Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: We investigate a model system for particle diffusion in elastically coupled one-dimensional narrow channels. The elastic coupling of the channels is such that channels mutually affect the stochastic dynamics of particles. This kind of constrained and coupled stochastic diffusion may occur in supramolecular lattices where pore occupancy by guest particles may induce a reversible mechanical deformation of the lattice hence, affecting particle evolution in neighbouring pores. The model is explored first for out-of-equilibrium conditions, where we look mainly at the kinetic properties of the system, and thereafter under equilibrium conditions, where we try to understand the nature of dynamic correlation within the coupled channel system. For an out-of-equilibrium version of the model the focus is placed on the steady state behaviour of the two elastically coupled finite channels. The channels are kept in contact with particle reservoirs at the boundaries. Three current-density regimes of different distinct behaviour are identified using a simulation experiment. The sensitivity of the system mean occupancy profile and the steady state particle flux to small and large coupling parameter strength are explored. We find that, for small coupling strength, the system steady state profile and flux behaviour can be approximated by a simple mean field theory ignoring density-density correlations. We present the analytic description of the system using a cellular automaton formalism and then we generalize the theory for a multi-coupled channel system using a hopping particle dynamics approach. For small coupling parameter values, the analytic results are confirmed by the stochastic simulation. From the equilibrium perspective, we model the elastically coupled channel system as a system of infinite narrow channels having a uniform guest particle occupancy and we calculate density fluctuation correlation functions. The elastic coupling between channels is modelled as short range interacting potential and the particle evolution is modelled through Langevin dynamics. The dynamics are cast into the functional integral formalism expressed in terms of the collective particle number density, current density and the associated density response fields. The resulting generating functional takes these fields into consideration within the random phase approximation (RPA) up to second order. For a short range interaction potential, we uncover the behaviour of the system by looking at the influence of the inter-channel interaction strength on the dynamic density-density correlation functions. We conclude that the system long time limit effective friction coefficient is reduced with increase in the coupling parameter values while the strength of thermal forces for the effective system becomes renormalized. We also find out that the RPA breaks down under certain conditions, signalling a transition to a behaviour that is no longer characterised by a homogeneous density. The work presented here provides the beginnings for microscopic insights into the filling, filtering and storage processes for which certain types of microporous materials can be utilised. / AFRIKAANSE OPSOMMING: Ons ondersoek ’n modelstelsel vir die diffusie van deeltjies in elasties gekoppelde, eendimensionele nou kanale. Die elastiese koppeling is sodanig dat die stogastiese dinamika wedersyds be¨ınvloed word. Hierdie gekoppelde en aan dwangvoorwaardes onderhewig diffusie kan in supermolekulˆere roosters gebeur waar die besetting van holtes deur deeltjies ’n omkeerbare meganiese vervorming van die kristalrooster kan veroorsaak en sodoende die tydontwikkeling in ’n aangrensende porie be¨ınvloed. Die model word eers vir nie-ewewig toestande ondersoek, waar ons hoofsaaklik die kinetiese eienskappe van die stelsel beskou, en daarna word dit vir ewewig ondersoek, waar ons die aard van die dinamiese korrelasie binne die gekoppelde kanaalstelsel probeer verstaan. Vir die nie-ekwilibrium weergawe van die model word die fokus op die gedrag van twee gekoppelde en eindige kanale se bestendige toestand gerig. Die porie¨e bly aan hulle eindpunte in kontak met reservoirs van deeltjies. Daar word drie deeltjiestroom-digtheid gebiede ge¨ıdentifiseer met behulp van ’n simulasieeksperiment. Die sensitiewiteit van die stelsel se gemiddelde deeltjiebesettingsprofiel en die deeltjievloed in ’n bestendige toestand is ondersoek vir groot en klein koppelingsparameters. Vir klein koppelingsterkte vind ons dat die stelsel se bestendige toestand deeltjiebesettingspofiel en deeltjievloed deur ’n eenvoudige gemiddelde-veld teorie beskryf kan word, waar digtheid-degtheids korrelasies verontagsaam kan word. Ons bied die analitiese beskrywing aan vir die gekoppelde stelsel deur van ’n sellulˆere outomaat-formalisme gebruik te maak, en om dan die teorie te veralgemeen vir ’n stelsel bestaande uit vele aanmekaar gekoppelde porie¨e ,deur gebruik te maak van ’n formalisme waarin deeltjies tussen holtes hop. Die analtiese resultate word vir kleine waardes van die koppelingsparameter deur ’n rekenaarsimulasie bevestig. Vir die ekwilibrium gesigspunt modelleer ons die gekoppelde stelsel van kanale as oneindig nou, met ’n homogene verdeling van die deeeltjiebesetting en ons bereken digtheids-korrelasiefunksies. Die elastiese vebinding tussen porie¨e word deur ’n kortrykwydte potensiaal gemodelleer en die deeltjies se dinamika met behulp van Langevindinamika. Die dinamika word met behulp van die funksionaal integraalformalisme uitgedruk in terme van die deeltjiegetaldigtheid-, stroomdigtheid- en meegaande antwoordvelde. Die resulterende genererende funksionaal neem hierdie hoeveelhede tot tweede order binne die “random field approximation” (RPA). Vir ’n potensiaal met kort rykwydte, ondersoek ons die stelsel se gedrag deur die dinamiese digtheid-digtheidskorrelasie te ondersoek. Ons lei af dat die stelsel se langtyd effektiewe wrywingsko¨effisi¨ent afneem met die toename in die koppelingsparameter se waardes terwyl die sterkte van die termiese kragte vir die effektiewe stelsel renormeer word. Ons vind ook dat die RPA onder sekere omstandighede sy geldigheid verloor, wat ’n oorgang kan beteken wat nie meer deur ’n homogene digtheid beskryf kan word nie. Die werk wat hier aangebied word dui die eerste stappe aan vir hoe mikroskopiese insigte vir vul-, filter- en stoorprosesse vir sekere tipes mikroporeuse materiale gebruik kan word.

This dissertation discusses, in brief, the production and transport property characterization of films made from the extrusion and biaxial stretching of [beta] nucleated isotactic polypropylene and the extrusion of PEBAX block copolymers. Multilayered films for modified atmosphere packaging applications were also produced by coextrusion and biaxial stretching of these two materials and similarly characterized. Current membranes for packaging applications are generally produced by coating a porous support with a polymeric solution to deposit an active layer for separation. The goal of this project is to displace membranes produced by solvent-based processes, which are environmentally hazardous and thus costly, with equivalent or superior materials produced using melt extrusion. / text

Since 2016 there are world-wide more mobile phone contracts than people on the planet, and in all these devices critical raw materials (CRMs) are incorporated.[1] For instance, commonly used silicon-based transistors are limited in their chemical modularity. Inorganic materials for solar cells and photocatalysis suffer from critical raw elements content, low apparent quantum efficiencies and photodegradation. Hence, considerable research interest in recent years is focused on development of new high-performance devices for optical and electronic applications that avoid CRMs entirely. To address all these problems materials chemists are exploring for new pathways towards making more sustainable and reliable materials. In that respect, porous organic π- conjugated polymers (POPs) are among the most promising candidates and have gained tremendous attention in materials research over the last decade, especially in the fields of photocatalysis, opto- and electrochemical sensorics, and microelectronics. Synthetic diversity, chemical and physical stability, as well as comparatively low production costs and scalability enable POPs to overcome the drawbacks of inorganic materials. Moreover, the absence of rare earth elements in the purely organic structure of POPs makes these materials more environmentally...

Polymeric membranes typically possess a broad pore-size distribution that leads to much lower selectivity in molecular and ionic separation when compared to membranes made of crystalline porous materials; however, they are highly desirable because of their easy processability and low cost. Recently, a novel type of conjugated microporous polymers (CMPs) has shown uniform pore size and high porosity. However, their brittleness nature has prevented them from preparing robust membranes and using in pressure-driven membrane processes. In this dissertation, we demonstrate the fabrication of robust polycarbazole-type conjugated microporous polymer membranes using an easy to scale-up electropolymerization strategy. The mechanical properties of the CMP membranes were greatly enhanced based on membrane structure optimization and molecular design. The prepared membranes exhibited high uniform sub-nanometer pores and a precisely tunable membrane thickness and properties, yielding high molecular/ionic sieving performance. In addition, using the co-electropolymerization method, the CMP membranes achieve dual softness and functionalization adjustments. The membrane structure comprises rigid monomers to inherit the structural uniformity and flexible and charged monomers to enhance mechanical flexibility and improve ion selectivity by combining the precise size sieving and the Donnan effect. The dual-adjustments result in the further enhancement of the CMP membranes in ionic sieving performance. Inspired by light-gated ion channels in living cells, we further develop a smart artificial light-gated ion channel membrane. The prepared CMP membranes, based on a conjugated microporous polymer (CMP) functionalized with azobenzene and precisely designed on the molecular level, show uniform pore channels and highly sensitive light-switchable response. The photoisomerization results in reversible geometric changes in pore channel size, leading to “on-off-on” light-control over the channels, which results in light-gated ion transport across the smart membrane. The softness adjustment, functionalization adjustment to CMP membranes, and the design of smart CMP membranes provide potential applications for this important category of polymer materials in the membrane field.

In recent years a significant portion of proton exchange membrane fuel cell (PEMFC) work has been focused on understanding and optimizing the functions of the microporous layer (MPL). Researchers have found that including this layer, composed of carbon black and TeflonTM (PTFE), between the gas diffusion layer (GDL) and catalyst layer (CL) of PEMFCs improves performance. The major benefit of the MPL in conventional fuel cells is that it improves water management and reduces contact resistances between cell layers. Although the functions of the MPL in conventional PEMFCs are well understood, the essential functions and optimal formulation of the layer in planar PEMFCs which operate without stack compression, are for the most part unknown. This work determines the essential functions and optimal composition, loading and sintering pressure of the MPL in a planar fuel cell design called a Ribbon Fuel Cell. Adhesion as well as performance data were gathered to determine the essential functions and formulation of the MPL which leads to high performance and durability in Ribbon Fuel Cells. Statistical models were created based on performance data of cells constructed with various MPLs; and a MPL composed of 45 wt% PTFE, loaded at 3.5 mg/cm° and sintered between 20 and 40 psi was found to exhibit optimal performance and durability. The reason why such a high PTFE content yields optimal results is because it strengthens the MPL, allowing it to successfully join various cell layers together, a function that is essential in Ribbon Cells which operate without external stack compression. / Master of Science

Here I report the hydrothermal chemistry of scandium, examining the behavior of the Sc³⁺ cation in various systems, including phosphates, phosphites, phosphonates and carboxylates. In total, 27 different materials, 23 of which are novel, have been synthesised and their structures solved. Seven different scandium phosphate-based materials have been successfully synthesised using amines and alkali hydroxides as structure directing agents, producing chain, layer and framework materials. Thermal analysis of these materials indicated that they were not stable upon removal of the template, because there are hydrogen bonding networks between the template and free OH groups on the phosphate groups. Certain conditions lead to the crystallization of either kolbeckite, Sc(PO₄).2H₂O, or a langbeinite-type structure, (NH₄)₂Sc₂(HPO₄)(PO₄)₂, which are dense frameworks. Investigation of scandium phosphites leads to the formation of more thermally stable frameworks. Investigation of scandium phosphite-based materials using different structure directing agents yielded three framework phosphite materials and one layered phosphite / phosphate. The use of lithium hydroxide and ethylenediamine within scandium phosphite systems resulted in the crystallization of a gainesite type framework, (LiSc(HPO₃)₂)and (H₃N(CH₂)₂NH₃)₂Sc₄(HPO₃)₈, which distorts in order to accommodate the amine, but not the lithium cation. Decreasing the potential for the formation of hydrogen bonding networks in the phosphite systems led to the formation of framework structures, however these structures did not retain their crystalline integrity upon removal of the template. In order to impart structure directing properties upon scandium-based materials but avoid the formation of hydrogen bonding networks upon which the crystalline integrity is dependent, scandium phosphonates were investigated. Seven different scandium phosphonate materials have been synthesised, two of which have been solved from powder diffraction data, and one from a combination of powder diffraction data, molecular modeling and single crystal data. Synthesis of scandium phosphonate materials yielded two thermally stable, porous materials with reversible water adsorption properties, NaSc(CH₃PO₃)₂•H₂O and Sc₂(O₃PCH₂(NHC₅H₁₀NH)₋CH₂PO₃)₃4H₂O. The success of this approach led to the examination of scandium carboxylate metal organic framework materials. The incorporation of Sc³⁺ into microporous carboxylate frameworks yielded three aliphatic scandium carboxylates and six aromatic scandium carboxylates. The scandium analogue of MIL-53 shows potential for gas adsorption studies, as well as illustrating that scandium carboxylates can be isostructural to metal carboxylate materials already published. The scandium terephthalate, Sc₂(O₂CC₆H₄CO₂)₃, is a small pore framework material with an unprecedented structure type, the adsorption properties of which have been examined using a variety of different small gas molecules and hydrocarbons, including X-ray analysis of the structures whilst adsorbing different molecules. ⁴⁵Sc MAS NMR has been performed on the materials prepared pure and characterized in this thesis, in order to establish a library of chemical shifts for scandium in different framework environments.

Conventionally, crystalline microporous materials such as zeolites and metal-organic frameworks (MOFs) are synthesized through the hydrothermal route or the trial-and-error approach. Other synthetic strategies may lead to the synthesis of microporous materials with new architectures or interesting properties. The general aim of this thesis is to investigate some new synthetic routes towards crystalline microporous materials. A top-down and post-synthesis method is reported in Chapter 4. Some zeolites are built up by layers and double-4-ring pillars. Germanium is preferentially located in the double-4-ring sites of a zeolite framework and is hydrolytically unstable. The idea of the top-down method is to disassemble these zeolites to the layer structures by dissolving the Ge-containing pillars and reassemble them to a new framework. This method is applied to the germanosilicate IWW and ITH zeolites for the first time. The effects of framework chemical compositions, Ge distributions and disassembling conditions on the top-down treatment process are investigated. The products obtained from the top-down treatment are characterised. An ionic liquid assisted strategy for the synthesis of zeolites is described in Chapter 5. The ionic liquid assisted strategy is a solvent free reaction. The raw materials are transformed to zeolites through a solid state reaction. The ionic liquids are first used as structure-directing agents (SDAs) in this solvent free reaction to replace the expensive quaternary ammonium hydroxide. A TON zeolite is synthesized using 1-ethyl-3-methylimidazolium bromide as the SDA. Moreover, the ionic liquid assisted strategy is considered as a “green chemistry” synthetic route due to the high yield of the zeolites and the minor production of waste water. Many aluminophosphates have been successfully synthesized through ionothermal routes. Most of them are synthesized using 1-alkyl-3-methylimidazolium based ionic liquids. A new ionic liquid, 1-(2-hydroxyl-ethyl)-3-methylimidazolium chloride ([HOEmim]Cl), is prepared and used for the ionothermal synthesis of aluminophosphate materials. A zeolite analogue with the CHA framework has been synthesized. At high synthetic temperatures, the products are large single crystals. The structures of the framework and the SDA are investigated by single crystal diffraction and other characterisation methods. Flexible MOF materials are usually synthesized by a trial-and-error approach. Recently a flexible MOF compound was synthesized using 5-sulfoisophthalic acid (SIP) as the ligand. It was proposed the sulfonate is weakly coordinated to the metal, which brings flexibility to the compound, and the carboxylate groups keep the framework intact. 2-sulfoterephthalic acid (STP) which also contains one sulfonate group and two carboxylate groups is believed to be an alternative ligand for the targeted synthesis of flexible MOFs. In Chapter 7, a MOF compound is synthesized using STP and 4, 4'-bipyridine (Bpy) as ligands to validate the proposed strategy can be generalized. Variable temperature single crystal diffraction analysis solves the structure and reveals a reversible structure transformation upon dehydration and rehydration.

L'exploitation des ressources non conventionnelles de roches mères telles que les schistes gazeux contribue de plus en plus au mix énergétique mondial en raison de la raréfaction des ressources conventionnelles. L'exploitabilité de ces réservoirs repose principalement sur la qualité, la teneur et le type de matière organique qu'ils contiennent. En effet, il est admis que plus de la moitié des hydrocarbures présents dans les schistes sont adsorbés dans la matière organique solide, appelée kérogène, dont la structure est microporeuse et amorphe, et qui représente à la fois la source et le réservoir d'hydrocarbures. Le kérogène se trouve sous forme dispersée dans la matière minérale et représente environ 5% de la masse totale de la roche. La compréhension des propriétés de transport des fluides à l'échelle des micropores, en particulier leur dépendance aux conditions thermodynamiques et aux propriétés structurelles du matériau, revêt une importance cruciale pour l'optimisation de la récupération de ces ressources. De ce point de vue, l'objectif principal de cette thèse vise à bien documenter les propriétés de transport des hydrocarbures à travers les kérogènes et améliorer leur description théorique. Pour ce faire, nous avons fait le choix d'étudier les propriétés de transport des fluides à travers ces matériaux en utilisant une approche numérique basée sur des simulations moléculaires de type dynamique moléculaire et Monte Carlo, conduites sur des modèles moléculaires de kérogène mature et sur un système modèle simplifié. Ceci nous a permis d’explorer les mécanismes de transport à une échelle où l'observation expérimentale est difficile, voire impossible, et également de nous situer dans des conditions thermodynamiques supercritiques (haute pression, haute température) caractéristiques des réservoirs de gaz de schiste. La première partie de ce travail a consisté à étudier les propriétés de transport et d'adsorption des fluides purs dans des structures de kérogène mature reconstruites par simulations moléculaires. Ensuite, la dépendance des propriétés de transport aux variations des conditions thermodynamiques (température à gradient de pression fixe) ainsi qu'à la distribution de tailles de pores a été étudiée. Concernant le deuxième objectif, afin de mieux comprendre et modéliser la diffusion des fluides à l'échelle d'une constriction microporeuse entre deux pores, nous avons étudié un système modèle constitué d'une seule fente microporeuse formée dans un solide mono-couche. L'étude a consisté à simuler la diffusion de transport d'un fluide à travers la constriction en variant les paramètres géométriques (rapport d’aspect entre la largeur du pore et la taille des molécules diffusantes) et thermodynamiques (température, chargement en fluide). Ces résultats de simulations ont été comparés aux prédictions d'un modèle théorique, fondé sur la théorie cinétique des gaz et la mécanique statistique classique, qui prend en compte l'effet de la température sur la porosité accessible ainsi que l'effet du chargement en fluide à l'entrée du seuil de pore. Un bon accord a été observé entre les valeurs simulées des coefficients de diffusion et les prédictions du modèle proposé. Ce système a ainsi contribué à la compréhension des phénomènes de tamisage moléculaire survenant lors du franchissement d'une constriction microporeuse, inhérents au transport de fluides dans les matériaux microporeux tels que le kérogène. / The share of unconventional resources in the global energy mix is expected to rise because of the shortage of conventional fossil resources. The major part of these unconventional resources are found in source rocks such as gas shales. The profitability of shale reservoirs strongly depends on the quality, type and content of organic matter contained in the rock. Indeed, it is admitted that more than half of the hydrocarbons stored in the shale are adsorbed in the solid organic matter, the so-called kerogen. The latter exhibits a microporous amorphous structure, and acts as both the source and the reservoir of hydrocarbons. Kerogen is finely dispersed in the mineral matrix and represents about 5% of the total mass of the rock. The understanding of the transport of fluids at the microporous scale is of crucial importance for optimizing the recovery of these resources. More specifically, how the structural properties of the microporous material and thermodynamic conditions influence its transport properties is an open question. In this regard, the main objective of this thesis is to document the transport properties of hydrocarbons through kerogens and to improve their theoretical description. To do so, we opted for a numerical approach based on molecular simulations of molecular dynamics and Monte Carlo codes performed on molecular models of mature kerogen, as well as simplified model systems. We thus explored transport mechanisms at the molecular scale, at which experimental observations are difficult, if not impossible. Supercritical thermodynamic conditions (high pressure, high temperature) were considered, which are characteristic of shale gas reservoirs. The first part of this work has consisted in studying the transport and adsorption properties of pure fluids in mature kerogen structures reconstructed by molecular simulations. We studied the dependence of the transport properties on the variations of the thermodynamic conditions (pressure gradient at a fixed temperature) as well as the influence of the pore size distribution. In order to better understand and describe the diffusion of fluids at the scale of a microporous constriction between two pores, the second objective of this thesis focused on a model system, which consisted of a single-layer solid with a slit aperture of controllable width. We simulated the diffusional transport of simple fluids through the constriction for various geometrical parameters (aspect ratio between the width of the pore and the size of the diffusing molecules) and thermodynamic conditions (temperature, fluid loading). These simulations results have been compared to the predictions of a theoretical model, based on the kinetic theory and classical statistical mechanics, which accounts for the effect of temperature on the accessible porosity and the effect of fluid loading at the entrance of the pore. A good agreement was observed between the simulated values of the diffusion coefficients and the predictions of the proposed model. The investigation of this simplified system helped in understanding the molecular sieving phenomena inherent to the transport of fluids in microporous materials such as kerogen.

Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-04-04T13:23:13Z No. of bitstreams: 1 AleffCruzdeCastro.pdf: 1452660 bytes, checksum: 8c8c4baa89c5a3373105fcb0cd29e65c (MD5) / Made available in DSpace on 2017-04-04T13:23:13Z (GMT). No. of bitstreams: 1 AleffCruzdeCastro.pdf: 1452660 bytes, checksum: 8c8c4baa89c5a3373105fcb0cd29e65c (MD5) Previous issue date: 2017-03-06 / CNPq, FAPEMA, CAPES, FSADU / Zeolites are microporous inorganic materials with a variety of applications in several areas of science and engineering. Their physical and chemical properties are attributed to the large internal surface area, and the chemical and hydrothermal stability, which are induced by the existence of well defined channels and/or cavities. These structural characteristics promote the use of zeolites as catalysts, molecular sieves, ion exchangers and, more recently, as electrochemical sensors. Taking in consideration these premises, this work describes the development of an electrochemical sensor obtained from the modification of the polyurethane graphite composite electrode with NiAlPO-5, a nickel-modified AFI aluminophosphate, and its application for determination of Cu2+ in ethanol biofuel. The synthesis of the aluminophosphates were conducted by the hydrothermal method and the obtained materials were characterized by X-ray diffraction, scanning electron microscopy, 31P nuclear magnetic resonance and UV-Vis and infrared spectroscopy. After synthesis and characterization, materials were used as modifiers (10%) in GPU electrodes in order to compare the performance of the unmodified and modified electrodes by Square Wave Anodic Stripping Voltammetry. The results showed that the incorporation of Ni to the material structure promotes an improvement in the electrical properties and analytical properties of the electrode. The analytical response of the sensor in the copper ion determination showed that the NiAlPO-5 electrode is more sensitive in terms of peak current than the electrolyte based on AlPO-5 only. The best response was obtained with the Ni/Al ratio of 0.5 on the NiAlPO-5 sensor. The experimental conditions of potential and deposition time, pulse amplitude, step potential, frequency and pH were optimized in an electrochemical cell containing 2 mL of ethanol, 8 mL of HCl 0.1 mol L-1 and Cu2+ concentration of 2.5×10-7 mol L-1. GPU/NiAlPO-5 modified sensor was then evaluated for electroanalytical determination of Cu2+ in ethanol biofuel samples presenting a linear response for Cu2+. Good results were obtained for the limit of detection (9.44×10-9 mol L-1), accuracy (recovery of 115%) and precision (RSD of 5.92%). / As zeólitas são materiais inorgânicos microporosos que apresentam uma grande variedade de aplicações em diversas áreas das ciências e engenharias. Suas propriedades físicas e químicas são atribuídas à grande área superficial interna e à estabilidade química e hidrotérmica, as quais são induzidas pela existência de canais e/ou cavidades bem definidos, tornando possível a sua utilização como catalisadores, peneiras moleculares, trocadores iônicos e, mais recentemente, como sensores eletroquímicos. Com base nisto, este trabalho apresenta o desenvolvimento de um sensor eletroquímico obtido a partir da modificação do eletrodo compósito de grafite poliuretana com NiAlPO-5, um aluminofosfato de estrutura AFI modificado com níquel, e sua aplicação na determinação de Cu2+ em amostras de etanol combustível. Os aluminofosfatos foram sintetizados através do método hidrotérmico e caracterizados por difração de raios-X, microscopia eletrônica de varredura, ressonância magnética nuclear de 31P e espectroscopia de UV-Vis e de infravermelho. Os materiais obtidos foram, então, utilizados como modificadores na proporção de 10% em eletrodos GPU, a fim de realizar-se uma comparação entre os eletrodos sem modificação e modificados com AlPO-5 e NiAlPO-5 mediante a utilização da técnica de voltametria de redissolução anódica com varredura de onda quadrada e o método de adição padrão. Os resultados mostraram que a incorporação do Ni à estrutura do material promove uma melhora nas propriedades elétricas e analíticas do eletrodo. A resposta analítica do sensor na determinação do íon Cu2+, mostrou que o eletrodo NiAlPO-5 é mais sensível, em termos de corrente de pico, que o eletrodo baseado apenas em AlPO-5. A melhor resposta foi obtida com a razão Ni/Al de 0,5 no sensor NiAlPO-5. As condições experimentais, potencial e tempo de deposição, amplitude de pulso, potencial de escada, frequência e pH foram otimizadas em uma célula eletroquímica contendo 2 mL de etanol, 8 mL de HCl 0,1 mol L-1 e uma concentração de Cu2+ de 2,5×10-7 mol L-1. O sensor modificado com NiAlPO-5 foi então avaliado para determinação eletroanalítica de Cu2+ em amostras de etanol combustível apresentando resposta linear para Cu2+. Bons resultados foram obtidos para o limite de detecção (9,44×10-9 mol L-1), limite de quantificação (3,15 x10-8 mol L-1), recuperação (115%) e precisão (5,92%).

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-01-03T12:20:02Z No. of bitstreams: 1 2015 - Tain? Dias Valente.pdf: 2209049 bytes, checksum: 5c25bcd5878b607ea484c8dbccb59903 (MD5) / Made available in DSpace on 2017-01-03T12:20:02Z (GMT). No. of bitstreams: 1 2015 - Tain? Dias Valente.pdf: 2209049 bytes, checksum: 5c25bcd5878b607ea484c8dbccb59903 (MD5) Previous issue date: 2015-12-17 / In the present dissertation it was conducted the study of the synthesis of mesoporous molecular sieve Al-SBA-15 by direct synthesis in agitated reactor having the following molar ratio: 14 SiO2: 1 Al2O3: 0.235 P123: 1800 H2O. Initially, a study was done to optimize the synthesis of Al-SBA-15. Through this study, it was found that the operating conditions that resulted in the SBA-15 sample with a higher degree of ordering were gel aging time equal to 15 hours at 40 ? C and then at 100 ? C for 8 hours. These optimal conditions were used to perform scaling up to 5 gallon reactor. Samples of Al-SBA-15 were subjected to carbonization in order to fill the pores of SBA-15 with carbonaceous material and prevent the collapse of its structure. The carbonized samples were used as a source of silica for the synthesis of mordenite in dry medium using the transmission technique in the vapor phase (VPT). The purpose of this procedure was to obtain the mordenite having mesopores. For the preparation of the mordenite by VPT, several conditions were used, varying the synthesis time and form of addition of the reactants, presence or absence of an organic driver. The samples were characterized by X-ray and nitrogen adsorption. It was observed that in most of the experiments, there was no formation of mordenite phase. In the experiments in this phase was obtained, there was no significant mesoporosity training. Apparently, the presence of carbonaceous material was not sufficient to preserve the mesoporous structure of SBA-15. Key / No presente trabalho foi realizado o estudo da s?ntese da peneira molecular mesoporosa Al-SBA-15 a partir da s?ntese direta em reator agitado apresentando a seguinte propor??o molar: 14 SiO2: 1 Al2O3: 0,235 P123: 1800 H2O. Inicialmente, foi feito um estudo visando otimizar a s?ntese da Al-SBA-15. Atrav?s deste estudo, foi verificado que as condi??es operacionais que resultaram na amostra de SBA-15 com maior grau de ordenamento foram com tempo de envelhecimento do gel de s?ntese igual a 15 horas a 40?C e depois a 100?C por 8 horas. Estas condi??es otimizadas foram utilizadas para efetuar o aumento de escala para o reator de 5 gal?es. As amostras de Al-SBA-15 foram submetidas a carboniza??o com o objetivo de preencher os poros da SBA-15 com material carbon?ceo e evitar o colapso de sua estrutura. As amostras carbonizadas foram utilizadas como fonte de s?lica para a s?ntese da mordenita em meio seco utilizando a t?cnica de transporte em fase vapor (VPT). O objetivo deste procedimento foi a obten??o de mordenita tendo mesoporos. Para o preparo da mordenita por VPT, v?rias condi??es foram utilizadas, variando o tempo de s?ntese e forma de adi??o dos reagentes, presen?a ou aus?ncia de um direcionador org?nico. As amostras obtidas foram caracterizadas por difra??o de raios X e adsor??o de nitrog?nio. Foi observado que na maioria dos experimentos n?o houve a forma??o da fase mordenita. Nos experimentos em que esta fase foi obtida, n?o foi observada forma??o de mesoporosidade significativa. Aparentemente, a presen?a de material carbon?ceo n?o foi suficiente para preservar a estrutura mesoporosa da SBA-15. Palavras chave: