Showing papers on "Gas separation published in 1987"

Gas Separation by Adsorption Processes

Abstract: Adsorbents and adsorption isotherms equilibrium adsorption of gas mixtures rate processes in adsorbers adsorber dynamics - bed profiles and breakthrough curves cyclic gas separation processes pressure-swing adsorption - principles and processes pressure-swing adsorption - models and experiments.

Polyimide gas separation membranes

Abstract: Semi-flexible aromatic polyimides, prepared by polycondensation of dianhydrides with phenylene diamines having alkyl substituents on all ortho positions to the amine functions incorporating at least in part 3,3',4,4'-benzophenone tetracarboxylic dianhydride, are auto photochemically crosslinkable. Membranes formed from this class of crosslinked polyimides have improved environmental stability and superior gas selectivity than the corresponding uncrosslinked polyimide. The range of gas permeation properties observed allows for the tailoring of membrane material for widely diverse gas separations. The high permeabilities of some gases from multicomponent mixtures is due to the optimization of the molecular free volume in the polymer.

Semipermeable thin-film membranes comprising siloxane, alkoxysilyl and aryloxysilyl oligomers and copolymers

Abstract: Novel semiperimeable membranes and thin film composite (TFC) gas separation membranes useful in the separation of oxygen, nitrogen, hydrogen, water vapor, methane, carbon dioxide, hydrogen sulfide, lower hydrocarbons, and other gases are disclosed. The novel semipermeable membranes comprise the polycondensation reaction product of two complementary polyfunctional compounds, each having at least two functional groups that are mutually reactive in a condensation polymerization reaction, and at least one of which is selected from siloxanes, alkoxsilyls and aryloxysilyls. The TFC membrane comprises a microporous polymeric support, the surface of which has the novel semipermeable film formed thereon, preferably by interfacial polymerization.

Process and dope for forming asymmetric gas separation membranes having graded density skins

Abstract: A process and dope are disclosed for forming high free volume, asymmetric gas separation membranes having graded density skins and macrovoid-free morphology from a solvent system comprising a Lewis acid, Lewis base, and a Lewis acid:base complex which dissolve hydrophobic polymers. The dopes have high total solids, high viscosity and low coagulation (g) values which enhance rapid gelation without the formation of macrovoids and which minimize densification. The dopc solvent system complexes are readily disassociated by the coagulation medium and the component molecules are miscible in the medium which provides for rapid desolvation of the formed membrane thus providing a membrane having low residual solvent retention.

Gas dehydration membrane apparatus

Abstract: This invention provides an apparatus and process for dehydrating gases, the apparatus comprised of uncoated, asymmetric membranes having controlled porosity. The membranes being formed of polymeric materials which have high transport selectivity for water vapor and sufficient porosity to provide adequate feed gas permeation sweep for the permeated water vapor ensuring conditions of continued effective dehydration. Uncoated asymmetric gas separation membranes have been found to be effective for dehydrating gases such as air, gases containing hydrocarbons, acid gases and admixtures of these gases. The membranes provided by the invention possess a unique combination of properties and characteristics which promote an effective process for the dehydration of gases.

Material selection considerations for gas separation processes

Abstract: Advantages and disadvantages associated with common membrane types used in gas separation operations are reviewed. Comparisons between dense-walled and several different types of asymmetric structures are made. In addition to overall membrane structure, the molecular natures of different membrane material types are treated. Tradeoffs between the use of rubbery and glassy polymers are considered first, followed by a treatment of the optimization of glassy membrane permeability and permselectivity properties. Material optimization principles are defined in terms of the basic thermodynamic solution and kinetic transport properties of polymers, and applications of these principles are illustrated for a modified poly(phenylene oxide) and a homologous series of polyimides derived from pyromellitic dianhydride.

Method for recovering hydrocarbon vapor

Abstract: A method for recovering hydrocarbon vapor wherein permeable mixed gases of high concentration hydrocarbon vapor and the residual mixed gases of low concentration hydrocarbon vapor are separated, through gas separation membrane, from initial mixed gases containing hydrocarbon vapor to absorb permeable mixed gases, and a method for recovering hydrocarbon vapor wherein initial mixed gases containing hydrocarbon vapor are brought into contact with liquid absorbent to recover hydrocarbon vapor, and gases of high concentration hydrocarbon vapor and gases of low concentration hydrocarbon vapor are separated, through gas separation membrane, from treated gases from which hydrocarbon vapor has been absorbed in the preceeding process.

The Esterification of Oleic Acid with Ethanol Accompanied by Membrane Separation

Abstract: The use of water-permeable membranes for gas separation in the esterification of oleic acid with ethanol was studied. The perfect conversion due to the equilibrium shift was obtained by using a polyimide membrane for removal of water vapor generated by the esterification.

A Study of Concentration Polarization Phenomenon on the Surface of a Gas Separation Membrane

Abstract: Mass transfer coefficients on the surface of porous glass membrane were obtained from separation tests of H2-CO mixtures. These data agree with the correlation presented by Ghosh and Upadhyay for mass transfer on an impermeable wall. In addition, effects of the selectivity of membrane and bulk composition on the concentration polarization phenomenon are discussed and the limiting permeability which is affected by the polarization is represented as a function of mass transfer coefficient.

Asymmetric gas separation membranes having graded density skins

Abstract: Asymmetric gas separation membranes having graded density skins and macrovoid-free morphology comprised of glassy, hydrophobic polymers are disclosed which are effective for separating gases with significant increases in permeation while maintaining equal or greater separation selectivity. The membranes have increased free volume and the graded density skin exhibits a density gradient which becomes more dense with increasing proximity to the surface, the membrane effectively decouples the interdependency between permeability and separation selectivity.

Gas separation membrane

Abstract: A gas separation membrane with excellent gas separation properties is disclosed. The gas separation membrane is substantially free from pinholes and consists essentially of a crosslinked polyolefin or a crosslinked polyarylene oxide. This gas separation membrane is produced by evaporating a solution containing a polyolefin or a polyarylene oxide having an active functional group which can form crosslinking site therebetween or which can react with a crosslinking agent to form a crosslinking site.

Hydrated metal ionomer membranes for gas separation

Abstract: The invention relates to a process of separating gases using a membrane fabricated from a polymer containing a perfluorinated backbone and pendant hydrated metal ionomer groups wherein the pendant hydrated metal ionomer groups contain cations of alkali metals, alkaline earth metals, or transition metals bound to SO 3 - . The hydrated membranes have improved gas permeabilities with comparable gas selectivities over the unhydrated membranes. The membranes may be used to separate gas mixtures containing such gases as carbon dioxide and methane.

Process for membrane separation of gas mixtures

Abstract: A method for the substantial separation of at least one gas component from a gas mixture to generate a residue gas substantially depleted of the gas components to be separated. A semipermeable membrane is provided which has a feed gas side and a sweep gas side. The feed gas side is contacted with a feed gas mixture containing at least one gas to be retained and at least one gas to be separated therefrom. The sweep side is simultaneously contacted with a sweep gas having a pressure lower than that of the feed gas. The partial pressure of certain gas components present on both sides of the membrane are balanced to cause the remaining gas components to diffuse in either direction across the membrane depending upon their differential partial pressures. Apparatus for the gas separation is also provided.

Gas separation and purification

Abstract: A method for gas separation of adsorbable components from less adsorbable components on fixed adsorbent beds, comprising the steps of: a) flowing a feed gas mixture under adsorption pressure to an adsorbent bed to selectively adsorb components from the feed gas onto the adsorbent bed, the bed having a feed end and a product end; and b) displacing the feed gas with a gas having a higher concentration of adsorbable components, whereby less adsorbable components are displaced from a portion of the bed; and c) depressurizing the bed by taking out gas simultaneously from at least two different locations of the bed to recover substantially pure less adsorbable components at the product end of the bed and to recover the adsorbable components from at least one of the different locations.

Method for preparing composite membranes for enhanced gas separation

Abstract: Composite membranes having advantageous combinations of selectivity and permeability are prepared by the coating of a separation layer on a porous support layer containing a controlled amount of liquid in the range of from about 10% to about 90% by weight of the liquid present in the fully wet support layer.

Ultrathin ethylcellulose/poly(4-methylpentene-1) permselective membranes

Abstract: An ultrathin, permselective membrane for use in gas or vapor separations. The membrane comprises a permselective layer of ethylcellulose in combination with one or more permselective layers of poly(4-methylpentene-1). The permselective membrane is preferably coated onto a microporous substrate, such as an asymmetric Loeb-Sourirajan type membrane. The resulting membrane has high gas fluxes and selectivities, and can be used, for example, to separate oxygen and nitrogen; hydrogen sulfide from nitrogen, methane or carbon dioxide; hydrogen from nitrogen; sulfur dioxide or ammonia from nitrogen; or water vapor from air. A method of preparing such a membrane is also provided, as is a gas separation process using the membrane.

Dehumidification method for mixed gas

Abstract: PURPOSE: To remove selectively water vapor effectively from various kinds of mixed gas at a high removal rate by using an aromatic polyimide gas separating membrane and carrying out gas separation at a specific temperature or more. CONSTITUTION: Mixed gas containing water vapor is continuously fed from a mixed gas feed opening 3 at a temperature of 60°C or more into a gas separation device 1 with a built-in aromatic polyimide gas separating membrane 2, and the mixed gas is flowed along the gas feeding side of the gas separating membrane 2. The water vapor in the mixed gas permeates the gas separating membrane 2 efficiently by carrying out gas separation of the gas separating membrane 2 at the temperature of 60°C or more, and the mixed gas (impermeable gas) sufficiently dehumidified and dried is prepared on the gas feeding side of the gas separating membrane 2, and said gas is exhausted out of an impermeating gas exhaust outlet 4. The water vapor permeating the gas separating membrane 2 is exhausted and removed out of a permeating gas exhaust outlet 5. COPYRIGHT: (C)1988,JPO&Japio

Gas separation method employing two kinds of membranes

Abstract: PURPOSE:To make it easy to control the dew point in the removal of low- volatile components, by allowing a mixed gas composed of at least any of H2, CO2 and CO and a volatile hydrocarbon gas to pass through two membrane modules having different adsorption rates for specific components. CONSTITUTION:A mixed gas composed of any of H2, CO2 and CO gases and a gas of volatile hydrocarbons is allowed to pass through a first-step membrane module through which high boiling-point components in the volatile hydrocarbon gas pass faster than methane. Subsequently, H2, CO2 or CO is separated from the resulting mixed gas by allowing the gas of H2, CO2 or CO to pass faster than the volatile hydrocarbon gas components. For example, by the use of a silicon membrane for the first-step membrane module 1 and a cellulose membrane or a second-step membrane module 2, a natural gas having a CO2 concentration of 6.23vol.% is allowed to pass through the modules, thereby obtaining a pipeline gas having a CO2 concentration of 2vol.%.

The use of polycarbonate containing semipermeable membranes in the separation of gases.

Abstract: An improved gas separation membrane comprises a thin discriminating layer consisting predominantly of a carbonate polymer derived from a bisphenol corresponding to formula I wherein R at each occurrence is independently H, CI, Br, or C 1 -C 4 alkyl and R 1 is -CO-, -S-, -SO 2 -, -0-, a C 1 -C 6 divalent hydrocarbon radical, or a C 1 -C 6 divalent fluorocarbon radical, or inertly substituted C 1 -C 6 divalent hydrocarbon radical, with the proviso that at least 25 weight percent of the moieties derived from the bisphenol of formula I present in the discriminating layer bear R groups which are exclusively Br or CI, said gas separation membrane exhibiting a separation factor for oxygen and nitrogen at the ambient temperature of at least 6.1. The membrane has particular application to separating oxygen from nitrogen, or a nitrogen-containing gas. •

Integrated capillary evaporator for use as a thermal-cycle heat-absorbing element

Abstract: 1. Heat absorbing element of a self-supplying, capillary-pumped cooling cycle, characterised by the use of a porous plastic for the integration of the components for liquid transport, liquid storage and gas separation.

Control of methane fermentation

Abstract: PURPOSE:To facilitate pH value control, by separating the gas generated in a methane fermentation tank into gas separation membrane transmitted gas and non-transmitted gas different in the concn of carbon dioxide and allowing both gases to pass through the methane fermentation tank by a three-way cock receiving change-over operation by a pH value controller CONSTITUTION:A part of the gas generated in a methane fermentation tank 1 is pressurized by a compressor 4 and separated into gas separation membrane transmitted gas and non-transmitted gas by a gas separator 5 The gas separation membrane transmitted gas and the non-transmitted gas pass through a gas injection three-way cock 6 to be passed through the methane fermentation tank 1 by a blower 7 The CO2 partial pressure of the gaseous phase in the tank changes and the pH value of the liquid phase therein changes This pH is detected by a sensor 2 and, when deviation is generated with respect to a definite pH set value, a cock change-over indication signal is sent to the gas injection three-way cock 6 by a pH value controller 3

Composite membranes of poly (methyl methacrylate) blends, their manufacture and their use

Abstract: Composite membranes are disclosed having a separation layer comprised of a mixture of poly(methy methacrylate) or a copolymer thereof and at least one cellulosic derivative resulting in enhanced separation and permeating characteristics of the overall composite membrane. Processes for making these composite membranes and the methods of using them are also disclosed. The membranes are particularly useful in gas separation applications and are most suited for the separation of hydrogen from a hydrogen containing stream.

Concentration of aqueous solution of organic substance

Abstract: PURPOSE: To separate an org. substance without swelling a gas separation membrane, by a method wherein an aqueous solution of an org. substance is evaporated by an evaporator to form a gaseous mixture of the vapor of the org. substance and steam and said mixture is separated by the steam permselective gas separation membrane. CONSTITUTION: An aqueous solution of an org. substance is introduced into an evaporator 1 from a raw material supply line A. The aqueous solution is evaporated in said evaporator 1 to form a gaseous mixture consisting of the vapor of the org. substance and steam and said mixture is again raised in temp. by an overheater 3 and regulated to predetermined pressure and temp. to be supplied to a gas separation membrane 4. The pressure on the primary side of said membrane is pref. set to about 760W5,000mmHg and the temp. on the same side thereof is pref. set to 70W150°C and, by operating the gas separation membrane 4 under this high temp. and high pressure condition, the permeation amount of steam can be increased. The conc. solution of the org. substance generated on the primary side of the membrane is recovered from a take-out line C and the steam sucked on the secondary side of the membrane is condensed by a cooler 5 to be returned to the evaporator from a reduced pressure tank 6 through a return line F. COPYRIGHT: (C)1988,JPO&Japio

Gas separation membrane.

Abstract: PURPOSE: To obtain the title gas separation membrane having higher strength than the membrane consisting of silicone and having a high separation factor of oxygen from nitrogen by using fluorine-contg polyphenylacetylene to form the membrane CONSTITUTION: The membrane is formed by using fluorine-contg polyphenylacetylene having a group shown by the general formula I Tungsten hexachloride, etc, are used as the polymerization catalyst to polymerize fluorine- contg phenylacetylene The obtained polymer having 01W10dl/g limiting viscosity, 50W250°C glass transition temp and 200W500°C thermal decomposition initiating temp by TGA is used The polymer is dissolved in a hydrocarbonic or halogenous solvent to obtain a 01W20wt% soln A thin membrane is prepared by using the soln A membrane having 01W100μm thickness, ≥10 -10 cc(STP)cm/ cm 2 sec cmHg oxygen permeation coefficient, and 3W5 oxygen separation factor can be obtained COPYRIGHT: (C)1987,JPO&Japio

Gas separation process

Abstract: of EP0241313A process for the enhanced separation of gases comprising: (a) contacting a feed gas stream (1) at an elevated pressure with a permeable membrane (4) capable of selectively permeating a first component thereof, thereby obtaining a first component enriched, second component depleted permeate portion (6) of said feed stream (1) at a reduced pressure, and a second component enriched, first component depleted non-permeate portion (5) of said feed stream (1) substantially at said elevated pressure; (b) withdrawing said non-permeate gas (5) from the permeable membrane (4); (c) passing said permeate gas (6) to the feed end of an adsorbent bed in a pressure swing adsorption system (9) capable of selectively adsorbing additional amounts of said second component therefrom at an upper adsorption pressure, with unadsorbed, purified first component gas being withdrawn as a high purity gas (10) from the product end of the bed; (d) countercurrently depressurizing the bed to a lower desorption pressure and/or purging said bed (9) to desorb and release a first and second component-containing regeneration stream (11) from the feed end of the bed (9); and (e) recycling said at least a portion of regeneration stream for combination with additional quantities of the feed gas stream, whereby the separation of the first component is achieved at a high purity and desirable recovery levels, with said second component being available at a desirably high pressure level. l

Functional separation membrane

Abstract: PURPOSE:To obtain the title functional separation membrane having a separation layer with high separation factor and permeation rate by using a nonwoven fabric with the surface having specified Bekk smoothness as the base material layer. CONSTITUTION:A nonwoven fabric such as a wet-type nonwoven fabric made of, for example, polyester fiber with the surface having >=10S Bekk smoothness is used as the base material layer 1. A soln. of, for example, sulfone in N,N- dimethylformamide is applied thereon, the material is immediately dipped in water to solidify the soln. and to remove the solvent, and a porous layer 2 is formed. A cross-linked silicone film is formed on the porous layer 2 as a substrate layer 3 by the coating method. The soln. of poly(4-methylpentene-1) in cyclohexane diluted with freon is applied on the substrate layer 3 as a separation layer 4, and then dried to produce a gas separation membrane.

Concentration of aqueous organic solution

Abstract: PURPOSE: To separate azeotropic organic components easily and at low cost by a system in which an azeotropic mixture solution is separated through the first liquid evaporation process, the second separation process using a gas separation membrane and the third distillation process of gas mixtures containing a high percentage of water vapor in that sequential order CONSTITUTION: Ethanol solution is evaporated by the first evaporator 1 The gas mixture consisting of evaporated ethanol vapor/water vapor thus obtained is heated to 130°C by a superheater 3, and this heated gas mixture is supplied to the primary side of a gas separation membrane 4 from a line C Then, the secondary side of said membrane is decompressed, and the permeating mixed gas is supplied to the second evaporator 5 from a line E An effluent mixed gas from the top of the evaporator is condensed by a cooler 6 through a line F, and the condensed product is returned to the first evaporator 1 through lines G, L The non-permeating ethanol vapor in the membrane is recovered through a line D, while water is recovered from the bottom of the second evaporator through lines H, K Vapor separation becomes feasible because of the vapor supplied instead of an aqueous organic solution for separation by the membrane Separation of organic mixture is easy because it is supplied to the membrane is the state not liquid but gas COPYRIGHT: (C)1988,JPO&Japio

Composite membrane for gas separation

Abstract: PURPOSE: To obtain the title membrane having good air-permeability in the vertical direction and excellent tensile strength by laminating a membrane for gas separation on a porous supporting material which consists of both a dense layer and a porous layer arranged with fibrous reinforcing material in the inside and has 50W80% void. CONSTITUTION: For example, nonwoven fabric is fixed on glass plate and a polyethersulfone resin soln. is uniformly applied thereon and immersed into aqueous coagulating liquid together with the glass plate and peeled therefrom and washed with water and thereafter dried. Thereby the following porous supporting material 12 is obtained which consists of both a dense layer 12a having hole diameter of the surface not less than 0.5μm and a cavity layer 12b arranged with fibrous reinforcing material 12c in the inside and having hole diameter not less than 0.5μm and has 50W80% void. A composite membrane is obtained by laminating a membrane 11 for gas separation such as polydimethylsiloxane, polyhydroxystyrene and a copolymer of polysulfone on the porous supporting material 12. This composite membrane is excellent in air-permeability in the vertical direction and tensile strength and air leak is not caused even when it is bonded to a module frame. COPYRIGHT: (C)1988,JPO&Japio