published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

<p>Over the past 40 years, research pertaining to membrane technology has lead to the development of a wide range of applications including beverage production, water purification and the separation of dairy products. For the separation of gases, membrane technology is not as widely applied since the production of suitable gas separation membranes is far more challenging than the production of membranes for eg. water purification. Hydrogen is currently produced by recovery technologies incorporated in various chemical processes. Hydrogen is mainly sourced from fossil fuels via steam reformation and coal gasification. Special attention will be given to Underground Coal Gasification since it may be of great importance for the future of South Africa. The main aim of this study was to develop low temperature CsHSO4/SiO2 composite membranes that show significant Idea selectivity towards H2:CO2 and H2:CH4.</p>

Separation processes are fundamental to all chemical engineering industries. Solvent separation, either liquid-liquid extraction or extractive distillation, is a specialised segment of separation processes. Solvents can be used either to optimise conventional distillation processes or for azeotropic systems, which can not be separated by conventional means. This work focuses on the performance of monoethanolamine (MEA) as a solvent in extractive distillation. Furthermore, the methodology of solvent evaluation is also studied. The preliminary assessment of solvent selection requires the determination of selectivity factors. The selectivity factor is defined as follows: P• = y,." . y, where y" is the activity coefficient at infinite dilution of the solute in the solvent. Subscript 1 and 2 refer to solute 1 and 2. A large selectivity factor implies enhanced separation of component 1 from 2 due to the solvent. Activity coefficients at infinite dilution were determined experimentally (gas-liquid chromatography) and predicted theoretically (UNIFAC group contribution method) for twenty-four solutes at three temperatures. Solutes used were alkanes, alkenes, alkynes, cyclo-alkanes, aromatics, ketones and alcohols. Most of this experimental work comprises data for systems which have not been measured before. Predicted and experimental values for y' were compared. For systems such as these (with polar solvents and non-polar solutes), UNIFAC results are not accurate and experimentation is vital. The experimental selectivity factors indicated tihat MEA could be an excellent solvent for hydrocarbon separation. Three binary azeotropic systems were chosen for further experimentation with MEA n-hexane (1) - benzene (2): fJ,~ = 31. Compared to other industrial solvents this is one of the largest values and MEA could serve as an excellent solvent. cyclohexane (1) - ethanol (2): fJ,~ = 148. This high value indicates an excellent solvent for this system. Acetone (1) - methanol (2): fJ,~ = 7.7. Further work involved vapour-liquid equilibrium experimentation at sub-atmospheric pressures in a dynamic recirculating stil l. The binary components with a certain amount of MEA were added to the still. The vapour and liquid mole fractions for the binary azeotropic components were measured and plotted on a solvent-free basis. The results are summarised below: n-hexane - benzene: Amount MEA added to still feed: 2%. MEA improved separability slightly. Further addition of MEA resulted in two liquid phases forming. cyclohexane - ethanol: Amount MEA added to still feed: 5% and 10%. Two liquid phases were formed for cyclohexane rich mixtures. Addition of MEA improved separability but did not remove the azeotrope. acetone - methanol: Amount MEA added to still feed : 5%, 10% and 20%. The ternary mixture remained homogenous and separability improved with addition of MEA. The binary azeotrope was eliminated. Due to the hetrogenous nature of the cyclohexane - ethanol system liquid-liquid equilibrium experimentation was performed to complete the analysis. Viable separation processes are possible for (a) cyclohexane - ethanol mixtures and for (b) acetone - methanol mixtures using MEA as the solvent. Comparison of various solvents used for the separation of acetone from methanol was possible by constructing equivolatility curves for the ternary systems. Results showed that MEA may possibly be the best solvent for this extractive distillation process. This study provides the following results and conclusions: • New thermodynamic data, important for the understanding of MEA in the field of solvent separations, was obtained. • Results show that the UNIFAC contribution method cannot be used to accurately predict polar solvent - non-polar solute y«> values. Experimentation is essential. • Selectivity factors indicate that MEA could be an excellent solvent for hydrocarbon separation. • The separation of the azeotropic cyclohexane - ethanol mixture is possible with a combination of extractive distillation and liquid-liquid extraction or simply liquid-liquid extraction using MEA as the solvent. • The separation of the azeotropic acetone methanol mixture is possible with extractive distillation using MEA as the solvent. The solvent MEA is possibly the best solvent for this separation. / Thesis (M.Sc.Eng.)-Univeristy of Natal, Durban, 2000.

Optimisation attempts within the petrochemical industry have led to interest in alternate solvents. The most widely used commercial solvents for the separation of hydrocarbons, by extractive distillation, are N-methylpyrrolidone and sulfolane. There has also been reference made to other solvents, such as N-formylmorpholine and the ethylene glycols [mono-, di-, tri- and tetra], being used. The alternate solvents proposed for this study were N-formylmorpholine, triethylene glycol and diethylene glycol. Infinite dilution activity coefficients, γ∞, provided a means of comparing the ease of separation of the different solutes using different solvents in extractive distillation. There is a substantial database of γ∞ measurements for systems involving N-methylpyrrolidone and hydrocarbons. A fairly large data set of γ∞ values of hydrocarbons in N-formylmorpholine has also been measured. Very little work has been conducted on the γ∞ values of hydrocarbons in either diethylene glycol or triethylene glycol. Gas liquid chromatography is one of the more common methods used to measure γ∞. To enable the measurement of γ∞ at higher temperatures, a pre-saturator was installed prior to the column. This ensured that the carrier gas entering the column was saturated with solvent and prevented the elution of solvent from the column. The γ∞ values of 25 solutes; including n-alkanes, alk-1-enes, alk-1-ynes, alcohols and aromatics; were measured at temperatures of 333.15, 348.15 and 363.15 K. The γ∞ measurements in N-formylmorpholine were used to verify this experimental set up and technique. Once the experimental set up had been proven, γ∞ in N-methylpyrrolidone, triethylene glycol and diethylene glycol were measured. Selectivities and capacities, at infinite dilution, of several solute combinations in the four solvents were then compared. In a few of these separation cases, the alternative solvents appeared to have better separation performance than N-methylpyrrolidone. The γ∞ values of three of the solutes in N-formylmorpholine and N-methylpyrrolidone were also measured using the novel cell design and measurement procedure suggested by Richon. It was found that this new technique required further development for the case of volatile solvents, since the results obtained using this technique did not compare favourably with the literature data. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2012.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Master of Science in Engineering. May, 2016 / Particle size and size range are among the characteristics that affect the segregation of particles in a jig hence they affect the separation efficiency. The effects of these variables on segregation of particles are not fully understood. This work aimed at contributing to knowledge in this area. To better understand how particle size and size range influence segregation, tests were conducted in which the effects of the density and shape of the particles on segregation were minimized by using as the feed material spherical glass beads of uniform shape and density. Batch experiments of two components systems of various particle sizes were conducted under the same set of jigging conditions: the jigging frequency and jigging time were respectively maintained at 60 cycles per minute and 999 seconds (16.65 minutes). The effect of these operating conditions on segregation was not investigated. At the end of each test run, the jig bed was split into horizontal slices and the composition of each slice was determined. The experimental results showed that below a particle size ratio of 1.50:1, the driving force for the segregation of particles, i.e. the particle size difference, was small hence a low degree of segregation was obtained. The degree of segregation increased above this ratio. However, above the size ratio of 2.00:1, interstitial trickling occurred. With the smaller particles tested (8, 6 and 4mm) poor segregation was observed when the size ratios were of 1.50:1 or less along with what is believed to have been remixing due to convective currents within the jig chamber. It was found that the particle size range had a more pronounced effect on size segregation than the particle size. From the results, it can be said that above a size ratio of about 1.50:1, size segregation is very pronounced. This suggests that density separations of real ores, where both the density and size of particles vary, would be impaired if the particle size range of the material fed to the jig exceeds this ratio. However, this needs further confirmation by testing multiple component systems.

Yin, Weixin = 非晶液態鈀-鎳-磷合金相位分離的證據 / 殷瑋欣. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Abstracts in English and Chinese. / Yin, Weixin = Fei jing ye tai ba-nie-lin he jin xiang wei fen li de zheng ju / Yin Weixin. / Acknowledgement --- p.i / Abstract --- p.ii / Contents --- p.iv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- A Brief Introduction to Metallic Glass --- p.1 / Chapter 1.2 --- Homogeneous Nucleation Frequency --- p.3 / Chapter 1.3 --- Heterogeneous Nucleation Frequency --- p.4 / Chapter 1.4 --- Spinodal Decomposition --- p.5 / Chapter 1.5 --- Conditions for Metallic Glasses Formation --- p.8 / Chapter 1.6 --- How to Get Large Undercooling --- p.9 / Chapter 1.7 --- Liquid Phase Separation --- p.10 / References --- p.12 / Figures --- p.13 / Chapter Chapter 2 --- Experimental Procedures and Techniques of Transmission Electron Microscopy --- p.18 / Chapter 2.1 --- Sample preparation --- p.18 / Chapter 2.1.1 --- Ni2P Preparation --- p.18 / Chapter 2.1.2 --- Alloying --- p.18 / Chapter 2.1.3 --- Fluxing --- p.18 / Chapter 2.2 --- Introduction to TEM Specimen Preparation --- p.19 / Chapter 2.2.1 --- "Grinding, Polishing and Punching" --- p.19 / Chapter 2.2.2 --- Final Thinning by Ion Miller --- p.20 / Chapter 2.2.3 --- Final Thinning by Twin Jet --- p.20 / Chapter 2.3 --- Introduction to Transmission Electron Microscopy Techniques --- p.21 / Chapter 2.3.1 --- Basic Instrumentations of TEM --- p.21 / Chapter 2.3.2 --- Elastic Scattering and Inelastic Scattering --- p.21 / Chapter 2.3.3 --- Image Contrast --- p.22 / Chapter 2.3.4 --- Dark Field Image and Bright Field Image --- p.24 / Chapter 2.3.5 --- EDX Mapping --- p.24 / Chapter 2.3.6 --- High Resolution Images --- p.25 / References --- p.26 / Figures --- p.27 / Chapter Chapter 3 --- Evidence of amorphous/liquid phase separation in Pd41.25Ni41.25P17.5 alloy --- p.32 / Chapter 3.1 --- Introduction --- p.32 / Chapter 3.2 --- Experimental --- p.34 / Chapter 3.3 --- Discussions --- p.42 / References --- p.44 / Figures --- p.45 / Chapter Chapter 4 --- Conclusions --- p.68

by Yuen Cheong Wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves [138]-[142]). / by Yuen Cheong Wing. / Acknowledgments --- p.ii / Abstract --- p.iii / Table of Contents --- p.v / Chapter Chapter 1: --- Introduction --- p.1-1 / Chapter 1.1 --- What is Metallic Glass? --- p.1-1 / Chapter 1.2 --- Use of Metallic Glass --- p.1-3 / Chapter 1.3 --- A Dilemma --- p.1-4 / Chapter 1.4 --- Glass Forming Ability --- p.1-5 / Chapter 1.5 --- Role of Liquid State Phase Separation in GFA --- p.1-6 / References --- p.1-9 / Figure --- p.1-10 / Chapter Chapter 2: --- Phase Separation Theory --- p.2-1 / Chapter 2.1 --- Free Energy Curve --- p.2-1 / Chapter 2.2 --- Nucleation and Growth --- p.2-2 / Chapter 2.2.1 --- Liquid state nucleation and growth --- p.2-2 / Chapter 2.2.2 --- Nucleation and growth during solidification --- p.2-4 / Chapter 2.3 --- Spinodal Decomposition --- p.2-5 / Chapter 2.3.1 --- Cahn-Hilliard linearized equation --- p.2-6 / Chapter 2.3.2 --- Temporal evolution --- p.2-9 / References --- p.2-12 / Figures --- p.2-15 / Chapter Chapter 3 ： --- Experimental Setup and Techniques --- p.3-1 / Chapter 3.1 --- Technique in Achieving High Undercooling --- p.3 -1 / Chapter 3.1.1 --- Effects and limitation of B203 --- p.3-1 / Chapter 3.1.2 --- Preparation of B203 --- p.3-3 / Chapter 3.1.3 --- Cleansing of apparatus --- p.3-4 / Chapter 3.2 --- Experimental --- p.3-5 / Chapter 3.2.1 --- Sample preparation --- p.3-6 / Chapter 3.2.2 --- Experimental setup --- p.3-7 / Chapter 3.2.3 --- Procedures --- p.3-8 / Chapter 3.3 --- Observing the Microstructure --- p.3-9 / Chapter 3.3.1 --- Cutting --- p.3-10 / Chapter 3.3.2 --- Molding --- p.3-10 / Chapter 3.3.3 --- Polishing --- p.3-11 / Chapter 3.3.4 --- Etching --- p.3-12 / Chapter 3.3.5 --- Observation --- p.3-12 / References --- p.3-14 / Table --- p.3-15 / Figures --- p.3-16 / Chapter Chapter 4: --- Metastable liquid phase separationin undercooled molten PD40. 5]\l40.5P19 --- p.4-1 / Abstract --- p.4-1 / References --- p.4-9 / Figures --- p.4-10 / Chapter Chapter 5 ： --- Transformation in undercooled molten PD40.5NI40.5P19 --- p.5-1 / Chapter 5.1 --- Abstract --- p.5-1 / Chapter 5.1 --- Introduction --- p.5-2 / Chapter 5.3 --- Experimental --- p.5-4 / Chapter 5.4 --- Results --- p.5-6 / Chapter 5.5 --- Discussions --- p.5-13 / References --- p.5-20 / Figures --- p.5-22 / Chapter Chapter 6 ： --- Solidification of liquid spinodal in undercooled PD40.5NI40.5P19 --- p.6-1 / Chapter 6.1 --- Abstract --- p.6-1 / Chapter 6.2 --- Introduction --- p.6-2 / Chapter 6.3 --- Experimental --- p.6-3 / Chapter 6.4 --- Results --- p.6-5 / Chapter 6.5 --- Discussions --- p.6-10 / References --- p.6-17 / Figures --- p.6-18 / Chapter Chapter 7: --- Conclusion --- p.7-1 / References --- p.7-4 / Bibliography --- p.B-1

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Vita. / Includes bibliographical references. / by Timothy George Peter Gutowski. / Ph.D.

Nine pages of Addenda and eight pages of Errata in back pocket. / Includes bibliographical references. / vii, 192, [78] : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1994

Thesis (M. Ing.)--University of Stellenbosch, 1997. / Bibliography. Also available via the Internet.