Abstract The aim of this thesis project was to gain new knowledge on the effect of phosphorus on the catalytic activity and characteristics of automotive exhaust gas catalyst components. The simultaneous roles of phosphorus and calcium were also studied. The first test series of powdery catalyst samples contained Rh and oxide (Test series 1) and the second, Pt and oxide or ZSM-5 (Test series 2). The catalysts were analyzed when fresh and after two ageing and phosphorus poisoning procedures developed in this work. The procedures consisted of adding poison via impregnation in an aqueous solution (for Test series 1) and in the gaseous phase under hydrothermal conditions (for Test series 2). The poison compounds formed and the changes in the washcoat were studied by using physisorption analyses, SEM, TEM, XRD, and FTIR-ATR. The poison content of the samples was determined by ICP-OES and XRF. Laboratory-scale activity measurements were done to investigate the catalytic activity. Thermodynamic calculations were used to obtain information about ageing conditions and phosphorus compounds formed during ageing. Phosphorus decreased the catalytic activity and the characteristic surface areas of the catalysts. Addition of calcium to a phosphorus-poisoned catalyst was found to have even a regenerating effect on the catalysts' activity. The poisoning methods developed in this study resulted in the same phosphorus compounds as can be found in vehicle-aged catalysts. Phosphorus was identified as cerium, zirconium, aluminium, and titanium phosphates. Phosphorus was detected in zeolites, but phosphorus-containing compounds were not observed. Phosphorus poisoning takes place in the gas phase at high operating temperatures and with high oxygen and water contents. It was also shown that the role of phosphorus poisoning was more pronounced than the role of hydrothermal ageing alone. Phosphorus poisoning mainly affects the oxide components used in this study, not the noble metals. The results can be utilized in the development of catalytic materials and catalyst compositions that can better tolerate phosphorus poisoning under hydrothermal conditions. The results can also be applied in evaluating the effects of phosphorus on different catalyst compositions and in estimating the age of commercial catalysts.

Anaerobic digestion (AD) has been shown to be an effective technique for energy recovery and stabilization of livestock wastes, municipal sludges and industrial wastewaters. However, further treatment is required to remove nitrogen from AD effluents to avoid detriments to surface and ground waters. The high free ammonia (FA) concentrations present in AD effluents can inhibit nitrification processes in conventional biological nitrogen removal (BNR) systems. The overall goal of this research was to develop a process for removal of nitrogen from AD swine waste (ADSW) effluent. The proposed solution was to incorporate particulate chabazite, which has a high cation exchange capacity, into a sequencing batch reactor (SBR) to adsorb ammonium and therefore ease nitrification inhibition. The process developed is called a chabazite-SBR. Three research questions were used to guide this research. First question (Chapter 3): How does chabazite pretreatment with groundwater (GW) affect the kinetics and cation exchange capacity during ammonium (NH4+) uptake? Kinetics and isotherm batch tests were performed with GW pretreated chabazite. In addition, sodium chloride (NaCl), and deionized water (DI) pretreated chabazite was included for comparison because these are typically used pretreatment methods. The Ion Exchange (IX) isotherm model was used to calculate the cation exchange capacity and the pseudo-first and film diffusion kinetics models were applied to quantify the effect of the pretreatment on the reaction rate. Results showed that the exchange capacity was slightly higher for GW pretreated chabazite compared with the other common pretreatment strategies; however, the enhancement was not significantly different. The kinetics of NH4+ uptake during the first four hours of contact was significantly improved by GW pretreatment when compared with other common pretreatment strategies. This was caused by an enhancement in film diffusion mechanisms. The findings of this first part of the research were important because it was shown that NaCl pretreatment is not needed to improve the kinetics and cation exchange capacity of chabazite. Second question (Chapter 4): How does addition of chabazite to ADSW centrate affect nitrification rates? Nitrification batch test with varying NH4+ concentrations were performed to identify the inhibitory NH4+ concentration. Additional nitrification batch tests treating real and synthetic waste with initial NH4+ concentration of 1,000 mg-N L-1 with added zeolite were performed. For the mixed liquor tested in this study, NH4+ concentrations must be maintained below 200 mg-N L-1 to relieve nitrification inhibition. Treatment of ADSW centrate requires a chabazite dose of 150 g L-1 to ease FA inhibition of nitrification. The rate of nitrification increased, by approximately a factor of 3, when chabazite was added to a batch reactor treating high NH4+ strength wastewater. However, Na+ release from the chabazite also plays a role in nitrification inhibition. The findings of this part of the research showed the potential for using chabazite for overcoming FA inhibition of nitrification during treatment of high NH4+ strength wastewater. Third question (Chapter 5): How effective is the chabazite-SBR in removing total nitrogen concentrations from ADSW centrate? A chabazite-SBR was operated for 40 weeks (cycles) to study the TN removal efficiency with varying carbon source. The efficiency of IX was also monitored over time. The chabazite-SBR process achieved stable TN removal from ADSW centrate during the 40 weeks of operation. Simultaneous nitrification-denitrification reduced chemical input requirements. Addition of an external organic carbon source at a rate of 3.2 g-COD g-N-1 resulted in maximum TN removal. An overall TN removal efficiency of 84% was achieved, with specific nitrification and denitrification rates of 0.43 and 1.49 mg-N g-VSS-1 hr-1, respectively. The IX stage of the chabazite-SBR was able to reduce FA concentrations to below the inhibitory level for nitrification inhibition over 40 chabazite-SBR cycles with no loss in IX efficiency over time and no fresh zeolite added to the reactor.

L’ autoradiolyse de l’eau tritiée HTO, adsorbée dans les zéolithes 4A présente des différences par rapport à la radiolyse de l’eau libre. Nous avons étudié les rôles joués par les zéolithes sur la décomposition de l’eau, en portant un intérêt particulier à l’influence de leur taux de chargement en eau. Premièrement, en exposant les zéolithes aux irradiations externes, nous avons reproduit sélectivement les gammes de dose oude débit de dose constatées en situation d’entreposage.Cette première approche permet de caractériser les échantillons irradiés, car non contaminés, et ainsi de mettre en évidence la très bonne stabilité des zéolithes4A. Puis, le suivi de la radiolyse dans le cas précis de l’eau tritiée adsorbée dans les zéolithes 4A nous a permis d’obtenir des rendements radiolytiques quantitativement représentatifs de ceux relevés en situation d’entreposage. La comparaison des quantités de gaz dégagés pour les trois types de rayonnements étudiés (électrons accélérés à 10 MeV, ! induits par la désintégration du 137Cs et "- induit par la désintégration du tritium) a montré l’importante influence du débit de dose plutôt que de la dose totale déposée. De plus,quelle que soit la source de rayonnement utilisée, les zéolithes 4A favorisent initialement le dégagement de dihydrogène et secondairement de dioxygène. A contrario, elles favorisent ensuite, selon leur taux d’hydratation, la recombinaison de ces deux produits de radiolyse. Différents processus radiolytiques etc atalytiques sont discutés pour expliquer ce résultat majeur, qui n’apparait pas lors de la radiolyse de l’eau libre et qui tend à valider ce mode d’entreposage. / Self-radiolysis of tritiated water (HTO) adsorbed in zeolites 4A shows differences compared tofree-bulk water radiolysis. We studied the roles of zeolites on that. We took special care with the influence of water loading ratio. We first exposed zeolites toexternal irradiations, reproducing selectively the doseor the dose rate measured in the case of tritiated waterstorage. This strategy enables the characterising of the samples after their irradiation since they are notcontaminated by tritium. Those experiments revealedthe high stability of zeolites 4A. We used a secondapproach which consisted in studying the precise case of self-radiolysis of tritiated water, in order to obtain radiolytic yields representative of HTO storage. The comparison between the quantities of gas released when zeolites are exposed to the three different sources that we used (electrons accelerated at 10 MeV, ! released by radioactive decay of 137Cs and "- released by radioactive decay of tritium) revealed the strong influence of the dose rate. More over, whatever the irradiation source,zeolites 4A first favour hydrogen release andsecondarily oxygen release too. On the contrary,zeolites favour next a recombination between those radiolytic products, with a dependence on their water loading ratio. Several processes are discussed to explain such a phenomena, not noticed during the free-bulkwater radiolysis

Abstract The production of liquid transportation fuels such as bioethanol and more recently also biobutanol from renewable resources has received considerable attention. In the production of bio-based alcohols, the separation steps are expensive as the mixtures to be separated are dilute. As an energy-efficient separation technology, pervaporation is considered to be a potential process in biofuel purification. One of the main constraints in the commercialization of pervaporation has been low membrane fluxes, and the consequent high costs due to the high membrane area needed. In order to obtain high fluxes, the membranes should be as thin as possible. In this thesis, the performance of ultra-thin zeolite membranes in pervaporation was investigated. Binary ethanol/water and n-butanol/water mixtures were studied using both hydrophobic and hydrophilic zeolite membranes for alcohol concentration, as well as dehydration. The development of pervaporation membranes and processes has been mainly empirical. Process modeling, however, is an indispensable tool in process design. In this work, the pervaporation performance of the studied membranes was evaluated on the basis of experimental results in combination with mathematical modeling. Due to the low film thickness of the studied membranes, the fluxes were generally higher than reported earlier. Nevertheless, the evaluation in this work showed that the pervaporation performance of the ultra-thin membranes decreased due to flux limitation by membrane support. In this work, pervaporation was modeled by applying both a semi-empirical and a detailed Maxwell-Stefan based mass transfer model. The latter model considers explicitly both adsorption and diffusion, i.e. the phenomena involved in separation by pervaporation. The description of the support behavior was included in the models. Maxwell-Stefan formalism was applied in unary pervaporation for the determination of diffusivities in zeolite membranes. The models performed well within the range of experimental data. Additionally, a practical modeling approach was developed in this work to predict the temperature dependency of adsorption on zeolites. The developed approach can be utilized, e.g., in pervaporation modeling. Thus, this thesis provides knowledge of using ultra-thin zeolite membranes in the pervaporation of alcohol/water mixtures, and offers tools for pervaporation modeling. / Tiivistelmä Kiinnostus uusiutuvista raaka-aineista valmistettavia liikennepolttoaineita, kuten bioetanolia ja -butanolia, kohtaan lisääntyy koko ajan. Biopohjaisten alkoholien tuotannossa etenkin erotusvaiheet ovat kalliita, koska erotettavat liuokset ovat laimeita. Pervaporaatio on energiatehokas kalvoerotusmenetelmä ja sen vuoksi potentiaalinen osaprosessi biopolttoaineiden tuotantoon. Pervaporaation kaupallistamisen merkittävimpiä rajoitteita ovat olleet alhaiset ainevuot, jotka johtavat suureen kalvopinta-alan tarpeeseen ja näin ollen korkeisiin kustannuksiin. Korkean ainevuon saavuttamiseksi kalvojen tulisi olla mahdollisimman ohuita. Tässä väitöstyössä tutkittiin hyvin ohuiden zeoliittimembraanien suorituskykyä pervaporaatiossa. Kohteena olivat binääriset etanoli/vesi- ja n-butanoli/vesiseokset, joista väkevöitiin alkoholeja tai poistettiin vettä hydrofobisia ja hydrofiilisiä zeoliittimembraaneja käyttäen. Pervaporaatiossa käytettävien kalvojen ja pervaporaatiota hyödyntävien prosessien kehitystyö on ollut pääasiassa kokeellista. Prosessimallinnus on kuitenkin tärkeä työkalu prosessisuunnittelussa. Tässä työssä membraanien suorituskykyä pervaporaatiossa arvioitiin sekä kokeellisesti että mallinnuksen keinoin. Käytettyjen kalvojen ohuuden ansiosta tässä työssä saavutetut ainevuot olivat yleisesti ottaen korkeampia kuin aiemmin raportoiduilla membraaneilla. Ohuilla kalvoilla tukimateriaalin aiheuttama aineensiirron vastus oli kuitenkin merkittävä, alentaen membraanien suorituskykyä. Tässä työssä pervaporaatiota mallinnettiin käyttäen sekä puoliempiiristä että yksityiskohtaisempaa Maxwell-Stefan -pohjaista mallia. Jälkimmäisessä mallissa adsorptio ja diffuusio, eli ilmiöt joihin erotus pervaporaatiossa perustuu, otetaan eksplisiittisesti huomioon. Myös tukimateriaalin vaikutukset huomioitiin käytetyissä malleissa. Maxwell-Stefan -mallinnusta käytettiin puhtaiden komponenttien pervaporaatiossa zeoliittimembraanin diffuusiokertoimien määrittämiseksi. Käytettyjen mallien suorituskyky kokeellisella alueella oli hyvä. Tässä työssä kehitettiin lisäksi helppokäyttöinen menetelmä aineiden adsorptiokäyttäytymisen ennustamiseen zeoliiteissa eri lämpötiloissa. Kehitettyä menetelmää voidaan hyödyntää esimerkiksi pervaporaation mallinnuksessa. Kokonaisuudessaan väitöstyöstä saadaan tietoa ultraohuiden membraanien käytöstä pervaporaatiossa sekä työkaluja pervaporaation mallinnukseen.

Sediments exposed in the Tugen Hills in the Central Rift of Kenya include an important hominin-bearing succession of volcaniclastic and fluvio-lacustrine deposits. The Hominin Sites and Paleolakes Drilling Project (HSPDP) retrieved a ~230 m core through a portion of the Chemeron Formation, containing a highly resolved succession of strata spanning events leading to the Plio-Pleistocene boundary (3.4-2.6 Ma). Trends in the character and abundance of zeolites indicate changes in paleoenvironmental conditions with varying stability identified through distinct facies assemblages. These seem to reflect high amplitude changes accompanying peak earth-orbital eccentricity at ~2.7 Ma, and relative stability at low eccentricity at ~2.9-2.7 Ma. This study suggests a decrease in K/Ca and an increase in Na/Ca with major fluctuations. Zeolites act as terrestrial climate proxies in the absence of biogenic material, aside from intervals of diatom-rich strata, and are suggesting episodes of strongest environmental fluctuations ~2.7-2.6 Ma and environmental stability ~2.9-2.7 Ma.

L'objectif de cette thèse était d'étudier l'influence de la texture poreuse et de l'acidité des catalyseurs d'hydrocraquage, sur l'activité et la sélectivité en distillats moyens. Dans notre étude, nous avons envisagé deux approches : d'une part la préparation des catalyseurs à partir de la zéolithe Y à texture poreuse optimisée, et d'autre part à partir d'une silice mésoporeuse de type MCM-48. Dans la première approche, l'optimisation de la texture poreuse a été réalisée par un traitement post synthèse de dessilication d'une zéolithe Y commerciale (CBV760). Les propriétés physico-chimiques des matériaux résultants ont été évaluées par différentes techniques de caractérisation. L'évaluation de ces matériaux en hydrocraquage de molécules modèles montre une très nette amélioration de la sélectivité en coupe moyenne par rapport à un catalyseur de référence à texture poreuse non optimisée. Dans la seconde approche, nos efforts ont été dirigés vers l'optimisation de l'acidité des solides de type MCM-48. Pour cela une méthode de greffage post-synthèse d'alumine à la surface de ce solide a été envisagée, conduisant à l'obtention d'une acidité suffisante pour la réaction d'hydrocraquage. L'évaluation catalytique de ces matériaux montre qu'ils sont des catalyseurs performants en hydrocraquage et en hydroisomérisation / The objective of this thesis was to prepare hydrocracking catalysts for heavy feedstocks with improved selectivity into middle distillates. In this study we followed two strategies: on the one hand the preparation of catalysts based on a zeolite Y with enhanced porosity, and on the other hand using a mesostructured silica (MCM-48). In the first approach, the optimization of the porous texture was realized by desilication of zeolite Y ( CBV760) in alkaline medium. Physico-chemical properties of obtained materials were investigated by various characterization techniques. The evaluation of these materials in the hydrocracking of model molecules shows a clear improvement of the selectivity into middle distillate with regards catalysts. In the second approach, our efforts were oriented towards the optimization of the acidity of MCM-48 type materials. To achieve this goal, an alumina layer was grafted on the surface of this material, generating an adequate acidity for the hydrocracking reaction. The catalytic evaluation of these materials shows a high selectivity inti middle distillates.

L'objectif de ce travail était le développement des nanocomposites d’EVOH/zeolites à base de charges telles que les zéolites pour l’encapsulation des cellules solaires organiques, et l’étude de leur comportement photochimique. Ce travail a porté sur l’étude du mécanisme de photooxydation des copolymères d’EVOH puis sur l'impact des zéolites sur ce mécanisme. Les propriétés fonctionnelles des nanocomposites d’EVOH/zéolites ont été étudiées en prenant en compte le taux de charge et la taille des particules. Les propriétés des copolymères d’EVOH et des nanocomposites d’EVOH/zéolites comme la transparence optique, la morphologie de surface, les propriétés mécaniques et thermiques, et les propriétés d'absorption de l'eau ont été étudiées. Sur la base des résultats obtenus, les meilleurs candidats pour l'encapsulation des cellules solaires organiques ont été proposés. Le mécanisme de photooxydation des copolymères a été proposé, la photostabilité des matériaux et l'impact des zéolites sur le comportement photochimique du polymère ont été étudiés. Le test électrique de calcium et le suivi des performances des cellules solaires organiques encapsulées ont été effectués afin d'évaluer l’efficacité des matériaux étudiés comme candidats potentiels pour une encapsulation efficace et stable des cellules solaires. / The goal of this work was to develop EVOH/zeolite nanocomposites based on inorganic fillers such as zeolites for potential encapsulation of OSCs and to investigate their photochemical behaviour. The research was focused on the photooxidation mechanism of pristine EVOH copolymers and on the impact of the filler addition on this mechanism. EVOH/zeolite nanocomposites functional properties were characterised taking into account different particle sizes and filler contents. Properties of EVOH copolymers and EVOH/zeolites nanocomposites such as optical transparency, surface morphology, mechanical and thermal properties, and water uptake properties were investigated. On the basis of obtained results, the best candidate(s) for encapsulation of organic solar cells has been proposed. The chemical degradation mechanism of pristine polymers has been proposed, the materials photostability and the impact of the zeolite particles on the photochemical behaviour of the polymer have been studied. Electrical calcium test and performance of encapsulated OSCs were carried out in order to evaluate the ability of the studied materials to be used as potential candidates for efficient and stable encapsulation coatings for OSCs applications.

Magister Scientiae - MSc / The current study investigated application of natural adsorbents in brine treatment. Brines are hypersaline waters generated in power stations and mining industries rich in Mg2+, K+, Ca2+, Na+, SO4 2- , Cl- and traces of heavy metals, thus there is a need for these brines to be treated to recover potable water and remove problematic elements. Natural adsorbents have been successfully used in waste water treatment because of their high surface area and high adsorptive properties when they are conditioned with acid or base. The investigation of pH showed that natural adsorbents did not perform well at low pH of 4 and 6. The adsorbents were able to work efficiently at the natural pH of 8.52 of the brine solution. These results show that natural adsorbents hold great potential to remove cationic major components and selected heavy metal species from industrial brine waste water. Heterogeneity of natural adsorbents samples, even when they have the same origin, could be a problem when wastewater treatment systems utilizing natural clinoptilolite and bentonite are planned to be developed. Therefore, it is very important to characterize the reserves fully in order to make them attractive in developing treatment technologies. / South Africa

Zeolites were used in this study to remove two types of non-radioactive ions (Cobalt-59 and Strontium-89) from wastewater. This was designed to model the use of ion-exchange technique to remove radioactive Co-60 and Sr-90 from low level wastewater from Al-Tuwaitha site. Al-Tuwaitha site is a nuclear research in Iraq was used for radio-medical and radio-chemical purposes before 1990. In this study, hierarchical microporous/macroporous structures were developed to overcome the diffusivity problem using zeolite. Diatomite and carbon were used to prepare the composite adsorbents by incorporating them with three types of zeolites (A, Y and clinoptilolite). From the XRD, SEM and EDAX measurement it was confirmed that successfully prepared of Iraqi palm tree leafs-Clinoptlolite (IPClinp) and Tamarind stones-Clinoptilolite (TSClinp) composites were obtained in this study as there is no evidence in literature of this being carried out before. The carbons were prepared successfully through the Pyrolysis method for 2h at 900°C in an inert atmosphere from two types of raw waste plant materials of Iraqi Palm Tree leafs (IP) and Tamarind stones (TS). For both types of carbons, the SEM images show organised porosities in different shapes. A third material used as a zeolite scaffold was diatomite (Celatom FW-14) a readily available natural material (dead algae).A hydrothermal treatment was used to build the hierarchical structure of zeolite onto carbon and diatomite materials, the scaffolds were seeded with nano-zeolite crystals prior to the treatment and thereafter mixed with the zeolite gel composition mixture in a stainless steel autoclave. Zeolite seeds were prepared using ball mill method to reduce the particle size of the commercial zeolite to sub-micron range for each type of zeolite. The surface area, morphology, element compositions and structure for each type of zeolite and composite material were characterised using BET method, SEM, EDAX and XRD. The amounts of each type of zeolite on the carbon composites were determined using TGA while that of the diatomite composite was determined by gravimetric analysis. The results show that each type of zeolite was successfully deposited and uniformly organised onto the surface of all support materials. All pure zeolites and composite materials were successfully tested to remove Co2+ and Sr2+ ions from aqueous solutions. It was found that the composite materials had higher ability to remove both ions relative to the pure zeolites. This increase is attributed to the deposition of zeolite (microporous) onto the macroporous structure (carbon and diatomite) which increased the flow accessibility within zeolite in the hierarchical structured composites. Comparison of the removal between the two metal ions indicates that all of the materials had higher uptake for Sr2+ than Co2+ ions. The highest adsorption capacities were realised with Tamarind Stone–ZeoliteA (TSA) in the order 120mg.gz-1and 290mg.gz-1 for Co2+ and Sr2+ ions, respectively. The effect of the experimental variables shows increasing uptake with increasing pH and initial ion concentrations while it decreased with increasing the solution temperature. The Co2+ loaded composites was subjected to vitrification process at 12000C for 2h. The encapsulated composites were leached for 90 and 120 days and no significant Co2+ was recorded in the leached solution. The results show that the composite materials can be used effectively to remove the radioactive ion of Co-60 and Sr-90 ion as they display the same chemical behaviour as Co-59 and Sr-89 studied in this work.

No description available.