Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-05-08T23:54:46Z No. of bitstreams: 1 POLIANA HARLANNE DANTAS FELIX – TESE(PPGEQ) 2015.pdf: 3400618 bytes, checksum: e0c31389002b48c7a27ae5a248a5146a (MD5) / Made available in DSpace on 2018-05-08T23:54:46Z (GMT). No. of bitstreams: 1 POLIANA HARLANNE DANTAS FELIX – TESE(PPGEQ) 2015.pdf: 3400618 bytes, checksum: e0c31389002b48c7a27ae5a248a5146a (MD5) Previous issue date: 2015-12-22 / Capes / A aplicação de catalisador heterogêneo para a síntese de biodiesel tem sido bastante estudada por ser de grande importância devido ao fato da possibilidade de reuso, além de permitir a utilização de diversas fontes lipídicas. As argilas têm, dentre esses uma alta eficiência, como suporte catalítico em virtude da sua capacidade de trocar cátions fixados na superfície assim como entre as lamelas, sem sofrer modificação na estrutura cristalina, com a inserção de óxidos metálicos de diversas espécies nesse tipo de material; surgem então, os novos catalisadores manométricos; logo, este trabalho, teve por finalidade, estudar e avaliar o potencial catalítico da argila Bentonítica sódica na sua forma natural e tratada quimicamente objetivando seu uso na obtenção do biodiesel. Os suportes catalíticos foram obtidos utilizando a argila bentonítica sódica como suporte, por meio de tratamentos químicos (pilarização, ativação ácida, impregnação com óxido de molibidênio). Todas as amostras catalíticas foram caracterizadas por Difração de Raios X (DRX), Microscopia Eletrônica de Varredura (MEV), Espectroscopia de Energia Dispersiva (EDS), Espectroscopia de Energia Dispersiva de Raios X (EDX) e Espectroscopia na Região do Infravermelho por Transformada de Fourier (FTIR). As curvas de difração indicaram a formação de picos característicos da estrutura do suporte e um deslocamento do pico característico, fato este atribuído ao tratamento químico ao qual foi submetido. As microscopias eletrônicas de varredura dos suportes catalíticos apresentaram uma morfologia irregular com deposição de partículas e aglomerados na superfície do material. Por EDX foram verificados os percentuais dos elementos que constituem a maior parte da composição química dos suportes, os quais são típicos de argilominerais montmorilonita e os maiores percentuais são de óxido de silício e de Alumínio, fato também observado pelo EDS. Os espectros das amostras obtidos por FTIR indicaram as bandas vibracionais que compõem as mesmas, como os grupos a Al-O, Si-O-Si, H2O e também o óxido de molibdênio resultado do processo de impregnação por dispersão física. A síntese do biodiesel deu-se pela reação de transesterificação entre o óleo de soja com o etanol na presença dos catalisadores obtidos. Os suportes catalíticos foram avaliados por percentual de conversão do óleo em éster utilizando-se dois sistemas reacionais denominados; (S1 - Reator Batelada com Pressão Autógena e S2 - Reator Parr). Os produtos obtidos nas sínteses foram caracterizados por cromatografia gasosa; identificou-se o maior percentual de conversão em ésteres da amostra acidificada com ácido clorídrico (BSA2) utilizando o sistema S2 com tempo reacional de 1h. Tal comportamento os potencializa como materiais promissores pois além de se mostrarem ativos, apresentaram um custo de produção relativamente mais baixo em referência a outros materiais já conhecidos e amplamente utilizados. / The application of a heterogeneous catalyst to the synthesis of biodiesel has been studied because it is of great importance due to the possibility of reuse, besides allowing the use of several lipid sources. The clays have a high efficiency as catalytic support due to their ability to exchange cations fixed on the surface as well as between the lamellae without modifying the crystalline structure with the insertion of metallic oxides of several species in this type of material ; Then the new gauge catalysts arise; The objective of this work was to study and evaluate the catalytic potential of the sodium bentonite clay in its natural and chemically treated form, with a view to its use in the production of biodiesel. The catalytic supports were obtained using sodium bentonite clay as a support, through chemical treatments (pillarization, acid activation, impregnation with molybdenum oxide). All the catalytic samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Dispersive Energy Spectroscopy (EDS), X-ray Dispersive Energy Spectroscopy (EDX) and Spectroscopy in the Infrared Region Fourier (FTIR). The diffraction curves indicated the formation of characteristic peaks of the support structure and a characteristic peak displacement, a fact attributed to the chemical treatment to which it was submitted. The scanning electron microscopes of the catalytic supports presented an irregular morphology with deposition of particles and agglomerates on the surface of the material. By EDX the percentages of the elements constituting the major part of the chemical composition of the substrates were verified, which are typical of montmorillonite clay and the highest percentages are of silicon oxide and aluminum, a fact also observed by EDS. The spectra of the samples obtained by FTIR indicated the vibrational bands that make up the same, such as the groups Al-O, Si-O-Si, H2O and also the molybdenum oxide resulting from the process of impregnation by physical dispersion. The synthesis of biodiesel was due to the reaction of transesterification between soybean oil and ethanol in the presence of the catalysts obtained. The catalytic supports were evaluated by percentage conversion of the oil into the ester using two reactive systems denominated; (S1 - Batch reactor with autogenous pressure and S2 - Parr reactor). The products obtained in the syntheses were characterized by gas chromatography; The highest percentage of conversion to esters of the sample acidified with hydrochloric acid (BSA2) was identified using the S2 system with a reaction time of 1h. Such behavior potentiates them as promising materials because in addition to being active, they presented a relatively lower cost of production in reference to other materials already known and widely used.

Made available in DSpace on 2016-08-19T12:56:40Z (GMT). No. of bitstreams: 1 dissertacao Antonio Fernandes.pdf: 992758 bytes, checksum: 0056f421b07eb8b8dcd8be248dd30af2 (MD5) Previous issue date: 2012-04-18 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The electrocatalytic activities of trimetallic catalysts based on platinum, tin and molibdenum, dispersed on Vulcan XC-72 carbon using an alcohol reduction method, were investigated for methanol and etanol oxidation reactions in acid solutions, with cyclic voltammetry, steady-state polarization curves and chronoamperometry. Among the catalysts Pt8Sn1Mo1/C, Pt7Sn1,5Mo1,5/C e Pt6Sn2Mo2/C investigated, the best performance was recorded on Pt6Sn2Mo2/C for the electrooxidation of metanol, as well as ethanol. In addition, such results when compared with those obtained on Pt/C sintesized by the same procedure, as well as on Pt/C-ETEK commercial sample, showed the higher electrocatalytic activity of the Pt6Sn2Mo2/C catalyst. / As atividades eletrocatalíticas de catalisadores trimetálicos à base de platina, estanho e molibdênio, suportados sobre o carbono Vulcan XC-72 pelo método de redução por álcool foram investigadas frente às reações de oxidação de metanol e de etanol, em soluções aquosas ácidas, com as técnicas de voltametria cíclica, curva de polarização de estado estacionário e cronoamperometria. Entre os catalisadores pesquisados Pt8Sn1Mo1/C, Pt7Sn1,5Mo1,5/C e Pt6Sn2Mo2/C, o melhor desempenho foi registrado com o Pt6Sn2Mo2/C, tanto para a eletrooxidação de metanol quanto de etanol. Além disso, mesmo quando comparado com os resultados obtidos sobre o catalisador Pt/C sintetizado pelo mesmo método quanto sobre uma amostra comercial da ETEK (Pt/C-ETEK), a atividade do catalisador Pt6Sn2Mo2/C mostrou-se superior.

Chez certains pathogènes, les flavohémoglobines (flavoHbs) jouent un rôle important dans le système de défense des microorganismes en leur conférant une résistance contre le stress nitrosant généré par les cellules du système immunitaire. Dans la mesure où ces protéines sont absentes chez l’homme, plusieurs études ont été réalisées en vue de comprendre le fonctionnement des flavoHbs au niveau moléculaire en les considérant comme des cibles attractives potentielles pour des inhibiteurs sélectifs. L’inactivation de ces enzymes chez les pathogènes entraîne une perte de virulence. Des composés chimiques (dérivés azolés) ont été identifiés comme étant capables d’inhiber leur activité enzymatique et d’affecter les facteurs de virulence bactérienne. Si ces composés sont très utilisés dans le traitement d’infections fongiques cutanées invasives, leur activité antibactérienne potentielle n’est pas encore exploitée.Typiquement, les flavoHbs sont composées de trois domaines : un domaine à hème de type globine, un domaine de site de fixation d’une flavine et un domaine de fixation du substrat de l’enzyme, le NADH. Les structures cristallographiques des flavoHbs montrent que ce sont des protéines capables d'adopter des conformations différentes selon la nature et la présence de ligand de l’hème mais aussi selon l’organisme d’origine. Ces différentes conformations se traduisent par une mobilité d’un seul des trois domaines sans modification majeure des deux autres domaines. Nous avons entrepris, dans ce travail, l’étude de la flavoHb d’une bactérie pathogène, Staphyloccocus aureus (pathogenic bacteria), peu étudiée dans la littérature et sa comparaison avec celle issue de Ralstonia eutropha (bactérie non pathogène), mieux caractérisée, afin de tenter d’apporter des informations nouvelles voire plus spécifiques de leur fonctionnement chez les pathogènes.Le travail présenté dans ce manuscrit décrit tout d’abord la caractérisation fonctionnelle et biochimique de la flavoHb de S.aureus, et approfondi celle de R. eutropha. Du fait de l’absence de structure cristallographique de la flavoHb de S. aureus, nous avons construit un modèle structural théorique en se basant sur l’homologie de séquence forte entre la séquence d’acide aminée de S. aureus et celle de Saccharomyces cerevisiae dont la structure 3D a été récemment déterminée. Dans l’hypothèse où le mécanisme enzymatique des flavoHbs implique une transition entre différentes conformations, les flavoHbs de R. eutropha et S. aureus ont été modifiées génétiquement au niveau du résidu phénylalanine suggéré par l’analyse structurale comme pouvant jouer un rôle dans la transition entre les différentes conformations. Les conséquences de la mutation de Phe396 en Ser ou Ala ont été analysées au regard des activités catalytiques et des propriétés biochimiques de l’enzyme mais aussi des propriétés des transferts d’électrons intramoléculaires entre les groupements prosthétiques (hème et flavine) par différentes techniques spectroscopiques. Ce travail a permis de montrer que l’effet de la substitution du résidu Phe sur les propriétés enzymatiques diffère selon la flavoHb considérée et révèle dans certains cas un site de fixation de substrat autre que le substrat natif. L’effet d’inhibiteurs (dérivés azolés) mais aussi des quinones et de composés aromatiques nitrés sur le fonctionnement des protéines natives et modifiées génétiquement ont été également étudiés dans ce travail, ces derniers composés pouvant agir en tant que "substrats subversifs" pour les flavoHbs, transformant leurs fonctions de protection en fonctions cytotoxiques.L’ensemble de ce travail a montré que, malgré des structures et des séquences protéiques très voisines, les flavoHbs issues de bactéries différentes sont susceptibles de se comporter différemment vis-à-vis de l’introduction d’une même mutation, de l’effet d’un même inhibiteur et peuvent le cas échéant présenter aussi des cycles catalytiques sensiblement différents. / For some pathogens, flavohemoglobins (FlavoHbs) play an important role in the defense of microorganisms by conferring them a resistance against nitrosative stress generated by the immune system cells. Since these protein are absent in human, several studies have been conducted in order to understand the functioning of these proteins at the molecular level, considering them as potential attractive targets for selective inhibitors. Their inactivation results a loss of virulence. Chemical compounds such as azole derivatives have been identified as being capable of inhibiting their enzymatic function and thereby affecting the bacterial virulence factors. If these compounds are widely used in the treatment of invasive fungal skin infections, their potential antibacterial activity is not yet operated.Typically, flavoHbs are composed of three domains: an N-terminal globin domain which harbors a single heme b and a C-terminal ferredoxin reductase-like FAD- and NAD-binding module. The crystallographic structures of flavoHbs show that these proteins are able to adopt different conformations depending on the nature and the presence of heme ligand but also depending on different organisms they are coming from. The different conformations are characterized by a rigid body motion of one of the three domains. We have undertaken in this work, the study of the Staphyloccocus aureus flavoHb, poorly studied in the literature, and compared it to the Ralstonia eutropha flavoHb (non pathogenic bacteria) to provide new and more specific information on behaviors of these proteins derived from pathogens.This PhD work describes first the functional and biochemical characterization of the S. aureus flavoHb. Due to the lack of its crystallographic structure, a theoretical structural model was designed based on the strong sequence homology between the amino acid sequence of S. aureus and Saccharomyces cerevisiae for which the 3D structure was recently determined. We hypothesized that the relative movement of protein domains could be a way to regulate its enzymatic activity by controlling the substrate accessibility. The Phe396 residue (nomenclature according to R. eutropha), suggested by the structural data to play an important role in the enzyme functioning, but also in the equilibrium between different conformations, was substituted by the Ala or Serine amino acids. The effects of the punctual mutations were investigated with respect to the enzyme functioning and biochemical properties. The mutations effect on the internal electron transfer between flavoHbs cofactors (heme and FAD) was also studied by spectroscopic techniques. This work showed that the impact of Phe substitution on the enzymatic properties is different, depending the considered flavoHb and revealed an additional binding site for other substrate than the native one. The effects of azole derivative inhibitors and also quinones and nitroaromatic compounds have been studied on native and genetically modified enzymes functioning. The latter compounds may act as the ‘subversive substrates’ for flavoHb, converting its protective functions into the cytotoxic ones.Taken as a whole, this work showed that, although the protein structures and sequences are similar, the flavoHbs from different bacteria may behave differently towards an identical mutation, an identical inhibitor and could display different catalytic cycles.

Thesis advisor: Dunwei Wang / Atomically dispersed catalysts refer to substrate-supported heterogeneous catalysts featuring one or a few active metal atoms that are separated from one another. They represent an important class of materials ranging from single atom catalysts (SACs) and nanoparticles (NPs). The study of SACs has brought an attention of understanding the reaction mechanism at the molecular level. SACs is a promising field, however, there are still many challenges and opportunities in developing the next generation of catalysts. Catalysts featuring two atoms with well-defined structures as active sites are poorly studied. It is expected that this class of catalysts will show uniqueness in activity, selectivity, and stability. However, the difficulty in synthesizing such structures has been a critical challenge. I tackled this challenge by using a facile photochemical method to generate active metal centers consisting of two iridium metal atoms bridged by O ligands and bound to a support by stripping the ligands of the organometallic complex. My research also unveiled the structure of this dinuclear heterogeneous catalysts (DHCs) by integrating various characterization resources. Direct evidence unambiguously supporting the dinuclear nature of catalysts anchored on metal oxides is obtained by aberration-corrected scanning transmission electron microscopy. In addition, different binding modes have been achieved on two categories of metal oxides with distinguishable surface oxygen densities and interatomic distances of binding sites. Side-on bound DHCs was demonstrated on iron oxide and ceria where both Ir atoms are affixed to the surface with similar coordination environment. The binding sites on the OH-terminated surface of Fe2O3 and CeO2 anchor the catalysts to provide outstanding stability against detachment, diffusion and aggregation. The competing end-on binding mode, where only one Ir atom is attached to the substrate and the other one is dangling was observed on WO3. Evidence supporting the binding modes was obtained by in situ diffuse reflectance infrared Fourier transform spectroscopy. In addition, the synergistic effect between two adjacent Ir atoms and the uniqueness of different coordinative oxygen atoms around Ir atoms were investigated by a series of operando spectroscopy such as X-ray absorption spectroscopy and microscopy at atomic level under the reaction condition. The resulting catalysts exhibit high activities and stabilities toward H2O photo-oxidation and preferential CO oxidation. Density functional theory calculations provide additional support for atomic structure, binding sites modes on metal oxides, as well as insights into how DHCs may be beneficial for these catalytic reactions. This research has important implications for future studies of highly effective heterogeneous catalysts for complex chemical reactions. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis (M. Tech. Chemistry, Dept. of Chemistry, Faculty of Applied and Computer Sciences)--Vaal University of Technology, 2010. / Membrane separation processes offer a promising alternative to energy-intensive separation processes such as distillation and solvent extraction. NF and RO are among the most investigated membrane processes with a potential use in the chemical industry. Carbon-carbon coupling reactions feature in the top ten most used reactions in the chemical industry. These reactions often use homogeneous palladium, nickel and other precious catalysts which are often difficult to separate from reaction products. This leads to potential product contamination and loss of active catalysts. This not only poses a threat to the environment but is also costly to the chemical industry. The purpose of this study was to investigate the efficiency of the recovery of the metal catalysts by selected membrane processes. Four commercial polymeric NF and RO membranes (NF90, NF270, BW30 and XLE) were selected for the study. Palladium catalysts commonly used in Heck and Suzuki coupling reactions were selected. These are Pd(OAc)2, Pd(OAc)2(PPh3)2, PdCl2 and Pd(PPh3)2Cl2. A range of organic solvents were also selected for the study. All the membranes were characterized for pure water permeability, pure solvent permeability, swelling, surface morphology and chemical structure. The chemical and catalytic properties of the catalysts were determined. Catalytic activity was investigated by performing coupling reactions. These catalysts generally performed well in the Heck coupling reaction with sufficient yields realized. The catalysts showed poor activities in the Suzuki and Sonogashira coupling reactions. These coupling reaction systems were affected by rapid palladium black formation. vi Catalyst retention studies showed the influence of membrane-solute interactions such as steric hindrance and size exclusion. The larger catalyst, Pd(OAc)2(PPh3)2 was rejected better by all the membranes irrespective of the solvent used. The smaller catalyst, Pd(OAc)2 was the most poorly rejected catalyst. This catalyst showed signs of instability in the selected solvents. An interesting finding from this study is that of higher rejections in water compared to other solvents for a particular catalyst. In this regard, the influence of solventsolute effects was evident. Generally, higher rejections were observed in solvents with higher polarity. This has been explained by the concept of solvation. It has been shown that solvents with different polarity solvate solutes differently, therefore leading to a different effective solute diameter in each solvent. Catalyst separation using NF90 membrane was attempted for the Heck coupling reaction system. The reaction-separation procedure was repeated for two filtration cycles with rapid activity decline evident. This was regarded as very poor showing of the catalyst separation efficiency of the membrane. Other authors in similar studies using SRNF membranes have reported reaction-separation processes of up to seven cycles. This observation shows the inferiority of polymeric membranes in organic solvent applications such as catalyst separation.

No description available.

La durabilité des piles à combustible à membrane échangeuse de protons, jugée à l’heure actuelle insuffisante, est principalement liée à la dégradation des supports de catalyseur cathodiques carbonés. Afin d’augmenter cette durabilité, un fin revêtement de dioxyde d’étain est effectué sur différents types de carbone (nanotubes, noirs et aérogel de carbone). L’objectif est d’obtenir un matériau alliant la morphologie et la conductivité électrique des carbones avec la stabilité thermodynamique du dioxyde d’étain. Plusieurs types de carbone avec des propriétés intrinsèques différentes ont été choisis afin d’avoir un large un panel de textures et de structures. Dans ces travaux de thèse, des études expérimentales ont été effectuées dans le but d’obtenir des revêtements d’oxyde d’étain fins, homogènes et couvrants. Ces études ont mis en l’avant l’influence primordiale de la texture et de la structure du carbone, mais aussi de la valeur du pH du milieu réactionnel sur la qualité et la quantité de revêtement. Il a aussi été montré que les mécanismes de transformation du précurseur en dioxyde d’étain dépendent de la valeur de ce pH. En améliorant les interactions entre la surface des carbones et des espèces réactives, il a été possible dans certains cas de diminuer grandement la quantité de précurseur tout en améliorant la qualité du revêtement. Les dépôts de nanoparticules de platine effectués sur des aérogels de carbone bruts et revêtus ont mis en avant un comportement différent du platine qui a tendance à s’agglomérer lorsqu’il est en contact avec le dioxyde d’étain. Les performances initiales ainsi que la durabilité des électrocatalyseurs en fonction de deux tests de vieillissement accéléré (classique ou démarrage/arrêt) ont ensuite été discutées, mettant en avant des résultats mitigés. / The proton exchange membrane fuel cell’s lifespan is insufficient because of the degradation of carbon used as cathodic catalyst supports. In order to reduce this degradation, a thin tin dioxide coating is synthesized on the surface of different carbonaceous materials (nanotubes, carbon blacks and aerogel). The aim is to combine the morphology and the electric conductivity of the carbon with the thermodynamic stability of the tin dioxide. Carbonaceous materials with different intrinsic properties are chosen for this study to test a wide range of textures and structures. Experimental studies were carried out in order to synthesize a thin, homogeneous and covering tin dioxide coating. The major influences of the texture and structure of carbonaceous materials but also the influence of the pH value on the quantity and quality of the coating are highlighted. It turns out that the mechanism of formation of tin dioxide depends on this pH value. Thanks to the improvement of the interactions between the carbon surface and the reactive species, it was possible, in some cases, to reduce drastically the quantity of precursor. Platinum nanoparticles deposition performed on various materials (raw or coated carbon aerogel) highlights a different platinum behavior. In fact, on the tin dioxide surface, nanoparticles tend to agglomerate together instead of making a homogeneous dispersion. Then, the initial performances and the durability of electrocatalysts tested with two accelerated stress tests (load protocol or start/stop protocol) are evaluated, spotlighting mitigate results.

Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-06T13:22:53Z No. of bitstreams: 1 arquivototal.pdf: 1661491 bytes, checksum: 603ad8044463f6291792eef191227188 (MD5) / Made available in DSpace on 2017-09-06T13:22:54Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1661491 bytes, checksum: 603ad8044463f6291792eef191227188 (MD5) Previous issue date: 2015-04-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The lectins are proteins capable of recognize and bond reversibly to carbohydrates without modifying them by a non-catalytic domain. In vegetables, they are synthetized as resistance factors against phytopathogens, and since they recognize structures present in the parasites, for their structural, catalytic and carbohydrate-specific characteristics give information on the action mechanisms against different parasitic species. Our study feature its catalytic activity of the lectin extracted from Abelmoschus esculentus (AEL) and evaluated their effects on phytophagous and phytopathogens for its application as a potential as crop protection and. We performed peptide analysis from AEL using mass spectrometry to determine conservative domains inherent to its molecular properties and protease activity inhibition toxicity, essays toxicity on the fruit fly Ceratitis capitata and root knot nematodes Meloidogyne javanica and Meloidogyne incognita on their different development stages through topical application, fungistatic activity on phytopathogenic fungi. AEL presents in its composition regions that are homologous to kunitz-type protease inhibitors, with the identification of conserved peptides for this class of proteins and protease inhibition activity (92%), which reveal its catalytic function and direct their action mechanisms on the different phytopathogens. It´s displayed insecticide effect on 3rd instar larvae and pupae, nematicide effect for the root knot nematodes acting mainly in larve hatched but did not presented fungistatic activity. / Lectina é um grupo de proteínas capaz de reconhecer e se ligar a carboidratos de forma reversível sem modifica-los por domínio não catalítico. Em vegetais, são sintetizadas como fator de resistência contra fitopatógenos por reconhecer estruturas presentes nestes parasitas e e suas características estruturais, catalíticas e carboidrato-específicos fornecem informações sobre seus mecanismos de ações em diferentes espécies de parasitas. O objetivo deste estudo foi caracterizar a atividade catalítica da lectina extraída de sementes de Abelmoschus esculentus (AEL) e avaliar seus efeitos sobre organismos fitófagos e fitopatógenos para sua utilização como um possível defensivo agrícola. Foram realizadas análises dos peptídeos da AEL por espectrometria de massas para detecção de domínios conservados inerentes a sua propriedade molecular e realização de atividade de inibição de proteases e ensaios de toxicidade em mosca de fruta Ceratitis capitata e nematoides de galha Meloydogine javanica e Meloydogine incógnita, nos seus diferentes estágios de desenvolvimento através de aplicação tópica e avaliação de sua atividade fungiostática sobre fungos fitopatogênicos, AEL apresentou em sua composição regiões homólogas à inibidores de protease do tipo kunitz, com identificação de 03 peptídeos conservados nesta classe de proteínas e atividade de inibição de protease (92%), os quais revelam sua função catalítica e direcionam seus mecanismos de ações nos diferentes parasitas. Apresentou efeito inseticida sobre larvas 3º instar e pupa, apresentou efeito nematicida sobre os nematoides de galhas, atuando principalmente sobre a eclosão das larvas, mas não apresentou atividade fungiostática.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-09-28T18:12:22Z No. of bitstreams: 1 VILMA MARIA SUDÉRIO - DISSERTAÇÃO PPGEQ 1995..pdf: 12571558 bytes, checksum: 00b0d5b9a33da42cdeac794bde348de8 (MD5) / Made available in DSpace on 2018-09-28T18:12:22Z (GMT). No. of bitstreams: 1 VILMA MARIA SUDÉRIO - DISSERTAÇÃO PPGEQ 1995..pdf: 12571558 bytes, checksum: 00b0d5b9a33da42cdeac794bde348de8 (MD5) Previous issue date: 1995-11-06 / Neste trabalho investigou-se a atividade catalítica da vermiculita natural (V-N) e trocada com cromo (III), (V-Cr) e cobalto (II), (V-Co), na reação de polimerização aquosa do metil metacrilato (MMA). utilizando bissulfito de sódio como iniciador. Foi estudada a influência de vários fatores, como: presença dos catalisadores V-N, V-Cr e V-Co. temperatura de calcinação dos catalisadores, massa dos catalisadores, tempo de polimerização, teor de cátions cromo (III) e cobalto(II) trocados, concentração de MMA e NaHSO? e temperatura de polimerização, sobre a velocidade de polimerização do MMA. A partir dos resultados obtidos foram observados os seguintes efeitos: 1) a V-N apresentou um efeito catalítico na reação, sendo que este efeito foi mais significativo quando os catalisadores V-Cr e V-Co foram utilizados, e que a V-Cr apresentou o maior efeito catalítico. A atividade catalítica cresceu, com o aumento dos teores dos cátions cromo e cobalto trocados; 2) o aumento da temperatura de calcinação de 100 até 800°C, das amostras V-Cr e V-Co, aumentaram a sua atividade catalítica. Entretanto, este aumento foi maior na temperatura de 400°C: 3) os efeitos dos outros fatores, citados no paragrafo anterior, mostraram um aumento na conversão do MMA. Porém, nos altos valores de conversão, foi observada a desativação dos sítios ativos, devido ao recobrimento das partículas dos catalisadores, pelo polímero formado; 4) o efeito catalítico das amostras estudadas é explicado com base no mecanismo em que a presença dos cátions de metais de transição na superfície da vermiculita. favorecem a dissociação do iniciador, produzindo maior quantidade de radicais de bissulfito, que em conseqüência aumentam a taxa de polimerização. / This work presents an investigation of the catalytic activity of the natural vermiculite (V-N) and that of vermiculite exchanged with chromium (III) (V-Cr) and Cobalt (II) (V-Co) for the aqueous polymerization of metil methacrylate (MMA), using sodium bissulfite as an initiator. The influence of various factors, as the presence of catalysts V-N, V-Cr e V-Co, calcination temperature of catalysts, catalyst mass, polymerization time, amount of exchanged chromium and cobalt cations, MMA and NaHSO? concentration and polymerization temperature, on the rate of polymerization of MMA has been studied. Based on the results obtained the following effects have been observed: 1) the samples of V-N, V-Cr and V-Co have shown catalytic activity on the aqueous polymerization reaction of MMA, and V-Cr being more significant. The catalytic activity was increased with the increase of the amounts of exchanged chromium and cobalt cations; 2) the increase in the calcination temperature from 100 to 800°C for the samples of V-Cr and V-Co increased their catalytic activity. However, this increase was highest for 400°C; 3) the effect of other factors mentioned in the previous paragraph also showed an increase in MMA conversion. However, for higher values of conversion, due to covering of the catalyst particles by the polymer formed, deactivation of the active sites was observed; 4) the catalytic effect of the samples studied is explained on the basis of mechanism that the presence of transition metal cations on the vermiculite surface favor the initiator dissociation and thereby more bissulfite radicals are produced which in consequence increase the polymerization rate of the MMA.

The Master´s thesis deals with the preparation of perovskite oxides by glycine synthesis with following characterization and analysis of catalytic activity. Especially is discussed crystallographic structure. In the theoretical part were first summarized the available information of the properties and usage of perovskite oxides. In the experimental part of the work was carried out the preparation of perovskite oxides and were made chemical analysis. Moreover a catalytic activity of selected perovskites has been studied and have been illustrated their crystal structure.