No description available.

Thesis (MTech (Chemical Engineering))--Peninsula Technikon, 2000. / Oxygen transport across biofilms and membranes may be a limiting factor in the operation of a membrane bio-reactor. A Gradostat fungal membrane bio-reactor is one in which fungi are immobilized within the wall of a porous polysulphone capillary membrane. In this study the mass transfer rates of gases (oxygen and carbon dioxide) were investigated in a bare membrane (without a biofilm being present). The work provides a basis for further transport study in membranes where biomass is present. The diaphragm-cell method can be employed to study mass transfer of gases in flat-sheet membranes. The diaphragm-cell method employs two well-stirred compartments separated by the desired membrane to be tested. The membrane is maintained horizontally. -The gas (solute) concentration in the lower compartment is measured versus time, while the concentration in the upper liquid-containing compartment is maintained at a value near zero by a chemical reaction. The resistances-in-series model can be used to explain the transfer rate in the system. The two compartments are well stirred; this agitation reduces the resistances in the liquid boundary layers. Therefore it can be assumed that in this work the resistance in the membrane will be dominating. The method was evaluated using oxygen as a test. The following factors were found to influence mass transfer coefficient: i) the agitation in the two compartments; ii) the concentration of the reactive solution and iii) the thickness of the membrane.

There is a pressing need for advanced solid-state materials that can be implemented in industrial gas separation processes to achieve separations with a significantly reduced energy input compared to what is typically required from current technologies. Although certain porous materials like zeolites bear some commercial significance for gas separation; their inherent lack of tunability limits the extent to which these materials may be exploited in industry. Zeolite-like Metal-Organic Frameworks (ZMOFs) are a sub-class of Metal-Organic Framework materials (MOFs) that show a structural semblance to zeolites while possessing the tunability advantages of MOF materials. ZMOFs which are topologically similar to certain zeolites can be functionalised and tuned in numerous ways to improve their gas separation properties. In this work, indium-based sod-ZMOF was tuned by cation-exchange and then characterised by different experimental tools such as single-crystal x-ray diffraction, elemental analysis and gas adsorption. It was found that various parameters like the choice of cation, the concentration of salt solution and the choice of solvent had a significant bearing on the cation-exchange of sod-ZMOF and its subsequent adsorption properties.

Matrimid was utilized for the preparation of membranes with asymmetric structures. A combination of well-known solvents for Matrimid which include 1- methyl-2-Pyrrolidone (NMP), tetrahydrofuran (THF), dichloromethane, tetrachloroethane as well as non-solvents n-butanol, xylene, and acetic acid were used. Cast solutions were prepared at room temperature for different combinations and compositions of polymer/solvent/non-solvent systems. PEG and Octa-(amino phenyl) POSS were introduced in some of the cast solutions. The membranes obtained were characterized by permeation test for gas permeabilities and selectivities, Scanning Electron Microscopy (SEM) and Nuclear Magnetic Resonance (NMR) Spectroscopy. The gas permeation test showed that the use of mixture of dichloromethane and tetrachloroethane as solvents with xylene non-solvent and acetic acid as stabilizer gave membranes with very high gas selectivity of 133 for CO2/N2 and 492 for CO2/CH4. Also, cast solutions containing PEG resulted in membranes with slightly enhanced selectivities from 30 to 42 for CO2/N2. Permeation results for CO2, N2 and H2 and the selectivities for gas pairs such as CO2/N2, CO2/CH4, are discussed in relation to the effect of pressure on the membrane permeance, they are also compared with existing results.

No description available.

This thesis investigates membrane gas separation and its application to post-combustion carbon capture from coal-fired power plants as alternative to the conventional amine absorption technology. The attention is initially focused on membrane module modelling, with the aim of obtaining more detailed predictions of the behaviour of the separation though spiral-wound and hollow-fibre modules. Both one- and bi-dimensional models are implemented, compared and tested for different separations. Module geometry is investigated as well as the effect on the performances due to possible fabrication defects. A key part of the work involves the integration of the customised models into UniSim® Design, the Honeywell process simulator. Thanks to the developed interface, multi-stage process designs are developed, compared with the available literature and linked to a rigorous economic analysis. In particular, a long-term indicator such as the Levelised Cost Of Electricity (LCOE) is evaluated and parametric analyses are conducted with respect to both material and process parameters.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 92-93.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 158-164). Available also in a digital version from Dissertation Abstracts.

This dissertation discusses the effect of synthesis route and ortho-position group on the thermal and transport properties of thermally rearranged polymers. Thermally rearranged polymers are polybenzoxazoles formed via the solid state rearrangement of ortho-functional polyimides. In this study, polymers were derived from 3,3'-dihydroxy-4,4'-diamino-biphenyl and 2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (HAB-6FDA). These HAB-6FDA polymers were synthesized using chemical and thermal imidization, and hydroxyl, acetate, propanoate, or pivalate ortho-position groups were considered. In these polymers, gas permeability increases as a function of conversion for all samples. The polyimide synthesis route does not affect the thermal or transport properties. However, the precursor ortho-position group strongly influences the thermal and transport properties of TR polymers. Additionally, it was determined that an increase in gas diffusivity was the primary cause of increased permeability as a function of thermal rearrangement. / text

Thermally rearranged polymers are formed from the solid-state thermal reaction of polyimides and polyamides that contain reactive groups ortho position to their diamine. These polymers have shown outstanding transport properties for gas separation applications. The thrust of this work is to critically examine the chemical and morphological structure of these polymers and to identify the fundamental contributions of gas sorption to permeability. To accomplish this goal, a series of TR polymers and TR polymer precursors have been synthesized and investigated for transport properties. As a function of conversion, diffusivity increases more dramatically than sorption, which explains the outstanding permeabilities observed for these samples. Modifications to the polymer backbone structure, which can be achieved by adding rigid functional groups such as hexafluoroisopropylidene-functional linking groups, can further be used to improve permeabilities. The precursor used to form TR polymers has dramatic effects on the final polymer transport properties. Despite having nearly identical polymer structure, TR polymers formed from polyamide precursors have lower combinations of permeability and selectivity than TR polymers formed from polyimide precursors. In addition to structure-property studies with TR polymers, this thesis also present comparisons of permeability, diffusivity, and sorption of sparingly soluble gases (i.e., hydrogen and helium) for hydrocarbon-based polymer, highly fluorinated polymers, perfluoropolymers, and a silicon-based polymer. An explanation for the unique transport properties of perfluoropolymers is presented from the standpoint of the solution-diffusion model, whereby perfluoropolymers have uniquely different solubility selectivities than hydrocarbon-based polymers. Additionally, a large database of sorption, diffusion, and permeability coefficients is used to determine the contributions of free volume on solubility selectivity in polymers. / text