Separation of CO2, the main global warming causing greenhouse gas, from other flue gases and from biogas has become of great interest due to the predicted effects of global warming that the world is already starting to experience. This research focuses on the separation of CO2 from CH4 and N2 gases using polymeric and mixed matrix membranes. Amine-based poly vinyl alcohol (PVA) polymeric membranes that had previously shown good gas separation results were adapted for use in this research. The physical aging of the adapted membrane was initially analyzed for 37 days and it was observed that the membrane stabilized after 21 days. The adapted membrane was then optimized using a 26 factorial design to improve the membranes’ performance with respect to CO2/N2 and CO2/CH4 selectivity when tested using single gas permeation experiments at near atmospheric conditions. This was done with the membrane components: PVA, formaldehyde, poly (allylamine hydroxide), potassium hydroxide, water and 2-aminoisobutyric acid. Zeolite 13X and ZIF-8 powdered adsorbents were incorporated in the optimized membranes to prepare mixed-matrix membranes with the goal of bettering the separation performance of the membranes. Membrane characterization was done on the best performing membranes through spectroscopy, microscopy, and contact angle measurements. This study concluded with feed pressure tests on the overall best performing membranes. The performance of the fabricated membranes was compared to other polymeric and mixed-matrix membranes and Robeson’s upper bound line. Overall, the polymeric optimized membranes seemed to perform better than the filled mixed matrix membranes due to the introduction of agglomerations and cracks with both the filler materials. Also, the separation performance of the membrane improved with a decrease in pressure. At 1.5 absolute pressure, the optimized membrane was able to achieve a CO2/N2 and CO2/CH4 selectivity of 5.94 and 2.13 respectively with a CO2 permeability of 15,813 Barrer.

La nanofiltration (NF) est un procédé applicable à la récupération des solvants organiques. Une membrane chimiquement stable est alors requise pour résister aux solvants organiques. Cette thèse traite de la préparation de membranes NF chimiquement stables par greffage de substrats céramiques mésoporeux et de l'étude de leurs propriétés de transport des solvants et des solutés. Dans le chapitre 1, l'état de l'art sur les techniques de greffage est présenté ainsi que celui sur le comportement au transport des membranes NF résistantes aux solvants.Dans les chapitres 2 et 6, des membranes d'ultrafiltration en alumine mésoporeuse sont greffées avec des groupements organiques hydrophobes ou hydrophiles. La diminution du diamètre des pores permet ainsi d'accéder à la nanofiltration. Au chapitre 5, un agent couplant est utilisé pour améliorer l'ancrage de ces groupements dans les pores. Ceci réduit cependant la perméabilité aux solvants, en comparaison aux mêmes membranes modifiées avec du polydiméthylsilane (PDMS) mais sans agent couplant. Dans le chapitre 6, la capacité de greffage de poudres d'alumine est mesurée pour des agents de greffage différant par : la masse moléculaire des chaines polyéthylènes glycol (PEG), la nature et le nombre de groupements alcoxy terminaux et la présence ou non de fonctions urée. Ces poudres sont analysés par thermogravimétrie, spectrométrie RMN du 29Si, spectroscopie FTIR, et mesures de surface spécifique. Les densités de greffage estimées varient avec la masse des greffons, la présence de fonctions urée, et le nombre de groupements alcoxy hydrolysables.Le comportement au transport de membranes greffées est étudié dans les chapitres 3, 4 et 6. Dans le chapitre 3, pour des membranes greffées avec du PDMS, ce comportement est décrit en incorporant des termes relatifs à la sorption des solvants dans l'équation Hagen-Poiseuille. Une membrane plus fermée est obtenue lorsque le solvant est fortement adsorbé dans la couche greffée. Dans le chapitre 4, la validité des modèles de rejet de soluté basés sur l'exclusion par la taille est discutée. Une forte influence du diamètre moléculaire du soluté et du rapport de ce diamètre avec celui des pores est observée, indiquant que le mécanisme d'exclusion par la taille est ici vérifié. Trois modèles de rejet sur la base d'exclusion par la taille, à savoir Ferry, Verniory et SHP, sont testés pour prédire, en l'absence de solvant, le rejet des solutés à partir des diamètres de pore mesurés par physisorption de diazote. Pour des colorants et des solutés de type PS ou PEG dans du toluène, les données expérimentales sont bien au-dessus des valeurs prédites par ces modèles. Les résultats suggèrent que le diamètre de pore effectif en présence de solvant fortement adsorbé tel que le toluène est inférieur à celui en l'absence de solvant, une hypothèse étant qu'il n'y a pas d'interactions importantes entre solvant et soluté ou entre le soluté et la surface des pores. Cela peut expliquer un rejet plus élevé des solutés dans des solvants non polaires comme le toluène que dans des solvants polaires tels que l'isopropanol pour les membranes greffées avec du PDMS. Dans le chapitre 6, la perméabilité de membranes greffées avec des PEG est étudiée pour différents solvants (polaires ou non polaires). Une relation linéaire entre le flux et la pression transmembranaire est observée, comme pour les membranes greffées avec du PDMS. Cela indique l'absence de processus induit par des effets de cisaillement dans le fluide en écoulement et variant avec la pression transmembranaire appliquée. Pour le colorant Noir Soudan, une sélectivité supérieure est observée dans l'éthanol que dans l'hexane alors que pour la perméabilité inférieure de l'éthanol est inférieure à celle de l'hexane. Ici aussi, ces phénomènes sont expliqués par la différence de sorption des solvants dans la couche greffée. Les conclusions générales et perspectives de cette étude sont présentées dans le chapitre 7. / Solvent nanofiltration is a potential technology to recover solvents. For this application, a chemically stable membrane that can endure continuous exposure towards organic solvents is required. This thesis deals with the preparation of chemically stable NF membranes through modification of mesoporous ceramic substrate by means of grafting and studying of their solvent and solute transport properties. In Chapter 1, the background of the grafting technique as well as studies on the SRNF transport behavior found in the literature was presented.In Chapter 2 and 6 of this thesis, mesoporous y-alumina UF membranes were grafted by hydrophobic and hydrophilic organic moieties to decrease the membrane pore diameter of the existing y-alumina UF membrane down to the nanofiltration range. In Chapter 5, the use of coupling agent to couple the grafted moiety forming a polymer network inside the ceramic pores during grafting results in a smaller membrane pore, but at the cost of a lower solvent permeability, when compared with PDMS-grafted alumina membranes where no coupling was applied. In Chapter 6, the grafting performance of γ-Al2O3 powder with various PEG grafting agents having different molecular weights, alkoxy groups, and ureido functionalities were analysed by TGA, 29Si-NMR, FTIR, and BET. The grafting densities are influenced by the molecular weights, the presence of the ureido functionality, and the number of hydrolyzable groups of the grafting agents. The transport behavior of PDMS grafted ceramic membranes and PEG grafted ceramic membranes were studied in Chapter 3, 4, and 6. In Chapter 3, the solvent transport behavior of PDMS grafted ceramic membranes was described by incorporating solvent sorption terms in the Hagen-Pouiseuille equation. A more closed membrane structure is realized when the solvent is strongly sorbed in the grafted moiety. In Chapter 4, the applicability of the existing solute rejection models based on size-exclusion mechanism to describe the solute rejection of membranes towards different types of solvent and solute were assessed. A strong function of rejection behavior with the ratio of the solute diameter versus the membrane pore diameter was observed, indicating that the size-exclusion mechanism may be applicable. Three rejection models based on size-exclusion, namely the Ferry, Verniory, and SHP models were used to predict the rejection of several solutes using pore diameter information from the N2 physisorption measurement when no solvent is present. For dye, PS, and PEG solutes in toluene, the experimental data fall well above the predicted σ for Ferry, Verniory, and SHP model suggesting that the membrane actual pore diameter in the presence of strongly sorbed solvent like toluene is smaller than that when no solvent is present, assuming that there is no important solvent-solute or solute-membrane interaction present in the observed rejection behavior. This may explain the higher rejection of solutes in nonpolar solvents like toluene than that in polar solvents such as isopropanol for PDMS grafted ceramic membranes. In Chapter 6, the permeability behavior of PEG grafted y-alumina membranes with respect to different types of permeating solvent (polar and nonpolar) was studied. A linear relationship between flux and TMP was observed, as was also found for PDMS grafted y-Al2O3 membranes. This indicates the absence of shear-flow induced behaviour in the applied TMP. A higher selectivity of Sudan Black in ethanol than in hexane accompanied by a lower permeability of ethanol than hexane were observed. Here also this phenomenon is explained by the difference in solvent sorption of the grafted moiety for different types of permeating solvents. Finally, the general conclusions and future work are presented in Chapter 7.

Includes bibliographical references (leaves 169-184) / xiv, 184 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the concept of membrane homeostatis, which implies that biological membranes tend to maintain a constant level of lipid fluidity in the face of potential exogenous and endogenous pertubations. Manipulations of dietary cholesterol and/or saturated (coconut oil) v/s unsaturated (sunflower seed oil) fatty acids have been used to study the relationship between membrane lipid composition, membrane lipid fluidity and membrane-bound enzymes of lipid metabolism; and, to see whether these enzymes act co-ordinately for the maintenance of a membrane homeostatis under these dietary conditions. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Sciences, 1986

No description available.

Thesis (Ph. D.)--Oregon Graduate Institute of Science and Technology, 1990.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 57-62).

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references (leaves 135-137).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 242-260). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: William J. Koros and Donald R. Paul. Vita. Includes bibliographical references.

Amorphous silica membranes have molecular sieving properties for the separation of hydrogen from gas mixtures at high temperature. Consequently, they are considered to be applied in separation of a shifted syngas coming out of a water-gas-shift-reactor into the syngas and hydrogen. This separation is a key to an Integrated Gasification Combined Cycle (IGCC) plant, which would allow reducing the carbon footprint in power generation industry. The main objective of this thesis was to carry out a preliminary assessment of suitability of currently available amorphous silica membranes for this separation. However, the separation properties of amorphous silica membranes reported in the open literature vary by orders of magnitude. Therefore, in the first part of this thesis the separation properties of hypothetical silica membrane with different pore size distributions were predicted from first principles. Considering different possible gas transport mechanisms, it was concluded that gas transport in amorphous silica membranes is dominated by the activated and non-activated Knudsen diffusion. The activation energy for transport of different species was predicted using the concept of suction energy. Then, with arbitrary pore size distributions gas permeance of hypothetical silica membrane was predicted for different gas species. Since the pore size distribution of amorphous silica membrane cannot be known a priori, the developed model was used to determine the pore size distribution based on experimentally measured single gas permeances of three different species (kindly provided by Natural Resources Canada, CANMET Energy Technology Center (CETC) laboratory in Ottawa) by minimizing the error of the calculated permeance ratios with respect to the experimental values. The results indicate that, depending on how the objective function is defined, more than one pore size distribution can be found to satisfy the experimental permeance ratios. It is speculated that by increasing the number of experimentally determined permeances, a more unique pore size distribution for the tested silica membrane can be obtained. However, even at this early stage, the developed model provides a rational explanation for the effect of membrane densification on the properties of silica membranes. More specifically, a simultaneous decrease in membrane permeance and selectivity due to membrane densification, reported in the literature, is explained by shrinking the size of pores beyond a certain critical value, which depends on the kinetic diameter of gas molecules that are being separated. Comparing theoretically determined permeances, which match experimentally observed permeance ratios, revealed that the experimental permeances are considerably smaller than the theoretical values. The ratio of the two provided the basis for a scaling factor, a new concept that was introduced in this thesis. To simulate membrane module performance, a novel approach was introduced. More specifically, co- and counter-current flow configurations as well as cross-flow configuration were modeled by assuming no change in feed composition over an infinitesimally small element of membrane area. This led to a system of linear, rather than differential equations, which was readily solved numerically.