Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 54-57.

No description available.

Proefschrift--Utrecht. / Includes bibliographical references.

Proefschrift--Utrecht. / Includes bibliographical references.

The orientational order of the methylene segments adjacent to the head group in the lamellar liquid crystalline phase of potassium palmitate/D₂0 was investigated using multinuclear magnetic resonance. Previous studies had shown that the orientational order near the soap--water interface decreased with decreasing temperature, contrary to intuition. To investigate this phenomenon, three isotopically substituted species of palmitic acid were synthesized: palmitic acid-d₃₁, 1-¹³C-2,2-H₂- palmitic acid-d₂₉, and 2,2,3,3-H₄- palmitic acid-d₂₇. These compounds were treated in two complementary fashions: the acids were dissolved in the liquid crystal 4 - (octyloxy) - benzoic acid (p - OOBA) and the corresponding potassium salts were dispersed in D₂0 at a constant water concentration. Dipolar and quadrupolar couplings were obtained from the ¹H, ¹³C, and ²H nmr spectra of these molecules, in nematic and lamellar liquid crystalline phases, as a function of temperature. In a parallel study, nmr spectra of acetic, propionic, and butyric-2,2 - d₂ acids dissolved in p - OOBA were recorded. In order to observe ¹H - ¹H dipolar couplings, a two dimensional spin echo (π/2 - t₁/2 - π - t₁/2 - echo) was necessary to remove heteronuclear dipolar couplings to the chain deuterons. A refocussing pulse applied simultaneously to the spins allowed observation of the heteronuclear ¹H - ¹³C dipolar couplings in the carbon 13 labelled compound. The complete orientational order matrix of the alpha methylene segment of potassium paImitate/D₂0 and of palmitic acid/p - OOBA was determined from the dipolar and quadrupolar couplings. As the temperature is decreased from 110°C to a temperature just above the gel-liquid crystalline phase transition (45°C), the orientation of the methylene segment of potassium palmitate is rotated by 3° towards a configuration in which the first C - C bond is parallel to the bilayer normal. This is in direct agreement with a previous model, the Abdollal model of lipid - water interaction, in which the decrease in orientational order was postulated to be a strictly geometric effect arising from electrostatic interactions of the lipid with the water. A mean field equilibrium statistical mechanical model, based on the Samulski Inertial Frame Model, was developed to simulate the experimental dipolar and quadrupolar nmr couplings. In potassium palmitate, electrostatic interactions, approximately constant at higher temperatures, increase dramatically as the phase transition is approached. In contrast mean field steric repulsive forces remain constant over the entire temperature range studied. This evidence also supports the Abdollal model of lipid - water interaction. The electrostatic interaction was shown to be of greater importance in the orientational ordering of the solutes in the liquid crystal than in potassium palmitate and this was attributed to intermolecular H - bonding between solute and p - OOBA. The ordering of the head group of carboxylic acids dissolved in p - OOBA was demonstrated to be remarkably similar regardless of the chain length of the solute. / Science, Faculty of / Chemistry, Department of / Graduate

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This project focused on scaling up the laboratory fermentation of biomass to carboxylic acids. Four 1050-gallon tanks were used to simulate four-stage countercurrent fermentation. Most laboratory fermentations have been performed with 1-L fermentors. The purpose of the pilot plant was to show that the process is scalable. The inocula were marine and terrestrial microorganisms. Office paper was used as an energy source, and chicken manure provided the necessary nutrients. The substrate was 80 wt% office paper and 20 wt% chicken manure. Calcium carbonate was used as a neutralizing agent and iodoform served as a methane inhibitor. The fermentor temperature was 40 oC and the pH was 6.0. The highest total acid concentration obtained was 32.4 g/L, operating with a volatile solids loading rate (VSLR) of 1 g/(L liq ·d) and a liquid residence time (LRT) of 80 days. Typical laboratory VSLRs and LRTs are 3 to 10 g/(L liq ·d) and 10 to 30 days, respectively. Similar VSLRs and LRTs were not achieved at the pilot scale because the design was limited by the ability to effectively separate large amounts of solids and liquids. The bulk of the effort was concentrated on overcoming temperature control and solids-handling issues. Design modifications included a redesigned temperature control system and a new material transfer method.

The MixAlco process, a proprietary technology owned by Texas A&M University, converts biomass (e.g., municipal solid waste, sewage sludge, paper, agricultural residues, and energy crops) into usable chemicals (e.g., acetic acid) and fuels (e.g., ethanol). Historically, calcium carbonate has been used as the buffer. Recently, it was found that using ammonium bicarbonate as the buffering agent enhances the fermentation conversion. In this case, fermentation broth contains ammonium salts (e.g., ammonium acetate, propionate, butyrate, pentanoate). Therefore, the downstream processing steps (including extraction, purification, esterification, and product separation) must be compatible with the ammonium carboxylate salts formed in the fermentation. This research focuses on converting fermentation broth carboxylate salts into their corresponding acids via "acid springing." Reactive extraction and thermal conversion (distillation) are crucial parts of the acid springing process. Because the components of the fermentation broth are over 80% ammonium acetate and 20% other ammonium carboxylate salts (ammonium propionate, butyrate, pentanoate, etc.), all the initial experiments in this study were performed using reagentgrade ammonium acetate to simplify the reaction. Later, actual fermentation broth was employed. The primary objective of this study was to provide the optimal operating conditions to make the downstream processing steps of the MixAlco process compatible with ammonium carboxylate salts formed in the fermentation. The optimal initial concentration for reactive extraction should be 150-200 g/L and the volume ratio of aqueous phase and extractant should be 1:1. The distribution coefficient reaches the maximum value when the concentration of TOA is 20% (vol %) in n-octanol. The batch distillation study shows that there are two reaction stages: (1) water leaves the system at 100-106 °C and (2) the acid-amine complex decomposes at 160-180 °C.

No description available.

No description available.