Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2007. / The catalytic selective oxidation of hydrocarbon molecules is the process where a selectively oxidized intermediate molecule is formed instead of the thermodynamically favoured total oxidation products, in the presence of a suitable catalyst. Examples are the selective oxidation of methane to synthesis gas at moderate temperatures, for which a catalyst is still needed and the selective oxidation of propene to acrolein over α-Bi2Mo3O12. The selective oxidation of propene over α-Bi2Mo3O12 occurs via a Mars-van Krevelen mechanism where the bulk oxygen in the catalyst is inserted into the propene molecule and leaves as part of the product, while being replaced with gaseous oxygen. From an economic perspective there is a need to produce synthesis gas from methane at low temperatures. It was seen in the literature that α-Bi2Mo3O12 is a mixed metal oxide that might be capable of achieving this. The feasibility of the selective oxidation of methane to synthesis gas with α-Bi2Mo3O12 was therefore investigated. However, it was found that the selective oxidation of methane over α-Bi2Mo3O12 is not feasible at moderate temperatures. To circumvent the problem of producing synthesis gas at low temperatures a membrane reactor was suggested that might be able to produce synthesis gas at moderate temperatures with conventional selective methane oxidation catalysts that thermodynamically favours carbon dioxide formation at low temperatures. No time on-stream experiments had been done previously for the selective oxidation of ...

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this thesis the synthesis of a range of model and siloxane functionalized salicylaldimine ligands and [N-(n-propyl)-(2-pyridyl)] diimine ligands are described. The functionalized ligands were obtained by the reaction of salicylaldehyde and 2-pyridinecarboxaldehyde with 3-aminopropyltriethyoxysilane. All ligands were characterized by FT-IR and 1H NMR spectroscopy. The salicylaldimine ligands were reacted with either Cu(II) or Pd(II) salts to form both the model and functionalized Cu(II) and Pd(II) complexes. The Cu(II) complexes were characterized using FT-IR, EPR and UV-VIS spectroscopy while the Pd(II) complexes were characterized using FT-IR, 1H NMR and 13C{1H} NMR spectroscopy. The diimine ligands were reacted with Cu(II) salts to form functionalized pyridinyl complexes which were characterized used FT-IR spectroscopy. Two mesoporous silica supports, MCM-41 and SBA-15 were synthesized. The siloxane functionalized salicylaldimine Cu(II) and Pd(II) complexes were immobilized onto these supports to produce heterogenized catalysts. These catalysts were characterized using a range of solid-state techniques: BET nitrogen adsorption/desorption, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), ICP-AES, and powder X-ray diffraction (XRD) analysis. The powder XRD and SEM analysis showed that the structural integrity of the catalyst supports was kept intact during the immobilization process. BET analysis and ICP-AES showed that the complexes had been attached to the silica supports. Both the model complexes and heterogenized catalyst systems were tested in the oxidation of benzyl alcohol to benzaldehyde. The model copper catalyst showed high activity in this reaction with molecular oxygen used as oxidant and the (2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical as co-oxidant. The immobilized copper complexes showed low activity in the same reaction. This was attributed to steric hindrance around the active site dye to its entrapment with the silica matrix thus hindering the formation of a key intermediate in the oxidation cycle due to steric hindrance. The palladium complexes were not active in the oxidation reaction when molecular oxygen was used as oxidant, but showed slight activity when hydrogen peroxide was used. / AFRIKAANSE OPSOMMING: In hierdie tesis word die sintese van ‘n reeks model sowel as gefunksioneerde salisielaldemien ligande en [N-(n-propiel)-(2-piridiel)] di-imien ligande beskryf. Die gefunksioneerde ligande is verkry deur die reaksie van salisielaldehied en en 2-piridienaldehied met 3-aminopropieltriëtoksiesilaan. Al die ligande is gekarakteriseer deur FT-IR en 1H-KMR spektroskopie. Die salisielaldimien ligande is met óf Cu(II) óf Pd(II) soute reageer om beide die model en gefunksioneerde Cu(II) en Pd(II) komplekse te vorm. Die Cu(II) komplekse is gekarakteriseer deur FT-IR, EPR en UV-Vis spektroskopie terwyl die Pd(II) komplekse deur FT-IR, 1H-KMR en 13C{1H}-KMR spektroskopie gekarakteriseer is. Die di-imien ligande is met Cu(II) soute reageer om gefunksioneerde piridinielkompekse te vorm wat deur FT-IR spektroskopie gekarakteriseer is. Twee mesoporeuse silika draers, MCM-41 en SBA-15 is gesintetiseer. Die siloksaan-gefunksioneerde salisielaldemien Cu(II) en Pd(II) komplekse is op hierdie draers geimobiliseer om geheterogeniseerde katalisatore te vorm. Hierdie katalisatore is gekarakteriseer deur van ‘n wye reeks vaste toestand tegnieke gebruik te maak: BET stikstof adsorpsie/desorpsie, skandeer elektron mikroskopie (SEM), termiese gravimetriese analise (TGA), ICP-AES en poeier-XRD analise. Die poeier-XRD en SEM analisies het aangetoon dat die strukturele integriteit van die katalisator draers behoue gebly het tydens die immobiliseringsproses. BET analise en ICP-AES het aangetoon dat die komplekse aan die silika draers geheg is. Beide die model komplekse en geimobiliseerde katalisators is getoets in die oksidasie van bensielalkohol na bensaldehied. Die model Cu(II) katalisator het hoë aktiwiteit in hierdie reaksie getoon met molekulêre suurstof as oksideermiddel en die (2,2,6,6-tetrametielpipiridien-1-iel)oksiel radikaal as ko-oksideermiddel. Die geimobiliseerde Cu(II) komplekse het lae aktiwiteit in dieselfde reaksie getoon. Dit is toegeskryf aan steriese hindernis rondom die aktiewe sentrum as gevolg van die verstrikking binne die silika matrys, wat die vorming van ‘n belangrike tussentoestand in die oksidasie-siklus verhinder. Die Pd(II) komplekse was nie aktief in die oksidasie-reaksie in die geval waar molekulêre suurstof as oksideermiddel gebruik is nie, maar het effense aktiwiteit getoon waneer waterstofperoksied gebruik is. / Sasol

The use of supported catalysts to essentially combine the positive traits offered by both homogeneous and heterogeneous catalysis has become a competitive field of research. In particular, hydrotalcite-like catalysts (HTIc) has proven to be valuable for this purpose. Various osmium - containing catalysts were synthesized according to the co-precipitation method viz. Os-Cu-HTIc, Os-Ni-HTlc and the Os-Co-HTlc. Techniques such as SEM, IR, EDS, XRD, ICP, BET and XPS were exploited during catalyst characterisation and these essentially confirm that the hydrotalcite (HT) structure has been obtained. Various olefin substrates, ranging from simple straight-chained alkenes to cyclic, allylic and halogenated olefins, were tested. The results are promising and suggest that the diols are produced both with high selectivity and in good yield. Further experiments suggest: 1) Ofthe various co-oxidants tested, N-methylmorpholine-N-oxide is most suitable 2) The reaction proceeds faster at 60 °C than at room temperature 3) The addition of water to the reaction mixture increases the rate of the reaction for most substrates and 4) The catalyst is thermally stable and produces better results when calcined at 200 0 C prior to use This thesis reports that a new heterogeneous catalytic system for the efficient and selective cisdihydroxylation of olefins has been developed - one which suggests no leaching of metal into the reaction solution and no over-oxidation products. / Thesis (M.Sc.)-University of KwaZulu Natal, 2004.

Metal–organic frameworks, or MOFs, have emerged as a new class of porous materials made by linking metal and organic units. The easy preparation, structural and functional tunability, ultrahigh porosity, and enormous surface areas of MOFs have led to them becoming one of the fastest growing fields in chemistry. MOFs have potential applications in numerous areas such as clean energy, adsorption and separation processes, biomedicine, and sensing. One of the most promising areas of research with MOFs is heterogeneous catalysis. This thesis describes the design and synthesis of new, carboxylate-based MOFs for use as catalysts. These materials have been characterized using diffraction, spectroscopy, adsorption, and imaging techniques. The thesis has focused on preparing highly-stable MOFs for catalysis, using post-synthetic methods to modify the properties of these crystals, and applying a combination of characterization techniques to probe these complex materials. In the first part of this thesis, several new vanadium MOFs have been presented. The synthesis of MIL-88B(V), MIL-101(V), and MIL-47 were studied using ex situ techniques to gain insight into the synthesis–structure relationships. The properties of these materials have also been studied. In the second part, the use of MOFs as supports for metallic nanoparticles has been investigated. These materials, Pd@MIL-101–NH2(Cr) and Pd@MIL-88B–NH2(Cr), were used as catalysts for Suzuki–Miyaura and oxidation reactions, respectively. The effect of the base on the catalytic activity, crystallinity, porosity, and palladium distribution of Pd@MIL-101–NH2(Cr) was studied. In the final part, the introduction of transition-metal complexes into MOFs through different synthesis routes has been described. A ruthenium complex was grafted onto an aluminium MOF, MOF-253, and an iridium metallolinker was introduced into a zirconium MOF, UiO-68–2CH3. These materials were used as catalysts for alcohol oxidation and allylic alcohol isomerization, respectively. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 5: Manuscript.</p>

The hydrogenation of β-ketoesters over chirally modified Ni catalysts is a celebrated and thoroughly researched example of an enantioselective heterogeneous catalytic reaction. Enantioselective heterogeneous processes, although extremely attractive in terms of fewer complications in the separation of products from the catalyst, are hindered in their viability as industrial applications due to the lack of detailed knowledge on how chirality is conferred to the metal surface. Surface science techniques have afforded substantial progress into determining mechanisms between modifier, reactant and catalyst to explain the source of enantioselectivity of the system. In this study, a combination of solution and ultra-high vacuum (UHV)-based experiments allow a more realistic interpretation of the surface chemistry underpinning the catalytic reaction as the key step in achieving enantioselective performance is the adsorption of chiral modifiers from solution. The behaviour of (S)-aspartic acid and (S)-lysine on Ni{111} and their interaction with the prochiral β-ketoester methylacetoacetate is investigated in this study to understand their potential as chiral modifiers for the system. In UHV, scanning tunnelling microscopy (STM), reflection absorption infrared spectroscopy (RAIRS), and temperature programmed desorption (TPD) are used to analyse the conformation and order of the amino acids on the metal, and their thermal stability. Additionally, liquid-solid interface RAIRS and X-ray photoelectron spectroscopy (XPS) are used to examine the modified Ni surface, prepared under aqueous conditions, to give an accurate representation of the catalytic studies. It has been found highly likely that, for (S)-aspartic acid modified Ni{111}, enantioselective sites exist at step or step/kink defects, formed by corrosive leaching of the Ni substrate. Conversely, lysine appears to bind with a high sticking probability to Ni, in the form of lysine islands, and does not appear to etch the Ni chirally. Finally, similar experiments have been carried out on Au{111}, where lysine was found to chiral restructure the surface and form nanofingers, and 2D Ni clusters grown on Au{111} in order to investigate the formation of possible metal-organic frameworks.

O objetivo principal deste trabalho foi avaliar o óleo produzido por cianobactérias como matéria-prima lipídica para sintetisar biodiesel pela rota etílica empregando catalisadores heterogêneos. Cinco linhagens de cianobactérias não produtoras de toxinas: Microcystis aeruginosa NPCD-1, Synechococcus sp. PCC7942, Chlorogloea sp. CENA170, Leptolyngbya sp. CENA104 e Trichormus sp. CENA77 foram inicialmente cultivadas e avaliadas, tomando por base parâmetros como: produtividade de biomassa celular, teor de lipídeo e composição em ácidos graxos. Os valores mais elevados de produtividade celular e de lipídeo foram obtidos para as linhagens M. aeruginosa NPCD-1, Trichormus sp. CENA77 e Synechococcus sp. PCC7942. As matérias-primas lipídicas oriundas das linhagens selecionadas foram ainda caracterizadas quanto as propriedades reológicas (viscosidade), térmicas (termogravimetria) e químicas (espectroscopia na região de infravermelho). Na etapa seguinte, as condições de cultivo das linhagens foram estudadas e otimizadas por meio de um planejamento fatorial avaliando as variáveis intensidade luminosa (50 a 150 ?mol m-2s-1) e concentração de Na2CO3 (0,5 a 1,5 g/L), considerando como variáveis resposta a produtividade celular e o teor de lipídeo. A análise estatística indicou que a intensidade de luz influenciou positivamente os valores de produtividade celular para todas as linhagens estudadas, enquanto a concentração de Na2CO3 influenciou negativamente apenas no cultivo da linhagem M. aeruginosa NPCD-1. Com relação à variável teor de lipídeo, para a linhagem M. aeruginosa NPCD-1 nenhuma variável apresentou significância dentro da faixa estudada. No entanto, para as outras linhagens, o emprego das variáveis estudadas nos níveis mais altos implicou valores mais elevados para o teor de lipídeo. Definidas as condições ótimas de cultivo, o trabalho foi direcionado para execução da reação de interesse do projeto, empregando dois catalisadores heterogêneos de comprovada potencialidade: óxido de nióbio impregnado com sódio (químico) e Novozym 435® (bioquímico). Os resultados obtidos demonstraram que ambos os catalisadores atuaram de forma eficiente, convertendo os ácidos graxos em seus respectivos ésteres de etila. Entretanto, a qualidade da biomassa (índice de acidez e presença de pigmentos) interferiu a atuação dos catalisadores de maneira diferenciada. Enquanto o catalisador químico foi sensível à presença de níveis elevados de acidez, como constatado no óleo de Trichormus sp. CENA77, o catalisador bioquímico pode ter adsorvido os pigmentos presentes em maior quantidade nessa matéria-prima, reduzindo sua atividade catalítica. Desta forma, com exceção do biodiesel dessa matéria-prima lipídica, parâmetros, tais como número de cetano, ponto de entupimento de filtro a frio, índice de saponificação e índice de iodo, foram estimados por modelos teóricos, visando à predição da qualidade do biodiesel obtido dos diferentes óleos de acordo com as especificações estabelecidas pelas normas oficiais. Do ponto de vista geral, os resultados obtidos neste trabalho foram promissores e demonstraram a potencialidade do uso de cianobactérias como fonte de matéria-prima lipídica na síntese de biodiesel. As amostras de biodiesel das biomassas lipídicas de Microcystis aeruginosa NPCD-1 e Synechococcus sp. PCC7942 obtidas pela catálise heterogênea química atenderam as especificações estabelecidas na ANP como biocombustível. / The main goal of this study was to evaluate the lipid extracted from cyanobacteria as feedstock source for the synthesis of biodiesel using heterogeneous catalysis and ethanol as acyl acceptor. Five cyanobacterial non-microcystin producer strains: Microcystis aeruginosa NPCD-1; Synechococcus sp. PCC7942; Chlorogloea CENA170; Leptolyngbya CENA104 and Trichormus sp. CENA77 were cultivated and evaluated taking into account the biomass productivity, lipid content and fatty acid composition. Results indicated that M. aeruginosa NPCD-1, Trichormus sp. CENA77 and Synechococcus sp. PCC7942 gave the best set of parameters and were selected for further characterization using analytical techniques, including: viscosimetry, thermogravimetry and infrared spectroscopy. Following this, the cultivation conditions were studied and optimized using a factorial design, taking into consideration as independent variables light irradiance (50 to 150 ?mol m-2s-1) and concentration of Na2CO3 (0.5 to 1.5 g/L) as a carbon source. Cell productivity and lipid content were taking as response variables. For all strains, the most important factor was the light irradiance, since it presented a significant effect for all responses. Depend on the cyanobacteria strain, the concentration of Na2CO3 was found to have either positive or negative influence on the response variables. While for the M. aeruginosa NPCD-1 the presence of the Na2CO3 in the culture medium negative affected both cell productivity and lipid level, for the other strains high levels of Na2CO3 increase the lipid levels. After establishing the optimum cultivation conditions the experimental work was directed towards to perform the reaction of interest, using cyanobacterial feedstocks and two heterogeneous catalysts: chemical (niobium oxide impregnated with sodium) and biochemical (Novozym 435®). The dataset obtained demonstrated that the formation of ethyl esters from the feedstocks was feasible for the tested catalysts. Both catalysts were efficient in converting all fatty acids present in the feedstocks into the corresponding ethyl esters; however the chemical catalyst gave higher conversion than the biochemical one. The lower quality of the Trichormus sp. CENA77 feedstock strong affected the performance of the catalysts in a different way. While the chemical catalyst was sensitive to high acidity level verified in this microbial oil, the biocatalyst performance was influenced by the presence of pigments which was adsorbed on the biocatalyst matrix reducing its catalytic activity. Except for this oil, parameters such as cetane number, cold filter plugging point, saponification number and iodine value were estimated by theoretical models to predict the quality of biodiesel according to the specifications established by official standards. The results obtained in this study were promising and demonstrated the potential of using cyanobacteria as a feedstock source in the biodiesel synthesis. The lipid biomass from M. aeruginosa NPCD-1 and Synechococcus sp. PCC7942 originated biodiesel samples with appropriate characteristics to be used as fuel that are in accordance with specifications recommended by ANP.

A exploração de fontes alternativas para a produção de energia e produtos químicos ganha cada vez mais relevância devido à crescente demanda mundial por energia, combustíveis e produtos sintéticos. Nesse contexto, a biomassa lignocelulósica passa a ser importante matéria prima e o uso de catalisadores heterogêneos uma via atrativa para a transformação química da biomassa. A associação do Ni com Nb2O5 é promissora para obtenção de um sistema catalítico multifuncional com propriedades ácidas e de hidrogenação. O Brasil é o maior produtor mundial de nióbio e possui enormes quantidades de biomassa lignocelulósica. Assim, o uso de catalisadores à base de nióbio para valorização da biomassa é uma maneira de se agregar ciência e tecnologia a estas matérias primas abundantes em nosso país. Dessa forma, o objetivo deste trabalho foi o desenvolvimento de catalisadores heterogêneos de Ni/Nb2O5 para a exploração da biomassa lignocelulósica como matéria prima para produção de combustíveis e produtos químicos. Nb2O5 foi preparado por duas rotas de síntese, hidrólise básica (HB) que produziu um material amorfo com partículas sem morfologia definida e a síntese hidrotérmica (HT), que produziu um material cristalino com morfologia de nano-bastões. O método HT gerou uma nióbia estável em condições hidrotérmicas e com propriedades texturais e ácidas bastantes superiores do que HB. Foi depositado Ni (5, 10, 15 e 25% m/m) em Nb2O5 e através de experimentos de redução monitorados in situ por técnicas de luz síncrotron ficaram estabelecidas as condições de ativação como sendo temperatura de 320oC e tempo de isoterma de no mínimo 1 h sob fluxo de H2. Isso para obtenção de cristalitos pequenos de Ni0 (2 a 25 nm) e para preservar as propriedades estruturais do suporte. Os catalisadores foram avaliados em reações de hidrodesoxigenação de éter difenílico e o sistema Ni/Nb2O5(HT) apresentou atividade para hidrogenólise da ligações éter, hidrogenação do anel aromático e hidrodesoxigenação, apresentando conversão completa do substrato e seletividade maior que 99% para cicloexano, além de poder ser reciclado por cinco ciclos de reação. 15%Ni/Nb2O5(HT) foi ativo e apresentou boa estabilidade na hidrodesoxigenação de um substrato real de lignina e produziu uma mistura de cicloalcanos e álcoois cíclicos em fase líquida com potencial para ser utilizada como biocombustíveis devido a sua baixa razão O/C. Experimentos exploratórios de conversão de celulose indicaram que o sistema catalítico Ni/Nb2O5(HT) também apresenta potencial para obtenção de polióis e glicóis a partir da fração de carboidratos da biomassa. / The exploitation of alternative resources for the production of energy and chemical products is gaining more and more relevance due to the growing world demand for energy, fuels and synthetic products. In this context, lignocellulosic biomass become an important raw material and the use of heterogeneous catalysts a very attractive way for biomass chemical transformation. The association of Ni with Nb2O5 is promising for obtaining a multifunctional catalytic system with acidic and hydrogenation properties. Brazil is the world\'s largest producer of niobium and has enormous amounts of lignocellulosic biomass. So, the use of niobium-based catalysts for biomass valorisation is a way for adding science and technology to these abundant raw materials in our country. Thus, the aim of this work is the development of heterogeneous Ni/Nb2O5 catalysts for the exploitation of lignocellulosic biomass as raw material for the production of fuels and chemicals. Nb2O5 was prepared by two routes of synthesis, basic hydrolysis (HB) that produced an amorphous material with particles with non-defined morphology and hydrothermal (HT) synthesis that produced a crystalline material with morphology of nano-rods. The HT method produced a stable niobia in hydrothermal conditions and with textures and acidic properties quite higher than HB. Ni (5, 10, 15 and 25 wt.%) was deposited on Nb2O5 and by in situ experiments of reduction monitored by synchrotron light techniques the activation conditions were established as being temperature of 320oC for at least 1 h under H2 flow. This condition enables the production of small crystallites of Ni0 (2 at 25 nm) and for preserving the structural properties of the support. The catalysts were evaluated in hydrodeoxygenation reactions of diphenyl ether and the Ni/Nb2O5(HT) system showed activity for hydrogenolysis of the ether linkages, hydrogenation of aromatic rings and hydrodeoxygenation, converting the substrate completely with selectivity higher than 99% for cyclohexane and being recyclable for five reaction cycles. 15% Ni/Nb2O5(HT) was active for hydrodeoxygenation of a real lignin substrate and exhibited good stability, producing a mixture of cyclic cycloalkanes and alcohols in a liquid phase with potential to be used as biofuels due to their low O/C ratio. Exploratory experiments of cellulose conversion indicated that the Ni/Nb2O5(HT) catalyst also has the potential for obtaining polyols and glycols from the carbohydrate fraction of the biomass.

Com o grande uso de agrotóxicos, aumentaram também os problemas relacionados à contaminação. Tentando remediar esses problemas, estudos baseados em processos oxidativos avançados, como a reação de Fenton, tem conseguido notoriedade, pois o radical hidroxila (&bull;OH) ataca os poluentes orgânicos de maneira não seletiva. Porém, tal reação em meio homogêneo não é tão atrativa, pois requer grandes quantidades de íons de ferro em solução em meio ácido. Entretanto, pesquisas demostram que é possível desenvolve-la em meio heterogêneo com uma variedade de catalisadores em condições mais brandas e, ainda sim, gerar radicais livres e promover a oxidação de contaminantes orgânicos em várias faixas de pH. Nesse sentido, o presente trabalho teve como objetivos o enriquecimento do rejeito magnético, subproduto da extração de fosfato, em magnetita e a avaliação da viabilidade do mesmo nas reações do tipo Fenton heterogênea, tendo como modelo o herbicida hexazinona. Primeiramente o material passou por separação granulométrica, onde foram geradas 7 amostras, de acordo com a abertura de cada peneira. Em seguida elas foram submetidas a redução do tamanho de suas partículas em moinhos de bolas e passaram por uma pré-caracterização por espectroscopia de florescência de raio-x, difração de raio-x, termogavimetria, calorimetria diferencial exploratório e análise do tamanho de suas partículas. De posse desses dados, todas as amostras foram submetidas ao ensaio de lixiviação ácida, para o enriquecimento do material em magnetita. Após esta etapa, uma amostra foi escolhida (MESH 28) e submetida novamente a lixiviação ácida e às etapas de caracterização anterior e também, a análise do tamanho de sua área superficial, microscopia eletrônica de varredura, e comportamento magnético qualitativo. Assim, a amostra escolhida foi empregada para catálise heterogênea, de acordo com um planejamento estatístico do tipo composto central, levando em consideração a concentração de H2O2 e a variabilidade do pH da solução. Os resultados obtidos mostram que nas condições testadas, a que se apresenta com maior potencial para aplicações reais é a que se utiliza de concentração de peróxido igual a 0,0625 mol/L e pH 7,5, podendo ser ainda \"otimizada\" através de estudos em condições próximas a esta. Portanto, o resíduo magnético enriquecido em magnetita tem potencialidade para ser utilizado como catalisador em reações do tipo Fenton para degradação de herbicidas em água. / With the heavy use of pesticides, also increased the contamination-related problems. Trying to reduce these problems, studies based on advanced oxidation processes, such as the Fenton reaction, has achieved notoriety because the hydroxyl radical (&bull;OH) attacks organic pollutants in a non-selective manner. However, such reaction in homogeneous medium is not so attractive because it requires large amounts of iron ions in solution in acidic medium. However, studies demonstrate that it is possible to develop it in a heterogeneous medium with a variety of catalysts in milder conditions and, yet, generate free radicals and promoting the oxidation of organic contaminants in various pH ranges. In this sense, the present study aimed to enrich the magnetic waste, by-product of phosphate extraction in magnetite and evaluate it viability of the reactions of the heterogeneous Fenton type, with reference to the hexazinone herbicide. Firstly, the material passed to granulometric separation, where were generated seven samples according to the opening of each sieve. Then they were subjected to size reduction of their particles in ball mills and passed through a pre-characterization by X-ray fluorescence, X-ray diffraction, thermogravimetry, calorimetry exploratory differential and analysis of its particle size. With this data, all samples were subjected to acid leaching test, to enrich the material with magnetite. After this step, a sample was selected (MESH 28) and resubmitted to acid leaching and to the previous steps of characterization of steps and also the analysis of the size of its surface area, electronic scanning microscopy and magnetic behavior qualitative. Thus, the chosen sample was used for heterogeneous catalysis, in accordance with the central composite statistic planning type, taking into consideration the concentration of H2O2 and the pH variability of the solution. The results show that under the conditions tested, that presents the greatest potential for real world applications is that utilizes peroxide concentration equal to 0.0625 mol/L and pH 7,5, can yet be \"optimized\" via studies in conditions close to this. Therefore, the magnetic residue enriched in magnetite has the potential to be used as a catalyst type in Fenton reactions for the degradation of herbicides in water.

L’oxydation catalytique du propylène en acroléine en phase gazeuse est un procédé complexe et fortement exothermique, faisant intervenir de nombreuses réactions consécutives et compétitives. Une des clés pour maximiser le rendement en acroléine est le contrôle rigoureux de la température du mélange réactionnel ; il s’agit de lever les limitations aux transferts thermiques, afin d’évacuer l’importante chaleur de réaction. Un échangeur-réacteur milli-structuré a ainsi été retenu pour intensifier le procédé. En effet, de par la taille millimétrique de ses canaux ainsi que le choix d’un dépôt du catalyseur industriel sur les parois internes de ceux-ci, les transferts de chaleur et de matière sont améliorés. Afin de réaliser ce dimensionnement, une étude préliminaire de la cinétique des réactions a été réalisée et un modèle cinétique a été déterminé. Ce dernier a été utilisé afin de dégager les conditions optimales de fonctionnement d’un canal réactif (température, nombre de canaux composition), et afin d’extrapoler ces conditions sur un agencement structuré des canaux réactifs. La forme des chambres de distribution et de collecte du réacteur-échangeur ainsi que sa structure ont été déterminées et optimisées afin d’atteindre un rendement élevé par un contrôle optimal de la température, de minimiser la maldistribution des fluides et d’assurer la sécurité du procédé. Ce réacteur-échangeur intensifié, à la géométrie complexe, a finalement été fabriqué par impression 3D, au sein du projet français FAIR (Fabrication Additive pour l’Intensification des Réacteurs) / The catalytic oxidation of propylene to acrolein is a complex and highly exothermic process carried out in the gas phase, involving consecutive and competitive reactions. To maximize the efficiency of this process, the temperature needs to be rigorously controlled and the thermal transfers must be maximized, in order to evacuate the heat released by the reactions. A millistructured reactor-exchanger has thus been chosen to intensify this process. Indeed, millimetric channels washcoated with an industrial catalyst provide intensified heat and mass transfer. To carry out this design, a preliminary study of the kinetics of these reactions was carried out and a kinetic model was determined. This model was then used to identify the optimal operating conditions of a single reactive channel (temperature, number of channels, composition), and to extrapolate these conditions for the design of an intensified reactor exchanger. The shape of the distribution and collect chambers of these reactive channels were then optimized to minimize maldistribution, maximize the acrolein yield with an optimal control of the temperature, and to ensure the safety of the process. This intensified reactor-exchanger with complex geometry was finally manufactured by 3D printing, within the French project FAIR (Additive Manufacturing for the Intensification of Reactors)

O objetivo principal deste trabalho foi avaliar o óleo produzido por cianobactérias como matéria-prima lipídica para sintetisar biodiesel pela rota etílica empregando catalisadores heterogêneos. Cinco linhagens de cianobactérias não produtoras de toxinas: Microcystis aeruginosa NPCD-1, Synechococcus sp. PCC7942, Chlorogloea sp. CENA170, Leptolyngbya sp. CENA104 e Trichormus sp. CENA77 foram inicialmente cultivadas e avaliadas, tomando por base parâmetros como: produtividade de biomassa celular, teor de lipídeo e composição em ácidos graxos. Os valores mais elevados de produtividade celular e de lipídeo foram obtidos para as linhagens M. aeruginosa NPCD-1, Trichormus sp. CENA77 e Synechococcus sp. PCC7942. As matérias-primas lipídicas oriundas das linhagens selecionadas foram ainda caracterizadas quanto as propriedades reológicas (viscosidade), térmicas (termogravimetria) e químicas (espectroscopia na região de infravermelho). Na etapa seguinte, as condições de cultivo das linhagens foram estudadas e otimizadas por meio de um planejamento fatorial avaliando as variáveis intensidade luminosa (50 a 150 ?mol m-2s-1) e concentração de Na2CO3 (0,5 a 1,5 g/L), considerando como variáveis resposta a produtividade celular e o teor de lipídeo. A análise estatística indicou que a intensidade de luz influenciou positivamente os valores de produtividade celular para todas as linhagens estudadas, enquanto a concentração de Na2CO3 influenciou negativamente apenas no cultivo da linhagem M. aeruginosa NPCD-1. Com relação à variável teor de lipídeo, para a linhagem M. aeruginosa NPCD-1 nenhuma variável apresentou significância dentro da faixa estudada. No entanto, para as outras linhagens, o emprego das variáveis estudadas nos níveis mais altos implicou valores mais elevados para o teor de lipídeo. Definidas as condições ótimas de cultivo, o trabalho foi direcionado para execução da reação de interesse do projeto, empregando dois catalisadores heterogêneos de comprovada potencialidade: óxido de nióbio impregnado com sódio (químico) e Novozym 435® (bioquímico). Os resultados obtidos demonstraram que ambos os catalisadores atuaram de forma eficiente, convertendo os ácidos graxos em seus respectivos ésteres de etila. Entretanto, a qualidade da biomassa (índice de acidez e presença de pigmentos) interferiu a atuação dos catalisadores de maneira diferenciada. Enquanto o catalisador químico foi sensível à presença de níveis elevados de acidez, como constatado no óleo de Trichormus sp. CENA77, o catalisador bioquímico pode ter adsorvido os pigmentos presentes em maior quantidade nessa matéria-prima, reduzindo sua atividade catalítica. Desta forma, com exceção do biodiesel dessa matéria-prima lipídica, parâmetros, tais como número de cetano, ponto de entupimento de filtro a frio, índice de saponificação e índice de iodo, foram estimados por modelos teóricos, visando à predição da qualidade do biodiesel obtido dos diferentes óleos de acordo com as especificações estabelecidas pelas normas oficiais. Do ponto de vista geral, os resultados obtidos neste trabalho foram promissores e demonstraram a potencialidade do uso de cianobactérias como fonte de matéria-prima lipídica na síntese de biodiesel. As amostras de biodiesel das biomassas lipídicas de Microcystis aeruginosa NPCD-1 e Synechococcus sp. PCC7942 obtidas pela catálise heterogênea química atenderam as especificações estabelecidas na ANP como biocombustível. / The main goal of this study was to evaluate the lipid extracted from cyanobacteria as feedstock source for the synthesis of biodiesel using heterogeneous catalysis and ethanol as acyl acceptor. Five cyanobacterial non-microcystin producer strains: Microcystis aeruginosa NPCD-1; Synechococcus sp. PCC7942; Chlorogloea CENA170; Leptolyngbya CENA104 and Trichormus sp. CENA77 were cultivated and evaluated taking into account the biomass productivity, lipid content and fatty acid composition. Results indicated that M. aeruginosa NPCD-1, Trichormus sp. CENA77 and Synechococcus sp. PCC7942 gave the best set of parameters and were selected for further characterization using analytical techniques, including: viscosimetry, thermogravimetry and infrared spectroscopy. Following this, the cultivation conditions were studied and optimized using a factorial design, taking into consideration as independent variables light irradiance (50 to 150 ?mol m-2s-1) and concentration of Na2CO3 (0.5 to 1.5 g/L) as a carbon source. Cell productivity and lipid content were taking as response variables. For all strains, the most important factor was the light irradiance, since it presented a significant effect for all responses. Depend on the cyanobacteria strain, the concentration of Na2CO3 was found to have either positive or negative influence on the response variables. While for the M. aeruginosa NPCD-1 the presence of the Na2CO3 in the culture medium negative affected both cell productivity and lipid level, for the other strains high levels of Na2CO3 increase the lipid levels. After establishing the optimum cultivation conditions the experimental work was directed towards to perform the reaction of interest, using cyanobacterial feedstocks and two heterogeneous catalysts: chemical (niobium oxide impregnated with sodium) and biochemical (Novozym 435®). The dataset obtained demonstrated that the formation of ethyl esters from the feedstocks was feasible for the tested catalysts. Both catalysts were efficient in converting all fatty acids present in the feedstocks into the corresponding ethyl esters; however the chemical catalyst gave higher conversion than the biochemical one. The lower quality of the Trichormus sp. CENA77 feedstock strong affected the performance of the catalysts in a different way. While the chemical catalyst was sensitive to high acidity level verified in this microbial oil, the biocatalyst performance was influenced by the presence of pigments which was adsorbed on the biocatalyst matrix reducing its catalytic activity. Except for this oil, parameters such as cetane number, cold filter plugging point, saponification number and iodine value were estimated by theoretical models to predict the quality of biodiesel according to the specifications established by official standards. The results obtained in this study were promising and demonstrated the potential of using cyanobacteria as a feedstock source in the biodiesel synthesis. The lipid biomass from M. aeruginosa NPCD-1 and Synechococcus sp. PCC7942 originated biodiesel samples with appropriate characteristics to be used as fuel that are in accordance with specifications recommended by ANP.