Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J47/00—Ion-exchange processes in general; Apparatus therefor
  • B01J47/12—Ion-exchange processes in general; Apparatus therefor characterised by the use of ion-exchange material in the form of ribbons, filaments, fibres or sheets, e.g. membranes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
  • B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
  • B01D71/82—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 characterised by the presence of specified groups, e.g. introduced by chemical after-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J39/00—Cation exchange; Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
  • B01J39/08—Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
  • B01J39/16—Organic material
  • B01J39/18—Macromolecular compounds
  • B01J39/20—Macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J41/00—Anion exchange; Use of material as anion exchangers; Treatment of material for improving the anion exchange properties
  • B01J41/08—Use of material as anion exchangers; Treatment of material for improving the anion exchange properties
  • B01J41/12—Macromolecular compounds
  • B01J41/14—Macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/144—Purification; Separation; Use of additives using membranes, e.g. selective permeation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/30—Polyalkenyl halides
  • B01D71/32—Polyalkenyl halides containing fluorine atoms
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals

Definitions

• This invention relates to the membrane separation mainly of olefin hydrocarbons from olefin/paraffin hydrocarbon mixtures. More particularly, the present invention relates to a type of a fluorinated polymeric membrane suitable for the facilitated transport separation of olefins from mixtures of olefins and paraffins in which a facilitating moiety is on the backbone of the polymeric membrane.
• Olefin compounds such as ethylene and propylene
• Paraffin compounds such as ethane and propane are also produced by the thermal decomposition steps.
• olefin production usually produces a mixture of olefins and paraffins.
• a typical distillation process reportedly can involve using a distillation column incorporating contact area equivalent to least 100 theoretical trays operating at a high pressure of about 23 atm and sub-zero degree temperature.
• a typical distillation process reportedly can involve using a distillation column incorporating contact area equivalent to least 100 theoretical trays operating at a high pressure of about 23 atm and sub-zero degree temperature.
• similar operation conditions at higher temperatures are also required.
• Membrane technology has been considered to replace distillation for olefin- paraffin separation.
• Commercially practical separation of many important olefin/paraffin mixtures, for example ethylene/ethane has been difficult to accomplish using selectively permeable polymeric membranes.
• Traditional polymeric membranes cannot discriminate well between ethylene and ethane with commercially attractive productivity because these compounds are similar in both molecular size and physical properties that affect selective permeability.
• FTMS Facilitated transport membrane separation
• a typical liquid carrier is an aqueous solution containing a metal salt.
• Olefin components associate preferentially with the carrier by reversibly complexing with the metal of the salt.
• a complexed olefin can transfer across the liquid filled membrane with significantly higher selectivity relative to the undesired paraffin feed components, than can be achieved by the non-metal- complexed olefin.
• Liquid state FTMS functions for olefin/paraffin separations to an extent but has drawbacks.
• a principal flaw is gradual depletion of carrier that causes permeance to diminish with service time.
• solvent or other moieties present in the liquid carrier that escape into the permeate stream need to be removed from the desired product components.
• a solid homogeneous FTMS membrane is prepared from a hydrophilic polymer such as polyvinyl alcohol.
• the membrane does not have a liquid carrier.
• a metal ion or metal salt capable of complexing with aliphatically unsaturated hydrocarbons, for example silver nitrate, is distributed homogeneously in the hydrophilic polymer.
• the polymer is crosslinked.
• Kimura et al. in US patent 4318714 discloses FTMS using a polymeric ion exchange membrane in which the polymer has electrostatically retained counter ions reversibly reactive to the gas molecules being separated.
• Example 4 describes high selectivity by pure component separation of ethylene and ethane by sulfonated polyxylylene oxide ion exchange resin that was immersed in AgN0 3 solution then rinsed in distilled water to remove residual AgN0 3 solution and Ag+ ions. The feed gases were humidified to 90% relative humidity.
• Eriksen et al. US 5191151 discloses a process for separating C 2 -C 4 olefins from Ci -C 6 paraffins using a membrane of an ion exchange resin of tetrafiuoroethylene/ perfluorovinylether sulfonated copolymer with Ag + ion eschange.
• the membrane is prepared by certain specific ion exchange methods that includes steps of converting the poly(perfluorosulfonic acid) from protonic form to anionic -S0 3 " form by contacting with an alkali metal solution, swelling the converted membrane in an alcohol, and exchanging a silver ion in the ionomer.
• the gas mixture feed For the membrane to separate olefin from paraffin, the gas mixture feed must be humidified.
• the novel metal exchanged fluorinated ionomer is a copolymer minimally including two repeating unit types. These are the polymerized derivative of a
• perfluorinated cyclic or cyclizable monomer and a strong acid highly fluorinated vinylether compound in which the acid moiety is exchanged with a cation of a Group 1 1 metals.
• Selected metal exchanged fluorinated ionomers are readily soluble and can be formed into thin, selectively gas permeable membranes by solution deposition methods. These membranes are suitable for separating olefins from olefin/paraffm mixtures. Good selectivity and transmembrane flux properties can be obtained without humidifying the membrane feed gas mixture.
• a solid state separation membrane comprising a nonporous selectively permeable layer consisting essentially of a metal exchanged fluorinated ionomer comprising repeating units A and B in which A is a polymerized derivative of a perfluorinated cyclic or cyclizable organic compound, and B has the formula
• X is S0 2 or CO
• Y is NS0 2 R f 1 or O
• R f and R f 1 are each independently perfluoroalkyl or perfluoroalkyl ether groups having 1 -20 carbon atoms
• M is a Group 1 1 metal
• the ion exchanged fluorinated ionomer comprises m and n fractions of total number of repeating units A and B respectively, each of m and n being greater than 0 and less than 1.0.
• a method of making a metal exchanged fluorinated ionomer for use in membrane separation of olefins from paraffins comprising the steps of: (A) providing a hydrolyzed copolymer comprising repeating units A being a polymerized derivative of a perfluorinated cyclic or cyclizable organic compound and repeating units B having the formula - CF 2 - CF -
• X is S0 2 or CO
• Y is NS0 2 R f 1 or O
• R f and R f 1 are each independently perfluoroalkyl or perfluoroalkyl ether groups having 1-20 carbon atoms
• B dissolving the hydrolyzed copolymer in a liquid comprising a polar solvent to form a polymer solution
• C providing a stoichometric excess of fine particles of a metal salt of a Group 11 metal
• D charging the fine particles of the metal salt to the polymer solution and agitating the polymer solution with intensity effective to maintain the particles in a uniform dispersion in the polymer solution for a duration effective to exchange the Group 11 metal with the acid form copolymer thereby forming a metal exchanged fluorinated ionomer
• E filtering the dispersion to remove substantially all residual particles of the metal salt and thereby providing a metal exchanged fluorinated ionomer solution.
• a method of making a membrane for the separation of olefins from a mixture with paraffins comprising the steps of: (I) providing a metal exchanged fluorinated ionomer solution produced by a method comprising the following steps (A) providing metal exchanged fluorinated ionomer comprising repeating units A and B in which A is a polymerized derivative of a perfluorinated cyclic or cyclizable organic compound, B has the formula
• X is S0 2 or CO
• Y is NS0 2 R f 1 or O
• R f and R f 1 are each independently perfluoroalkyl or perfluoroalkylether groups having 1-20 carbon atoms
• M is a Group 11 metal
• Also provided is a method of separating an olefin from a feed mixture of the olefin with a paraffin comprising the following steps: (A) providing a selectively permeable membrane comprising a nonporous active layer consisting essentially of a metal exchanged fluorinated ionomer comprising repeating units A and B in which A is a polymerized derivative of a perfluorinated cyclic or cyclizable organic compound, B has the formula
• X is S0 2 or CO
• Y is NS0 2 R f 1 or O
• R f and R f 1 are each independently perfluoroalkyl or perfluoroalkylether groups having 1-20 carbon atoms
• M is a Group 11 metal
• this invention provides a metal exchanged ionomer solution comprising (I) a liquid solvent system comprising a polar solvent, and (II) a metal exchanged fluorinated ionomer comprising repeating units A and B in which A is a polymerized derivative of a perfluorinated cyclic or cyclizable organic compound, and B has the formula
• X is S0 2 or CO
• Y is NS0 2
• R f and R f 1 are each independently perfluoroalkyl or perfluoroalkylether groups having 1-20 carbon atoms
• M is a Group 11 metal, and in which the metal exchanged fluorinated ionomer is dissolved in the liquid solvent system.
• This invention is directed to separating olefins from mixtures (occasionaly herein, "feed mixtures") of olefins with paraffins.
• "Olefins” refers to chemical compounds having at least one carbon-carbon double bond. Other functional groups, such as ketone, esters, or alcohols may also be present.
• Paraffins refers to chemical compoujids free from carbon-carbon double bonds.
• Preferred olefins in this invention are mono-saturated hydrocarbons of the formula C n H 2n wherein n is 2 to 30.
• Preferred paraffins are saturated hydrocarbons of the formula C n H 2n+2 wherein n is 2 to 30
• the invention is very effective for separating an olefin having a particular number of carbon atoms in the range of 2-30 from a feed mixture comprising that olefin and the paraffin that has the same number of carbon atoms.
• the feed mixture can include more olefins and paraffins than the one olefin and one paraffin that have the common particular number of carbon atoms. Often the feed mixture is in the gaseous state.
• this invention relates to novel methods of making and using a new metal ion exchange polymer, more specifically, a metal exchanged fluorinated ionomer.
• This ionomer comprises at least two types of repeating units "A" and "B" in random order with a generalized -[A] m -[B] sandwich backbone configuration.
• A is a polymerized derivative of a perfluorinated cyclic or cyclizable organic compound.
• B is a highly polymerized derivative of a fluorinated vinylether compound in which the acid moiety is exchanged with a cation of Group 1 1 metals.
• the metal exchanged fluorinated ionomer thus has a structure of formula (1)
• A is the polymerized derivative of perfluorinated cyclic or cyclizable organic compound
• m and n are the respective fractions of total number of repeating units A and the highly fluorinated vinylether compound derivative in the ionomer
• X is S0 2 or CO
• Y is NS0 2 Rf ] or O
• Rf and Rf 1 are each independently perfluoroalkyl or perfluoroalkylether groups having 1-20 carbon atoms, and
• M is a Group 1 1 metal.
• the metal exchanged fluorinated ionomer can be formed by several
• copolymerization strategies involve copolymerizing appropriate perfluorinated cyclic or cyclizable organic compound monomers and highly fluorinated vinylether compound monomers selected to obtain desired repeating units A and B, respectively.
• the vinylether compound is perfluorinated.
• the sulfonyl fluoride group in the resulting copolymer can be hydrolyzed and acidified to the acid form in which OH replaces F.
• the acidic hydrogen is then exchanged with a metal salt of M to obtain the metal exchanged fluorinated ionomer.
• the acidic hydrogen on nitrogen is then exchanged with a metal salt of M to obtain the metal exchanged fluorinated ionomer.
• X CO
• the acidic hydrogen is then exchanged with a metal salt of M to obtain the metal exchanged fluorinated ionomer.
• Another strategy calls for copolymerizing the perfluorinated cyclic or cyclizable organic compound monomer with the monomer that is the acid form of the highly fluorinated vinylether compound and then exchanging the terminal hydrogen atom of the R f or R f 1 group with M. It is also contemplated that the perfluorinated cyclic or cyclizable organic compound monomer can be copolymerized with comonomer being the metal ion exchanged form of the highly fluorinated vinylether compound to directly yield the metal exchanged fluorinated ionomer.
• Preferred Group 11 metals, M are silver and copper.
• perfluorinated cyclic or cyclizable organic compound are perfluoro-2,2-dimethyl-l,3-dioxole (“PDD”).
• PDD perfluoro-2-methylene ⁇ 4- methyl- 1 ,3-dioxolane
• PFVE perfluoro (alkenyl vinylether)
• TFMD 2,2,4- trifluoro-5 trifluoromethoxy-1,3 dioxole
• PDD perfluoro-2,2-dimethyl-l,3-dioxole
• PMD perfluoro-2-methylene ⁇ 4- methyl- 1 ,3-dioxolane
• PFVE perfluoro (alkenyl vinylether)
• TFMD 2,2,4- trifluoro-5 trifluoromethoxy-1,3 dioxole
• vinylethers containing sulfonyl fluoride such as SEFVE
• CF2 CFOCF2CF2S02F
• CF2 CFOCF2CF2CF2CF2S02F
• vinylether carboxylates such as
• CF2 CFOCF2CF(CF3)OCF2CF2C02CH3.
• the preferred highly fluorinated vinylether compound is SEFVE.
• the ionomer can optionally include additional repeating units of polymerized fluorinated compounds, with the proviso that repeating units A and B are also present.
• additional repeating units are those of formula (1) disclosed by Watakabe et al. in US patent no. 7,220,508, the disclosure of which is hereby
• CTFE chlorotrifluoroethylene
• VDF vinylidene fluoride
• TrFE trifluoroethylene
• IEPP poly(PDD/SEFVE) sometimes preferred to as "IEPP” ionomer. It is a copolymer of PDD and SEFVE in which the fluorine atom of the terminal sulfonylfluoride group is replaced by an oxygen and a metal ion.
• silver metal ion exchanged ionomers of formula (2) have been discovered to provide excellent permeability and selectivity when used as the active layer of a selectively gas permeable membrane for the separation of olefins from mixtures with paraffins. Without wishing to be bound by a particular theory , * it is believed that the silver facilitates the transport of the olefin.
• Other metal ions that may be used include copper and gold.
• the proportions of repeating units A to repeating units B in the polymer chain, i.e., m:n ratio, for highly effective selectively permeable ionomers can range widely.
• the mole fraction of repeat units B in the ionomer is at least about 0.05, preferably at least about 0.1, more preferably at least about 0.2, and most preferably at least about 0.4.
• the preferable mole fraction of repeat units B is at most about 0.5
• the mole fraction of repeat units A is at least about 0.3 and, when no optionally additional fluorinated compound repeating units are present, will be an amount complementary to B totaling to 1.0.
• One embodiment of a method of making the novel ionomer involves multiple steps generally beginning with copolymerizing A and B precursor monomers and then hydrolyzing the resulting polymer to replace terminal sulfonyl fluoride atoms with hydrogen to produce an acid form ionomer.
• the acid form precursor ionomer poly(PPD/SEFVE-H) has structure as shown in formula (3).
• Watakabe et al. US 7220508 discloses a procedure suitable for making this poly(PPD/SEFVE-H) precursor that is exemplified in US '508 Examples 1 and 2.
• the disclosure of US '508 along with entire disclosures of all U.S. patents and patent applications identified in this application are hereby incorporated by reference herein.
• TFE/SEFVE-H ionomer with an alkali metal solution to exchange the alkali metal in the ionomer, exposing the alkali exchanged ionomer to an alcohol to swell the ionomer, and then contacting the swollen alkali metal exchanged fluorinated ionomer with a silver- containing aqueous solution to obtain a silver exchanged ionomer.
• Additional preferred steps include separating the alkali metal exchanged fluorinated ionomer from excess alkali metal solution and heating the alkali metal exchanged fluorinated ionomer to about 100-350°C for up to 3 hours prior to swelling, removing excess alcohol from the swollen alkali metal exchanged fluorinated ionomer, and removing excess silver solution from the silver exchanged ionomer.
• Erikson discloses that the silver exchanged TFE/SEFVE ionomer is useful for separating C2-C4 olefins from Ci-C 6 paraffins.
• the present novel method provides a simpler and very efficient way to obtain an operative metal exchanged fluorinated ionomer for use in membranes having superior ability to separate olefins from mixtures with paraffins.
• This method starts by dissolving precursor poly(PDD/SEFVE-H) ionomer (formula (3)) in an appropriate solvent.
• novel metal exchanged fluorinated ionomers such as PDD/SEFVE (“IEPP”) ionomers and corresponding precursor acid form ionomers, is that they are soluble in liquid mixtures of fluorosolvents and common, non- fluorinated, polar solvents.
• Some of the novel metal exchanged fluorinated ionomers are soluble in liquid that consists essentially of polar solvents.
• the term "consists essentially of polar solvents” means that the solvent system exclusively utilizes polar solvents or optional other components, but is substantially free of very fluorinated solvents known and selected for ability to dissolve highly and perfluorinated polymers.
• the optional other components are usually in minor proportions, and do not materially affect the basic and novel characteristics of the invention.
• the relative fractions of PDD and SEFVE monomers in the copolymer determine whether a fluorosolvent is called for.
• metal exchanged fluorinated ionomer containing up to about 20 mole % polymerized SEFVE will be soluble in mixtures of fluorinated solvent and common polar solvent.
• IEPP containing more than about 20 mole % SEFVE can dissolve in polar solvents alone. Accordingly, for many compositions, use of extraordinary and usually high priced fluorinated solvents is avoided.
• Products such as thin film membranes of IEPP metal exchanged fluorinated ionomer can be made at reasonable cost using easily obtainable solvents by industry standard liquid deposition techniques such as dipping, spraying, roller coating, doctoring and the like.
• Representative common polar solvents that are suitable to solubilize IEPP copolymers include methanol, ethanol, isopropanol, ethyl chloride, methyl chloride and methylene chloride, dimethylformamide, dimethylsulfoxide, sulfolane, N,N'-dimethyl- imidazolidinone, benzyl alcohol, phenol, cresol and the like.
• fluorosolvents that are primarily intended for solubilizing fluorinated polymers and that are suitable for use in the novel process include
• perfluoroalkanes such as perfluorohexane, perfluoroheptane and perfluorooctane, available from 3M Company, Minneapolis, Minnesota under the tradenames PF5060, PF5070 and PF5080, respectively.
• Other representative fluorinated solvent materials that can be used include FluorinertTM FC-75 and FC-770 Electronic Liquids, and NovecTM HFE-7100, NovecTM HFE-7200, and NovecTM 7300 Engineered Fluids also from 3M.
• Fluorinert FC-75 is a solvent of perfluorinated compounds primarily with 8 carbons, believed to include 2-butyltetrahydrofuran.
• Fluorinert FC770 contains C1-C3 perfluoro N-alkyl morpho lines among other perfluorinated compounds.
• Novec HFE-7100 includes methyl nonafluoroisobutyl ether and methyl nonafluorobutyl ether.
• Novec HFE-7200 includes ethyl nonafluoroisobutyl ether and ethyl nonafluorobutyl ether.
• Novec 7300 contains 1,1,1 ,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)-pentane.
• the acid form precursor PDD/SEFVE-H ionomer can be dissolved in merely ordinary polar organic solvent, such as ethyl alcohol, provided that the mole fraction of SEFVE repeating units of the polymer is at least about 0.2. If the SEFVE repeating unit mole fraction is less, then either a specialty, fluorinated solvent or a blend of polar organic and fluorinated solvents can be used.
• polar organic solvent such as ethyl alcohol
• a subsequent step of the novel method calls for charging a solid metal salt directly to the ionomer solution.
• the metal salt should be in fine particulate form and poorly soluble in the in the ionomer solution.
• poorly soluble is meant that the metal salt solubility should be at most about 10 g/L, preferably at most about 5 g L, more preferably at most about 2 g/L and most preferably at most about 1 g/L.
• the metal salt to be insoluble in the ionomer solution, that is, at most about 0.01 g/1.
• the preferred metal suitable for the ion used with this is silver. Silver salt of any composition that satisfies the particule size and solubility criteria just mentioned may be used.
• Representative silver salt compounds include silver carbonate, cyanide, diethyldithiocarbamate, iodate, nitrate, oxide, phosphate, sulfate, acetate, bromide.
• the solid silver may be heated prior to adding to adding to the solution to facilitate exchange reaction with the polymer.
• the salt temperature should not be raised to a point that adversely affects the polymer.
• With metal salt added solution should be heated to reflux temperature of the solution solvent to disassociate the metal ion from the salt.
• reflux will release carbon dioxide and silver will associate with the polymer by ion exchange.
• the temperature is in the range of about 30 -100°C.
• the ionomer/solvent solution should be agitated effectively to maintain the silver salt in suspension. Typically ion exchange occurs within about an hour. Thereafter the solution can be cooled to room temperature. The excess solid silver salt is then filtered from the ionomer solution. Finally, the polymer can be isolated from the filtrate solution by evaporating the solvent using heat and vacuum.
• the ionomer can be converted from acid to metal form by contacting a solution of a soluble metal salt in an appropriate solvent that is a non-solvent for the ionomer being converted.
• the metal bearing ionomer precipitates.
• the dispersion is heated, cooled, and filtered and rinsed to isolate metal exchanged fluorinated ionomer from the solution.
• solid ionomer can be dispersed in a salt solution of aqueous silver nitrate. The dispersion is heated, typically for up to several hours, cooled, filtered and the solids rinsed with water to yield silver-exchanged ionomer.
• Both conversion methods described above involve heterogeneity of the polymer and metal salt component phases.
• the polymer in solution contacts a solid form metal salt.
• the solid polymer is contacted by soluble salt in solution.
• a main advantageous feature of these methods is that the metal is exchange into the ionomer is substantially complete without an excess of free metal salt present in the polymer product.
• the second monomer e.g., SEFVE is initially hydrolyzed to acid form SEFVE-H.
• the hydrolyzed intermediate is then converted to the desired metal salt.
• the second monomer in metal salt form can then be polymerized with the acyclic or cyclizable fluorinated first monomer, e.g., PDD.
• a polar fluorinated solvent such as trifluoroacetic acid can be used to provide a suitably soluble reaction medium for the first monomer.
• the resulting polymer can be isolated from the polymerization mass and used to form a membrane without further purification.
• metal of insoluble metal salt can be exchanged with polymer in solution.
• the novel ion exchanged ionomer can be cast from solution to form a thin film nonporous selectively permeable gas separation membrane.
• the IEPP ionomer solution can be formed into a membrane without an intermediate step of isolating the IEPP ionomer in solid form. All types of conventional solvent casting membrane formation techniques can be used.
• the solution is deposited as a thin film onto a porous support, excess fluid is drained and the wet IEPP ionomer solution solvent is evaporated to produce a composite membrane.
• Any type of membrane support suitable for solvent deposition can be used, such as flat sheet, pleated sheet, spiral wound, ribbon tube, hollow fiber and the like.
• novel membranes with non-porous active selectively permeable layers of IEPP are remarkably effective for separating olefins from mixtures with paraffins. They are especially useful for separating olefins and paraffins of similar molecular weight and size that are difficult to segregate by conventional methods.
• the extraordinary separation performance is shown in Table II.
• Another significant feature of the novel membrane compositions and processes of this invention is that humidifying the olefin/paraffin feed gas mixture and/or the permeate olefin enriched product is not necessary to achieve commercially productive separation performance.
• This is a departure from traditional membrane separation of olefin/paraffin mixtures typified by processes disclosed in Eriksen US 5191151 that call for the presence of water vapor in the gaseous streams of silver-exchanged ionomer membranes.
• the feed and/or permeate gas mixtures may be humidified. With humidification this invention has been discovered to provide far superior separation performance of olefins from paraffins than is obtained by comparable conventional membrane processes.
• Example 1 Forming silver-exchanged PDD-SEFVE copolymer
• the PDD/SEFVE copolymer was hydrolyzed with KOH dissolved in a
• poly(PDD/SEFVE-H) copolymer (4.9 g) was dissolved in 50 ml of ethyl alcohol at room temperature, i.e., about 25°C. While stirring the solution 1.0 g Ag2C03 powder was added to obtain a suspension. The suspension was heated close to the boiling point of ethyl alcohol and refluxed for 1 hour.
• the suspension was then cooled to room temperature and then filtered to remove residual solid Ag2C03 from the solution.
• the filtrate solvent was evaporated by oven drying at 100°C for 1 hour to yield 4.0 g dry yellow granules of IEPP(Ag+) silver exchanged copolymer.
• the copolymer thus produced is acceptable for practical uses. However, this process can entrain reduced silver not bound to the polymer chain. To recover that reduced silver metal back to polymeric ionic silver, the following optional additional steps can be performed.
• the yellow granules can be repetitively rinsed with dilute hydrogen peroxide and water and re-filtered to obtain a white powder of copolymer.
• An IEPP(Ag + ) copolymer having about 60 mole % PDD repeating units and about 40 mole % SEFVE repeating units was made by a procedure as in Ex. 1.
• the copolymer was dissolved at room temperature in a solution of 70 wt% isopropyl alcohol and 30 wt% Novec 7300 fluid to make 1.2 wt% polymer solution.
• An asymmetrically porous sheet of polyacrylonitrile (PAN) microfiltration membrane was dipped into the polymer solution. The wet sheet was removed and held vertically to drain the excess liquid.
• PAN polyacrylonitrile
• copolymer-coated membrane was then dried in an oven at 100°C overnight to form a non- porous composite membrane.
• PAN substrate membranes coated with IEPP(Ag + ) having different ratios of PDD:SEFVE were made by a procedure substantially as described in Ex. 2. Each membrane was placed in a permeation test cell. A dry gas mixture of 80 wt% propane and 20 wt% propylene was fed at 69 kPa (10 psi) to one side of the cell at a flow rate of 200 standard cm 3 ("sec") per min. maintained by mass flow controllers. The gas mixture permeated the nonporous membranes and permeate stream flow was measured by a bubble flow meter. Nitrogen gas was swept across the permeate side of the membrane at rates in the range of 25-200 scc/min.
• a copolymer was synthesised from a 100:200 PDD:SEFVE mole ratio
• PDD/SEFVE- imide copolymer with repeating unit A of polymerized PDD and repeating unit B of CF 2 -CF(OCF 2 CF(CF 3 )OCF 2 CF 2 S0 2 NHS0 2 CF 3 ).
• the PDD/SEFVE-imide (0.5 g) was mixed in 10 mL water with 85 mg of silver carbonate powder and stirred about 12 hours to exchange silver ions for protons.
• the solid product was filtered and washed with water after which 10 mL of 10 wt% hydrogen peroxide was added.
• microporous substrate to form a membrane.
• the membrane was tested (Ex. 8a) by permeating a 20 wt% propylene/80 wt% propane gas mixture at 60 psi (414kPa) using the procedure described in Exs. 3-5. Selectivity was calculated from measurements of component permeances. The permeation procedure was repeated (Ex. 8b). Results are shown in Table III.
• a PDD/SEFVE-silver exchanged ionomer was prepared as in Ex. 1.
• a 2 wt% solution of this ionomer in a 30 wt% Novec HFE 7300/ 70 wt% isopropyl alcohol solvent mixture was coated on a PAN substrate to fabricate a membrane as described in Ex. 2.
• the membrane was evaluated by permeating pure ethylene and ethane gases separately in duplicate trials (9a, 9b) at the same pressure. A second membrane of same composition was also prepared and the same evaluation was repeated at lower pressure (9c). Results are presented in Table III.
• Example 9 Propylene/Propane Separations with PDD-POESF-Ag+ membrane
• % propylene was humidified to 80% relative humidity ("RH") by bubbling through water at about 24°C and then fed into the cell in contact with the feed side of the membrane.
• RH relative humidity
• Duplicate trials (11a, 1 lb) were conducted and separation results are presented in Table III.
• a membrane of PDD/SEFVE copolymer with silver counter ion was fabricated as in Ex. 2.
• a 10 vol.% ethylene/90 vol.% ethane gas mixture was separated by the membrane in duplicate trials. Results are shown in Table III.
• a membrane of PDD-SEFVE-VF 2 -Ag+ copolymer was prepared as in Ex. 10. The membrane was used in several trials of separating propylene/propane gas mixtures. In each of these trials, a humidified nitrogen sweep gas stream of 300 mL/min was blown through the permeate side of the membrane at 2.8 kPa (0.4 psi). Humidity of the sweep for trials 13a - 13c were respectively 87%>,77%, and 81% RH, respectively. Feed gas mixtures were 10°C, 15°C, and 23°C, and were humidified to 85%, 84% and 81% RH, in trials 13a- 13c, respectively. Data is presented in Table III.
• a membrane was fabricated as in Example 2, and used in successive trials of separating a 414 kPa (60 psi) pressurized, 10 vol.% propylene/90 vol.% propane, room temperature gas mixture.
• Various sweep gas configurations were employed * in the trials.
• the feed mixture was not humidified.
• the vapor above a sealed tank of water was admitted via a transfer line to the permeate chamber of the test cell and drawn across the permeate side of the membrane under vacuum of 6.7 kPa (50 Torr) absolute pressure as a sweep gas.
• Trial 14b was the same except that the transfer line closed such that the permeate side was maintained under dry vacuum and the feed was not humidified.
• a humidified nitrogen gas sweep blown through the permeate side of the membrane cell at 2.8 kPa (0.4 psi) was used and the feed mixture was also humidified. Data are presented in Table III.
• Ex. 14c demonstrates that excellent olefin- to-paraffin selectivity and olefin permeance is obtained with a facilitated transport membrane according to this invention. Due to the inert gas from the sweep stream, the permeate stream usually would need further separation in additional unit operations to remove the inert gas and become suitable for practical use as a chemical process raw material. By comparison, Ex. 14a provides equivalent high olefm-to-paraffin selectivity and moderately lower yet remarkably high olefin permeance. However, this configuration presents the likely more significantly advantageous feature that the sweep stream contains no non-condensable vapor component, such as nitrogen or other inert gas.
• non-condensable is meant that the vapor component does not substantially completely condense from the gas state at upon exposure to temperature in the range of about -40°C to about 0°C and absolute pressure in the range of about 1.3 kPa (lOmmHg) to about 101 kPa (760 mmHg). Consequently highly enriched olefin product can be relatively simply obtained by merely processing the humid permeate stream through a low temperature condenser to condense and drain entrained water vapor. An additional separation of non- hydrocarbon inert sweep compound from the olefin enriched permeate is thus avoided.
• a repeat feed B repeat feed repeat feed Olefin Paraffin O/P Pressure meance meance Selec unit mole% unit mole% unit mole% "O" vol/vol psi (kPa) (GPU) (GPU) tivity

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