membrane 320 to give first retentate gas mixture 335 on the first side 325 of the first membrane 320 and first permeate gas mixture 340 on the second side 330 of the first membrane 330. The first retentate gas mixture is the methane stream.

[00108] Figure 4 illustrates one embodiment of the present invention, membrane separation system 400. Feed gas mixture 401 can be split at junction 403 to form feed gas mixture 403 and feedforward feed gas mixture 444. Feed gas mixture 403 can be compressed in compressor 405 to form compressed feed gas mixture 410. Compressed feed gas mixture 410 enters first stage 415, having first membrane 420. The compressed geed gas mixture 410 contacts the first side 425 of the first membrane 420 to give a first retentate gas mixture 435 on the first side 425 of the first membrane 420 and a first permeate gas mixture 445 on the second side 430 of the first membrane 420. The first retentate gas mixture 435 is the methane stream. The first permeate gas mixture can be mixed with a suitable proportion of feedforward feed gas mixture 444 at junction 442 to form output stream 445. Output stream 445 can be a combustible methane stream.

[00109] Figure 5 illustrates one embodiment of the present invention, membrane separation system 500. Feed gas mixture 501 can be mixed at junction 502 to form feed gas mixture 503. Feed gas mixture 503 can be compressed in compressor 505 to give compressed feed gas mixture 510. Compressed feed gas mixture 510 enters first stage 515, having first membrane 520. The feed gas mixture 510 contacts the first side 525 of the first membrane 520 to give first retentate gas mixture 545 on the first side 525 of the first membrane 520 and first permeate gas mixture 540 on the second side 530 of the first membrane. The first permeate gas mixture 540 can be a combustible methane stream, or a non-combustible methane stream. The first retentate gas mixture 545 can enter second stage 550, having second membrane 555. The first retentate gas mixture 545 contacts the first side 560 of the second membrane 555 to give a second retentate gas mixture 565 on the first side 560 of the second membrane 555 and a second permeate gas mixture 575 on the second side 570 of the second membrane 555. The second permeate gas mixture 575 is fed back to be mixed at junction 502 with feed gas mixture 501 . The second retentate gas mixture 565 can be the methane stream.

[00110] Figure 6 illustrates one embodiment of the present invention, membrane separation system 600. Feed gas mixture 601 can be mixed at optional junction 695 before entering compressor 605 to give compressed feed gas mixture 606. Compressed feed gas mixture 606 can be mixed at junction 607 to give feed gas mixture 61 0. Feed gas mixture 610 enters first stage 615, having first membrane 620. Feed gas mixture 610 contacts the first side 625 of the first membrane 620 to give first retentate gas mixture 635 on the first side 625 of the first membrane 620 and first permeate gas mixture 630 on the second side 630 of the first membrane 620. First retentate gas mixture 635 is the methane stream. The first permeate gas mixture 640 can enter compressor 645 to give compressed first permeate gas mixture 650. The first permeate gas mixture 650 enters second stage 655 having second membrane 660. The first permeate gas mixture 650 contacts the first side 665 of the second membrane 660 to give second retentate gas mixture 680 on the first side 665 of the second membrane 660 and second permeate gas mixture 675 on the second side 670 of the second membrane 660. The second retentate gas mixture 680 can be mixed with the feed gas mixture at junction 607 after compressor 605 or at junction 690 prior to compressor 605. The second permeate gas mixture can be a combustible or non-combustible methane stream.

[00111 ] Figure 7 illustrates one embodiment of the present invention, membrane separation system 700. Feed gas mixture 701 can be mixed at junction 702 to form feed gas mixture 703. Feed gas mixture 703 can be compressed using compressor 704 to give compressed feed gas mixture 705. Compressed feed gas mixture 705 can be mixed at junction 706 to give feed gas mixture 707. Feed gas mixture 707 can enter first stage 710, having first membrane 715. The feed gas mixture 707 contacts the first side 720 of the first membrane 715 to give first retentate gas mixture 730 on the first side 720 of the first membrane 715 and first permeate gas mixture 765 on the second side 725 of the first membrane 715. The first retentate gas mixture can enter second stage 735, having second membrane 740. The first retentate gas mixture contacts the first side 745 of the second membrane 740 to give a second retentate gas mixture 755 on the first side 745 of the second membrane 740 and a second permeate gas mixture 760 on the second side 750 of the second membrane 740. The second retentate gas mixture 755 can be the methane stream. The second permeate gas mixture 760 can be mixed with feed gas mixture 701 in a suitable proportion at junction 702. The first permeate gas mixture 765 can enter compressor 770 to give compressed first permeate gas mixture 775. Compressed first permeate gas mixture 775 can enter third stage 780, having third membrane 785. The first permeate gas mixture 775 contacts the first side 790 of the third membrane 785 to give third retentate gas mixture 7105 on the first side 790 of the third membrane 785 and third permeate gas mixture 7100 on the second side 795 of the third membrane 785. The third permeate gas mixture 7100 can be a combustible methane stream or a non- combustible methane stream.

[00112] Figure 8 illustrates one embodiment of the present invention, membrane separation system 800. Feed gas mixture 801 can be mixed at junction 802 to give feed gas mixture 803. Feed gas mixture 803 can enter compressor 805 to give compressed feed gas mixture 810. Feed gas mixture 810 enters first stage 815, having first membrane 820. The feed gas mixture 810 contacts the first side 825 of the first membrane 820 to give first retentate gas mixture 835 on the first side 825 of the first membrane 820 and first permeate gas mixture 880 on the second side 830 of the first membrane 820. The first retentate gas mixture 835 enters second stage 840, having second membrane 845. The first retentate gas mixture contacts the first side 850 of the second membrane 845 to give second retentate gas mixture 860 on the first side 850 of the second membrane 845 and second permeate gas mixture 865 on the second side 855 of the second membrane 845. The second retentate gas mixture 860 can be the methane stream. The second permeate gas mixture 865 can pass through junction 870 to form stream 875 which can be combined with feed gas mixture 801 at junction 802. The first permeate gas mixture can enter the third stage 885, having third membrane 890. The first permeate gas mixture contacts the first side 895 of the third membrane 890 to give third retentate gas mixture 81 10 on the first side 895 of the third membrane 890 and third permeate gas mixture 8105 on the second side 8100 of the third membrane 890. The third permeate gas mixture can be a combustible or non- combustible gas mixture. The third retentate gas mixture 8110 can be pass through valve 81 15 give a suitable amount of third retentate gas mixture 8120 which can combine in a suitable proportion at junction 870 with second permeate gas mixture 865 to give gas stream 875, which can be combined in a suitable proportion with feed gas mixture 801 at junction 802.

[00113] Figure 9 illustrates one embodiment of the present invention, gas separation system 900. Feed gas mixture 901 can enter compressor 902 to give compressed feed gas mixture 903. Compressed feed gas mixture 903 can be mixed at junction 904 to give feed gas mixture 905. Feed gas mixture 905 enters first stage 910, having first membrane 915. The feed gas mixture 905 contacts the first side 920 of the first membrane to give a first retentate gas mixture 930 on the first side 920 of the first membrane 915 and a first permeate gas mixture 935 on the second side 925 of the first membrane 91 5. The first permeate gas mixture 935 can be a combustible methane stream or a non- combustible methane stream. The first retentate gas mixture 930 enters the second stage 940, having second membrane 945. The first retentate gas mixture 930 contacts the first side 950 of the first membrane 945 to give second retentate gas mixture 960 on the first side 950 of the second membrane 945 and second permeate gas mixture 955 on the second side 955 of the second membrane 945. The second retentate gas mixture 960 can be the methane stream. The second permeate gas mixture 965 can enter compressor 970 to give compressed second permeate gas mixture 975. The second permeate gas mixture 975 enters third stage 980, having third membrane 985. The second permeate gas mixture 975 contacts the first side 990 of the third membrane 985 to give third retentate gas mixture 9105 on the first side 990 of the third membrane 985 and third permeate gas mixture 9100 on the second side 995 of the third membrane 985. The third permeate gas mixture 9100 can be a combustible methane stream or a non-combustible methane stream, and can optionally be combined with first permeate gas mixture 935 in any suitable proportion to generate a stream having a desired methane content. The third retentate gas mixture 9105 can be combined in a suitable proportion with compressed feed gas mixture 903 at junction 904 to give feed gas mixture 905.

[00114] Figure 10 illustrates one embodiment of the present invention, gas separation system 1 000. Feed gas mixture 1001 can enter compressor 1002 to give compressed feed gas mixture 1003. Feed gas mixture 1003 enters first stage 1005, having first membrane 1010. The feed gas mixture 1 003 contacts the first side 1015 of the first membrane 1010 to give first retentate gas mixture 1 025 on the first side 1015 of the first membrane 1 010 and first permeate gas mixture 1026 on the second side 1020 of the first membrane 1010. The first permeate gas mixture can be mixed at junction 10125 to give mixed first permeate gas mixture 10130, which can be a combustible methane gas stream or a non-combustible methane gas stream. The first retentate gas mixture 1025 can be mixed at junction 1030 to give mixed first retentate gas mixture 1035. The first retentate gas mixture 1035 enters second stage 1040, having second membrane 1 045. The first retentate gas mixture 1035 contacts the first side 1 050 of the second membrane 1045 to give a second retentate gas mixture 1 060 on the first side 1050 of the second membrane 1045 and a second permeate gas mixture 1065 on the second side 1055 of the second membrane 1 045. The second retentate gas mixture can be the methane stream. The second permeate gas mixture can enter compressor 1070 to form compressed second permeate gas mixture 1075. The second permeate gas mixture 1075 enters the third stage 1080, having third membrane 1085. The second permeate gas mixture 1075 contacts the first side 1090 of the third membrane 1 085 to give third retentate gas mixture 10105 on the first side 1090 of the third membrane 1 085 and third permeate gas mixture 10100 on the second side 1 095 of the third membrane 1085. The third retentate gas mixture 10105 can enter compressor 101 10 to give compressed third retentate gas mixture 10120, which can be combined at junction 1030 with first retentate gas mixture 1015. The third permeate gas mixture 10100 can be combined at junction 10125 with first permeate gas mixture 1026.

[00115] The present invention can be better understood by reference to the following examples which are offered by way of illustration. The present invention is not limited to the examples given herein.

General

[00116] Characterization. The molecular properties of the polymers were characterized with nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Crosslinked membranes were fabricated and evaluated for mixed CO2/CH4 separation using various crosslinking chemistries, including Pt-catalyzed hydrosilylation, amine-epoxy ring opening polymerization, and free radical polymerization. Thermal properties of the membranes were investigated with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).

[00117] Membrane fabrication. The membranes were made by spreading the polymer formulations on porous supports and then performing crosslinking. The spreading methods included press, draw-down, and doctor-blade coating. The porous supports were commercial polymer membranes with defined thickness and porosity, such as polyester (PE), polypropylene (PP), and polyethersulfone (PES).

[00118] Gas permeation test. Gas permeability coefficients and ideal selectivities in a binary gas mixture were measured using a permeation cell including upstream (feed/retentate) and downstream (permeate) chambers that were separated by the membrane. The upstream chamber had one gas inlet and one gas outlet. The downstream chamber had one gas outlet. The upstream chamber was maintained at 100 psig pressure and was continuously supplied a mixture of CO2 gas and CH4 gas (85:15 molar ratio) at a flow rate of between 150-180 standard cubic centimeters per minute (seem). The membrane was supported on a stainless-steel filter disk with a diameter of 55 mm. The membrane area was defined by a placing a silicone rubber gasket with a diameter of 50 mm (Exotic Automatic & Supply) on top of the

membrane. The downstream chamber was maintained at ambient pressure and was connected to a 6-port injector equipped with a 1 -mL injection loop. On command, the 6-port injector injected a 1 -mL sample into a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). The amount of gas permeated through the membrane was calculated by calibrating the response of the TCD detector to the gases of interest. The reported values of gas permeability and selectivity were obtained from measurements taken after the system had reached a steady state in which the permeate side gas composition became invariant with time.

[00119] Permeability of gas component i was calculated by the following equation : Pj=V-5/(A-t-Ap), wherein Pj is the permeability for a gas i in the membrane, V is the volume of gas i which permeates through the membrane, δ is the thickness of the membrane, A is the area of the membrane, t is time, Δρ is the pressure difference of the gas i at the retentate and permeation side.

Permeance, or normalized permeability, for a particular gas i in a given membrane was calculated by the following equation: Mj=V/(A-t-Ap), wherein V,

A, t, and Δρ are as defined in this paragraph, and Mj is permeance for a gas i in the membrane. Ideal selectivity (a) of gas pair i and j is determined by a=Pj/Pj=Mj/Mj.

Grafted Polymers

Example 1 . Fluorocarbon-a-PMS-co-PEG-g-PMS random copolymers and membranes therefrom.

[00120] Trimethylsilyl-terminated polymethylhydrogensiloxane (M_w = 13360,

DP = 220, active H = 1 .67 wt%, viscosity = 240 cSt at room temperature), allyloxy PEG monomethyl ether (DP = 6.5), and 1 -((2'- allyloxy)ethyl)tridecafluorohexane were mixed in a round-bottom flask. The mixture was flushed with N2 for 15 minutes. Hexachloroplatinic acid (dissolved in isopropanol, 0.1 M, Pt = 2.4 wt% Pt) was added to a final Pt concentration of 30 ppm. The mixture was heated to 80 °C overnight (ca. 15 hours).

Completion of the reactions was indicated by Si-H signature of the products in infrared spectroscopy and by ¹ H and ^{1 9}F NMR. The reaction is illustrated in Scheme 1 .

Scheme 1 .

[00121 ] Membranes were made by crosslinking the copolymers using PEG diallyl ether (DP = 1 1 ) in the presence of Karstedt's catalyst (in

polydimethylsiloxane, Pt = 0.5 wt%) on a polyethylene support (final Pt concentration = 100 ppm). The cure was achieved at 80 °C overnight in ambient atmosphere.

[00122] Compositions of the polymers and membrane performances are summarized in Table 1 and Figure 1. Figure 1 illustrates ideal selectivity and permeability versus the molar fraction of poly(alkylene oxide)-substituted siloxy- units in various membranes, in accord with various embodiments.

[00123] Table 1 . Polymer and membrane characteristics for Example 1 , where EO% indicates mole percent poly(alkylene oxide)-substituted siloxy-units.

[00124] Differential scanning calorimetry results are shown in Table 2, which indicate the polymers had higher Tg than the parent

polymethylhydrogensiloxane polymer, but still well below room temperature.

[00125] Table 2. Differential scanning calorimetry results for polymers of Example 1 . Melt Melt Melt

Compound ^T9 Melt onset 1 peak 1 peak 2

° C ° C ° C ° C J/g

1 .3 -77.4 -40.8 -22.9 None 5.5

1 .4 -70.4 -29.0 -14.8 None 17.7

1 .5 -79.9 -28.2 -16.0 None 30.1

1 .6 -83.5 -23 -14.3 None 34.7

1 .1 -84.2 -25.9 -15.4 None 41 .1 allyloxy PEG

monomethyl ether None -52.9 -27.6 -10.3 103 starting material

TMS-terminated

PHMS starting -139.3 None None None None material

Example 2. Trimethvlsi vloroDvl-a- PMS-co-PEG-a-PMS random copolymers and membranes therefrom.

[00126] Trimethylsilyl-terminated polymethylhydrogensiloxane (M.

DP = 220, active H = 1 .67 wt%, viscosity = 240 cSt at room temperature), allyloxy PEG monomethyl ether (DP = 6.5), and allyltrimethylsilane were mixed in a Parr reactor. The mixture was flushed with N2 for 15 minutes.

Hexachloroplatinic acid (dissolved in isopropanol, 0.1 M, Pt = 2.4 wt% Pt) was added to a final Pt concentration of 30 ppm. The mixture was heated to 80 °C overnight (ca. 15 hours). Completion of the reactions was indicated by Si-H signature of the products in infrared spectroscopy and by ¹ H NMR. The reaction is illustrated in Scheme 2.

Scheme 2.

[00127] Membranes were made by crosslinking the copolymers using PEG diallyl ether (DP = 1 1 ) in the presence of Karstedt's catalyst (in

polydimethylsiloxane, Pt = 0.5 wt%) (final platinum concentration^ 00 ppm) on a polyethylene support. Cure was achieved at 80 °C overnight in ambient atmosphere. Compositions of the polymers and their membrane performances are summarized in Table 3 and Figure 2. Figure 2 illustrates ideal selectivity and permeability versus molar fraction of poly(alkylene oxide)-substituted siloxy- units in various membranes.

[00128] Table 3. Polymer and membrane characteristics for Example 2, where EO% indicates mole percent of poly(alkylene oxide)-substituted siloxy-units.

[00129] Synthesis of glycidylpropyl-g-PMS copolymers. To a deaerated solution of trimethylsilyl-terminated polymethylhydrogensiloxane (M_w = 13360, DP = 220, active H = 1 .67 wt%, viscosity = 240 cSt at room temperature) and allylglycidyl ether in isopropanol was added hexachloroplatinic acid (dissolved in isopropanol, 0.1 M, Pt = 2.4 wt% Pt) to a final Pt concentration = 30 ppm. The mixture was stirred at ambient temperature for 30 minutes and was

subsequently brought to reflux overnight. ^ H NMR indicated full conversation of the starting materials. The reaction is illustrated in Scheme 3.

[00130] Synthesis of 3'N-(2"-aminoethyl)aminoisobutyl-g-PMS-co-PDMS copolymers. An amino-functionalized polysiloxane (poly[3'N-(2"- aminoethyl)aminoisobutyl]methylsiloxane, dihydoxy-terminated, M_w > 1 5000, viscosity = 1500 cSt at room temperature), octamethylcyclotetrasiloxane (D4) and polydimethylsiloxane (DP = 9, viscosity = about 5 cSt at room temperature) were charged to a 2 liter three neck round bottom flask equipped with a Dean- Stark trap, a condenser, an overhead stirrer, heating mantle, and temperature probe under nitrogen. Potassium hydroxide was added to the mixture under stirring. An exotherm was observed immediately. Thickening and water production were seen in about 30 minutes. Heating was then commenced. The content of the flask was heated to 145 °C for 7 hours. The reaction was allowed to cool down to room temperature and acetic acid (1 :1 molar ratio the KOH) was added dropwise. The mixture was stirred at low rpm to thoroughly quench KOH overnight. The opaque paste was pressure filtered through a 1 -μιτι filter membrane under nitrogen to afford clear viscous liquids. Cyclics were removed under high vacuum at 150 °C. The reaction is illustrated in Scheme 4.

Scheme 4

[00131 ] An amino-functionalized polysiloxane (poly[3'N-(2"- aminoethyl)aminoisobutyl]methylsiloxane, dihydoxy-terminated, M_w > 1 5000, viscosity = 1500 cSt at room temperature, octamethylcyclotetrasiloxane (D4), and polydimethylsiloxane (DP = 9, viscosity = about 5 cSt at room temperature) were charged to a 2 liter three neck round bottom flask equipped with a Dean- Stark trap, a condenser, an overhead stirrer, heating mantle, and temperature probe under nitrogen. Potassium hydroxide was added to the mixture under stirring. An exotherm was observed immediately. Thickening and water production were seen in about 30 minutes. Heating was then commenced. The content of the flask was heated to 145 °C for 7 hours. The reaction was allowed to cool down to room temperature and acetic acid (1 :1 molar ratio the KOH) was added dropwise. The mixture was stirred at low rpm to thoroughly quench KOH overnight. The opaque paste was pressure filtered through a 1 -μιτι filter membrane under nitrogen to afford clear viscous liquids. Cyclics were removed under high vacuum at 150 °C. Quantity of the starting materials and chemical composition of the aminopolymers can be seen in Table 4. Compound 3.3 was a polysiloxane with 30 mol% of [3'N-(2"- aminoethyl)aminoisobutyl]methylsiloxane units, 70% mol% dimethylsiloxane units, M_w = 1 1200, N content = 6.26 mmol/gram.

[00132] Table 4. Starting material and product characteristics for

aminopolymers 3.1 -3.3.

[00133] Synthesis of decaf luorohexyl-modified polyaminosiloxanes.

Compound 3.3 was mechanically stirred with 1 -decafluorohexyl-2,3- epoxypropane at 80 °C for 4 hours. Disappearance of epoxy signatures in IR indicated completion of the reactions. Two polymers with N/oxirane=1 .2 (Compound 3.4) and 2.2 (Compound 3.5) were prepared. The reaction is illustrated in Scheme 5.

[00134] The decaf luorohexyl-modified polyaminosiloxanes 3.4 and 3.5 were mixed with the glycidylpropyl-g-PMS copolymer shown in Scheme 3 at three different loading levels and spread on a polyethylene support. The formulations were cured at 80 °C overnight in ambient atmosphere. The membranes containing Compound 3.5 were too tacky to be tested at all epoxy loading percents. The performance of membranes made from Compound 3.4 is summarized in Table 5.

[00135] Table 5. Polymer and membrane characteristics for Example 3.

Example 4a. Synthesis of 3-(2'methoxyethoxy)propene (PEG-| , Compound 4a

[00136] A three-necked, 1000-mL flask equipped with a thermometer, mechanical stirrer, and dropping funnel was charged with potassium hydroxide (56.06 g, 1 .0 mol) and 2-methoxyethanol (65 ml_, 62.3 g, 0.82 mol). The resulting mixture was cooled in an ice bath and stirred using a mechanical stirrer for 1 .75 hours. Allyl bromide (72 ml_, 100 g, 0.82 mol) was added dropwise, keeping the internal temperature below 10°C. After the solution is stirred overnight, the sticky white solid is collected by suction filtration and the collected solids are washed with hexanes (300 ml_). Volatiles in the combined yellow filtrate were evaporated by rota-vap at room temperature. After vacuum fractional distillation, Compound 4a.1 was obtained as a clear liquid. Yield: 31 .23 g (32.8%). The reaction is illustrated in Scheme 6. Scheme 6.

Example 4b. Synthesis of diethylene glycol all yl monomethyl ether (PEG2, Compound 4b.1 ).

[00137] A three-necked, 1000-mL flask equipped with a thermometer, mechanical stirrer, and dropping funnel was charged with potassium hydroxide (56.07 g, 1 .0 mol) and diethyleneglycol monomethyl ether (96.3 ml_, 98.5 g, 0.82 mol). The resulting mixture was cooled in an ice bath and stirred using a mechanical stirrer for 1 .75 hours. Allyl bromide (72 ml_, 100 g, 0.82 mol) was added dropwise, keeping the internal temperature below 10°C. After the solution is stirred overnight, the sticky white solid is collected by suction filtration and the collected solids are washed with hexanes (300 ml_). Volatiles in the combined yellow filtrate were evaporated by rota-vap and vacuum-dried overnight. After vacuum fractional distillation, 23716-140 was obtained as a clear li uid. Yield: 1 13.96 g (86.7%). The reaction is illustrated in Scheme 7.

Scheme 7.

Example 4c. Synthesis of triethylene glycol all yl monomethyl ether (PEG3, Compound 4c.1 ).

[00138] A three-necked, 1000-mL flask equipped with a thermometer, mechanical stirrer, and dropping funnel was charged with potassium hydroxide (44.89 g, 0.8 mol) and triethyleneglycol monomethyl ether (128.03 ml_, 131 .36 g, 0.8 mol). The resulting mixture was cooled in an ice bath and stirred using a mechanical stirrer for 1 hour. Allyl bromide (69.23 ml_, 96.78 g, 0.8 mol) was added dropwise, keeping the internal temperature below 10°C. After the solution is stirred overnight, the sticky white solid is collected by suction filtration and the collected solids are washed with hexanes (200 ml_). Volatiles in the combined yellow filtrate were evaporated by rota-vap and vacuum-dried overnight. After vacuum fractional distillation, Compound 4c.1 was obtained as a clear liquid. Yield: 123.66 g (75.7%). The reaction is illustrated in Scheme 8.

Scheme 8. Example 5. PEG_n-g-PMS and membranes therefrom.

[00139] Trimethylsilyl-terminated polymethylhydrogensiloxane (M_w = 13360,

DP = 220, active H = 1 .67 wt%, viscosity = 240 cSt at room temperature) and PEG_n (n=1 , 2, 3, 6.5, 11 , and 16) was heated to 70 °C in the presence of hexachloroplatinic acid (dissolved in isopropanol, 0.1 M, Pt = 2.4 wt% Pt) (final Pt concentration = 30 ppm) overnight. The reaction was exothermic and turned homogeneous within an hour. The reactions did not require workup and usually gave quantitative yield. The reaction is illustrated in Scheme 9.

Scheme 9.

[00140] Membranes were made by crosslinking the copolymers with PEG diallyl ether (DP = 1 1 ) in the presence of Karstedt's catalyst (in

polydimethylsiloxane, Pt = 0.5 wt%) (final platinum concentration = 100 ppm) on a polyethylene support. The cure was achieved at 80 °C overnight in ambient atmosphere. All results were averages of at least 3 parallel membrane tests, unless otherwise noted. Chemical compositions and gas separation performance of the materials are summarized in Table 6.

[00141 ] Table 6. Polymer and membrane characteristics for Example 5, where EO% indicates mole fraction of poly(alkylene oxide)-substituted siloxy-units.

a A small amount of Si-H crosslinker aid polydimethylsiloxane- polyhydrogenmethylsiloxane copolymer (M_w = 721 , viscosity = 5 cSt at room temperature, active H = 0.78 wt%) was used to ensure cure.

b Only single data point was obtained.

c Formulation failed to cure, even with extra crosslinker aid.

Example 6. PEG-g-cvclomethylhvdroaensiloxanes and membranes therefrom. [00142] Cyclomethylhydrogensiloxanes (CMHS) and allyloxy PEG monomethyl ether (DP = 6.5) were heated to 75 °C in the presence of hexachloroplatinic acid (dissolved in isopropanol, 0.1 M, Pt = 2.4 wt% Pt) (final Pt concentration of 30 ppm). The reaction completed in 5-6 hours as indicated by ^"Ή NMR. The reaction is illustrated in Scheme 10.

Scheme 10.

[00143] Membranes were made by crosslinking the copolymers with PEG diallyl ether, (DP = 1 1 ) in the presence of Karstedt's catalyst (in

polydimethylsiloxane, Pt = 0.5 wt%) (final platinum concentration = 100 ppm) on a polyethylene support. Curing was achieved at 80 °C overnight in ambient atmosphere. The chemical composition of the polymers and their membrane performance are summarized in Tables 7 and 8. All membrane results in this Example were averages of three replications, unless otherwise noted.

[00144] Table 7. Polymer characteristics for Example 6.

[00145] Compound 6A is a cyclic crosslinker, having active H = 0.48 wt%, viscosity = 40 cSt at room temperature, and having the following structure, wherein m and n are 4 or 5, meaning 4 or 5 repeating Si(CH3)H-0 units:

[00146] Compound 6B is a cyclic crosslinker, having active H = 0.32 wt%, viscosity = 130 cP at room temperature, and having the following structure, wherein m and n are 4 or 5, meaning 4 or 5 repeating -Si(CH3)2-0 units and Si(CH₃)H-0 un

[00147] Table 8. Membrane characteristics for Example 6.

Example 7a. Synthesis of M-D2oD20^PEGD20^ep .

[00148] A random organopolysiloxane copolymer comprising trimethylsilyloxy (M) terminal groups, dimethylsiloxy units (D), methyl siloxy units with pendant mono-acetate-terminal polyethylene glycoloxypropyl groups (D^PEG), and methylsiloxy units with pendant glycidoxypropyl units (D^eP) was prepared as follows. 63.02 g of mono-allyl, mono-aceteate capped polyethyleneglycol having a number average degree of polymerization of 12 ethylene glycol units (Dow Chemical) (AllylPEGI ) was combined with 14.79 g allyl glycidyl ether (Sigma-Aldrich) and 77.8 g isopropyl alcohol (IPA) (Fisher) in a 250 cc 3-neck round bottom flask. The headspace of the flask was lightly purged with a blanket of dry nitrogen containing 4 % oxygen (v/v), and the contents were magnetically stirred while heating to 70 °C. 0.10 g of a Karstedt's catalyst solution diluted in IPA to an effective Pt concentration of 2.45 wt% (Catalyst

Solution X) was added to the flask, followed by a controlled addition of 40.0 g of a 50% solution of a random copolymer having the approximate average structure M-D20-D 42-M with a slight degree of branching in the siloxane backbone, where D' represents a methylhydridosiloxy group, in IPA through an addition funnel (Copolymer X). Evidence of the reaction exotherm was observed by a small but detectable increase in reaction temperature immediately following introduction of a steady stream of the Copolymer X solution. The rate of addition was controlled to prevent excessive heating of the flask. After 40 minutes, the reaction mixture was tested by infrared

spectroscopy (Nicolet 6700 FTIR equipped with Smart Miracle ATR accessory (ZnSe crystal)) and revealed essentially complete disappearance of the silicon- hydride peak near 2160 cm^-1 . The reaction was allowed to continue for 3 h at 70 °C before cooling. The product was recovered in neat form by rotary evaporation of the I PA and analyzed by ²⁹Si and ^{1 3}C NMR and gel permeation chromatography (GPC). The results confirmed that the silicon hydride bonds on the D' groups were completely reacted with an approximately equimolar substitution of glycidoxypropyl and mono-acetate-terminal polyethylene glycoloxypropyl units with no significant rearrangement of the siloxane backbone nor of the polyethyleneglycol chains, yielding a random copolymer comprising an approximate of structure M-D2nD20^PEG'-⁾20^e'^:)M, wherein the

D^PEG units have the same distribution and length of ethyleneglycol units as the AllylPEGI reagent, with a slight degree of branching in the siloxane backbone. Example 7b. Synthesis of M-D₂nD2n^{P EG'P PQ}D2P^epM-

[00149] A random organopolysiloxane copolymer comprising trimethylsilyloxy (M) terminal groups, dimethylsiloxy units (D), methyl siloxy units with pendant mono-acetate-terminal polyethyleneglycol-co-propyleneglycoloxypropyl groups PEG-PPO) _anc| methylsiloxy units with pendant glycidoxypropyl units (D^eP) was prepared as follows. 315.02 g of mono-allyl, mono-acetate capped polyethyleneglycol-block-propyleneglycol (Dow Chemical) (Allyl PEG-PP01 ) which comprised a mixture of 65 wt% mono-acetate capped polyethyleneglycol- block-propyleneglycol having a number average of approximately 12 units each of ethylene glycol and propylene glycol, and 35 wt% mono-acetate capped polyethyleneglycol-block-propyleneglycol having a number average of approximately 30 units each of ethylene glycol and propylene glycol, was combined with 25.89 g allyl glycidyl ether and 340.90 g IPA in a 1 liter baffled 3- neck round bottom flask. The headspace of the flask was lightly purged with a blanket of dry nitrogen, and the contents were magnetically stirred while heating to 70 °C. 0.31 g of Catalyst Solution X was added to the flask, followed by a controlled addition of 70.05 g of a 50% solution of Copolymer X in IPA through an addition funnel. After approximately 30 minutes, another 0.50 g of Catalyst Solution X was added. The solution remained slightly hazy in appearance, so another 0.27 g of Catalyst Solution X was added after an additional hour, immediately resulting in a clear solution - indicating successful incorporation of the polyether onto the siloxane backbone. The extent of reaction was confirmed by infrared spectroscopy which revealed essentially complete disappearance of the silicon-hydride peak near 2160 cm^"'' . The reaction was allowed to continue for an additional hour at 70 °C before cooling. The product was recovered in neat form by rotary evaporation of the IPA and analyzed by ²⁹Si and ^{1 3}C NMR and gel permeation chromatography (GPC). The results confirmed that the silicon hydride bonds on the D' groups were completely reacted with an approximately equimolar substitution of glycidoxypropyl and mono-acetate- terminal polyethylene glycoloxypropyl units with no significant rearrangement of the siloxane backbone nor of the polyethyleneglycol chains, yielding a random copolymer comprising an approximate of structure M-D2nD20^PE(^^~

wherein the _DPEG-PPO units have the same distribution and length of ethyleneglycol and propylene glycol units as the AllylPEG-PP01 reagent, with a slight degree of branching in the siloxane backbone.

Example 7c. (Hypothetical) Formation of membranes from polymers of Examples 7a and 7b using amine/epoxy mechanism.

[00150] The epoxy functional units on polyalkyleneoxide-grafted

organopolysiloxane copolymers of Examples 7a and 7b are used as crosslinking sites when combined with suitable amine-functional compounds, for example, Compounds 3.1 -3.5, to form membranes.

Example 7d. (Hypothetical) Formation of membranes from polymers of Examples 8a and 8b using epoxy polymerization.

[00151 ] The epoxy functional units on the polyalkyleneoxide-grafted organopolysiloxane copolymers of Examples 7a and 7b are crosslinked by use of a suitable epoxy polymerization catalyst, for example, a photoacid generator, to form membranes.

Linear block copolymers.

Example 8. PDMS-b-PEG copolymers via Pt-catalyzed addition cure and membranes therefrom.

[00152] Si-H terminated PDMS and PEG diallyl ether (DP = 11 ) were hydrosilylated in toluene with hexachloroplatinic acid (dissolved in isopropanol, 0.1 M, Pt = 2.4 wt% Pt) as catalyst. The reaction was heated to 80°C overnight. The completion of the reaction was confirmed by IR and NMR. The reaction is illustrated in Scheme 11 .

Scheme 1 1 .

[00153] Membranes were made by crosslinking the copolymers with PEG diallyl ether (DP = 1 1 ), polydimethylsiloxane-polyhydrogenmethylsiloxane copolymer (M_w = 721 , viscosity = 5 cSt at room temperature, active H = 0.78 wt%) in presence of Karstedt's catalyst (in polydimethylsiloxane, Pt = 0.5 wt%) (final Pt concentration =100 ppm) on a polypropylene support. The membranes were cured at 90°C overnight in ambient atmosphere. All the results are the averages of three test measurements. The chemical composition and test results are summarized in Table 9.

[00154] Table 9. Polymer and membrane characteristics for Example 8.

[00155] Compound 8A has a degree of polymerization of 6.5, viscosity = 5 cSt at room temperature, active H = 0.21 wt%, M_w = 949, and has a formula of

(CH₃)2SiH-0-[Si(CH3)2-0-]₆.5-SiH(CH₃)2.

Example 9. PDMS-b-PEG copolymer via Pt-catalvzed addition cure and membrane therefrom.

[00156] Si-H terminated PDMS and dimethylallyl PEG ether (chain length = 25 DP) were hydrosilylated in toluene with hexachloroplatinic acid (dissolved in isopropanol, 0.1 M, Pt = 2.4 wt% Pt) as catalyst. The reaction was heated to 80°C overnight. The reaction is illustrated in Scheme 12.

Scheme 12.

[00157] Membranes were made by crosslinking the copolymers with PEG diallyl ether (DP = 1 1 ), polydimethylsiloxane-polyhydrogenmethylsiloxane copolymer (M_w = 721 , viscosity = 5 cSt at room temperature, active H = 0.78 wt%) in presence of Karstedt's catalyst (in polydimethylsiloxane, Pt = 0.5 wt%) (final Pt concentration = 100 ppm) on a polypropylene support. The

membranes were cured at 90 °C overnight in ambient atmosphere. Only the membrane formulated from the copolymer of Compound 8A and dimethylallyl PEG ether was tested. All the results are the averages of three test measurements. The chemical composition and test results are summarized Table 10.

[00158] Table 10. Polymer and membrane characteristics for Example 9.

[00159] 1 ,1 ,3,3-Tetramethyldisiloxane and dimethylallyl PEG ether (chain length = 25 DP) were hydrosilylated in toluene in the presence of

hexachloroplatinic acid (dissolved in isopropanol, 0.1 M, Pt = 2.4 wt% Pt). The reaction was heated to 80 °C overnight. The product was further hydrosilylated with allylglycidyl ether (AGE). The reaction was heated to 60 °C overnight. The excess AGE was removed by vacuum evaporation at 80 °C overnight. The reaction is illustrated in Scheme 13.

Scheme 13.

[00160] Membranes were made by crosslinking the product with an aminosilicone (Compound 3.3) on a polyethersulfone support. The films were cured at 150°C overnight. The chemical composition and test results are summarized in Table 11 .

[00161 ] Table 1 1 . Polymer and membrane characteristics for Example 10.

[00162] The starting material polymer was an allylglycidyl ether (AGE)- terminated linear copolymer of PEG and PDMS, terminated by epoxy groups, viscosity = 1500 cSt at room temperature. The structure of the polymer can be described by the final product in Scheme 13, having n=35, p=15, and x=2.5. The polymer was mixed with Compound 3.3 and drawn down onto a polyethersulfone support using a 10 mil drawdown bar and cured at 150 °C overnight. The chemical composition and test results are summarized in Table 12.

[00163] Table 12. Polymer and membrane characteristics for Example 10.

[00164] General. The separation data given in the Examples that follow were determined using the Membrane Unit v3.0a of Aspen HYSYS v7.2 software package. Inputs included stream pressures and temperatures, feed composition, and membrane area of each stage.

Example 1 1 (Comparative, hypothetical). [00165] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 1 -stage polyimide membrane process, as illustrated in FIG. 3, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The permeate CH4 lost in the process corresponds to 8.9 mol% of the CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 20 GPU and a CO2/CH4 selectivity of 45. The total feed pressure to the process is 25 bar. The total membrane area to achieve this degree of separation is 1420 m².

Example 12 (Comparative, hypothetical).

[00166] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 1 -stage polyimide membrane process, as illustrated in FIG. 4, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The permeate CH4 lost in the process corresponds to 0 mol% of the

CH4 in the incoming 500 Nm³/h because the permeate stream is utilized in a combined heat and power process. The composition of the permeate stream entering the combined heat and power process is 30.4% CH4. Each membrane stage has a CO2 permeance of 20 GPU and a CO2/CH4 selectivity of 45. The total feed pressure to the process is 25 bar. The total membrane area to achieve this degree of separation is 890 m².

Example 13 (Comparative, hypothetical).

[00167] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 2-stage polyimide membrane process, as illustrated in FIG. 5, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The permeate CH4 lost in the process corresponds to 0.5 mol% of the CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 20 GPU and a CO2/CH4 selectivity of 45. The total feed pressure to the process is 25 bar. The total membrane area to achieve this degree of separation is 4940 m².

Example 14 (Comparative, hypothetical).

[00168] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 2-stage polyimide membrane process, as illustrated in FIG. 6, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The permeate CH4 lost in the process corresponds to 0 mol% of the CH4 in the incoming 500 Nm³/h because the permeate stream is utilized in a combined heat and power process. The composition of the permeate stream entering the combined heat and power process is 30% CH4. Each membrane stage has a CO2 permeance of 20 GPU and a CO2/CH4 selectivity of 45. The total feed pressure to the process is 25 bar. The total membrane area to achieve this degree of separation is 5300 m².

Example 15 (Comparative, hypothetical).

[00169] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500 Nm³/h is purified with a 3-stage polyimide membrane process, as illustrated in FIG. 7, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The permeate CH4 lost in the process corresponds to 0.5 mol% of the

CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 20 GPU and a CO2/CH4 selectivity of 45. The total feed pressure to the process is 25 bar. The total membrane area to achieve this degree of separation is 1870 m².

Example 16 (Comparative, hypothetical).

[00170] A 50/50 mol/mol C0₂/CH₄ stream having a flow rate of 500

Nm³/h is purified with a 3-stage polyimide membrane process, as illustrated in FIG. 8, to produce a 98 mol% CH4 stream for injection into a natural gas grid.

The permeate CH4 lost in the process corresponds to 0.5% of the CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 20 GPU and a CO2/CH4 selectivity of 45. The total feed pressure to the process is 25 bar. The total membrane area to achieve this degree of separation is 1900 m². Example 17 (Comparative, hypothetical).

[00171 ] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 3-stage polyimide membrane process, as illustrated in FIG. 9, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The permeate CH4 lost in the process corresponds to 0.5 mol% of the CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 20 GPU and a CO2/CH4 selectivity of 45. The total feed pressure to the process is 25 bar. The total membrane area to achieve this degree of separation is 1960 m².

Example 18 (Comparative, hypothetical).

[00172] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500 Nm³/h is purified with a 3-stage polyimide membrane process, as illustrated in FIG. 10, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The permeate CH4 lost in the process corresponds to 0.5 mol% of the

CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 20 GPU and a CO2/CH4 selectivity of 45. The total feed pressure to the process is 25 bar. The total membrane area to achieve this degree of separation is 1890 m².

Example 19 (Hypothetical).

[00173] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 1 -stage membrane process, as illustrated in FIG. 3, the membrane(s) of each stage including a cured product of a silicone composition including a silicone-polyether copolymer having curable silicon-bonded groups, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid.

The permeate CH4 lost in the process corresponds to 0% of the CH4 in the incoming 500 Nm³/h because the permeate stream is utilized in a combined heat and power process. The composition of the permeate stream entering the combined heat and power process is 30% CH4. Each membrane stage has a

CO2 permeance of 600 GPU and a CO2/CH4 selectivity of 12. The total feed pressure to the process is 5 bar. The total membrane area to achieve this degree of separation is 220 m².

Example 20 (Hypothetical).

[00174] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 1 -stage membrane process, as illustrated in FIG. 4, the membrane(s) of each stage including a cured product of a silicone composition including a silicone-polyether copolymer having curable silicon-bonded groups, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid.

The permeate CH4 lost in the process corresponds to 0% of the CH4 in the incoming 500 Nm³/h because the permeate stream is utilized in a combined heat and power process. The composition of the permeate stream entering the combined heat and power process is 30% CH4. Each membrane stage has a CO2 permeance of 600 GPU and a CO2/CH4 selectivity of 12. The total feed pressure to the process is 5 bar. The total membrane area to achieve this degree of separation is 200 m².

Example 21 (Hypothetical).

[00175] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 2-stage membrane process, as illustrated in FIG. 5, the membrane(s) of each stage including a cured product of a silicone composition including a silicone-polyether copolymer having curable silicon-bonded groups, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid.

The CH4 lost in the permeate stream of the process corresponds to 2.1 % of the CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 600 GPU and a CO2/CH4 selectivity of 12. The total feed pressure to the process is 5 bar. The total membrane area to achieve this degree of separation is 2040 m².

Example 22 (Hypothetical).

[00176] A 50/50 mol/mol C0₂/CH₄ stream having a flow rate of 500

Nm³/h is purified with a 2-stage membrane process, as illustrated in FIG. 6, the membrane(s) of each stage including a cured product of a silicone composition including a silicone-polyether copolymer having curable silicon-bonded groups, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid.

CO2 permeance of 600 GPU and a CO2/CH4 selectivity of 12. The total feed pressure to the process is 5 bar. The total membrane area to achieve this degree of separation is 800 m².

Example 23 (Hypothetical).

[00177] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 3-stage membrane process, as illustrated in FIG. 7, the membrane(s) of each stage including a cured product of a silicone composition including a silicone-polyether copolymer having curable silicon-bonded groups, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The CH4 lost in the permeate stream of the process corresponds to 0.5% of the

CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 600 GPU and a CO2/CH4 selectivity of 12. The total feed pressure to the process is 5 bar. The total membrane area to achieve this degree of separation is 929 m².

Example 24 (Hypothetical).

[00178] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 3-stage membrane process, as illustrated in FIG. 8, the membrane(s) of each stage including a cured product of a silicone composition including a silicone-polyether copolymer having curable silicon-bonded groups, to produce a 98 mol% CH4 stream for injection into a natural gas grid. The CH4 lost in the permeate stream of the process corresponds to 0.5% of the CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 1400 GPU and a CO2/CH4 selectivity of 10.5. The total feed pressure to the process is 5 bar. The total membrane area to achieve this degree of separation is 340 m².

Example 25 (Hypothetical).

[00179] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500

Nm³/h is purified with a 3-stage membrane process, as illustrated in FIG. 9, the membrane(s) of each stage including a cured product of a silicone composition including a silicone-polyether copolymer having curable silicon-bonded groups, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The CH4 lost in the permeate stream of the process corresponds to 0.5% of the

CH4 in the incoming 500 Nm³/h. Each membrane stage has a CO2 permeance of 500 GPU and a CO2/CH4 selectivity of 10.5. The total feed pressure to the process is 5 bar. The total membrane area to achieve this degree of separation is 942 m².

Example 26 (Hypothetical).

[00180] A 50/50 mol/mol CO2/CH4 stream having a flow rate of 500 Nm³/h is purified with a 3-stage membrane process, as illustrated in FIG. 10, the membrane(s) of each stage including a cured product of a silicone composition including a silicone-polyether copolymer having curable silicon- bonded groups, to produce a 98 mol% CH4 retentate stream for injection into a natural gas grid. The CH4 lost in the permeate stream of the process corresponds to 0.5% of the CH4 in the incoming 500 Nm^/h. Each membrane stage has a CO2 permeance of 1400 GPU and a CO2/CH4 selectivity of 10.5.

The total feed pressure to the process is 5 bar. The total membrane area to achieve this degree of separation is 966 m².

[00181 ] The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those of ordinary skill in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

Claims

CLAIMS We claim:

1 . A membrane comprising:

a cured product of a silicone composition, the silicone composition comprising a silicone-polyether copolymer having curable silicon-bonded groups;

wherein the membrane comprises

i) an unsupported membrane that is free-standing; or

ii) a supported membrane comprising a porous or permeable substrate, wherein the membrane is on the substrate.

2. The membrane of claim 1 , wherein the curable silicon-bonded groups are independently chosen from a hydrogen atom, hydroxy group, hydrolysable group, radiation-curable group, free radical-curable group, epoxide-containing group, aliphatic unsaturated carbon-carbon bond-containing group, and a combination thereof.

3. The membrane of any one of claims 1 -2, wherein the silicone composition is a hydrosilylation-curable silicone composition comprising

(A) a silicone-polyether copolymer having an average of at least two silicon-bonded hydrogen atoms per molecule;

(B) a cross-linking agent having an average of at least two aliphatic unsaturated carbon-carbon bonds per molecule; and

(C) a hydrosilylation catalyst;

wherein the ratio of the number of moles of silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane (A) to the number of moles of aliphatic unsaturated carbon-carbon bonds in the cross-linking agent (B) is from about 0.1 to 20.

4. The membrane of claim 3, wherein the cross-linking agent (B) is chosen from:

(i) at least one organic compound having an average of at least two aliphatic unsaturated carbon-carbon bonds per molecule,

(ii) at least one organosilane having an average of at least two silicon-bonded aliphatic unsaturated carbon-carbon bond-containing groups per molecule, (iii) at least one silicone resin having an average of at least two silicon-bonded aliphatic unsaturated carbon-carbon bond-containing groups per molecule,

(iv) at least one organosiloxane having an average of at least two silicon-bonded aliphatic unsaturated carbon-carbon bond-containing groups per molecule, and

(v) a mixture comprising at least two of (i), (ii), (iii), and (iv).

5. The membrane of any one of claims 1 -4, wherein the silicone-polyether copolymer is at least one of a linear block copolymer and a graft copolymer.

6. The membrane of any one of claims 1 -5, wherein the silicone-polyether copolymer is a graft copolymer, wherein the linear block copolymer has the formula X[R¹ ₂SiO(R¹ ₂SiO)_mR¹ ₂Si-R²-0(C_nH₂nO)p-R²-]q(R¹ ₂SiO)_rR¹ ₂SiX, wherein each R¹ is independently C-| -C-| Q hydrocarbyl or C-| -C-| Q halogen- substituted hydrocarbyl; each R2 is C-| -C-| o hydrocarbylene; each X is independently a curable silicon-bonded group chosen from a hydrogen atom, hydroxy group, hydrolysable group, radiation-curable group, free radical-curable group, epoxide-containing group, aliphatic unsaturated carbon-carbon bond- containing group, and a combination thereof; m is about 0 to 100; n is about 2 to 4; p is about 1 to 100; q is about 1 to 100; and r is about 0 to 100.

7. The membrane of claim 6, wherein the graft copolymer comprises about 0 to 99 mol% of siloxy units having the formula I, about 1 to 100 mol% of siloxy units having the formula II, about 0 to 80 mol% of siloxy units having the formula III, and about 0 to 66 mol% of siloxy units having the formula IV:

R¹ ₂Si0₂/₂ (I) R¹ ESi0₂/₂ (II) HR¹ Si0₂/₂ (III) R¹ ₃Si0_{1 /2} (IV), wherein each R¹ is independently C-| -C-| Q hydrocarbyl or C-| -C-| Q halogen- substituted hydrocarbyl; each E is chosen from -R²0(C_nH_2nO)pR³ and formula V:

wherein is C-| -C-| Q hydrocarbylene, is chosen from R1 , -H, and a curable group that makes E a silicon-bonded curable group, n is about 2 to 4, and p is about 1 to 100.

8. The membrane of any one of claims 1 -7, wherein the silicone composition is an epoxy/amine-curable silicone composition comprising (A) a silicone-polyether copolymer having an average of at least two silicon-bonded epoxy-substituted organic groups per molecule; and (B) a polyamine.

9. The membrane of any one of claims 1 -8, wherein the silicone composition is a condensation-curable silicone composition comprising

(A) a silicone-polyether copolymer having an average of at least two silicon-bonded hydrogen atoms, hydroxy groups, or hydrolysable groups per molecule; and

(B) a condensation catalyst.

10. A method of separating gas components in a feed gas mixture, the method comprising contacting a first side of a first membrane comprising a cured product of a silicone composition with a feed gas mixture comprising at least a first gas component and a second gas component to produce a first permeate gas mixture on a second side of the first membrane and a first retentate gas mixture on the first side of the first membrane, wherein the first permeate gas mixture is enriched in the first gas component, the first retentate gas mixture is depleted in the first gas component, and the silicone composition comprises a silicone-polyether copolymer having curable silicon-bonded groups.

1 1. The method of claim 10, wherein the first permeate gas mixture comprises carbon dioxide and the feed gas mixture comprises carbon dioxide and methane, wherein the method generates a combustible output stream comprising at least part of the first retentate gas mixture combined with at least part of the feed gas mixture, the combustible output stream having a concentration of methane of about 20 to 100% (v/v), and further comprising burning the permeate in a gas turbine generator.

12. The method of any one of claims 10-11 , wherein the process comprises multiple stages, each stage comprising contacting an additional membrane with at least one of the retentate gas mixture and the permeate gas mixture from a previous stage, wherein at least one of the additional membranes is a cured product of the silicone composition.

13. The method of any one of claims 10-12, further comprising contacting a first side of a second membrane comprising a cured product of a silicone composition with at least part of the first retentate gas mixture to produce a second permeate gas mixture on a second side of the second membrane and a second retentate gas mixture on the first side of the second membrane, wherein the second permeate gas mixture is enriched in the first gas component, the second retentate gas mixture is depleted in the first gas component, and the silicone composition comprises a silicone-polyether copolymer having curable silicon-bonded groups.

14. The method according to any one of claims 10-13, further comprising contacting a first side of a second membrane comprising a cured product of a silicone composition with at least part of the first permeate gas mixture to produce a second permeate gas mixture on a second side of the second membrane and a second retentate gas mixture on the first side of the second membrane, wherein the second permeate gas mixture is enriched in the first gas component, the second retentate gas mixture is depleted in the first gas component, and the silicone composition comprises a silicone-polyether copolymer having curable silicon-bonded groups.

1 5. The method according to any one of claims 13-14, further comprising contacting a first side of a third membrane comprising a cured product of a silicone composition with at least part of the first retentate gas mixture, the first permeate gas mixture, the second permeate gas mixture, the second retentate gas mixture, or a combination of one of at least part of the second permeate gas mixture and at least part of the second retentate gas mixture and one of at least part of the first permeate gas mixture and at least part of the first retentate gas mixture to produce a third permeate gas mixture on a second side of the third membrane and a third retentate gas mixture on the first side of the third membrane, wherein the third permeate gas mixture is enriched in the first gas component, the third retentate gas mixture is depleted in the first gas component, and the silicone composition comprises a silicone-polyether copolymer having curable silicon-bonded groups.