Thesis (Ph. D.)--University of Wisconsin, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Iowas, 1929. / Biography.

Ph.D.

No description available.

(A) Diffusion Studies A study has been made on the effects of some selected halide salts on the structure of formamide by measuring molecular diffusion coefficients, A neutral molecule, ferrocene v/as allowed to diffuse in pure formamide and in halide salts solutions of formamide and its diffusion coefficients were determined, A test molecule was chosen rather than a test ion in order to avoid electrostatic effects due to ion--ion and ion-dipole interactions. Graphs of diffusion coefficient versus concentration of salts were drawn and the shapes of these curves have been discussed in terms of the "microscopic" and "macroscopic" effects of these salts on formamide structure. Use of two diffusion techniques was made - (i) an electrochemical diffusion method based on the Cottrell equation and (ii) a diaphragm-cell method based on steady-state diffusion. Only the latter was successful. A number of experimental methods were investigated in order to find a suitable analytical method for determining ferrocene (necessary for the diaphragm-cell measurements). A method for preparing radioactive ferrocene and a successful radiometric analytical technique were developed. (B) Thermodynamics Studies In this section the vapour pressures of binary mixtures of water-formamide, water-N-methylformamide and water-dimethylformamide were measured using a Zimmerli manometric gauge over several temperatures. The graphs of partial pressures of water (determined by a transpiration technique) vorsus mole fractions of water are given and explained in terms of the nature of interactions of water and the amides. Bj' means of the Clausius-Clapeyron equation the enthalpies of vaporization of water were calculated and the results versus water mole fractions are shown in graphs. In the case of water-formamide, the enthalpies of vaporization and the enthalpies of viscous flow are compared.

Orientador: Theo Guenter Kieckbusch / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-15T23:02:38Z (GMT). No. of bitstreams: 1 Queiroz_MariseBonifacio_D.pdf: 2421839 bytes, checksum: 864f367f1ae8ca6c17e48aa7cc7fa709 (MD5) Previous issue date: 2010 / Resumo: Sob o ponto de vista termodinamico, fondant e uma solucao supersaturada de sacarose e a qualidade da textura (cristalizacao) e controlada pela adicao de xarope de glicose e pelo 'batimento' da mistura. As formulacoes conhecidas de fondant usam xarope de milho e essa tese avaliou o uso de xarope de mandioca produzido com materia-prima e tecnologia nacionais. Inicialmente realizou-se a determinacao experimental de curvas de equilibrio solido-liquido para misturas de sacarose com os dois xaropes (milho e mandioca) em temperaturas de 25 e 30º C. De acordo com os resultados encontrados no estudo de solubilidade dos sistemas a 30º C, o xarope de milho normalmente utilizado na industria de confeitos com o objetivo de retardar a cristalizacao da sacarose, pode ser substituido pelo xarope de mandioca no mesmo nivel de adicao, O estudo da cristalizacao foi feito em dois sistemas distintos. Inicialmente a producao de fondant foi em batelada, em escala de laboratorio e serviu para estabelecer parametros de processo, formulacoes indicativas e condicoes previas para a otimizacao do batimento em sistema continuo. Um batedor continuo em escala planta-piloto foi entao projetado, construido em aco inoxidavel e posto a funcionar. Para a otimizacao do batimento em sistema continuo utilizou-se o delineamento experimental com um planejamento fatorial completo 23 com pontos axiais e centrais. As variaveis estudadas foram a porcentagem de xarope de mandioca na formulacao, a velocidade de rotacao da rosca e a temperatura de cristalizacao/batimento. Como resposta mediu-se a atividade de agua e a textura (resistencia da massa cristalizada a compressao) do fondant. A caracterizacao da microestrutura do fondant foi baseada na determinacao da Distribuicao do Tamanho de Cristais (DTC) pela analise de imagem gerada por microscopia otica e por espalhamento de luz. O estudo indica que Fondant produzido com xarope de mandioca, com uma atividade de agua apropriada (garantia de estabilidade microbiologica) e textura adequada pode ser obtido usando teores de xarope de glicose superiores a 20% (minima atividade de agua), temperatura inicial de batimento de 60 ºC e uma velocidade de rotacao da rosca de 110 rpm / Abstract: From the thermodynamic point of view, fondant is a supersaturated solution of sucrose and the quality of the texture (crystallization) is controlled through addition of glucose syrup and by the 'beating' intensity of the mixture. Fondant is usually manufactured with corn syrup. In this research its replacement by cassava syrup, recently introduced in the Brazilian market, and produced with national technology was evaluated. Initially the solid-liquid equilibrium condition for the mixtures of sucrose and both syrups (corn and cassava), at 25 and 30 ºC was experimentally determined. The similar saturation conditions at 30 ºC, indicated that corn syrup normally used in the candy industry with the objective to delay the crystallization of sucrose could be substituted by the cassava syrup at the same addition level. The investigation considered two systems for the production of fondant. Initially, using a lab-scale batch system for the beating, the process parameters, indicative formulations and previous conditions for the optimization of a continuous beating conditions were established. A continuous pilot-plant scale beating system was then design, built in stainless steel and the limiting operating conditions established. For the optimization of the continuous system parameters an experimental design based on a 23 complete factorial design with axial and central points was setup. The percentage of cassava syrup in the formulation, the rotation of the screw (impeller) and the crystallization/beating temperature were the independent variables. The water activity and the texture (resistance of the crystalline mass to compression) of the fondant were used as responses variables. The microstructure of the crystalline system was characterized in terms of the Crystal Size Distribution (CSD) using optic microscopy analysis and light scattering. Fondant manufactured with cassava syrup showed appropriate water activity (microbiological stability) and adequate texture parameters when formulations with at least 20% of cassava syrup (for lower water activity) at an initial beating temperature of 60 ºC were submitted to screw rotation speed of 110 rpm / Doutorado / Engenharia de Processos / Doutor em Engenharia Química

Dissolved oxygen was studied in distilled water and salt solutions by means of nuclear magnetic resonance. The free induction technique was employed to measure the spin lattice relaxation time, T-^, for oxygen-free distilled water and for water containing oxygen under one atmosphere of air and one atmosphere of oxygen at temperatures of 1° to 75°C. The same measurements were made for solutions of 0.5 M sodium chloride at temperatures of 1° to 40°C. The spin lattice relaxation probability, 1/T[subscript 1(c)], in the presence of paramagnetic oxygen, was attributed to two relaxation mechanisms: the first a dipole-dipole interaction and the second a hyperfine interaction. The two terms were evaluated from measurements of T[subscript 1(c)] at two different magnetic field strengths at 20°C. Using the theoretical relationship between the dipole-dipole term and η/T, the results were used to evaluate the hyperfine term at different temperatures. The activation energy obtained from the variation of the dipole-dipole term with temperature was assumed to represent the energy required to break one hydrogen bond between two water molecules. The activation energy found for the hyperfine term was taken as a measure of the breaking of a hydrogen bond between one oxygen molecule and an aggregate of water molecules. The activation energy of the hyperfine term was found to be a function of temperature. Comparison of this quantity with heats of solution of dissolved oxygen in distilled water and salt solution showed a similar pattern of change in both. Oxygen supersaturation was studied in sea water cultures of Nitzschia closterium and Chlorella strain "A" at a temperature of 12°C. Saturation values up to 200% were reached under illumination with light energy of 9.2x10[power -3] langlies/min. Nitzschia was found to be more photosynthetically active, under the same culture conditions, than Chlorella. Oxygen production by Nitzschia was shown to be a function of the difference in photosynthetic pigment concentrations (chlorophyll-a — non-astacin carotenoid), total alkalinity, and the change in catalytic activity of the medium. Variation of oxygen concentration in Nitzschia cultures under light and dark periods indicated a mechanism by which oxygen may escape as microbubbles to the atmosphere. The rate of oxygen desupersaturation was measured in water free of organisms. The rate increased with increase of ion content and with the surface to volume ratio of the water column, but was not influenced by addition of siliceous particulate matter to the supersaturated water. Small addition of a surface active agent (heptanoic acid) increased the oxygen desupersaturation rate but further addition decreased the rate. / Science, Faculty of / Chemistry, Department of / Graduate

There are a number of interesting and as yet unresolved problems concerning the dissolution rates and solubilities of various drugs. It seems clear that the inherent properties of crystals (i.e. surface and bulk structure and properties) and their relationship to solubility and dissolution rate need to be more clearly understood before explanations for these observations can be offered. The approach taken in this study to the problem of dissolution is to consider the method of preparation and its effect on crystal structure. This study attempts to show that, in addition to properties of the solid state such as polymorphism, solvation and degree of crystallinity, the dissolution kinetics may be affected by: a) the anisotropic nature of crystalline solids and hence crystal habit b) the type and number of crystal defects incorporated into a crystal during growth. Inorganic salts such as nickel sulfate hexahydrate (NiSO₄ α 6H₂O) and potassium perchlorate (KCIO₄) provided suitable model, crystalline materials as they grew as large, well-formed crystals with distinct habits. KCIO₄ crystals could be easily cleaved and etched and grew with relatively low dislocation densities. The dissolution anisotropy of NiSO₄ a 6H₂O crystals was studied using a single crystal dissolution method by measuring the movement of the (111) and (112) crystal faces with time in a flowing solvent using a travelling microscope. The observed apparent rate constant, Kobs for the (112) face was greater than for the (111) face at all flow rates but anisotropy was less pronounced at the lower flow rates, The apparent rate constants for the transport and surface controlled reactions, Kt and Kr were of the same order of magnitude suggesting that the overall dissolution reaction was under mixed control at the lower flow rates. Activation energies were slightly higher than the normal range for transport processes. Kr (112) > Kr (111) indicating that anisotropy was probably due to differences in the rate of the surface reaction. At high flow rates there was a change to a predominantly surface controlled reaction. It is likely that dissolution anisotropy is due to the differences in activation energy for the two faces. The effect of habit modification on the dissolution rate of NiSO₄ a 6H₂0 in 60% v/v ethanol was studied using a rotating basket method. Bipyramidal crystals were grown in a fluidized-bed crystallizer and platy crystals were recrystallized from supersaturated solutions of nickel sulfate containing small amounts of gelatin. Acicular crystals were prepared by the topotactic dehydration of acicular crystals of NiSO₄.7H₂O. DSC thermograms of platy and acicular habits were similar but differed from the bipyramidal habit probably due to differences in vapor pressures exerted by the habits. The observed dissolution rate constant, K'obs. for the bipyramidal and acicular crystals was similar and greater than the platy habit at both low and high rotation rates, the difference being less pronounced at the lower rotation speed. At the high rotation speed dissolution was under mixed transport-surface control . The difference in K' obs must be due to different values of the overall surface energy of the crystals. KCIO₄ crystals were grown in silica gels and the crystals from three growth levels (and hence grown at different rates) were cleaved, etched and the dislocation etch pits counted using a differential interference contrast microscope. Crystals grown at the fastest rate had the highest mean dislocation densities and the highest K'obs values as determined using the rotating basket method. Conversely, crystals grown at the lowest rate had a low mean dislocation density and low K'obs values. The differences in K'obs were not due to impurities but to differences in the energy content of crystals resulting from the incorporation of differing numbers of dislocations into the crystals. / Pharmaceutical Sciences, Faculty of / Graduate

Methods of determining the aqueous solubilities of twelve chlorinated benzenes were evaluated in pure and in different water matrices. In pure water, results were comparable with the calculated values. Higher chlorinated tetrachlorobenzenes (TeCBs), pentachlorobenzenes (PCBz), and hexachlorobenzenes (HCBs) gave better precision and accuracy than lower chlorinated monochlorobenzenes (MCBs), dichlorobenzenes (DCBs), or trichlorobenzenes (TCBs).

The focus of this research project was to develop a fundamental understanding of the structure-gas transport property relationship in Nafion® to investigate its potential use as a gas separation membrane material for natural gas (NG) applications including carbon dioxide removal from NG, helium recovery, higher-hydrocarbon removal, and nitrogen separation from methane. Separation processes account for ~45% of all energy used in chemical plants and petroleum refineries. As the drive for energy savings and sustainability intensifies, more efficient separation technology becomes increasingly important. Saudi Arabia ranks among the world’s top 5 NG producers. Commercial hydrocarbon-based glassy polymers often lose their gas separation properties in the presence of condensable, highly sorbing NG components such as CO2, ethane, propane, n-butane, and C5+ hydrocarbons. This deterioration in gas separation performance results from penetrant-induced dilation and plasticization of the polymer matrix, leading to significant methane and higher hydrocarbon losses. Polymers that have intrinsically low affinity to high-solubility NG components may be less susceptible to plasticization and therefore offer better performance under actual field conditions. By virtue of their strong carbon-fluorine bonds and chemical inertness, perfluoropolymers exhibit very low affinity for hydrocarbon gases. Nafion®, the prototypical perfluoro-sulfonated ionomer, comprising hydrophilic sulfonate groups phase-separated from a hydrophobic perfluorocarbon matrix, has demonstrated interesting permeability and selectivity relationships for gas pairs relevant to NG applications. Gas transport properties of Nafion® indicated gas solubility behavior similar to rubbery polymers but with sieving properties more commonly observed in low free volume glassy polymers. Nafion® demonstrated very low solubility for CO2 and hydrocarbon gases; the trend-line slope of solubility versus penetrant condensability in Nafion® was almost 2.5 times lower than that of typical hydrocarbon polymers, highlighting Nafion’s® effectiveness in resisting high-solubility induced plasticization. Additionally, Nafion® showed extraordinarily high permselectivities between small gases (He, H2, CO2) and large hydrocarbon gases (C1+): He/CH4 = 445, He/C3H8 = 7400, CO2/CH4 = 28, CO2/C3H8 = 460, H2/CH4 = 84 and H2/C3H8 = 1400 owing to its tightly packed chain domains. These high selectivities could potentially be harnessed for helium recovery and CO2 removal in natural gas applications, and hydrogen recovery from refinery gas streams. Pressure-dependent pure- and mixed-gas permeabilities in Nafion® were determined at 35 °C. Nafion® demonstrated two divergent pressure-dependent permeability phenomena: gas compression and plasticization. In pure-gas experiments, the permeability of the permanent gases H2, O2, N2 and CH4 decreased with increasing pressure due to polymer compression, whereas the permeability of the more condensable gases CO2, C2H6 and C3H8 increased dramatically due to solubility-induced plasticization. Binary CO2/CH4 (50:50) mixed-gas experiments showed reduced performance with up to 2-fold increases in CH4 permeability from 0.075 to 0.127 Barrer, and a 45% drop in selectivity (from 26 to 14), between 2 and 36 atm total pressure as a result of CO2-induced plasticization. At a typical NG CO2 partial pressure of 10 atm, Nafion® exhibited 24% lower CO2/CH4 selectivity of 19, with a 4-fold lower CO2 permeability of 1.8 Barrer relative to a commercial cellulose acetate (CA) membrane. Ternary CO2/CH4/C3H8 (30:50:20) experiments quantified the effect of CO2 and C3H8 plasticization. The presence of C3H8 reduced CO2 permeability further due to a competitive sorption effect causing a 31% reduction in CO2/CH4 selectivity, relative to its pure-gas value of 29, at 16 atm total feed pressure. The strong cation-exchanging sulfonate groups in Nafion® provided an opportunity to tailor the material properties by incorporating metal ions through a simple ion-exchange process. Nafion® neutralized with Fe3+ was investigated as a potential approach to mitigate CO2-plasticization. XRD results demonstrated an increase in crystallinity from 9% in Nafion H+ to 23% in Nafion Fe3+; however, no significant changes in the average inter chain spacing was observed. Raman and FT-IR technique qualitatively measured the strength of the ionic bond between Fe3+ cation and sulfonate anion. The strong crosslinking effect in Fe3+-cation-exchanged membrane demonstrated substantial increase in permselectivity: N2/CH4 selectivity increased by 39% (from 2.9 to 4.0) and CO2/CH4 selectivity increased by 25% (from 28 to 35). Binary CO2/CH4 (50:50) mixed-gas experiments at total feed pressures up to 30 atm quantified the effect of CO2 plasticization on the CO2/CH4 separation performance. Nafion® Fe3+ demonstrated better resistivity to plasticization enduring approximately 30% CH4 permeability increases from 0.033 Barrer at 2 atm to 0.043 Barrer at 15 atm CO2 partial pressure. At 10 atm CO2 partial pressure, CO2/CH4 selectivity in Nafion® Fe3+ decreased by 28% to 28 from its pure-gas value of 39, which was a significant improvement compared to Nafion® H+ membrane that decreased by 42% to 19 from its pure-gas value of 32.