For many years the problem of separating aliphatic and aromatic compounds has been at the forefront of the petroleum and oil refining industries. This separation is often effected using liquid-liquid extraction or extractive distillation. Both of these processes require the addition of a solvent to bring about separation. The aims of this work were to investigate the use of "mixed" solvents, such as those used in the Arosolvan process, for their application in liquid-liquid extraction and extractive distillation as well as to provide related thelmodynamic data for systems containing mixed solvents. In the last part of this work, a computer program was developed to theoretically predict the effectiveness of a number of solvents on a user-defined separation. The solvents used for liquid-liquid extraction were chosen based on their similarities to those in the Arosolvan process and were of the form, {N-methyl-2-pyrollidone (NMP) + glycerol, a glycol or water} where the glycol was either monoethylene glycol (MEG), diethylene glycol (DEG) or triethylene glycol (TEG). The additives were combined in various mixing ratios to NMP to determine a mixing ratio for which the effect of the solvent is possibly optimized (a list of all solvents and mixing ratios used are presented in this work). Solvent selectivity and the range of compositions over which separation could occur determined the effectiveness of the solvents. This work dealt with the separation of n-hexane and toluene. In order to determine the selectivity and range of compositions, the liquid-liquid equilibria (LLE) of systems containing n-hexane + toluene + solvent had to be determined. LLE was measured using a simple equilibrium cell at 298 K and 1 atm. The phase separation boundaries (binodal curves) were determined using a titration method. The results obtained in this work showed an increase in the range of compositions over which the mixture of n-hexane and toluene could be separated (i.e a larger range of mixing ratios over which these components could be separated from each other) from the pure NMP solvent to the mixed solvent cases. This implies that there is a The range of compositions over which separation could be affected is given (for the solvents) in descending order: NMP + 50% glycerol> NMP + 10% water > NMP + 30% MEG > NMP + 5% water > NMP + 30% glycerol> NMP + 10% glycerol > NMP + 10% MEG > NMP + 10% DEG > NMP + 10% TEG > NMP + 5% DEG > 100% NMP. The selectivities of the solvents showed a remarkable increase from the pure NMP case to the mixed solvent cases. The maximum selectivity obtained for the NMP + 10% DEG system was over 1200 compared to a maximum selectivity of just 6 for the pure NMP system. The maximum selectivities obtained in descending order were as follows: NMP + 10% DEG > NMP + 10% TEG > NMP + 10% glycerol > NMP + 10% MEG > NMP + 30% MEG > NMP + 50% glycerol > NMP + 10% water > NMP + 5% water > NMP + 30% glycerol > NMP + 5% DEG > 100% NMP. The binodal curves were modelled using the Hlavaty, ,8-density and log-y functions. The maximum standard deviations obtained were 0.075, 0.078 and 0.05 for each of the functions respectively. The equilibrium data was modelled using the UNIQUAC and NRTL thermodynamic models and showed excellent agreement. This work showed better agreement to the NRTL functions due to the fact that the non-randomness parameter, a ij , may be chosen arbitrarily. The results obtained in this work indicate that the use of mixed solvents greatly increases the effectiveness ofNMP used for the separation of n-hexane and toluene. It is suggested that further studies be performed on a wider range of aliphatic and aromatic compounds in order to determine whether this is a generic behaviour or just true for n-hexane and toluene. The effectiveness of each solvent for extractive distillation was determined by its separation factor. In order to determine separation factors, the activity coefficients at infinite dilution (IDACs) had to be measured. This was done using a gas-liquid chromatography technique. The solvents employed in this study were NMP, Glycerol, MEG, TEG, NMP + 10% glycerol, NMP + 10% MEG, NMP + 10% DEG, NMP + 10% TEG. The solutes used were: pentane, heptane, hexane, toluene and benzene. The separation factors were determined for each alkane/aromatic pair per solvent. The pure solvent cases were then compared to the mixed solvent cases. The mixed solvents did not show results as promising for extractive distillation applications as they did for liquid-liquid extraction. TEG displayed the best selectivities for each of the alkane/aromatic separations except for the heptane/benzene pair, for which NMP + 10% glycerol proved to be the most effective solvent. When compared to the results obtained from the original UNIF AC model, the IDACs obtained in this work showed up to a 99% deviation. This is due to the fact that the model does not work well for all types of molecules and does not predict the equilibrium of "unlike" molecules adequately. It is suggested that other mixing ratios and different solvents be used to further investigate the effectiveness of mixed solvents for extractive distillation applications. It is further recommended that a computer aided data logging system be developed to determine residence times. This would not only provide more accurate results, but also provide a database for future reference. The computer program that was developed using the original UNIF AC method contains a database of 28 commonly used industrial solvents. This program enables the user to compare graphically the effectiveness of each of the solvents on the desired separation. Due to the limitations of the original UNIF AC method, the program does not work well for all types of molecules. However, the model can be changed without altering the prografnming structure to include a modified version of the UNIFAC model depending on the users needs. The program although written from an extractive distillation standpoint can be extended to include liquid-liquid equilibrium predictions. The main benefit of such a program is to eliminate time-consuming experimental work required to narrow down a long list of solvents required for a particular separation by theoretically predicting the best solvents for the job. The solvent database can also be expanded when new solvents become available or the user needs change / Thesis (M.Sc. Eng)-University of Natal, Durban, 2003.

Les Liquides Ioniques [LI] à température ambiante forment une nouvelle classe de matériaux, prometteurs dans des applications diverses. Les avantages que les LI soulèvent par rapport aux autres liquides moléculaires ou sels fondus résident dans la facilité à changer leurs propriétés intrinsèques en jouant sur la nature chimique de la combinaison [cation-anion]. Cependant, on n’est pas encore près à prédire les propriétés d’un LI en connaissant uniquement sa composition chimique. Par conséquent, nous avons fait des expériences de diffraction de rayons-x et de neutrons, complétées par une série de simulations de dynamiques moléculaires sur une famille de LI à bases de cations d’alkyl-methylimidazolium et d’anion Bromure. Ainsi, en changeant la longueur de la chaine alkyl, nous avons comparé la structure et la dynamique de trois LI de chaines ethyl, butyl et hexyl. La comparaison des résultats structuraux obtenus par la simulation avec ceux des rayons-x donnèrent complète satisfaction. Des résultats intéressants ont été obtenus, spécialement ceux issus de la comparaison de la structure et la dynamique du LI 1-ethyl-3-methylimidazolium Bromide en phase cristalline et liquide. Par ailleurs, l’hétérogénéité en phase volumique a pu être quantifiée ce qui a permis de déterminer que la ségrégation augmente avec la longueur de la chaine alkyl cationique. / Room temperature ionic liquids constitute a class of materials with many promising applications in very diverse fields. Their potentiality stems from the fact that their properties are very different from those of typical molecular solvents and furthermore they can be tailored by modifying the combination of ions forming the liquid. However it is not yet possible to predict which species will produce a particular set of properties. Therefore we have done a systematic computer simulation study on a series of three room temperature ionic liquids based on the alkyl-methylimidazolium cation combined with the bromium anion. The length of the alkyl chain of the cation and the anions has been increased progressively, going from ethyl to butyl and hexyl, in order to explore the structural and dynamical changes brought about by such change. Simulation results are also compared satisfactorily to high-energy x-ray diffraction and quasi elastic neutron scattering data obtained by us. Our results show that the structure of liquid 1-ethyl-3methylimidazolium Bromide presents large similarities with the crystal one. This resemblance appears also when the local dynamics of the ethyl chain is investigated using neutron spectroscopy. Moreover we have quantified the heterogeneity found in the bulk state, finding that segregation is favored by the length of the cation’s alkyl chain.

Amperometric gas sensors are widely used for environmental and industrial monitoring. They are sensitive and cheap but suffer from some significant limitations. The aim of the work undertaken in this thesis is the development of ‘intelligent’ gas sensors to overcome some of these limitations. Overall the thesis shows the value of ionic liquids as potential solvents for gas sensors, overcoming issues of solvent volatility and providing a wide potential range for electrochemical measurements. Methods have been developed for sensitive amperometry, the tuning of potentials and especially proof-of-concept (patents Publication numbers: WO2013140140 A3 and WO2014020347 A1) in respect of the intelligent self-monitoring of temperature and humidity by RTIL based sensors. Designs for practical electrodes are also proposed. The specific content is as follows. Chapter 1 outlines the fundamental principles of electrochemistry which are of importance for the reading of this thesis. Chapter 2 reviews the history and modern amperometric gas sensors. Limitations of present electrochemical approaches are critically established. Micro-electrodes and Room Temperature Ionic Liquids (RTILs) are also introduced in this chapter. Chapter 4 is focused on the study of analysing chronoamperometry using the Shoup and Szabo equation to simultaneously determine the values of concentration and diffusion coefficient of dissolved analytes in both non-aqueous and RTIL media. A method to optimise the chronoamperometric conditions is demonstrated. This provides an essential experimental basis for IL based gas sensor. Chapter 5 demonstrates how the oxidation potential of ferrocene can be tuned by changing the anionic component of room temperature ionic liquids. This ability to tune redox potentials has genetic value in gas sensing. Chapters 6 and 7 describe two novel patented approaches to monitor the local environment for amperometric gas detection. In Chapter 6, an in-situ voltammetric ‘thermometer’ is incorporated into an amperometric oxygen sensing system. The local temperature is measured by the formal potential difference of two redox couples. A simultaneous temperature and humidity sensor is reported in Chapter 7. This sensor shows advantageous features where the temperature sensor is humidity independent and vice versa. The Shoup and Szabo analysis (Chapter 4) requires ‘simple’ electron transfer and as such the reduction of oxygen in wet RTILs can be complicated by dissolved water. Chapter 8 proposes a method to stop oxygen reduction at the one electron transfer stage under humid conditions by using phosphonium based RTILs to ‘trap’ the intermediate superoxide ions. Chapters 9 and 10 report the fabrication of low cost disposable electrodes of various geometries and of different materials. The suitability of these electrode for use as working electrodes for electrochemical experiments in aqueous, non-aqueous and RTIL media is demonstrated. Their capability to be used as working probes for amperometric gas sensing systems is discussed.

L'une des préoccupations de la chimie moderne est de développer des procédés éco-compatibles : une tendance consiste à remplacer les solvants organiques par les Liquides Ioniques (LI). Ainsi ces travaux décrivent l'utilisation des LI dans deux réactions à économie d'atomes : l'addition de Michael et la réaction de cycloaddition 1,3-dipolaire catalysée (ou non) par un sel de cuivre (CuAAC). La première partie des travaux relate l'emploi de Liquides Ioniques Super-Acides (LISA), connus pour générer une activation électrophile. Une optimisation du LISA a été effectuée sur une réaction-modèle, puis l'application à d'autres électrophiles et nucléophiles a été étudiée. La pureté du LISA influe sur la chimiosélectivité : s’il est partiellement hydrolysé, la réaction d'annélation de Robinson devient prépondérante. La version asymétrique du processus a été abordée, montrant qu'il est possible d'obtenir un excès énantiomérique à partir de dérivés d'acides aminés. La seconde partie de l'étude a permis de mettre au point une synthèse de (triazolylméthyl)vinylphosphonates à partir d'un acétoxyméthylvinylphosphonate selon une procédure monotope reposant sur la cycloaddition 1,3-dipolaire dans différents LI. Nous avons ensuite montré que le LI joue aussi le rôle d'activateur pour cette réaction. / In the context of sustainable chemistry, an alternative to conventional organic solvents is the use of ionic liquids. These works reported here aims to describe the use of ionic liquids (IL) in two atoms economy reactions, namely the Michael addition reaction and 1,3-dipolar cycloaddition catalyzed (or not) by a copper salt (CuAAC). In the first part of the work reports the use of Super-Acid Ionic Liquids (SAIL), which initiate an electrophilic activation. After optimization of SAIL on a reaction model, application to other electrophiles and nucleophiles is discussed. The purity of SAIL affects the chemioselectivity: if the SAIL is partially hydrolyzed, a Robinson annulation predominates. The asymmetric version of the process is investigated, showing that it is possible to carry out an enantioselective reaction with amino acid derived SAIL. The second part of the study deals with setting up an original synthesis of (triazolylmethyl)vinylphosphonate from acetoxymethylvinylphosphonate using a one-pot procedure involving a 1,3-dipolar cycloaddition in different LI. We further showed that the ionic liquid can also act as an activator for this reaction.

O OME é empregado no tratamento de curto e longo prazo em diferentes desordens gastrointestinais. É um inibidor da bomba de prótons, que atua seletivamente na enzima H+/K+ ATPase. É completamente metabolizado pelas enzimas do citocromo P450 gerando três metabólitos principais: HOME, OMES e OS. É utilizado no tratamento de refluxo gastroesofágico em pacientes que sofrem de obesidade e sobrepeso no período anterior e posterior à cirurgia bariátrica. Entretanto, a realização deste procedimento cirúrgico pode prejudicar a absorção de nutrientes e medicamentos. Assim, a determinação das concentrações plasmáticas do OME é de grande importância clínica para o ajuste de dose evitando-se o comprometimento do tratamento. Portanto, foram desenvolvidos e validados dois métodos para quantificação do OME e metabólitos em amostras de plasma: LLE, método padrão e OS-DLLME e avaliada a IL-DLLME como método alternativo de extração. O método padrão, LLE, foi desenvolvido para quantificação do OME e metabólitos em amostras de plasma por HPLC-UV. A análise foi feita em uma coluna cromatográfica Zorbax Eclipse XDB - C18 (25 cm x 4,6 mm, partículas de 5 ?m) (Agilent Technologies, Palo Alto, CA, EUA) e coluna de guarda Zorbax Eclipse XDB - C18 (12,5 mm x 4,6 mm, partículas de 5 ?m) e FM composta por ACN: água (30:70, v/v), na vazão de 1 mL/min, detecção em 302 nm. Nestas condições foi possível a separação do OME e metabólitos em menos de 20 minutos. O método apresentou-se linear no intervalo de concentração plasmática de 20- 1000 ng/mL (r>0,99). Os parâmetros de precisão, exatidão, efeito carry-over e estabilidade estão em conformidade com o guia de validação da ANVISA (2012). O método foi satisfatoriamente aplicado em amostras de plasma de 20 pacientes submetidos à cirurgia bariátrica, no período pré e pós-cirúrgico. Outros dois métodos foram avaliados utilizando a técnica de microextração em fase líquida (DLLME). O método de OS-DLLME foi desenvolvido e validado para quantificação do OME e metabólitos em amostras de plasma por LCMS/ MS. A análise foi realizada na mesma coluna cromatográfica descrita anteriormente com FM composta por ACN:tampão formiato de amônio 10 mM pH 8,5 (50:50, v/v) vazão de 0,4 mL/min. Foram monitorados os íons precursores do OME, HOME, OMES e PI. As amostras de plasma foram pré-tratadas com ISO e com sobrenadante foi desenvolvida a OS-DLLME. Os parâmetros da OS-DLLME (tipo e volume de solvente extrator e dispersor, pH, força iônica do meio, tempo de agitação, tempo de centrifugação, volume de diluição da amostra e volume de amostra) foram otimizados com o auxílio de um delineamento experimental Plackett Burmann seguido por um CCD. Ao final uma metodologia de superfície de resposta facilitou a determinação da condição ótima de extração utilizando a ferramenta desejabilidade (D) na qual as condições otimizadas foram: 400?L de plasma, 2,5 mL de solução tampão tetraborato de sódio 0,1 mM pH 9,5, 120 ?L de CHCl3, 500 ?L de ISO, 0% de NaCl, 5 minutos de centrifugação, sem agitação das amostras. Posteriormente, o método foi aplicado com sucesso para análise de amostras de plasma de 5 pacientes submetidos à cirurgia bariátrica, no período pré e pós-cirúrgico.A IL-DLLME foi avaliada como técnica de extração utilizando ILs como solventes extratores alternativos. A análise foi realizada na mesma coluna cromatográfica com fase móvel no modo eluição por gradiente composta por ACN:água: 0-10 min, 5:95; 10,0-15 min, 10:90; 15,01-40 min, 30:70, v/v, vazão de 1 mL/min e detecção em 302 nm. Foram avaliados três ILs comerciais e oito ILs sintetizados no laboratório (NPPNS). Foram avaliados os parâmetros da IL-DLLME: solvente dispersor, IL extrator, pH e composição da solução tampão. Também foi realizada a avaliação por RMN dos IL utilizados. Dentre os ILs comerciais foi selecionado o OMImPF6, e dentre os ILs sintetizados foi selecionado o C8PF6. Entretanto, não foi possível o desenvolvimento do método devido a escassa quantidade de IL comercial. Em relação aos ILs sintetizados foram observados problemas na síntese e purificação, como presença de interferentes que coeluiam juntamente com os analitos avaliados. Entretanto, apesar deste método não ter sido validado foi possível obter valores de recuperação, para ambos os IL selecionados, superiores a 40%. / OME is used in the short- and long-term treatment of different gastrointestinal disorders. It is a proton pump inhibitor, which selectively acts on the enzyme H + / K + ATPase. It is completely metabolized by the cytochrome P450 enzymes generating three main metabolites: HOME, OMES and OS. It is used in the treatment of gastroesophageal reflux in patients who are obese and overweight in the period before and after bariatric surgery. However, performing this surgical procedure may impair the absorption of nutrients and medications. Thus, the determination of plasma concentrations of OME is of great clinical importance for dose adjustment, avoiding compromised treatment. Thus, two methods were developed for the quantification of OME and metabolites in plasma samples: LLE, standard method and OS-DLLME and IL-DLLME as an alternative method of extraction. The standard method, LLE, was developed for quantification of OME and metabolites in plasma samples by HPLC-UV. The analysis was done on a Zorbax Eclipse XDB-C18 (25 cm x 4.6 mm, 5 ?m particles) (Agilent Technologies, Palo Alto, CA, USA) and Zorbax Eclipse XDB-C18 (12, 5 mm x 4.6 mm, 5 ?m particles) and mobile phase composed of ACN: water (30:70, v / v) at the flow rate of 1 mL / min, detection at 302 nm. Under these conditions it was possible to separate OME and metabolites in less than 20 minutes. The method was linear in the plasma concentration range of 20-1000 ng / mL (r> 0.99). The parameters of accuracy, accuracy, carry-over effect and stability are in accordance with ANVISA\'s validation guide (2012). The method was satisfactorily applied in plasma samples from 20 patients submitted to bariatric surgery in the pre- and post-surgery period. Two other methods were evaluated using the liquid phase microextraction technique (DLLME). The OS-DLLME method was developed and validated for quantification of OME and metabolites in plasma samples by LC-MS / MS. The analysis was performed in the same chromatographic column described above with mobile phase composed of ACN: 10 mM ammonium formate buffer pH 8.5 (50:50, v / v) flow rate of 0.4 mL / min. The precursor ions of OME, HOME, OMES and PI were monitored. Plasma samples were pre-treated with ISO and the supernatant was grown to OS-DLLME. The parameters of OS-DLLME (type and volume of solvent extractor and dispersant, pH, ionic strength of medium, agitation time, centrifugation time, sample dilution volume and sample volume) were optimized with the aid of an experimental design Plackett Burmann followed by a central composite outline. At the end, a response surface methodology facilitated the determination of the optimal extraction condition using the desirability tool (D) in which optimized conditions were: 400?L of plasma, 2.5 mL of buffer solution 0.1 mM sodium tetraborate pH 9,5, 120 ?L CHCl3, 500 ?l ISO, 0% NaCl, 5 minutes centrifugation, without sample shaking. Subsequently, the method was validated and successfully applied for analysis of plasma samples from 5 patients submitted to bariatric surgery in the pre and post-surgical period. IL-DLLME was evaluated as an extraction technique using ILs as alternative extractive solvents. The analysis was performed on the iv same mobile phase chromatographic column in the gradient elution mode composed of ACN: water: 0-10 min, 5:95; 10.0-15 min, 10:90; 15.01 - 40 min, 30:70, v/v, flow rate of 1 mL / min and detection at 302 nm. Three commercial ILs and eight ILs synthesized in the laboratory (NPPNS) were evaluated. The parameters of IL-DLLME were evaluated: dispersing solvent, IL extractor, pH and buffer composition. NMR evaluation of the ILs used was also performed. Among the commercial ILs, OMImPF6 was selected, and C8PF6 was selected among the ILs synthesized. However, the development of the method was not possible due to the small amount of commercial IL. Concerning ILs synthesized, problems were observed in the synthesis and purification, as presence of interfering factors that coeluted together with the analyzed analytes. Thus, although this method was not validated, it was possible to obtain recovery values, for both ILs selected, higher than 40%.

Mgr. Martina Nádherná PhD. Thesis Applications of ionic liquids in electrolytes for amperometric gas sensors and Li-ion batteries SUMMARY The dissertation presents the results of preparation and characterisation of new aprotic electrolytes based on ionic liquids for the solid-state electrochemical gas sensors and for the electrochemical energy storage devices - secondary lithium-ion batteries. In the part dealing with the solid-state amperometric sensor for NO2 research was aimed at development of new solid electrolyte. This electrolyte is developed as a system of ionic liquid embedded in the structure of a polymer, when the ionic liquid joints the properties of a solvent and a dissolved salt. The electrolyte therefore does not contain any volatile component and is long-term chemically and electrochemically stable. Several series of electrolytes were prepared with different polymers or macromonomers and imidazolium-based ionic liquids. The composition, especially the polymer-IL ratio was optimized. The electrolytes were successfully tested in a solid-state NO2 sensor with a gold minigrid serving as the indicating electrode. The research included the determination of basic electrochemical parameters and study of the sensor behaviour under different conditions. The influence of atmosphere humidity,...

A dissertação está dividida em duas partes. A primeira trata da eletroquímica fundamental utilizando líquidos iônicos como eletrólito suporte e molécula de estudo. São abordados os fenômenos de estabilidade anódica e catódica, com ênfase no mecanismo de degradação do líquido. Além disso, é apresentado um estudo sobre a oxidação eletrocatalítica de hidrogênio nesse ambiente. Quanto a esse aspecto são abordados aspectos mecanísticos e físico-químicos da reação. Técnicas eletroquímicas, modelagem e simulações numéricas foram utilizadas para investigação e hipotetização dos processos. A segunda parte da dissertação consiste do estudo da interação entre óxidos de platina e alguns compostos orgânicos (ácido fórmico, metanol e etanol). O estudo foi realizado em termos da evolução do potencial de circuito aberto com acompanhamento das espécies reativas através da espectroscopia de infravermelho in situ. Os dados obtidos são analisados sob a luz dos conhecimentos levantados pela área de eletrocatálise e sistemas dinâmicos. Modelagem e simulação do sistema permitiram o entendimento do papel individual das diversas etapas envolvidas sobre o comportamento geral do sistema. / This dissertation is divided on two parts. The first one deals with fundamental electrochemistry employing an ionic liquid as supporting electrolyte and as a subject of study by itself. Phenomena like the anodic and cathodic stability of the liquid, emphasizing its degradation mechanism is presented. It is also shown a study of the electrocatalytic oxidation of hydrogen in this environment. For this case, efforts were made to unravel mechanistic aspects of the reaction, as well as physical chemical features. Electrochemical techniques and numerical simulations were used for investigation and understanding of that system. The second part presents a study of the interaction between platinum oxides and some organic compounds, namely: formic acid, methanol and ethanol. The study was performed under open circuit conditions by following the temporal evolution of the potential and also the concentration of some chemical species by using in situ infrared spectroscopy. Data were analyzed under the guide of knowledge constructed by the fields of electrocatalysis and dynamical systems. Modelling and simulation allowed understanding the individual role of the various participants species on the global behavior of the system.

A adição de sais de lítio à líquidos iônicos gera mudanças em propriedades físicas relevantes, que comprometem sua possível aplicação em baterias de lítio, como aumento de viscosidade e redução da condutividade iônica. Possíveis causas para tais efeitos foram estudadas através da utilização de Espectroscopia Raman e Espectroscopia de Efeito Óptico Kerr. Foram estudadas as misturas dos liquídos iônicos: 1-butil-3metilimidazólio, N-(3- etóxietil)-N-metilmorfolínio e cátion 1-(3-etóxietil)-2,3-dimetilimidazólio possuindo em comum o contra-íon bis(trifluorometanosulfonil)imideto com diferentes concentrações de bis(trifluorometanosulfonil)imideto de lítio. O trabalho se dividiu em duas etapas principais, na primeira utilizou-se a espectroscopia Raman e observou-se o desdobramento da banda referente ao ânion em aproximadamente 740 cm-1, em dois diferentes picos, após a adição de lítio ao sistema. Esta observação forneceu indícios da ocorrência de mudanças estruturais possivelmente relacionadas a formação de agregados entre os ânions e o Li+. A partir destes resultados a obtenção de um valor aproximado para o número de coordenação médio dos cátions Li+ foi possível através da comparação da intensidade relativa dos dois picos para diferentes concentrações de sal. Foi ainda estudado o efeito da adição de água no sistema, causando o desaparecimento do pico Raman formado após a adição do sal de lítio, o que evidencia a capacidade da mesma de reduzir o efeito de agregação dos ânions ao redor do Li+. Na segunda etapa do trabalho, a técnica de espectroscopia de efeito óptico Kerr via detecção heterodina foi utilizada para a observação do perfil de relaxação orientacional nos sistemas descritos acima, a fim de examinar mudanças nos processos dinâmicos presentes após a adição sal inorgânico ao sistema. Os resultados foram analisados no contexto da teoria de acoplamento de modos, de maneira que utilizou-se um modelo fenomenológico desenvolvido através da observação de diferentes sistemas e da aplicação das equações propostas no modelo esquemático de Sjögren para a descrição da função de correlação polarizabilidade-polarizabilidade obtida pelo experimento. Os parâmetros encontrados demonstraram um alto grau de concordância com as observações estruturais observadas na primeira etapa, fornecendo evidências de que o lítio é capaz de afetar as estruturas locais presentes no líquido iônico puro de uma maneira similar ao efeito Chemla. O trabalho demonstrou que os mesmos princípios necessários para a síntese de líquidos iônicos a temperatura ambiente, primando a redução das interações atrativas entre os cátion e ânions para a estabilização da fase líquida, possui como efeito colateral o fato de que diversas moléculas apresentam interações mais fortes com seus íons alterando suas propriedades, neste caso prejudicando a utilização de líquidos iônicos como solventes alternativos em baterias de lítio. / The introduction of lithium salts to room temperature ionic liquids causes unwanted changes to the electrochemically relevant properties of these compounds, such as increase in viscosity and the reduction of ionic conductivity. Possible causes for these effects were studied with spectroscopic techniques such as Raman spectroscopy and Optical Kerr Effect spectroscopy. Mixtures of three different ionic liquids containing the cations: 1-butyl-3- methylimidazolium, N-(3-etoxyethyl)-N-methylmorfolinium and cátion 1-(3-etoxyethyl)-2,3- dimethylimidazolium and possessing the common counter ion bis(trifluoromethane sulfonyl)imide with lithium bis(trifluoromethane sulfonyl)imide. This work was divided in two parts, the first consisting of the use of Raman spectroscopy and the observation of the changes in the 740 cm-1 peak, pertaining to anion vibration after the introduction of lithium to the system, shown as the appearance of a new peak at higher frequencies. The approximate average lithium coordination number was determined by comparison of the relative intensities for different salt concentrations. The effect of water absorption in this system was also observed, showing that water molecules tend to hinder the formation of aggregates between the anion and Li+. The second step was carried out with the use of optically heterodyne detected optical Kerr effect spectroscopy to the analysis of the orientational relaxation profile for the systems described above. Results were analyzed through the application of Mode Coupling Theory models, both a phenomenological model obtained by the observation of different classes of liquids and the Mode Coupling Schematic model proposed by Sjögren were used to describe the polarizability-polarizabilty correlation function obtained from the experiments. The parameters obtained showed a high degree of correlation with the results obtained in the first part indicating that the introduction of a highly polarizing cation to the pure ionic liquid causes an effect similar to the Chemla effect observed in inorganic salt mixtures. The work showed evidences that the same principles used for the synthesis of room temperature ionic liquids, i.e. the reduction of attractive interactions between cation and anion or the addition of alkyl chains to reduce symmetry, result in various different compounds showing stronger interactions with the different ions resulting in changing properties, in this case hindering the use of ionic liquids as alternative green solvents for lithium ion batteries.

O presente trabalho teve como objetivo a produção de ânodos de mistura de óxidos metálicos de composição nominal Ti/Ru0,3Ti0,7O2 utilizando um líquido iônico como solvente no preparo da solução precursora. A utilização deste tipo de solvente permite a síntese de materiais com morfologia e estrutura específicas, visto sua influência nas propriedades dos materiais. Neste trabalho foram utilizados líquidos iônicos baseados no imidazol, com o intuito de avaliar os efeitos do tamanho da cadeia carbônica ligada ao anel aromático heterocíclico, utilizando para comparação um eletrodo comercial (De Nora do Brasil). Por meio da caracterização física foi possível verificar que os eletrodos produzidos no laboratório apresentaram um filme mais compacto e com a formação de grânulos, o que indica um aumento na densidade de metais depositados. Além disso, o aumento na temperatura de calcinação favoreceu a deposição do óxido metálico catalítico (RuO2) na superfície do eletrodo ao se utilizar o hidrogenossulfato de 1-butilimidazólio ([HBIm]HSO4) como solvente na solução precursora. O eletrodo comercial apresentou uma área superficial superior aos eletrodos produzidos no laboratório, sendo a maior parte dessa área referente aos sítios internos desse eletrodo. O ânodo produzido utilizando [HBIm]HSO4 calcinado a 550 °C apresentou 15% mais remoção do pesticida alaclor em meio de sulfato que o eletrodo comercial, além de um consumo energético 16% menor. No caso das eletrólises realizadas na presença de cloreto, houve uma menor remoção do pesticida, apesar da melhora na resposta eletroquímica dos eletrodos nesse meio. Esse desempenho negativo pode estar relacionado à geração de substâncias que apresentam aderência à superfície dos eletrodos durante o processo de oxidação, obstruindo parcialmente a superfície ativa. / The present work aims to the production of mixed metal oxide anodes with nominal composition Ti/Ru0,3Ti0,7O2 using an ionic liquid as solvent in the preparation of the precursor solution. The use of this type of solvent allows the synthesis of materials with specific morphology and structure, since their influence on the properties of the materials. In this work, ionic liquids based on imidazole were used in order to evaluate the effects of the carbon chain size bonded to the heterocyclic aromatic ring, using a commercial electrode (De Nora do Brasil) for comparison. By means of the physical characterization, it was possible to verify that the laboratory made electrodes presented a more compact film with formation of granules, which indicates an increase in the deposited metal density. Moreover, the increase in the calcination temperature favored the deposition of the catalytic metal oxide (RuO2) on the surface of the electrode by using 1-butylimidazolium hydrogen sulfate ([HBIm]HSO4) as the solvent in the precursor solution. The commercial electrode presented a surface area superior to the laboratory made anodes, being the greater part of that area referring to the internal sites of this electrode. The anode produced using [HBIm]HSO4 calcined at 550 °C showed 15% more alachlor removal in sulfate medium than the commercial electrode, in addition to a 16% lower energy consumption. In the case of the electrolysis carried out in the presence of chloride, there was less pesticide removal, despite the improvement in the electrochemical response of the electrodes in this medium. This negative performance may be related to the generation of substances that have adhesion to the surface of the electrodes during the oxidation process, partially obstructing the active surface.

Neste trabalho, serão apresentados o comportamento eletroquímico e espectro-eletroquímico dos polímeros condutores poli(sulfeto de fenileno fenilenamina) (PPSA) e poli(anilina) (PANI) no líquido iônico bis(trifluorometanosulfonil)imideto de 1-butil-2,3-dimetilimidazólio (BMMITFSI). Os experimentos eletroquímicos em BMMITFSI mostram que o PPSA apresenta dois processos redox reversíveis sem sinais de perda de eletroatividade e mostram também a obtenção da PANI pela polimerização eletroquímica da anilina com os dois processos redox típicos das transformações em leucoesmeraldina ↔ esmeraldina ↔ pernigranilina, sem a necessidade de adição de ácidos e sem nenhum sinal de degradação em potenciais elevados. Os experimentos de UV-Vis e Raman Ressonante evidenciaram a estabilização das estruturas oxidadas formadas em líquido iônico tornando este fato a principal razão para o comportamento reversível dos processos redox de ambos os polímeros. Os experimentos de resistência in situ da PANI, demonstraram que a pernigranilina obtida em potenciais elevados é mantida na forma condutora. Estes fenômenos observados em ambos os polímeros indicam que a alta atmosfera iônica do BMMITFSI, estaria estabilizando as estruturas mais oxidadas (dicátions) em potenciais elevados, o que evita a degradação e perda de eletroatividade do PPSA e permite a condutividade da PANI na forma pernigranilina sal. / In this work, the electrochemical and spectroelectrochemical behavior of Poly(phenylenesulfide phenyleneamine) (PPSA) and polyaniline (PANI) conducting polymers in a room temperature ionic liquids, 1-butyl-2-3-dimethylimidazolium bis(trifluorometanessulfonil)imide (BMMITFSI) is presented. Electrochemical experiments of a PPSA in BMMITFSI show two reversible redox processes without loss of electroactivity. Aniline polymerization to obtain PANI films with typically two redox processes due to leucoemeraldine ↔ esmeraldine ↔ pernigraniline transformations was also carried out in the absence of acids, and even cycling till high positive potentials, no degradation signals were observed. UV-Vis and Resonance Raman studies show the stabilization of dications in BMMITFSI as the main reason to the reversible redox behavior observed on both conducting polymers and the in-situ resistance measurements corroborated the stabilization of pernigraniline salt at high oxidation potentials in the conducting form of PANI. These results obtained in room temperature ionic liquid shows that the high ionic medium given by the BMMITFSI would shield the positive charges, which would stabilize the dication species at high potentials, avoiding the degradation and loss of electroaticity of PPSA and allowing charge transport on pernigraniline salt.