A waste acid stream is being produced by a local petrochemical company (SASOL) at a rate of 10 000 -12 000 tons per annum and contains approximately 44-mole % butyric acid, 20 % isobutyric acid and 10 % valeric acid. Whilst this stream is currently being incinerated, SASOL has requested an investigation into the possibility of separating and purifying butyric acid and isobutyric acid from this waste acid stream. The goal of this project was to determine a separation and purification route for butyric acid and isobutyric acid from SASOL'S waste acid stream. In order to achieve this, vacuum distillation and freeze crystallization were chosen for the recovery and purification of the acids respectively. Vapour-liquid equilibrium data for key component pairs present in the waste acid stream (propionic acid + butyric acid, isobutyric acid + butyric acid, butyric acid + isovaleric acid and butyric acid + hexanoic acid) were experimentally determined in a dynamic VLE still. The measured VLE data was successfully correlated us ing the gamma-phi approach. with the NRTL activity coefficient model representing the liquid phase and the virial equation of state describing the vapour phase. Using these equations. the VLE data obtained from the experimental work was then regressed to provide interaction coefficients for the NRTL model. which were then used in the Hysys process simulator to explore a range of design alternatives for distillation. Hysys simulations showed that greater than 80 % butyric acid and isobutyric acid can be recovered from the waste acid stream in a single distillation column containing 18 theoretical stages and an optimum reflux ratio of 3.8. The simulation was performed at a pressure of 58kPa and a maximum operating tempe rature of 150°C. Batch distillation experiments performed in a batch rectification column at 250kPa recovered more than 90% of both the butyric acid and isobutyric acid from a 450ml sample of the waste acid stream. A subsequent batch experiment concentrated the recovered acids into a distillate containing more than 95 % butyric acid and isobutyric acid combined. To investigate freeze crystallization as a suitable operation for purifying butyric acid and isobutyric acid a solid-liquid phase equilibrium curve for the system was generated us ing the Van Hoft equation. The generated curve showed that butyric acid and isobutyric acid could be theoretically purified (>98%) by operating two crystallizers at -20°C and -55°C respectively. A simple freeze crystallization experiment produced butyric acid with greater than 94% purity. An economic feasibility study conducted on the process showed that separation and purification of the acids by this process (distillation and crystallization) could create a business opportunity with revenue of approximately R47 million per annum. Preliminary estimates for capital investment amounted to approximately R5.4 million. for which the payback period was estimated at less than one year. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2001.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Considering the hypothesis that GABA and oxidative stress are involved in the development of oral movements associated with important neuropathologies, the present study investigated the possible ability of V. officinalis in the prevention of vacuous chewing movements (VCMs) induced by reserpine in rats. Adult male rats were treated with reserpine (1 mg/kg, s.c.) and/or with V. officinalis (in the drinking water). VCMs, locomotor activity and oxidative stress measurements were evaluated. The neuroprotective effect of V. officinalis against iron-induced cell toxicity was investigated in brain cortical slices. Furthermore, we carried out the identification of valeric acid and gallic acid by HPLC in the V. officinalis tincture. Our findings demonstrate that reserpine caused a marked increase on VCMs and the co-treatment with V. officinalis was able to reduce the intensity of VCM. Reserpine did not induce oxidative stress in cerebral structures (cortex, hippocampus, striatum and substantia nigra). However, a significant positive correlation between DCF-oxidation (an estimation of oxidative stress) in the cortex and VCMs (p<0.05) was observed. Moreover, a tendency for a negative correlation between Na+K+- ATPase activity in substantia nigra and the number of VCMs was observed (p= 0.06). In vitro, V. officinalis protected brain cortical slices viability against Fe(II)-induced neurotoxicity. In conclusion, V. officinalis had in vitro and in vivo neuroprotective effects in rats, i.e., reduced Fe(II) neurotoxicity and reserpine-induced VCMs, probably via modulation of oxidative stress in specific brain nucleus and its GABA-mimetic action. However, the mechanisms involved in this protective activity needs to further investigated to better understand the action of V. officinalis. / Considerando as hipóteses do papel da neurotransmissão gabaérgica e do estresse oxidativo no desenvolvimento de movimentos orais associados a neuropatologias importantes, o presente estudo investigou a possível habilidade da tintura de V. officinalis na prevenção dos movimentos de mascar no vazio (MMV) induzidos por reserpina em ratos. Os animais foram tratados com reserpina (1 mg/Kg, s.c.) e/ou com V. officinalis (na água de beber). MMV, atividade locomotora e medidas de estresse oxidativo foram avaliadas. O efeito neuroprotetor da V. officinalis contra a toxicidade celular induzida por ferro foi investigada em fatias de córtex cerebral. Além disso, fez-se a identificação do ácido valérico e do ácido gálico por HPLC na tintura de V. officinalis. Os resultados demonstram que a reserpina causou um aumento nos MMV quando comparado com o seu veículo e o co-tratamento com V. officinalis foi capaz de reduzir a intensidade dos MMV. A reserpina não alterou de forma significativa alguns parâmetros de estresse oxidativo analisados nas estruturas do cérebro (córtex, hipocampo, estriado e substantia nigra). Porém, uma correlação positiva entre os níveis de oxidação da DCF (uma estimativa do estresse oxidativo) no cortex e o número de MMV (p<0.05) foi observada. Além disso, foi observada uma tendência a haver uma correlação negativa entre a atividade da Na+/K+- ATPase na substantia nigra e o número de MMV (p= 0.055). In vitro, V. officinalis protegeu as fatias de córtex cerebral contra a neurotoxicidade induzida por ferro. Desta forma, pode-se concluir que a V. officinalis apresentou efeitos neuroprotetores em ratos tanto in vitro quanto in vivo, ou seja, reduziu a neurotoxicidade induzida por ferro e os MMV induzidos por reserpina, provavelmente via modulação do estresse oxidativo em núcleos específicos do cérebro e sua ação gabamimética. Porém, os mecanismos envolvidos nesta atividade protetora necessitam de mais investigações para melhor entender a ação da V. officinalis.