Showing papers on "Gas separation published in 1993"

Polymeric Gas Separation Membranes

Abstract: This short Perspective conveys to the general reader of Macromolecules basic approaches of materials science of polymeric membranes for gas and vapor separation. The relations between the polymer structure and transport properties of rubbery and glassy membrane materials are considered. On the basis of acquired information, several methods for quantitative prediction of permeability were developed, and their comparative analysis is given in the Perspective. The past decade was marked by the appearance of a number of novel interesting membrane materials, which will be briefly described in the text. In conclusion, novel approaches for achieving highly permeable and permselective materials (e.g., mixed matrix membranes) will be considered as well as several relevant but not solved so far problems of membrane gas separation.

Polymeric gas separation membranes

Abstract: Theory of Gas Transport in Membranes Membrane Polymers Physical Structure Fabrication Processes Configurations, Packaging and Engineering/System Design Applications

Gas transport properties of polyphenylene ethers

Abstract: Gas transport properties of the polyphenylene ethers poly(2,6-dimethyl-1,4-phenylene oxide)PDMPO, and poly(2,6-diphenyl-1,4-phenylene oxide), PDPPO, and the thioether poly(1,4-phenylene sulfide), PPS, have been measured as a function of pressure and temperature. The PPS material and free volume correlations were used to estimate the behavior of the unavailable poly(1,4-phenylene oxide), PPO. The results show that symmetrical substitution of phenyl groups on the backbone of polyphenylene ether, PDPPO, increases the gas transport properties by one order of magnitude relative to the unsubstituted material, PPO. Symmetrical methyl substitution, PDMPO, however, increase the permeability, apparent diffusion and sorption coefficients even further. The gas transport coefficients correlate with the fractional free volume of the polymers. PDMPO has the largest fractional free volume and gas transport coefficients followed by PDPPO and the PPS. The results show that substitution of phenyl groups, which leads to polymers that have better thermal and oxidative stability than methyl substituted ones, can be a useful means for increasing free volume and gas permeability coefficients. While methyl groups appear to be more effective for the latter, the enhanced chemical stability of phenyl rings may be useful when gas separation membranes are to be used in harsh environments. © 1993 John Wiley & Sons, Inc.

Gas separation process

Abstract: A process for separating condensable organic components from gas streams (1). The process makes use of a membrane (2) made from a polymer material that is glassy and that has an unusually high free volume within the polymer material. Condensable organic components are removed as permeate stream (4), while a residue non-permeate stream is removed as stream (3).

Process for cooling the feed gas to gas separation systems

Abstract: The present invention provides a process for utilizing one stream from a gas separation unit in an evaporation cooler to provide cool water which is used to cool the feed gas mixture by direct or indirect contact prior to entering the gas separation unit.

Gas separation membranes made from blends of aromatic polyimide, polyamide or polyamide-imide polymers

Abstract: The present invention provides for gas separation membranes with superior gas transport properties made from a blend of certain polymers. In particular, certain alkyl substituted aromatic polyimides, polyamides or polyamide-imides are blended with certain aromatic polyimides to provide a gas separation membrane with superior productivity and good selectivity.

Polyimide and polyamide-imide gas separation membranes

Abstract: Novel polyimide and polyamide-imide gas separation membranes and the process of using such membranes to separate one or more gases from a gaseous mixture is disclosed. The polyimides and polyamide-imides are formed from a blend of diamines containing the ester derived from 1,3-diamino-2-hydroxypropane.

Start-up and shut down processes for membrane systems and membrane systems useful for the same

Abstract: The present invention relates to processes and apparatuses for starting up and shutting down membrane gas separation systems comprising at least one gas separation membrane module and at least one membrane dryer module.

Gas separation and purification by polymeric adsorbents: flue gas desulfurization and sulfur dioxide recovery with styrenic polymers

Abstract: High-surface-area polystyrenic sorbents possess all necessary properties for flue gas and tail gas desulfurization: high SO 2 adsorption capacity and diffusion rate, high SO 2 /CO 2 selectivity, and hydrophobicity. NO chemisorbs on these polymers at room temperature, but the NO-treated polymers retain all of the above properties. Model simulations show that pressure swing adsorption cycles using these NO-treated polymers can effectively remove well over 90% of the SO 2 from the flue gases and, at the same time, generate SO 2 -concentrated desorption products containing well over 5% by volume of SO 2 . The desorption products can be readily converted to elemental sulfur

Adsorbent filled membranes for gas separation

Abstract: The influence of specific adsorbents (zeolites and molecular sieve carbons) on the gas separation properties of polymeric membranes has been studied. Two main parameters, the pore size and the hydrophilic character of the zeolite, are investigated with respect to their effect on the overall membrane performance in the separation of carbon dioxide / methane and of oxygen / nitrogen. A model has been developed which describes the permeabilities of the components as a function of the zeolite volume fraction in the membrane.

On the mechanism of gas transport in rigid polymer membranes

Abstract: Conventional polymers are compared as gas separation membrane materials with tailormade polymers. The increased permeability of the latter are due to their higher free volume available for gas transport. The increased free volume is associated with the rigidity polymer backbone. Free volume is obtained by subtracting the occupied volume, calculated using group contributions from the polymer specific volume. Wide Angle X-ray techniques are used to obtain average d-spacings that are interpreted in terms of average intermolecular space, and that are related to permeability data. These highly permeable rigid polymer membranes have high glass transition temperatures. The physical parameters, that is, Tg and the jump in heat capacity (ΔCp), are obtained with Differential Scanning Calorimetry, and are used to obtain an estimation of free volume. A good correlation for a series of random copoly[p, m-phenylene(4-phenyl)-1,2,4-triazoles] is obtained. A relationship between permeability and a free volume term, which can be estimated from thermodynamic properties, is equally valid for a wide variety of conventional polymers.

Gas‐separation applications of miscible blends of isomeric polyimides

Abstract: Blends of polyimide isomers containing hexafluoroisopropylidene in the central moiety of the diamine residue have been studied. The isomers differed by having either a meta or a para linkage between the diamine and dianhydride residues. The miscibility of these materials was investigated by studying the glass transition temperature behavior using differential scanning calorimetry. Mixtures of isomer pairs, such as 6FDA–6FmDA and 6FDA–6FpDA, exhibited one glass transition temperature. Tg, and were therefore miscible. Mixtures of nonisomer pairs exhibited two Tg's and were immiscible. The gas sorption and transport properties of the blends of the 6FDA–6FmDA and 6FDA–6FpDA isomers were characterized for a variety of gases at 35°C for pressures up to 60 atm. The permeabilities and permselectivities in the miscible blends fell between those of the pure components and were approximately logarithmic averages of the pure component properties. The miscibility of the polyimide isomers enables one to tailor the composition of the material to optimize the gas separation and mechanical properties. © 1993 John Wiley & Sons, Inc.

Method for capturing nitrogen from air using gas separation membrane

Abstract: This invention comprises an improved process for generating Nitrogen from air in which a vacuum is placed on the permeate side of a gas separation membrane, usually of the polysulfone type, resulting in highly enhanced flow rates and nitrogen purity sufficient for oil and gas pipeline repair use and for use in grain silos.

Plasma polymerization of silicon organic membranes for gas separation

Abstract: Silicon organic vapours were plasma polymerized under low ion bombardment conditions at 300 K on the anode of a capacitively coupled parallel plate reactor working at 13.56 MHz. The plasma process and the film properties were characterized with respect to the deposition rate, the film density and the C, H, N content analysed by the combustion method. The qualification of the films for gas-selective membranes is tested on a microporous support and compared with silicone rubber membranes. Pormeation measurements were carried out with N2, O2, CO2, He, C4H10 and CH4. Films prepared from hexamethyldisiloxane vapour at a low power input of 10 W exhibit 20 at.% C and 62 at.% H and a film density of 1.4 g cm-3. At a film thickness of 500 nm high gas separation ratios were achieved, e.g. CO2/N2 = 8 and C4H10/N2 = 21. By using hexamethyldisilazane, a decrease in gas solution capacity is observed. Incresing the plasma power or the admixture of oxygen to the process has the same effect, since it results in higher cross-linking and less flexibility of the film material. In addition, the higher deposition rate at elevated plasma power or oxygen admixture can result in microporous films. The existence of micropores is proven by temperature-dependent permeation measurements, a simple leak-sealing method and indirectly by a decrease in the film density.

Fluorinated aromatic polyimide, polyamide and polyamide-imide gas separation membranes

Abstract: Novel fluorinated aromatic polyimide, polyamide and polyamide-imide gas separation membranes and the process of using such membranes to separate one or more gases from a gaseous mixture is disclosed. The polyimides, polyamides and polyamide-imides are formed from diamines of the formula ##STR1## where Ar' is any aromatic diol moiety and X is independently fluorinated alkyl groups having 1 to 6 carbon atoms, most preferably a trifluoromethyl group, m is an integer from 1 to 4, preferably 1.

Separations of Hazardous Organics from Gas and Liquid Feedstreams Using Phosphazene Polymer Membranes

Abstract: In this paper the liquid-liquid and gas separation properties for the separation of hazardous organic feed streams using pervaporation and gas separation methods with poly[bis(phenoxy)phosphazene] based membranes are reported. Liquid transport behavior was determined using pervaporation techniques. The preliminary gas separations were studied using a mixed gas separation method which we have described previously. Using the membrane pervaporation technique, separation factors of 10,000 have been routinely achieved for the separation of methylene chloride from water. Other tests have shown similar results for the removal of hydrocarbon vapors from air. Membranes were prepared using solution casting techniques. Solvent evaporation rates during the casting and subsequent curing processes were controlled to provide a consistent membrane microstructure. These results suggest that polyphosphazene membrane technology could effectively be used in cleaning up air and ground water that has been contaminated...

Preparation of polycarbonate/metal salt gas separation membranes

Abstract: Polycarbonate (PC) membranes possess high O2/N2 selectivity and mechanical strength, but have low gas permeability. In order to improve the pure PC membrane's gas permeability and selectivity of O2/N2, in this study we attempt to combine transition metal salts into the membrane to form a complex membrane. Tensile strength and elongation at break of the membrane are not significantly changed. The effect of casting solution composition and solvent evaporation time on morphology, gas permeability, and selectivity of O2/N2 of PC membranes are studied. The gas permeabilities of PC/DMF/Metals membranes are significantly improved, as compared to those of pure PC membrane. For example, an oxygen permeability of 137 cm3 (STP)-cm/cm2-sec-cmHg and separation ratio of oxygen to nitrogen of 4.0 for PC/DMF/CuCl2 membrane with [PC/CH2Cl2]/[CuCl2/DMF] = 17/3 mL/mL, and CuCl2/DMF = 0.1 g/mL, can be obtained. The FT–IR spectra and elementary analysis suggest that there is interaction among metal, DMF, and PC. © 1993 John Wiley & Sons, Inc.

Alkyl substituted polyimide, polyamide and polyamide-imide gas separation membranes

Abstract: Novel aromatic polyimide, polyamide and polyamide-imide gas separation membranes and the process of using such membranes to separate one or more gases from a gaseous mixture is disclosed. The polyimides, polyamides and polyamide-imides are formed from diamines of formula (I) where Ar' is (a), Q is nothing or an aromatic group and Z is independently alkyl groups having 1 to 10 carbon atoms, most preferably a tertiary butyl group, n is an integer from 0 to 4, preferably 1.

Selective membrane valve for ternary gas mixture separation : model of mass transfer and experimental test

Abstract: The prospects for the gas separation membrane system with mobile liquid extractants flowing between two membranes (membrane valve) are discussed. The use of mobile membranes allows separation of multicomponent gas mixtures which are difficult to separate by conventional methods and leads to selectivity factors with the separate extraction of each component. The proposed technique for separation of gases was tested by separation of CO 2 /CH 4 /H 2 gas mixtures on a membrane valve with membranes from poly(vinyltrimethylsilane) (PVTMS) and flowing liquid membranes containing H 2 O and monoethanolamine solutions as carrier of CO 2 . The initial CO 2 /CH 4 /H 2 gas mixture consisted of 40% CO 2 , 30% CH 4 , and 30% H 2 , respectively. The concentrations of each of the separated gases obtained were more than 90% on the outlets of the membrane valve. The phenomenological theory of selective gas permeation in a membrane valve in four possible modes is considered. Computer simulation of the separation process in a membrane valve was carried out

Passive gas separator and accumulator device

Abstract: A separation device employing a gas separation filter and swirler vanes for separating gas from a gasliquid mixture is provided. The cylindrical filter utilizes the principle that surface tension in the pores of the filter prevents gas bubbles from passing through. As a result, the gas collects in the interior region of the filter and coalesces to form larger bubbles in the center of the device. The device is particularly suited for use in microgravity conditions since the swirlers induce a centrifugal force which causes liquid to move from the inner region of the filter, pass the pores, and flow through the outlet of the device while the entrained gas is trapped by the filter. The device includes a cylindrical gas storage screen which is enclosed by the cylindrical gas separation filter. The screen has pores that are larger than those of the filters. The screen prevents larger bubbles that have been formed from reaching and interfering with the pores of the gas separation filter. The device is initially filled with a gas other than that which is to be separated. This technique results in separation of the gas even before gas bubbles are present in the mixture. Initially filling the device with the dissimilar gas and preventing the gas from escaping before operation can be accomplished by sealing the dissimilar gas in the inner region of the separation device with a ruptured disc which can be ruptured when the device is activated for use.

Hydrous gel membranes for gas separation

Abstract: This invention relates to hydrous gel membranes for gas separation which comprise support membranes formed by solvent-soluble polymeric materials containing in their repeating unit a bulky structural part and hydrophilic functional groups represented by the following general formula (1) ##STR1## (R 1 , R 2 , R 3 , and R 4 designate hydrogen, alkyl group, and halogen and R 5 and R 6 designate any one of --H, --SO 3 H, --COOH, and --OH) and water or an aqueous solution of substances with affinity for CO 2 substantially uniformly retained in the support membranes. The membranes show not only high CO 2 permeation and CO 2 selectivity but also long-term stable membrane performance and ease of fabricability into membranes and are capable of recovering a large volume of CO 2 generated at stationary sites efficiently at low cost.

Relaxation phenomena in dense gas separation membranes

Abstract: Solution-diffusion membranes are widely used for the separation of gaseous and liquid mixtures. The separation of air (O2/N2), landfill gas (CH4/CO2) and purge gas streams (NH3/H2) in the ammonia synthesis are examples for state-of-the-art membrane gas separation processes. For the separation of liquid mixtures by means of a membrane process, i.e., pervaporation, the splitting of azeotropic mixtures of ethanol-water mixtures is a well established technique.

Method and device for separating gas mixtures formed above liquids

Abstract: In a method for separating a gas mixture above a liquid a separating device with a gas separation membrane having retentate side and a permeate side is employed. A vacuum at the retentate side of the gas separation membrane and a vacuum at the permeate side of the gas separation membrane are provided. The gas mixture, resulting from transferring a liquid from one storage container to another container upon contact with the surroundings, is fed to the retentate side of the gas separation membrane by the vacuum present at the retentate side and the permeate side. The flow volume per time unit of the gas mixture fed to the separating device is greater than a flow volume per time unit of the liquid being transferred. On the retentate side of the gas separation membrane a gas-diminished retentate is generated and on the permeate side of the gas separation membrane a gas-enriched permeate is produced. The flow volume per time unit of the permeate is equal to the flow volume per time unit of the liquid being transferred.