Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2006. / An understanding of the behaviour of chromium in mattes equilibrated with chrome-saturated slags is essential for the prediction and control of chromium deportment in these melts. The main ore reserves of South Africa’s platinum group metals (PGM) are associated with the Merensky and UG2 reefs of the Bushveld Complex. The gradual depletion of the pyroxenitic Merensky reef over the years has necessitated the PGM industry to exploit the underlying chromiterich UG2 reef. The problem with UG2 reef is that it contains significant amounts of chromium, this being typically 5% (reported as Cr2O3) against <1% for the Merensky reef (in concentrates). Chromium has a number of deleterious effects on base-metal smelting processes. Under given conditions, it forms chromite spinels, which can accumulate and, over a period of time, form undesirable build-ups resulting in reduced furnace operational volume. The chromite spinels also tend to increase slag viscosity, thereby impacting negatively on the slag/matte separation, which leads to matte entrainment in slag. Moreover, high viscosities lead to problems with tapping of the furnace melts. Finally it can be said that chromium that deports to the matte during smelting will normally tend to precipitate as spinels during subsequent converting, and lead to the formation of very stable and unwanted slag foams in the converter. In literature, there exists very little published work on the behaviour of chromium in sulphur-saturated systems such as matte-smelting furnaces. The few publications that exist in this area do not cover the effect of controlling all the pertinent variables simultaneously on the behaviour of chromium in mattes in equilibrium with chromium-containing slags. Hence the main focus of the oxygen fugacities on the mineralogical and deportment behaviour of chromium in a matte-slag system. All the three variables (temperature, oxygen fugacity (pO2), and sulphur fugacity (pS2)) were investigated at three levels. Temperatures studied were 1300°C, 1400°C, and 1500°C. Oxygen and sulphur fugacities were established by controlling the mix-ratios of purified carbon dioxide, carbon monoxide, sulphur dioxide, and argon. Oxygen fugacities were maintained at 10-10atm, 10-8atm, and 10-6atm; whereas sulphur fugacities were maintained at 10-6atm, 10-4atm, and 10- 2atm. In order to investigate the effect of each of these three variables (temperature, pS2, and pO2) at different levels of the other variables, a completely randomised 33 full factorial experimental design was adopted. The study revealed that chromium is generally present in matte as both dissolved CrS and as precipitated oxidic and sulphidic chromium spinel phases. It was shown that as the conditions become more oxidising (pO2 = 10-6atm), CrS (which is soluble in matte) becomes a predominant phase, and as the conditions become more reducing (pO2 = 10-10atm), the sulphospinel, daubreelite (FeCr2S4), becomes a more predominant phase. Oxidic chromium spinels were found to be present in matte under the more oxidising conditions (pO2 of 10-6atm) of this investigation. The presence of the above-mentioned phases was confirmed using X-ray diffraction. Subject to the experimental conditions employed in this research, chromium was found to partition the least to matte under the conditions of; low temperature, high pO2, and low pS2. Conversely, chromium was found to partition the most to matte under the conditions of; high temperature, low pO2, and high pS2.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Membrane fouling is universally considered to be one of the most critical problems in the wider application of membranes in filtration separation. Fouling is caused by the deposition of particles not only on the surface of the membrane, but also inside the membrane pores, which reduces permeate flux and leads to a reduction of the efficiency and the longevity of the membrane. The backpulsing cleaning method can be used to remove deposited foulants from the surface of the membrane, without having to shut down the plant. Ultrasonic time-domain reflectometry (UTDR) is a nondestructive technique, used to detect and measure the growth of fouling layer on the membrane surface during microfiltration and ultrafiltration processes. In this study flat-sheet microfiltration (MF) and ultrafiltration (UF) membranes were fouled during a cross-flow filtration processes using dextrin, yeast or alumina (feed pressure 100 kPa and feed flow rate 0.45 liter/minute), in a flat cell. Infrasound frequency backpulsing, in the permeate space, was used to clean the membranes. Backpulsing was carried out using the permeate water or soap solutions. The peak pressure amplitude of the pulses used to clean the membranes was 140 kPa, the pulsing was applied at a frequency of 6.7 Hz. The main objectives of this research were: (1) to obtain a fundamental understandimg of how foulants deposit on membrane surfaces and how the foulant deposits can be removed using the backpulsing cleaning technique during MF and UF, (2) to use the ultrasonic measurement technique for monitoring the growth and removal of the fouling layer on the membrane surface and (3) Use scanning electron microscopy (SEM) as a direct measurement technique to analyze the structure the foulant deposits on membrane surfaces before and after cleaning. Results showed that a flux value of between 55% and 98% of the clean water flux value can be achieved by backpulsing cleaning. UTDR was successfully applied to monitor membrane cleaning and provide information about the growth and removal of fouling layers on the membrane surface. / AFRIKAANSE OPSOMMING: Membraanaanvuiling is wêreldwyd bekend as een van die mees kritieke probleme wat die wyer aanwending van membrane vir skeidingsprosesse benadeel. Aanvuiling word veroorsaak deur die deponering van partikels, nie net op die oppervlak van die membraan nie, maar ook binne-in die membraanporieë, wat die volgende tot gevolg het: 'n afname in vloed deur die membraan, 'n afname in die effektiwiteit van die membraan, en 'n korter membraanleeftyd. Die teenpulsskoonmaakmetode kan gebruik word om die aanvuilingslaag vanaf die membranoppervlakte te verwyder sonder dat dit nodig is om die membraantoetsapparaat af te skakel. Ultrasoniese-tydsgebied-weerkaatsing (UTW) is 'n nie-vernietigende tegniek wat gebruik kan word om die groei van 'n aanvuilingslaag op 'n membraanoppervlakte tydens mikrofiltrasie (MF) of ultrafiltrasie (UF) te identifiseer en te meet. In hierdie studie is plat-vel MF en UF membrane bevuil gedurende 'n kruisvloeifiltrasieproses deur gebruik to maak van dekstraan, gis of alumina, in 'n plat sel. Infraklank-frekwensieteenpols, in die permeaatgebied, is gebruik om die membrane skoon te maak. Hiervoor is die proseswater of 'n seepoplossing gebruik. Die maksimum drukamplitude van die pulse wat gebruik is was 140 kPa, en die puls was aangewend teen 'n frekwensie van 6.7 Hz. Die hoofdoelwite van hierdie studie was die volgende: (1) om inligting in te win oor hoe aanvuilingsmateriale op membraanoppervlaktes gedeponeer word tydens MF en UF en hoe hulle verwyder kan word deur gebruik te maak van die teenpulsskoonmaaktegniek; (2) om van die teenpulsskoonmaaktegniek gebruik te maak om die groei van die bevuilingslaag asook die verwydering daarvan op die membraanoppervlakte te monitor; en (3) om van skandeerelektronmikroskopie (SEM) as 'n direkte analitiesetegniekgebruik te maak om die struktuur van die aanvuilingsmateriaal voor en na die die skoonmaakproses te analiseer. Deur gebruik te maak van teenpulsskoonmaak kon die membraanvloed tot tussen 55–98% van die oorspronklike suiwerwatervloed verbeter word. Sodoende is ultrasoniese-tydsgebiedweerkaatsing suksesvol gebruik om die skoonmaak van membrane te monitor asook om inligting in te win i.v.m. die groei en verwydering van die aanvuilingslae op die membraanoppervlaktes.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2006. / South Africa has a variety of sources for humic substances that may be utilised for the large-scale production of specialised fertilizers. Humic substances are dark coloured fully decomposed remains of plant and animal organic matter. Amongst the sources that were investigated in this study, a 5-weeks old compost (C5W), a 6-weeks old compost (C6W), a compost prepared by Medallion Mushroom farm for the production of mushrooms (CB1), a compost produced as waste material after mushroom production (CB2), recycled water used in compost (i.e. CB1) preparation for mushroom production (“Goodie water,” GW) and black liquor from pulp industry (BL), black liquor showed the best potential for the large scale production of humic acids in South Africa. The quantity and quality of humic acids in these materials were determined by using the basic acid-precipitation method and E6/E6 ratio analyses of the products. Extracting humic acids from black liquor was optimised by comparing three possible variations to the standard humic acid-precipitation method (HAp), namely, lignin extraction/humic acid precipitation method (LHAp), humic acid precipitation/acid treatment method (HApA) and lignin extraction/humic acid precipitation/acid treatment method (LHApA). The method of extraction had a substantial impact on the quantity and quality of humic acids produced. Humic acid precipitation method followed by humic acid precipitation/acid treatment method (HApA) demonstrated high quantities of humic acids compared to lignin extraction/humic acid precipitation method (LHAp) and lignin extraction/humic acid precipitation/acid treatment method (LHApA). Analyses such as Fourier Transform Infrared (FTIR) spectroscopy, Ultraviolet Visible Spectroscopy (UV-VIS), High Performance Liquid Chromatography (HPLC) and Elemental Analysis demonstrated that the quality of humic acids produced from black liquor was similar to those reported previously. The type of material (e.g. softwood, hardwood and bagasse) used for black liquor production significantly affected the elemental and molecular composition of humic acids produced. The quality of humic acids produced was affected by both lignin extraction and acid treatment. However, chemical analyses indicated that the features of the humic acids extracted from black liquor correlated with their lignin origin. Humic acids from hardwood and softwood black liquor had a low nitrogen and high sulphur content compared to those extracted from black liquor produced from bagasse material. Although chemical and instrumental analysis of humic acids was quite reasonable for all humic acids produced, LHAp method was favoured for the extraction of humic acids from pine liquor due to the high quantity of humic acids produced (low S and ash contents). The humic acids extracted by means of HAp method and HApA had a positive effect on plant growth, when extracted from bagasse and Eucalyptus black liquors. Humic acids extracted by HAp from pine liquor had an inhibitory effect on plant growth. A possible process flow for the large-scale production of humic acids from black liquor was formulated. The possible process flow indicated that with the amounts of black liquor produced from pulp industry production of humic acids in South Africa is a possibility. Nevertheless, there is still more that needs to be done to investigate the cost effectiveness of this production prior its implementation. HAp method was most suitable for the production of humic acids from Eucalyptus and bagasse liquors in terms of quantity and plant response but LHAp method was more suitable for the production of humic acids from pine liquor in terms of both quantity and quality.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2009. / AFRIKAANSE OPSOMMING: Die effek van teenpolsing op die aanvuiling van 'n 2.5-duim spiraal kruisvloei ultrafiltrasie element is eksperimenteel ondersoek. Teenpolseksperimente met 'n organiese (dekstraan) oplossing en 'n anorganiese (kaolien) suspensie is uitgevoer deur gebruik te maak van 'n polipropileenmembraan (100 000 molekulêre massa snypunt). Die konsentrasie van die dekstraanoplossing was tussen 250 en 750 mg/L en die konsentrasie van die kaolien oplossing was tussen 100 en 300 mg/L. Teenpolsing behels die aanwending van drukpolse van tussen 100 en 150 kPa aan die kant van die produk (permeaat). Die polstussenposes het gewissel tussen 1 en 15 s en die duur van die polse tussen 0.1 en 0.5 s. Die vloeitempo was tussen 500 en 1500 L/h, en die toegepaste druk was 100 kPa. Eksperimentele resultate het getoon dat terugpols effektief was vir die vermindering van membraanaanvuiling, en die verbetering van vloei deur die membraan. Met aanhoudende terugpolsing het die netto vloei toegeneem met toenemende terugpolsdruk. Daar was 'n effense toename met 'n toename in kruisvloeitempo en 'n sterk afname met toenemende voeroplossingkonsentrasie. Die beste terugpols parameters vir die twee verskillende aanvuilingsmateriale was soos volg: 0.2 s polsduur, 3 s polstussenpose en 150 kPa terugopolsdruk vir die dekstraanoplossing; en 0.2 s polsduur, 5 s polstussenpose en 150 kPa terugopolsdruk vir die kaoliensuspensie. Die beste resulate behaal vir vloei onder hierdie kondisies was 3-maal en 1.5-maal hoër as die vloei behaal sonder polsing, vir dekstraan en kaolien, onderskeidelik. Nadat die membraan aan aanvuiling, gevolg deur terugpolsing, blootgestel is, is dit skoongemaak deur skoon water met terugpolsing te gebruik. Die vloei van die skoon membrane wat voorheen met dekstraan en kaolien aangevuil is was 62% en 71% van die oorspronklike vloei, onderskeidelik. Die Taguchi metode met 'n L9 ortagonale reeks is gebruik om die belangrike terugpolsfaktore te bepaal wat 'n maksimum permeaatvloei tot gevolg gehad het. Die polsdruk het die grootste effek op die membraanvloei gehad. Polstussenpose en polsduur het 'n onbeduidende effek en die dwarsvloeitempo het 'n swak effek op membaanvloei gehad. Daar moet egter opgelet word dat hierdie waarnemings slegs van toepassing is binne die eksperimentele grense soos bepaal in die inleidende ondersoek van hierdie studie.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The discovery that the reaction of CO2 with primary amines in both aqueous and non-aqueous media provides a viable chemical method for determining the effective interfacial mass transfer area for separation column internals has lead to an increase in the interest of studying the reaction kinetics and determining the governing reaction rate expressions. For the absorption studies conducted on these systems, many authors assumed that power rate law reaction kinetics govern the reaction rate, which simplified the derivation of absorption correlations. This has already been proven to be an over simplifying assumption, since many authors suggest a non-elementary rate expression based on the pseudo-steady state hypothesis for the reactive zwitterion intermediate to be valid. An evaluation of the existing reaction rate expressions for the homogeneous liquid phase reaction of CO2 and mono-ethanolamine (MEA) in a 2-propanol solvent system was performed. The reaction rate profiles of CO2 and MEA at 25ºC, 30ºC and 35ºC, and relative initial concentrations of [MEA]i = [CO2]i, [MEA]i = 2.5[CO2]i, [MEA]i = 4[CO2]i were determined by means of an isothermal CSTR set-up. Scavenging of the unreacted MEA with benzoyl chloride provided the means to be able to stop the reaction in the product stream. This in turn allowed for the construction of concentration- and reaction rate profiles. The reaction rate data was modelled on various rate expressions by means of a MATLAB® non-linear estimation technique, employing the Levenberg-Marquard algorithm for minimizing the loss function. It was concluded that the rate expressions proposed in literature are insufficient and a rate expression derived fundamentally from first principals is proposed: [ ][ ] [ ] [ ][ ] [ ]2 MEA 1 2 2 -r = k CO RNH - k2 Z + k3 Z RNH2 - k4 S where ki are the reaction rate constants, Z is the zwitterion reactive intermediate and S the salt product of the overall reaction mechanism. In order to be able to determine the effective interfacial mass transfer area, the absorption rate per unit area or specific rate of absorption for the solute gas as a rate expression function of species concentration must firstly be determined. This is achieved by performing experimental absorption runs on a gas-liquid contactor of known surface area. This study incorporated the well known wetted wall experimental set-up. The aim was to construct and implement a wetted wall set-up and conduct absorption experiments for a gas side CO2 concentration range stretching from pure CO2 to diluted gas mixtures absorbing into solutions of varying MEA concentrations. Validation of the set-up was done by performing experiments at similar conditions to a previous study. The study then proceeded to determine the absolute and specific absorption rates at CO2 mass percentages of 100%, 78%, 55% and 30% into solutions of MEA concentrations of 0.25 and 0.3 mol/L. These runs were conducted at 25ºC and 30ºC. The wetted wall was designed to facilitate absorption studies at column heights of 60, 90 and 105mm. This allowed the investigation of the effect that surface area and column height has on the absolute rate of absorption as well as the CO2 and MEA concentrations in the liquid phase It was found that the specific absorption rate is independent of contact time, which is consistent with the rapid nature of the reaction. It was furthermore found that an increase in MEA concentration caused an increase in the absorption rate. The effect of temperature is linked with the solubility of CO2 in the solution. As the temperature increases, the solubility of CO2 decreases, but the absorption rate increases. The result is that it seems as if a change in temperature has no effect on the absorption rate, when in actual fact it does. An increase in the amount of CO2 absorbed is noticed for an increase in wetted wall surface area. This is expected and indicates that there is an increase in the amount of CO2 absorbed as the column length increases. Stopping the absorption reaction by means of MEA scavenging with benzoyl chloride at various column heights will allow for the construction of a concentration profile for both CO2 and MEA as a function of column height. These profiles will allow for the derivation of a non-elementary rate expression governing the specific absorption rate. This has been identified as ‘n area of great interest for future investigation. / AFRIKAANSE OPSOMMING: ‘n Groot navorsingsbelangstelling in die reaksiekinetika van CO2 en monoethanolamien (MEA) het ontstaan sedert die ontdekking dat hierdie reaktiewe sisteem ook ‘n goeie metode is vir die bepaling van die effektiewe massaoordragsoppervlakte van gestruktureerde pakkingsmateriaal. Die klem val op die bepaling van eerstens die mees geskikte en akkurate model om die reaksiekinetika te beskryf wat dan gebruik kan word om die absorbsiekinetika deeglik te karaktariseer. Sommige van die vorige navorsers het vereenvoudigende aannames gemaak rakende die reaksiekinetika ten einde die bepaling van geskikte absopsievergelykings te vergemaklik. Ander het gevind dat die nie-elementêre, pseudo-gestadigde toestand hipotese gebasseer op die reaktiewe zwitterioon tussenproduk van die reaksie ‘n meer verteenwoordigende kinetiese model is. Hierdie studie is eerstens gemik op die evaluasie van die bestaande reaksiekinetikavergelykings deur die homogene vloeistoffase reaksie van CO2 met mono-etanolamien (MEA) in die oplosmiddel, 2-propanol te ondersoek. Die studie is uitgevoer in ‘n isoterme CSTR sisteem by onderskeidelik 25ºC, 30ºC en 35ºC en MEA konsentrasies van [MEA]i = [CO2]i, [MEA]i = 2.5[CO2]i en [MEA]i = 4[CO2]i. Die voorgestelde reaksiekinetikavergelykings was gemodelleer met ‘n nie-lineêre datapassingstegniek verskaf deur die sagtewarepakket, MATLAB® wat die Levenberg- Marquard algoritme gebruik om die resfunksie te minimeer. Uit die teorie en datapassing word die volgende vergelyking voorgestel: [ ][ ] [ ] [ ][ ] [ ]2 MEA 1 2 2 -r = k CO RNH - k2 Z + k3 Z RNH2 - k4 S waar ki die reaksietempokonstante voorstel, Z die zwitterioontussenproduk en S die soutproduk. Die eerste stap in die bepaling van die effektiewe massaoordragsarea van gestruktureerde pakkingsmateriaal is om ‘n geskikte vergelyking of korrelasie vir die spesifieke absorpsie van die gas te bepaal. Dit word gedoen deur absoprsie eksperimente te doen op toerusting van bekende oppervlakarea. Hierdie studie het die reeds bekende ‘wetted wall’ opstelling gebruik. Die hoof doelwit van hierdie absorpsiestudie was om ‘n werkende opstelling te bou en absorpsie eksperimente vir CO2 konsentrasies wat strek van suiwer CO2 tot verdunde mengsels uit te voer. Die konsentrasie MEA is ook gevarieër. Die geskiktheid van die opstelling is eerstens getoets deur eksperimentele lopies uit te voer by soorgelyke toestande as ‘n vorige studie. Die doel van die studie is om die absolute en spesifieke absorpsietempos van CO2 by gasfase massapersentasies van 100%, 78%, 55% en 30% in MEA/2-propanol oplossings met MEA konsentrasies van 0.25 en 0.3 mol/L te bepaal. Die lopies is uigevoer by beide 25ºC en 30ºC. Die opstelling is ook ontwerp om absorpsie eksperimente by verskillende kolomhoogtes uit te voer. Hierdie hoogtes is 60, 90 en 105mm. Hierdie studie het tweedens gefokus op die effek wat absorpsiearea en kolomhoogte op die absorpsietempo van CO2 het. Die resultate van die studie toon dat die absorpsietempo onafhanklik is van kontaktyd. Dit stem saam met die vinnige reaksietempo. ‘n Toename in MEA konsentrasie het ‘n toename in spesifieke absorpsietempo tot gevolg, terwyl die effek van temperatuur gekoppel kan word aan die oplosbaarheid van CO2. Soos die temperatuur toeneem, neem die absolute absorpsietempo toe, maar die oplosbaarheid van CO2 neem af, dit het beide ‘n toenemende en afnemende effek op die spesifieke absorpsietempo. Die hoeveelheid CO2 geabsorbeer neem toe met ‘n toename in kolomhoogte. Die konsentrasie MEA in die uitlaatvloeistof toon ‘n skynbare eksponensiële afname met ‘n toename in kolomhoogte. ‘n Studie gemik om die konsentrasieprofiele van CO2 en MEA as ‘n funksie van kolomhoogte te bepaal, word voorgestel. Absorpsiemodelle en korrelasies kan dan afgelei word uit hierdie profiele, wat die berekening van die effektiewe massaoordragsarea akkuraat sal maak. Dit sal deel vorm van toekomstige navorsing.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Mass transfer efficiency in distillation, absorption and stripping depends on both thermodynamic efficiency and hydrodynamic behaviour. Thermodynamic efficiency is dependent on the system kinetics while hydrodynamics is the study of fluid flow behaviour. The focus of this thesis is the hydrodynamic behaviour in tray columns, which affects entrainment. In order to isolate hydrodynamic behaviour from the thermodynamic behaviour that occurs inside sieve tray columns, investigations are conducted under conditions of zero mass transfer. When the gas velocity is sufficiently high to transport liquid droplets to the tray above, entrainment occurs. The onset of entrainment is one of the operating limits that determines the design of the column and thus impacts on the capital cost. By improving the understanding of the parameters that affect entrainment, the design of the tray and column can be improved which will ultimately increase the operability and capacity while reducing capital costs. Existing correlations predicting entrainment in sieve tray columns are based on data generated mainly from an air/water system. Previous publications recommend that more testing should be performed over larger ranges of gas and liquid physical properties. An experimental setup was therefore designed and constructed to test the influence of the following parameters on entrainment: 1. gas and liquid physical properties 2. gas and liquid flow rates 3. tray spacing The experimental setup can also measure weeping rates for a continuation of this project. The hydrodynamic performance of a sieve tray was tested with air and water over a wide range of gas and liquid flow rates and at different downcomer escape areas. It was found that the downcomer escape area should be sized so that the liquid escaping the downcomer always exceeds a velocity of approximately 0.23 m/s in order to create a sufficient liquid seal in the downcomer. For liquid velocities between 0.23 and 0.6 m/s the area of escape did not have an effect on the percentage of liquid entrained. It was also established that entrainment increases with increasing gas velocity. The rate at which entrainment increases as the gas velocity increase depends on the liquid flow rate. As soon as the liquid flow rate exceeded 74 m3/(h.m) a significant increase in entrainment was noted and the gas velocity had to be reduced to maintain a constant entrainment rate. This is because the increased liquid load requires a longer flow path length for the froth to fully develop. The undeveloped froth, caused by the short (455 mm) flow path, then creates a non-uniform froth that is pushed up against the column wall above the downcomer. Consequently, the froth layer is closer to the tray above resulting in most of the droplets ejected from the froth reaching the tray above and increasing entrainment. By reducing the gas velocity, the froth height and ejecting droplet velocity is reduced, resulting in a decrease in entrainment. The results from the experiments followed similar trends to most of the entrainment prediction correlations found in literature, except for the change noted in liquid flow rates above 74 m3/(h.m). There was, however, a significant difference between the experimental results and the correlations developed by Hunt et al. (1955) and Kister and Haas (1988). Although the gas velocities used during the air/water experiments were beyond the suggested range of application developed by Bennett et al. (1995) their air/water correlation followed the results very well. The entrainment prediction correlation developed by Bennett et al. (1995) for non-air/water systems was compared with the experimental air/water results to test for system uniformity. A significant difference was noted between their non-air/water prediction correlation and the air/water results, which motivates the need for a general entrainment prediction correlation over a wider range of gas and liquid physical properties. Based on the shortcomings found in the literature and the observations made during the experiments it is suggested that the influence of liquid flow path length should be investigated so that the effect on entrainment can be quantified. No single correlation was found in the literature, which accurately predicts entrainment for a large range of liquid loads (17 – 112 m3/(h.m)), high superficial gas velocities (3 – 4.6 m/s) and different gas and liquid physical properties. It is therefore recommended that more work be done, as an extension of this project, to investigate the influence of gas and liquid physical properties on entrainment (under zero mass transfer conditions) for a large range of liquid (5 – 74 m3/(h.m)) and gas (2 – 4.6 m/s) flow rates. In order to understand the effect of droplet drag on entrainment, tray spacing should be varied and increased to the extent where droplet ejection velocity is no longer the mechanism for entrainment and droplet drag is responsible for droplet transport to the tray above. Since it is difficult and in most cases impossible to measure exact gas and liquid loads in commercial columns, another method is required to measure or determine entrainment. Since liquid hold-up was found to be directly related to the entrainment rate (Hunt et al. (1955), Payne and Prince (1977) and Van Sinderen et al. (2003) to name but a few), it is suggested that a correlation should be developed between the dynamic pressure drop (liquid hold-up) and entrainment. This will contribute significantly to commercial column operation from a hydrodynamic point of view.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Development of analytical methods to characterise biodiesel has become central to the overall success of the marketing of biodiesel fuel. In this regard, different bodies including the American Society for Testing and Materials (ASTM) and the European normalization (EN) have come up with various methods to determine important biodiesel parameters such as total glycerol, methanol and the fatty acid methyl esters (FAMEs), etc. Various studies have been conducted on the parameters mentioned above using a variety of instrumentation and sample preparations. The best methods reported are those that have been adopted by both the ASTM and EN standards. The purpose of this study was to develop alternative analytical methods to both the recommended ASTM and EN methods and, in some cases, to make modifications to both standards (ASTM D 6571 and EN 14214) and methods to determine total and bound glycerol, the ester content and also methanol content in biodiesel. Moreover, water washing after transesterification and the effect this practice has on biodiesel cold flow properties such as kinematic viscosity, cloud and pour point and density were evaluated. The possibility of using the iodine value to predict the feedstock source of an unknown biodiesel was also investigated. Six different vegetable oil samples were transesterified with methanol and used for this study. The six samples used were palm, crown, sunflower, waste vegetable oil (wvo), peanut and rapeseed biodiesel. Quantitative results indicated that the use of programmable temperature volatilisation (PTV) for total glycerol did not produce the required repeatability of between 1-4% relative standard deviation(RSD) for total glycerol analyses in biodiesel with precision of 25%, 86%, 25% and 56% for free glycerol (FG), monoglycerides (MG), diglycerides (DG), and triglycerides (TG) respectively. The standard requires a relative standard of between 1-4% As an alternative to the method using gas chromatography, normal phase high performance chromatography (HPLC) with binary gradient elution was used to determine the bound glycerol content. This method proved accurate and repeatable with RSD % of 0.33, 1.12, and 1.2 for TG, DG and MG respectively. Following the EN14103 protocol (European standard ester determination), the Zebron ZBWAX column which is comparable to the specification recommended by EN14103 but afforded the determination of ester content from the esters of myristic acid (C14:0) to behenic acid (C22:0) with reproducibility with RSD % of 6.81, 1.91, 7.27, 0.64, 1.18, 1.55, 6.03, 1.96, and 5.21 for methyl esters of myristic, palmitic, stearic, oleic, linoleic, linolenic, arachidoic, gadoleic and behenic acid respectively. Solid phase micro extraction (SPME) using GC-MS was developed as an alternative to both the EN14110 and ASTM D93 protocols for determining the methanol content in biodiesel. For this method, polyethylene glycol fibre (PEG) was used together with a deuterated methanol internal standard and a DB-FFAP (60m×0.25um×0.25um) column. Less volume of sample was required as compared to the EN14214 method. This method was found to be sensitive, accurate and repeatable with a RSD % of 4.82. The Iodine number of biodiesel decrease compared to their corresponding feed stock and therefore predicting the feed stock of an unknown biodiesel was going to be difficult .Results from this study indicated that it is not possible to predict the feed stock source of an unknown biodiesel from its iodine value. The effect of water washing after phase separation on biodiesel cold flow properties such as kinematic viscosity, density, cloud and pour point depended on the type of biodiesel produced. We observed that water washing after transesterification caused an increase in all the cold flow properties of sunflower biodiesel, whereas only the densities and kinematic viscosities increased in the case of palm and waste vegetable oil biodiesel. The cloud and pour point of the latter two diesel samples remained unchanged after water washing. Thus, the effect of water washing on biodiesel cold flow depended on the type of biodiesel. Blending a highly saturated biodiesel (fewer numbers of double bonds) with a less saturated biodiesel (higher number of double bonds) resulted in an improvement of both the pour and cloud points of the resultant biodiesel blend. / AFRIKAANSE OPSOMMING: Die ontwikkeling van analitiese metodes om biodiesel te karakteriseer word tans as ‘n kernmaatstaf gesien om biodiesel suksesvol te bemark. Hiervoor het verskeie liggame wat die Amerikaanse Vereniging vir Toetsing van Materiale (AVTM) en die Europese Normalisering (EN) insluit met verskeie standaard analitiese metodes vorendag gekom om belangrike biodiesel parameters soos bv. totale gliserol, metanol en vetsuur metielesters te meet. Om hierdie parameters te bepaal is van ‘n wye verskeidenheid toetse met verskillende instrumente en monsterbereidings gebruik gemaak. Die beste metodes is deur beide die AVTM en EN aanvaar. Die doel van hierdie studie was om metodes te ontwikkel wat as alternatiewe kan dien tot die wat deur die AVTM en EN voorsgeskryf is. In sommige gevalle is aanpassings tot beide die standaarde (AVTM en EN) en metodes aangebring om die totale en gebonde gliserol-, esteren metanolinhoud te bepaal. Verder is die effek van ‘n water wasstap na transesterifikasie op biodiesel se kouevloei eienskappe gevalueer wat eienskappe soos kinematiese viskositeit, vertroebelingspunt, gietingspunt en digtheid insluit. Die moontlike gebruik van die Jodiumpunt om die bron van die voerstof van ‘n onbekende diesel te bepaal is ook ondersoek. In hierdie studie is ses verskillende oliemonsters van plantaardige oorsprong gebruik wat d.m.v. metanol getransesterifiseer is. Hierdie monsters het palm-, kroon-, sonneblom-, afvalplant-, grondboontjie- en raapsaadolie ingelsuit. Tydens die studie is programmeerbare temperatuur vervlugtiging (PTV) vergelyk met inkolom inspuiting soos deur AVTM D6584/EN14214 vir totale gliserol analise voorgeskryf. Kwantitatiewe resultate het getoon dat die PTV metode nie die verlangde akkuraatheid van ‘n relatiewe standaardafwyking (RS) van 1-4% vir beide vrye en gebonde gliserol kon handhaaf nie. Die akkuraatheid was in die omgewing van 25%, 86%, 25% en 56% vir vrye gliserol (VG), monogliseriede (MG), digliseriede (DG) en trigliseriede (TG), onderskeidelik. Normale fase hoë werkverrigting vloeistofchromatografie met ‘n binêre elueeringsgradiënt is as alternatief tot gaschromatografie (GC) ondersoek om die gebonde gliserolinhoud te bepaal. Al was die GC metode meer sensitief, het die vloeistofchromatografie metode ‘n hoë graad van akuraatheid en herhaalbaarheid getoon met RS% waardes van 0.33, 1.12 en 1.2 wat vir TG, DG en MG, onderskeidelik, verkry is. ‘n Zebron ZB-WAX kolom is vir die EN14103 protokol gebruik. Behalwe vir ‘n groter lengte kon hierdie kolom met spesifikasies soos deur EN14103 voorgeskryf vergelyk word. Met die gebruik van hierdie kolom kon die esterinhoud van miristiensuur (C14:0) tot behensuur (C14:0) bepaal word. ‘n Hoë graad van herhaalbaarheid met RS% waardes van 6.81, 1.91, 7.27, 0.64, 1.18, 1.55, 6.03, 1.96 en 5.21 vir die metielesters van miristien-, palmitien-, stearien-, oleïn-, linoleïn-, linoleen-, aragidoon-, gadoleïen- en behensuur is onderskeidelik verkry. Om die metanolinhoud van die biodiesel te bepaal is soliede fase mikroekstraksie (SFME) m.b.v. gaschromatografie-massaspektrometrie (GC-MS) as alternatiewe tot EN14110 en AVTM D93 ontwikkel. In hierdie metode is daar van poliëtileenglikolvesels (PEG) en gedeutereerde metanol saam met ‘n DB-FFAP kolom (60 mm x 0.25 mm x 0.25 mm) gebruik gemaak. Hierdie metode het ‘n kleiner monstervolume as die EN14214 metode benodig en was sensitief, akkuraat en hehaalbaar wat tot ‘n RS% waarde van 4.82 gelei het. Op grond van die Jodiumwaarde van biodiesel en hul ooreenstemmende voerstowwe het hierdie studie bevind dat die Jodiumwaarde nie gebruik kan word om die voerstof van ‘n onbekende diesel kan voorspel nie. Die effek van ‘n water wasstap na faseskeiding op verskeie kouevloei eienskappe soos kinematiese viskositeit, vertroebelingspunt, gietingspunt en digtheid het van die tipe diesel afgehang. Dit is bevind dat ‘n water wasstap na transesterifikasie ‘n toename in al die kouevloeieienskappe van sonneblomdiesel tot gevolg gehad het. In teenstelling hiermee het slegs die kinematiese viskositeit en digtheid van palm- en afvalplantdiesel vermeerder terwyl hul vertroebelings- en gietingspunte onveranderd gebly het. Die hipotese dat ‘n water wasstap na transesterifikasie tot swak kouevloei eienskappe lei is dus as onwaar bevind aangesien hierdie eienskappe deur die tipe biodiesel bepaal word. Deur ‘n hoogs versadigde biodiesel (lae aantal dubbelbindings) met ‘n minder versadigde biodiesel (hoë aantal dubbelbindings) te vermeng het tot ‘n verbetering van beide die vertroebelings- en gietingspunte gelei. / Centre for Renewable and Sustainable Energy Studies

Thesis (MIng) --Stellenbosch University, 1999. / ENGLISH ABSTRACT: A method was developed at the Atomic Energy Corporation of South Africa (AEC) for the plasma based production of tetrafluoroethylene (TFE). The process involves the feeding of carbon particles into a direct-current CF4 plasma. The resultant plasma gas is quenched rapidly to obtain TFE and other fluorocarbons. The mixing of the particles with the plasma gas is very important in order to achieve a high C:F-ratio in the gas phase, which promotes the desired reactions. The gas enthalpy in the reactor is a governing factor in the TFE yields that are obtained. In this study research was done on particle mixing and the enthalpy distribution in the laboratory scale reactor. An enthalpy probe was used as the main diagnostic tool. Results indicated that particle mixing is quite uniform throughout the reactor. A basic one-dimensional mechanistic model of the reactor was also expanded to assist in· the scale-up of the process. In its present form the model is adequate for predicting trends in the reactor. The model could still be expanded further to include reaction kinetics and internal heat transfer in the particles. Considering the restrictions of the model, satisfactory agreement was obtained between the model and experimental results. / AFRIKAANSE OPSOMMING: 'n Proses vir die plasmagebaseerde produksie van tetrafluoroetileen (TFE) is deur die Atoomenergiekorporasie van Suid-Afrika (AEK) ontwikkel. Koolstofpartikels word in 'n gelykstroomCF4- plasma gevoer en die resulterende plasmagas word vinnig geblus ten einde TFE en ander fluoor-koolstofverbindings as produkte te verkry. Goeie vermenging van die koolstofpartikels met die plasmagas is van uiterste belang ten einde 'n hoe C:F-verhouding, wat die gewenste reaksies bevorder, in die gasfase te verkry. Die entalpie van die plasmagas in die reaktor is 'n bepalende faktor in die opbrengs TFE wat verkry word. Vir die doel van hierdie werkstuk is navorsing op laboratoriumskaal gedoen oor partikelvermenging en die entalpie-verspreiding in die reaktor. Die hoof diagnostiese apparaat wat vir die doel aangewend is, is die entalpiesonde. Resultate toon dat partikelvermenging naastenby uniform deur die reaktor voorkom. Verder is 'n basiese een-dimensionele meganistiese model van die reaktor uitgebrei ten einde van nut te wees in die opskaling van die proses. In sy huidige vorm is die model voldoende om algemene neigings in die reaktor te voorspel. Die model kan nog verder uitgebrei word om reaksie-kinetika en interne hitte-oordrag in die partikels in te sluit. Die beperkings van die model in ag genome, is ooreenstemming tussen die model en eksperimentele resultate egter bevredigend.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In a floating medium filter, polymeric beads with a density less than that of water form a floating bed which removes suspended material. Polyolefinic beads (polypropylene and polyethylene) are commonly used as filter media in this application. The geometric properties of the beads, and to a lesser extent the surface properties, strongly influence the performance of the filter. In the case of water treatment, the primary performance requirement is the production of a filtrate with turbidity ≤ 1.0 NTU. The influence of geometric properties on the performance of existing upflow filtration systems has not been extensively researched. The aim of this thesis was therefore to investigate the effects of floating medium granule size and shape on the performance of the floating medium filter (FMF). Towards this goal a pilot plant consisting of a dosing and flocculation unit and a clear PVC column with an inner diameter of 0.3 m and height of 2.8 m was designed and constructed, allowing the effect of media type, bed depth and filtration conditions to be investigated. Artificial feed water for use during the experimental work was made up by dissolving 250 mg/L of bentonite in tap water (≈ 60 NTU). Four median grain sizes (d50 = 2.28, 3.03, 3.30, and 4.07 mm) of polypropylene plastic granules were used. Two media shapes (cubic and disc) were evaluated. The effect of filtration rising velocity, medium depth, and coagulant chemical dosage were investigated using a complete 23 full factorial experimental design. Filter performance was evaluated in terms of filtrate turbidity and headloss development. The direction of filtration was upward in all the experiments. It was found that optimal conditions for turbidity removal were low filtration rate (36.8 L/m2· min), longer media depth (0.6 m) and optimum coagulant dose (23 mg/L). At these conditions the best medium was the one with d50 = 2.28 mm, for which a minimum turbidity of 0.4 NTU was achieved, and which was able to provide 624 L of filtrate of ˂ 1.0 NTU using a bed of 0.014 m3. For this medium headloss was 109 mm H2O at breakthrough, while the other three media showed a headloss of 42 mm H2O at breakthrough. Visual observation indicated that removal of solids took place primarily in the first 0.3 m of the floating bed in the case of the smallest medium, but that solids removal took place over the full depth of the bed for the other three media. It was found that bed depth had the strongest influence on performance for a given medium type. Experimental observation showed that coagulant dosage played an important role in floc size. A higher coagulant dosage (23 mg/L) resulted in a larger floc size which gave better performance. A lower velocity gradient was favourable for the formation of larger flocs. Some effect of media shape was noted, although it appeared that media size was dominant. It is concluded that FMF show promise for application in the water treatment. FMF, however, can be applied successfully as pre-filtration unit for treatment of high turbid water. Proper medium selection in conjunction with operating conditions can enhance performance of the filter. Smaller medium would give better turbidity removal but high headloss development and more frequent backwashing becomes necessary than with larger medium. / AFRIKAANSE OPSOMMING: In ʼn dryfmediumfilter vorm polimeriese korrels met ʼn laer digtheid as dié van water ʼn dryfbedding wat swewende materiaal verwyder. Poli-olefiniese korrels (polipropileen en poliëtileen) word algemeen in hierdie toepassing as filtermedia aangewend. Die geometriese kenmerke, en in ʼn mindere mate die oppervlakkenmerke, van die korrels het ʼn groot invloed op die funksionering van die filter. In geval van waterbehandeling is die hooffunksioneringsvereiste die produksie van ʼn filtraat met ʼn troebelheid van ≤ 1.0 NTU (“nephelometric turbidity units”). Die invloed van die geometriese kenmerke van filtermedia op die funksionering van bestaande stroomop-filtreerstelsels is nog nie omvattend nagevors nie. Die doel van hierdie tesis is dus om ondersoek in te stel na die uitwerking van die korrelgrootte en -vorm van ʼn dryfmedium op die funksionering van die dryfmediumfilter (DMF). Hiervoor is ʼn proefaanleg met ʼn doseer- en uitvlokkingseenheid sowel as ʼn deursigtige pilaar van polivinielchloried (PVC) met ʼn binnedeursnee van 0.3 m en ʼn hoogte van 2.8 m ontwerp en gebou, met behulp waarvan verskillende mediumtipes, beddingdieptes en filtreeromstandighede ondersoek kon word. ʼn Kunsmatige watertoevoer vir die proefneming is vervaardig deur 250 mg/L bentoniet in kraanwater op te los (≈ 60 NTU). Polipropileenplastiekkorrels met vier verskillende deursneë (d50 = 2.28; 3.03; 3.30 en 4.07 mm) is gebruik, en twee mediumvorms (kubus- en skyfvormig) is beoordeel. Die uitwerking van filtrasiestygsnelheid, mediumdiepte en die dosis koaguleermiddel is met behulp van ʼn volledige 23-faktoriaalontwerp ondersoek. Filterfunksionering is aan die hand van filtraattroebelheid en verlies aan drukhoogte beoordeel. Alle proefnemings is teen ʼn opwaartse filtrasierigting uitgevoer. Daar is bevind dat die beste omstandighede vir die verwydering van troebelheid ʼn lae filtrasiekoers (36.8 L/m2 per minuut), ʼn groter mediumdiepte (0.6 m) en ʼn optimale dosis koaguleermiddel (23 mg/L) is. In hierdie omstandighede was die beste medium die een met ʼn d50 van 2.28 mm, waarvoor ʼn minimum troebelheid van 0.4 NTU verkry is, en wat 624 L filtraat van 1.0 NTU met behulp van ʼn bedding van 0.014 m3 kon lewer. By deurbraak het hierdie medium egter ʼn drukhoogteverlies van 109 mm H2O getoon, teenoor die ander drie media se 42 mm H2O op dieselfde punt. Visuele waarneming dui daarop dat, met die kleinste medium, vaste stowwe hoofsaaklik oor die eerste 0.3 m van die dryfbedding verwyder is, teenoor die volle diepte van die bedding vir die ander drie media. Beddingdiepte blyk dus die grootste invloed te hê op funksionering wat enige bepaalde mediumtipe betref. Proefwaarneming toon dat die dosis koaguleermiddel ʼn belangrike rol in vlokgrootte speel. ʼn Hoër dosis koaguleermiddel (23 mg/L) het ʼn groter vlokgrootte en dus beter funksionering tot gevolg. ʼn Laer stygsnelheid blyk ook die beste te wees vir die vorming van groter vlokke. Hoewel mediumvorm oënskynlik ʼn mate van ʼn rol speel, is mediumgrootte eerder die dominante faktor. Volgens die studie blyk DMF belowend vir aanwending in waterbehandeling te wees, veral as voorfiltreereenheid vir die behandeling van baie troebel water. Behoorlike mediumkeuse saam met die regte bedryfsomstandighede kan die funksionering van die filter verder verbeter. Kleiner media sal troebelheid beter verwyder, maar het ʼn groot verlies aan drukhoogte tot gevolg, en sal dus meer gereelde terugspoeling as groter media verg.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Partially oxygenated aromatic compounds, e.g. quinones, hydroquinones and cresols, play a vital role in the fine chemical industry and were initially prepared by stoichiometric oxidation processes that produce toxic products that are hazardous towards the environment. As a result, it was important to investigate environmentally friendly processes for the hydroxylation of aromatic compounds. This resulted in newer methods using Ti-substituted microporous zeolites as catalysts with hydrogen peroxide as oxidant in the presence of a solvent. However, the methods were found to be ineffective for large, bulky substrates due to the small pore structure. This led to using Ti-mesoporous materials as catalysts but suffered from two drawbacks; the hydrophilic nature and low hydrothermal stability of the catalyst structure. Ti-microporous and Ti-mesoporous materials acting as catalysts for the oxidation of bulky substrates achieved environmentally friendly processes but obtained low conversions and quinone yields. Therefore, the challenge has been to develop a process that is environmentally friendly, achieves high conversions, where the catalyst acts truly heterogeneous and obtains high quinone yields for the hydroxylation of bulky substrates. Recently, micropores/mesopores catalysts incorporating advantages of both micropores and mesopores materials were synthesised and seemed promising for the hydroxylation of bulky substrates. This study focuses on synthesising and evaluating the feasibility of various Ti-substituted catalysts for improving the hydroxylation of the bulky substrate, 2-methylnaphthalene (2MN) with hydrogen peroxide as oxidant in the presence of a solvent, acetonitrile. The oxidation of 2MN produces 2-methyl-1,4-naphthoquinone (2MNQ). 2MNQ is also known as menadione or Vitamin K3 and acts as a blood coagulating agent. The catalysts synthesised for this study were mesoporous catalysts, Ti- MCM-41 and Ti-MMM-2 and microporous/mesoporous catalysts, Ti-MMM-2(P123) and a highly ordered mesoporous material. The main objective of this study was to design an efficient process that is environmentally friendly and achieves high 2MN conversions and 2MNQ yields. This was achieved by evaluating the various catalysts synthesised, reaction conditions, testing if the catalyst was truly heterogeneous and identifying the products formed from the process. The designed process was proved to be environmentally friendly because the system did not produce products that were harmful towards the environment. The products identified in this study were 2MNQ, 2-methyl-1-naphthol, 2-naphthaldehyde, 3-ethoxy-4-methoxybenzaldehyde and menadione epoxide. An investigation was conducted to determine which catalyst synthesised favoured this process by quantifying the effect reaction conditions have on the various catalysts. The reaction conditions were defined in terms of the hydrogen peroxide volume, catalyst amount, solvent volume, substrate amount, reaction time and reaction temperature. The desired catalyst for this study obtained the highest 2MN conversions in comparison with the other catalysts and favoured the formation of 2MNQ. The catalyst achieving the highest conversions and favouring 2MNQ in most cases for this investigation was the highly ordered mesoporous material. Improving operating conditions to obtain high 2MNQ yields for the oxidation of 2MN to 2MNQ over the highly ordered mesoporous material was determined by varying the reaction conditions with the one factor at a time approach and a factorial design. The one factor at a time approach showed that best 2MNQ yields were obtained at 1 g substrate when investigating a change in substrate amount between 0.5 g and 2 g. Best 2MNQ yields were obtained at 10 ml solvent when investigating a change of solvent volume between 5 ml and 20 ml. The 2MNQ yield increased with increasing the catalyst amount (50 mg to 200 mg), hydrogen peroxide volume (1 ml to 6 ml) and increasing the reaction times (2 hour to 6 hours) at reaction temperatures, 120°C and 150°C. The yield decreased with increasing the reaction time (2 hours to 6 hours) at reaction temperature, 180°C. A preliminary 2 level factorial design was prepared to observe if there were any important interactions affecting the 2MNQ yield. The results from the factorial design indicated that the hydrogen peroxide volume had the most influence on the 2MNQ yield followed by the reaction time-reaction temperature interaction and reaction temperature. From the factorial design, the yield increased by increasing the hydrogen peroxide volume and reaction temperature whilst decreasing the reaction temperature-reaction time interaction. The highest 2MNQ yields and 2MN conversions obtained for the hydroxylation of 2MN to 2MNQ over the highly ordered mesoporous material in this study were in the ranges 48-50 % and 97-99 %, respectively. This study indicates that the process system, reaction conditions and catalyst type have an impact on the products formed, 2MN conversion, 2MNQ selectivity and 2MNQ yield. The highly ordered mesoporous material was found to be truly heterogeneous because no leaching occurred and the catalyst could be recycled without losing its catalytic activity and selectivity for at least two catalyst cycles. It can be concluded that the highly ordered mesoporous material is therefore a promising catalyst for the selective oxidation of bulky substrates with aqueous H2O2 because it produces an environmentally friendly process, achieves high conversions, obtains high quinone yields and the catalyst truly acts heterogeneous. / AFRIKAANSE OPSOMMING: Gedeeltelik geoksideerde aromatiese verbindings (bv. kinone, hidrokinone en kresole) speel ‘n belangrike rol in die fynchemiebedryf. Hierdie verbindings is aanvanklik voorberei deur stoïchiometriese oksidasie prosesse wat gifstowwe nadelig vir die omgewing veroorsaak. Daarom is dit belangrik om omgewingsvriendelike prosesse vir die hidroksilering van aromatiese verbindings te ondersoek. Hierdie ondersoeke het gelei tot nuwe metodes wat Ti-vervangde mikroporeuse seoliete as katalisator met waterstofperoksied as oksideermiddel in die teenwoordigheid van ʼn oplosmiddel benut. Dit is egter gevind dat hierdie metodes oneffektief is vir groot, lywige substrate weens die fyn poriestruktuur van die katalisator. Dit lei tot die gebruik van Ti-mesoporeuse materiale as katalisators, maar toon twee tekortkominge, naamlik die hidrofiliese aard en lae hidrotermiese stabiliteit van die katalisatorstruktuur. Ti-mikroporeuse en Ti-mesoporeuse materiale benut as katalisators vir die oksidasie van lywige substrate lewer omgewingsvriendelike prosesse, maar vermag lae omsetting en kinoonopbrengs. ʼn Uitdaging is dus om ʼn omgewingsvriendelike proses te ontwikkel met hoë omsetting, waar die katalisator werklik heterogeen optree en hoë kinoonopbrengs lewer vir die hidroksilering van lywige substrate. Katalisators vir die hidroksilering van lywige substrate wat die voordele van beide mikroporieë/mesoporieë ten toon stel is onlangs gesintetiseer, met belowende resultate. Hierdie studie is ingestel op die sintetisering en evaluering van uitvoerbaarheid van verskeie Tivervangde katalisators vir die optimering van die hidroksilering van die lywige substraat, 2- metielnaftaleen (2MN), met waterstofperoksied as oksideermiddel met asetonitriel as oplosmiddel. Die oksidering van 2MN produseer 2-metiel-1,4-naftokinoon (2MNK), ook bekend as vitamien K3, ʼn bloedstollingsmiddel. Die katalisators vervaardig vir hierdie studie was die mesoporeuse katalisators, Ti-MCM-41 en Ti-MMM-2, en die mikroporeuse/mesoporeuse katalisor Ti-MMM-2(P123), sowel as ʼn hoogs geordende mesoporeuse materiaal. Die hoofdoel van hierdie studie was om ʼn doeltreffende, omgewingsvriendelike proses met hoë 2MN omsetting en 2MNK opbrengs te ontwerp. Voorgenoemde is vermag deur verskeie gesintetiseerde katalisators en reaksiekondisies te evalueer, om te toets of katalisators werklik heterogeen is, en om die prosesprodukte te identifiseer. Die ontwerpte proses kan beskou word as omgewingsvriendelik, aangesien die stelsel geen produkte lewer wat skade aan die natuur kan veroorsaak nie. 2MNK, 2-metiel-1-naftol, 2-naftaldehied, 3- etoksi-4-metoksibensaldehied en menadioonepoksied is in hierdie studie geïdentifiseer as prosesprodukte. Om te bepaal watter gesintetiseerde katalisators hierdie proses begunstig, is ʼn ondersoek geloods om die effek van reaksiekondisies op die verskeie katalisators te kwantifiseer. Die reaksiekondisies is omskryf in terme van waterstofperoksiedkonsentrasie, katalisatorhoeveelheid, oplosmiddelvolume, substraathoeveelheid, reaksietyd en reaksietemperatuur. Die gewenste katalistor vir hierdie proses was die katalisator wat die hoogste 2MN omsetting lewer en die vorming van 2MNK bevorder. Die hoogs geordende mesoporeuse materiaal was in hierdie ondersoek die katalisator met die hoogste omsetting wat ook 2MNK-vorming bevorder het in die meeste gevalle. Om die beste bedryfstoestande vir hoë 2MNK opbrengs vanaf die oksidering van 2MN oor hoogs geordende mesoporeuse materiaal te bepaal, is die reaksiekondisies verander deur met een faktor op ʼn slag te verander, sowel as faktorverandering volgens ʼn faktoriaalontwerp. Die een-faktor-op-‘nslag benadering het getoon dat die 2MNK opbrengs ʼn maksimum bereik waar die substraathoeveelheid tussen 0.5 g en 2 g wissel, met die oplosmiddelvolume tussen 5 ml en 20 ml. Die opbrengs het ietwat verbeter met ʼn groter hoeveelheid katalisatorhoeveelheid (van 50 mg na 200 mg), terwyl die opbrengs drasties verbeter het waar die waterstofperoksiedvolume van 3 ml tot 6 ml verhoog is. Die opbrengs het ook verbeter met ʼn styging in reaksietemperatuur (van 120°C tot 180°C) met reaksietydintervalle van 1 tot 6 ure. Die opbrengs het egter gedaal by 180°C waar reaksietye langer as 2 ure. Volgens die resultate van die een-faktor-op-‘n-slag benadering blyk dit dat reaksietemperatuur, waterstofperoksiedvolume, katalisatorhoeveelheid en reaksietyd faktore is wat verhoogde 2MNK opbrengs bevorder. Hierdie reaksiekondisies is geselekteer vir die faktoriaalontwerp. ʼn Voorlopige 2- vlak faktoriaalontwerp is voorberei om te bepaal of daar enige belangrike interaksies is wat die 2MNK opbrengs beïnvloed. Die resultate van die faktoriaalontwerp het aangetoon dat waterstofperoksiedvolume die grootste invloed op 2MNK opbrengs het, gevolg deur die interaksie van reaksietyd en reaksietemperatuur, en dan reaksietemperatuur. Die faktoriaalontwerp resultate toon verder dat opbrengs verhoog met toenemende waterstofperoksiedvolume en reaksietemperatuur, terwyl die opbrengs verlaag soos wat die reaksietyd-reaksietemperatuur interaksie toeneem. Hierdie studie het hoogste 2MNK opbrengs van 48-50% en 2MN omsetting van 97-99% vir die hidroksilering van 2MN na 2MNK oor hoogs geordende mesoporeuse materiale behaal. Hierdie studie bevestig bevindinge van die literatuur dat die prosesstelsel, reaksiekondisies en katalisatortipe ʼn groot impak het op prosesprodukte, 2MN omsetting, 2MNK selektiwiteit en 2MNK opbrengs. In hierdie navorsingstudie is bevind dat hoë 2MN omsetting en 2MNK opbrengs behaal word by hoë reaksietemperature met kort reaksietye en hoë waterstofperoksiedvolumes. Dit is gevind dat die hoogs geordende mesoporeuse materiaal werklik heterogeen is, aangesien geen loging plaasgevind het nie, en aangesien die katalisator hergebruik kon word sonder verlies aan katalisatoraktiwiteit en –selektiwiteit, vir ten minste twee katalisatorsiklusse. ʼn Gevolgtrekking kan gemaak word dat die hoogs geordende mesoporeuse materiaal ʼn belowende katalisator vir die selektiewe oksidering van lywige substrate met waterige H2O2 is, aangesien dit ʼn omgewingsvriendelike proses lewer met hoë omsetting, hoë kinoonopbrengs en katalisatorgedrag wat waarlik heterogeen is.