In molecular transition metal catalyst architectures, ligand design plays a crucial role in enhancing the efficiency of catalytic reactions. Selected ligands can play a bifunctional role in ligand-assisted catalysis, providing first coordination sphere basic sites and facilitating formation of multinuclear species through monomer bridging, as well as through their electronic and steric effects. This research addresses the underutilization of SNS complexes in various catalytic cycles. Our aim is to expand their activity in different cycles, unlocking untapped reactivity. Specifically, we focus on SNS ligands with soft thiolate and hard amido donors, comparing their catalytic performance in diverse coupling reactions. This comparative study provides insights into the suitability of these ligands with different transition metals, contributing to the understanding of ligand-assisted catalysis. Chapter 1 introduces these concepts and outlines the relevant catalytic reactions studied herein. To gain a deeper understanding of the chemistry involved, a comparative analysis of the reactivity differences between transition metal complexes with similar coordination structures is conducted. This investigation is crucial as it provides valuable insights into the design of suitable ligands for transition metal catalysts. Specifically, Chapters 2 and 3 of this thesis delve into a comparison of the reactivity of coordination complexes with identical metal centers and similar ligands, or even the same molecular formula, in catalysis. In the second chapter, we introduce a new cobalt (II) complex bearing an (SNS) amido ligand for the bifunctional hydroboration of carbonyls. Following an unsuccessful attempt to mono-protonate the amido donor in the bis(amido) complex Co(SᴹᵉNSᴹᵉ)₂ (2.1) treatment with 1 equivalent of 1,3-bis(1-adamantyl)imidazolium chloride (IAd•HCl) resulted in the liberation of one protonated ligand, affording CoᴵᴵCl(SᴹᵉNSᴹᵉ)(a-IAd) (2.2) with an "abnormally" coordinated IAd ligand, i.e., specifically bound through C4 instead of C2 of the imidazole ring. Compound 2.2 exhibited excellent catalytic activity in the hydroboration of aldehydes, displaying high substrate tolerance under mild reaction conditions and short reaction times. Stoichiometric reactions of 2.2 with pinacolborane (HBpin) revealed a bifunctional catalyst activation step, generating free SNS-amine, ClBpin and the active cobalt dihydride catalyst. Generation of an analogous catalyst with a normally coordinated IAd ligand showed poor reactivity in the hydroboration of aldehydes and was unable to effect ketone hydroboration. In Chapter 3, two tetranuclear copper(I) complexes bearing thiolate [Cu(SNSᴹᵉ)]₄ (3.1) and amido [Cu(SNSᴹᵉ)]₄ (3.2) SNS ligands are synthesized and their catalytic activity in a base-free azide-alkyne cycloaddition is compared. Complex 3.1 (1 mol%) demonstrated excellent reactivity for performing this 'click' reaction in water, exhibiting a broad substrate scope and enabling the production of various triazole compounds, including bioactive compound 3.16, which holds potential as an anti-cancer drug. DFT calculations suggested a proton shuttle role for the thiolate donor in conversion of the Cu-coordinated terminal alkyne to the key Cu-alkynyl intermediate. On the other hand, complex 3.2 exhibited reactivity similar to copper chloride. This observation was attributed to the basic nature of the amido ligand, which undergoes protonation by the coordinated alkyne C-H bond, with subsequent dissociation of the SNS-amine from the copper. Without a ligand to stabilize the copper in the less stable +1 oxidation state, a disproportionation reaction occurs, leading to catalyst deactivation. Chapter 4 introduces two palladium(II) thiolate complexes: PdI(κ³-SNSᴹᵉ) (4.1) exhibits catalytic activity in promoting the Heck cross-coupling reaction, while Pd(κ²-SNSᴹᵉ)₂ (4.2) affords no coupling product. In concert with triethylamine base, catalyst 4.1 efficiently produces olefin products with excellent yields, even at low catalyst loadings, and exhibits broad substrate tolerance over a 5 h reaction period. In contrast, the limited catalytic activity of 4.2 can be rationalized by proposing the formation of a Pd(N₂S₂) complex through ligand imine coupling at elevated temperatures, a reaction reported previously for Ni and Co analogs. The tetra-coordinated ligand formed through this isomerization occupies critical coordination sites around the metal, thereby preventing oxidative addition of the organohalide substrate, a key step in the Heck reaction mechanism. This work sheds light on the divergent catalytic behaviors of these two intriguing complexes. Finally, in Chapter 5 we assess what has been learned and identify relevant implications for further work.

Proteasome inhibitors bortezomib and carfilzomib are FDA-approved anticancer agents that have contributed to significant improvements in treatment outcomes. However, the eventual onset of acquired resistance continues to limit their clinical utility, yet a clear consensus regarding the underlying mechanisms has not been reached. Bortezomib and carfilzomib are known to target both the constitutive proteasome and the immunoproteasome, two conventional proteasome subtypes comprising distinctive sets of catalytic subunits. While it has become increasingly evident that additional, ‘intermediate’ proteasome subtypes, which harbor non-standard mixtures of constitutive proteasome and immunoproteasome catalytic subunits, represent a considerable proportion of the proteasome population in many cell types, less is known regarding their contribution to cellular responses to proteasome inhibitors. Importantly, previous studies in murine models have shown that individual proteasome subtypes differ in sensitivity to specific proteasome inhibitors. Furthermore, research efforts in our laboratory and others have revealed that proteasome catalytic subunit expression levels and activity profiles are altered when human cancer cells acquire resistance to proteasome inhibitors. We therefore hypothesized that changes in the relative abundances of individual proteasome subtypes contribute to the acquired resistance of cancer cells to bortezomib and carfilzomib. A major obstacle in testing our hypothesis was a lack of chemical probes suitable for use in identifying distinct proteasome subtypes. We addressed this by developing a series of bifunctional proteasome probes capable of crosslinking specific pairs of catalytic subunits colocalized within individual proteasome complexes and compatible with immunoblotting-based detection of the crosslinked subunit pairs. We confirmed the utility of these probes in discerning the identities of individual proteasome subtypes in a multiple myeloma cell line that abundantly expresses catalytic subunits of both the constitutive proteasome and immunoproteasome. Our findings indicate that constitutive proteasomes, immunoproteasomes, and intermediate proteasomes co-exist within these cells and support conclusions drawn from previous studies in other cell types. We also established non-small cell lung cancer cell line models of acquired bortezomib and carfilzomib resistance in which to test our hypothesis. Using immunoblotting and proteasome activity assays, we discovered that changes in the expression levels and activities of individual catalytic proteasome subunits were associated with the emergence of acquired resistance to bortezomib or carfilzomib. These changes were inhibitor-dependent and persisted after the selective pressure of the inhibitor was removed. Finally, results obtained using our bifunctional proteasome probes suggest that the altered abundance of an intermediate proteasome subtype is associated with acquired proteasome inhibitor resistance. Collectively, our results provide evidence linking changes proteasome composition with acquired proteasome inhibitor resistance and support the hypothesis that such changes are involved in resistance mechanisms to these inhibitors.

The purpose of this doctoral thesis is to investigate and develop catalytic processes mediated by iridium(III) complexes. By understanding the mechanisms, the weaknesses of the designed catalysts can be identified and be overcome in the following generation. The thesis is composed of two general sections dedicated to the synthesis and applications of homogeneous catalysts and to the preparation of heterogeneous catalysts based on metal-organic frameworks (MOFs). After a general introduction (Chapter 1), the first part of the thesis (Chapters 2-4, and Appendix 1) covers the use of several homogeneous bifunctional [Cp*Ir(III)] catalysts in a variety of chemical transformations, as well as mechanistic studies. Chapter 2 summarizes the studies on the N-alkylation of anilines with benzyl alcohols catalyzed by bifunctional Ir(III) complexes. Mechanistic investigations when the reactions were catalyzed by Ir(III) complexes with a hydroxy-functionalized N-heterocyclic carbene (NHC) ligand are discussed, followed by the design of a new generation of catalysts. The chapter finishes presenting the improved catalytic performance of these new complexes.    A family of these NHC-iridium complexes was evaluated in the acceptorless dehydrogenation of alcohols, as shown in Chapter 3. The beneficial effect of a co-solvent was investigated too. Under these base-free conditions, a wide scope of alcohols was efficiently dehydrogenated in excellent yields. The unexpected higher activity of the hydroxy-containing bifunctional NHC-Ir(III) catalysts, in comparison to that of the amino-functionalized one, was investigated experimentally. In the fourth chapter, the catalytic process presented in Chapter 3 was further explored on 1,4- and 1,5-diols, which were transformed into their corresponding tetrahydrofurans and dihydropyrans, respectively. Mechanistic investigations are also discussed. In the second part of the thesis (Chapter 5), a Cp*Ir(III) complex was immobilized into a MOF. The heterogenization of the metal complex was achieved efficiently, reaching high ratios of functionalization. However, a change in the topology of the MOF was observed. In this chapter, the use of advanced characterization techniques such as X-ray absorption spectroscopy (XAS) and pair distribution function (PDF) analyses enabled to study a phase transformation in these materials. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.</p>

As hidrolases, principalmente as peptidases e lipases, são responsáveis pelo alto faturamento no mercado mundial e pelos diversos empregos industriais e biotecnológicos. A obtenção destas proteínas ocorre pela aplicação dos microrganismos a bioprocessos, tanto de forma selvagem quanto por expressão heteróloga. Neste contexto, existe uma busca incessante por enzimas mais estáveis e com maior atividade catalítica, e algumas técnicas têm sido utilizadas para o melhoramento destes parâmetros. A obtenção da peptidase e lipase pelo fungo Fusarium oxysporum foi realizada por bioprocesso submerso, gerando picos de 165 U/mL em 72 horas e 633 U/mL em 48 horas, respectivamente. A peptidase foi purificada utilizando a resina Sephadex G-50 de exclusão de massa e caracterizada utilizando um substrato peptídico com supressão intramolecular de fluorescência. A classe da proteína foi determinada como serino peptidase e demonstrou características neutra e estável quanto ao pH em uma faixa ampla. A temperatura ótima foi de e 50 °C e a partir dos ensaios de estabilidade térmica foi evidenciado a manutenção da atividade proteolítica de 60-90% até 60 °C no período de uma hora. Quanto à eficiência catalítica, os subsítios S1, S2 e S\'1 tem certa especificidade, pois não demonstram eficiência catalítica quando há a presença dos seguintes aminoácidos nas respectivas posições dos substratos P1 (ácido aspártico, prolina e isoleucina), P2 (ácido aspártico, histidina, lisina, asparagina e triptofano) e P\'1 (ácido aspártico, ácido glutâmico e prolina), ao contrário dos subsítios S3, S\'2 e S\'3, onde todos aminoácidos apresentaram eficiência catalítica. A lipase foi purificada utilizado resina iônica e apresentou características básica e estabilidade em pH neutro, sua temperatura ótima foi de 35 °C e manutenção da atividade catalítica em pelo mens 50% após 1 hora de exposição a 25 a 40 °C. A produção da quimera deu-se pela busca de uma peptidase e uma lipase provenientes do fungo F. oxysporum no banco de dados, elas foram então fusionadas utilizando um linker composto por cinco aminoácidos (GGAGG) nas regiões C-terminal da peptidase e N-terminal da lipase. Ambas atividades foram detectadas na quimera, tornando-a funcional. A aplicação biotecnológica de ambas enzimas selvagens e recombinante é um passo importante para inovação, e de acordo com as características apresentadas cada enzima pode ser aplicada a diversos processos industriais, desde detergentes a biorremediação / proteins is wild-type microorganisms by bioprocesses or by heterologous expression. In this context, there is an incessant search for more stable enzymes with higher catalytic activity, and some techniques have been used to improve these parameters. Obtainment of peptidase and lipase by the fungus Fusarium oxysporum was performed by submerged bioprocess, generating peaks of 165 U / mL in 72 hours and 633 U / mL in 48 hours, respectively. Peptidase was purified using the Sephadex G-50 size exclusion resin and characterized using a peptide substrate with intramolecular fluorescence suppression. The enzyme class was determined as serine peptidase and demonstrated neutral and stable characteristics in a wide range of pH. The optimum temperature was 50 ° C and the thermal stability assays showed the maintenance of the proteolytic activity from 60 to 90% up to 60 ° C within one hour of exposure. As for catalytic efficiency, the S1, S2 and S\'1 subsites have a certain specificity, since they do not demonstrate catalytic efficiency when the following amino acids are present in the respective positions of the substrates P1 (aspartic acid, proline and isoleucine), P2 (aspartic acid, Histidine, lysine, asparagine and tryptophan) and P\'1 (aspartic acid, glutamic acid and proline), unlike subsites S3, S\'2 and S\'3, where all amino acids showed catalytic efficiency. The lipase was purified using ionic resin and presented basic characteristics and stability at neutral pH, its optimum temperature was 35 ° C and maintenance of the catalytic activity by 50% after 1 hour of exposure at 25 to 40 ° C. Production of the chimera was done by the search of a peptidase and a lipase from the fungus F. oxysporum in the database, they were then fused using a linker composed of five amino acids (GGAGG) in the C-terminal regions of the peptidase and N- Terminal portion of the lipase. Both activities were detected in the chimera, making it functional. The biotechnological application of both wild and recombinant enzymes is an important step for innovation, and according to the characteristics presented each enzyme can be applied to several industrial processes.

[pt] A síntese direta de dimetil éter (DME) a partir de gás de síntese é catalisada a partir de catalisadores bifuncionais que possuem duas propriedades: uma hidrogenante que catalisa a formação de metanol a partir de gás de síntese e a outra desidratante que se encarrega da formação do dimetil éter a partir do metanol. Catalisadores bifuncionais com componente hidrogenante baseado em Cu, Zn e Al e componente desidratante baseado na zeólita H-ferrierita foram sintetizados, avaliando-se, o método de preparação, a influência do alumínio no componente hidrogenante e a razão componente desidratante versus componente hidrogenante. Dos diferentes métodos de preparação utilizados: precipitação-deposição, coprecipitação-impregnação e coprecipitação-sedimentação foram os dois últimos que apresentaram melhores resultados na conversão de gás de síntese além de apresentar a formação do precursor do catalisador de síntese de metanol. Os catalisadores foram caracterizados por: absorção atômica, análise térmica gravimétrica, adsorção de N2, difração de raios-x, redução com temperatura programada (RTP), dessorção com temperatura programada de amônia (DTPNH3), dessorção com temperatura programada de hidrogênio (DTP-H2) e microscopia eletrônica de transmissão. Verificou-se que o catalisador bifuncional apresenta um entupimento no volume de poros de aproximadamente 50 por cento. Os resultados dos raios-x identificaram a formação das fases auricalcita, hidrozincita, malaquita e rosacita nos catalisadores com componente hidrogenante baseado em Cu e Zn dos catalisadores com componente hidrogenante baseado em Cu, Zn e Al, e razão atômica Cu/Zn/Al:55/30/15, se observou somente a fase hidrotalcita. A inclusão de alumínio no componente hidrogenante favoreceu a formação de partículas de CuO muito pequenas, conforme observado na microscopia eletrônica de transmissão e difração de raios-x. A análise da DTP-H2 mostrou que os catalisadores preparados por coprecipitação-impregnação apresentam áreas de cobre um pouco maiores. A DTP-NH3 identificou a presença de sítios ácidos de Lewis e de Bronsted que ainda permanecem na H-ferrierita após a preparação do catalisador bifuncional. Sítios ácidos de Bronsted diminuem em maior proporção no catalisador bifuncional quando é preparado pelo método de coprecipitação-impregnação. Os testes catalíticos mostraram não existem grandes diferenças entre os catalisadores bifuncionais preparados por ambos os métodos e que o alumínio no componente hidrogenante não melhora a atividade catalítica destes catalisadores na síntese direta de DME. Concluiu-se que a etapa limitante do processo é a hidrogenação e que esta é dominada pelo cobre e que a H-ferrierita é um excelente componente desidratante pela sua elevada acidez. / [en] The direct synthesis of dimethyl ether from syngas is catalyzed by bifunctional catalysts: the hydrogenation function that catalyzes the methanol formation and the dehydration function to produce dimethyl ether from methanol. Bifunctional catalysts with Cu, Zn and Al as hydrogenation component and Hferrierite zeolite as dehydration component had been synthesized. It was evaluated the method of preparation, the influence of aluminum present in the hydrogenation component and dehydration/hydrogenation component ratio. The coprecipitating impregnation and coprecipitating sedimentation methods were used to form the precursor of hydrogenation component. The catalysts had been characterized by atomic absorption, thermal gravimetry analysis, N2 adsorption, xrays diffraction, TPR, ammonia TPD, hydrogen TPD and transmission electronic microscopy. It was verified that the bifunctional catalyst lost 50 percent of its pore volume. The results of x-rays identified the formation of aurichalcite, hydrozincite, malachite and rosacite phases in the catalyst based on Cu and Zn. However, in the catalyst based on Cu, Zn and Al (for an atomic ratio, Cu/Zn/Al:55/30/15) only the hidrotalcite phase was found. It was observed that the aluminum introduction in the hydrogenation component favors the formation of very small particles of CuO as verified in transmission electronic microscopy and x-rays diffraction. The NH3-TPD identified the presence of Lewis and Bronsted acid sites that still remain in the H-ferrierite after the preparation of the bifunctional catalysts. Bronsted acid sites had an importante decrease in the bifunctional catalysts when it is prepared by the method of coprecipitating impregnation. The catalytic tests showed that the catalysts prepared by the coprecipitating sedimentation method, present higher conversions and DME selectivitys than the prepared by coprecipitating impregnation. The presence of Al in the hydrogenation component doesn`t improve the catalytic activity. It can be concluded that the H-ferrierite is an excellent dehydration component for its high acidity and that the methanol synthesis can be limitant in the process of direct synthesis of DME from syngas.

Histone deacetylases (HDACs) are a class of enzymes that play a crucial role in DNA expression by removing an acetyl group from the ɛ-N-acetyl lysine residue on histone proteins. Out of 18 isoforms of HDAC enzymes which are classified into 4 classes, only 11 of them are metalloenzymes that require zinc for its catalytic activity. HDACs are considered promising target for drug development in cancer and other parasitic diseases due to their role in gene expression. Histone deacetylase inhibitors (HDACi) can cause cell cycle arrest, and induce differentiation or apotosis. While HDACi shows promising antitumor effects, their mechanism of action and selectivity against cancer cells have not been adequately defined yet. In addition, low oral bioavailability, short half-life time, bone marrow toxicity, and cardiotoxicity limit their use in clinic. Therefore, there is considerable interest in developing compounds with selectivity and specificity towards individual family members of HDACs. The prototypical pharmacophore for HDAC inhibitors consist of a metal-binding moiety that coordinates to the catalytic metal ion within the HDAC active site, a capping group that interacts with the residues at the entrance of the active site and a linker that appropriately positions the metal-binding moiety and capping group for interactions in the active site. It has been shown that modification of cap, cap linking moiety, linker or zinc binding group (ZBG) shows promises of superior potency and isoform selectivity. My thesis research involves manipulating different aspects of the pharmacophoric model to yield not only more potent, selective, and effective drugs but also to help understand the biology of HDAC isoforms. In addition, I was successful in extending studies on HDAC isoforms to other zinc metalloenzymes such as leishmanolysin (gp63) and spliceosome associated zinc-metalloenzymes to understand biology of these zinc metalloenzymes by developing potent and selective small molecule inhibitors. This will aid in improvement of existing therapeutics for treatment of cancer, leishmania, malaria and other genetic disorders.

Histone deacetylase (HDAC) inhibitors (HDACi) have demonstrated a wealth of biological effects, including anti-proliferative, anti-inflammatory, anti-parasitic, and cognition-enhancing activities. The recent FDA approvals of the inhibitors SAHA and FK-228 have validated HDACi clinical use in cutaneous T cell lymphoma, while numerous clinical trials are currently ongoing using HDACi against a variety of disease states. While the future of the HDAC field looks increasingly promising, there are lingering issues hindering broader use. Recent data point to dysregulation of specific HDAC isoforms in many disease states. However, most current HDACi are pan-inhibitors, lacking the specificity to target individual isoforms. Adding to this, there are currently 18 identified HDAC isoforms, and most lack a defined crystal structure, further complicating the task of designing isoform-specific inhibitors. Most importantly, HDACi have demonstrated a lack of efficacy against solid tumors in the clinic, a major obstacle to broader use in cancer therapy. Several of these issues could more fully be addressed through specific targeting of HDACi, and could bring HDACi into wider and more efficacious pharmaceutical use. Targeting the specific tissue or organelle where HDAC dysregulation occurs could confer greater efficacy in vivo. To this end, we have created four classes of compounds: (1) aryltriazolyl HDACi that potently inhibit HDAC activity and prostate cancer cell growth, (2) dual-targeted inhibitors of Topoisomerase II and HDAC and (3) dual-targeted inhibitors of Topoisomerase I and HDAC, both of which have potent inhibition against both target enzymes as well as cancer cell lines, and finally (4) macrocyclic HDACi that potently inhibit the growth of lung cancer cell lines and preferentially target lung tissue in vivo.

Submitted by Edileide Reis (leyde-landy@hotmail.com) on 2013-04-23T13:34:03Z No. of bitstreams: 1 Rubens Barreto.pdf: 1566824 bytes, checksum: a78825b9f4c5548178c44817e0bf8aba (MD5) / Made available in DSpace on 2013-04-23T13:34:03Z (GMT). No. of bitstreams: 1 Rubens Barreto.pdf: 1566824 bytes, checksum: a78825b9f4c5548178c44817e0bf8aba (MD5) Previous issue date: 2008 / Neste trabalho, foi estudado o efeito do conteúdo de irídio na atividade, seletividade e estabilidade de catalisadores de platina, irídio e germânio suportados em alumina, destinados à reforma catalítica de nafta de petróleo. As amostras foram preparadas por impregnação dos sais metálicos (ácido hexacloroplatínico, ácido hexacloroirídico e cloreto de germânio) na g-alumina, de modo a obter 0,3 % de platina e de germânio e teores vairados de irídio (0,03; 0,06; 0,09 e 0,15 %). Os sólidos obtidos foram caracterizados por redução termoprogramada, espectroscopia no infravermelho com transformada de Fourier de monóxido de carbono adsorvido, dessorção à temperatura programada de piridina, desidrogenação de cicloexano e isomerização de npentano, usadas para avaliar as funções metálica e ácida, respectivamente. O desempenho foi avaliado na reforma de n-octano. Os catalisadores usados nessa reação foram analisados por oxidação termoprogramada. Os resultados mostraram que o irídio catalisa a redução da platina, enquanto o germânio exerce um efeito inibidor; esses efeitos dependem da quantidade de irídio nos sólidos, devido às diferentes interações entre os metais e com o suporte. Ambos os metais modificam eletronicamente a platina, tornando-a mais rica (irídio) ou mais deficiente (germânio) em elétrons. Entretanto, nos catalisadores trimetálicos, o efeito do germânio sobre a platina só se torna significativo em concentrações mais elevadas de irídio (0,15 %), que promove a redução do germânio, gerando sólidos com espécies de platina em diferentes estados eletrônicos. A presença do germânio diminui a concentração de sítios ácidos fracos e aumenta aqueles de acidez moderada e forte, enquanto o irídio provoca alterações na concentração de sítios de diferentes forças ácidas, dependendo do seu teor nos sólidos. A atividade catalítica dos sítios metálicos na desidrogenação do cicloexano diminui devido ao germânio enquanto o irídio (em teores superiores a 0,03 %) causa um aumento, devido à sua atividade dedidrogenante; este efeito aumenta com o teor de irídio nos sólidos. Nos catalisadores trimetálicos a atividade dos sítios metálicos é mais baixa que no sistema monometálico de platina, devido ao efeito simultâneo dos dois metais, que podem estar formando ligas com a platina e/ou encobrindo seus sítios ativos diminuindo sua atividade de desidrogenação. A adição de irídio e de germânio a catalisadores de platina suportada em alumina aumenta a sua atividade na isomerização do n-pentano e diminui a atividade de hidrogenólise. Nos catalisadores trimetálicos, a seletividade a compostos aromáticos é inferior àquela dos sistemas bimetálicos e o orto-xileno é o isômero mais favorecido. O germânio aumenta a estabilidade dos catalisadores enquanto o irídio exerce um efeito inverso. A produção de compostos aromáticos diminui com o aumento do teor de irídio no catalisador, enquanto um comportamento inverso é observado com relação à seletividade a produtos isômeros. A razão entre as seletividades a compostos isômeros e aromáticos cresce com o conteúdo de irídio, de modo que se um reformado mais rico em compostos aromáticos é desejado, deve-se usar um catalisador com baixos teores de irídio. Por outro lado, uma composição com concentração de irídio mais alta produz um reformado mais rico em compostos isômeros e, portanto, mais adequado ao uso como combustível. / Salvador

Made available in DSpace on 2016-06-02T19:56:44Z (GMT). No. of bitstreams: 1 3706.pdf: 2821060 bytes, checksum: 5975ad59eeeedfbd6e16578292306171 (MD5) Previous issue date: 2011-08-01 / Universidade Federal de Sao Carlos / The objective of this study was to verify the influence of the Si/Al ratio (11.5, 15.0, 25.0, 40.0 and 140.0) in zeolite ZSM-5 in the conversion, activity, selectivity and stability as bifunctional catalysts (Pt/H-ZSM-5) applied to the isomerization reaction of n-hexane. To prepare the bifunctional catalysts, initially the zeolites were submitted, successively, to ion exchange with ammonium cations, ion exchange cations with platinum, calcination and activation process. From the results of the isomerization of n-hexane, it was observed that with the increase of the Si/Al ratio, that is, decreasing the amount of aluminum, there was a reduction in activity and conversion. This is due to decrease the number of acid sites present, responsible to isomerize the carbocation generated in these sites. In contrast, the increase of the Si/Al ratio leads to a better selectivity to the formation of isomers. Among the catalysts, the Pt/H-ZSM-5 (15.0) showed the best result of conversion and activity. In order to compare the Pt/H-ZSM-5 catalysts, the reaction was carried out using the isomerization catalyst Pt/H-Beta (9.0). This catalyst had the best result that all the others, this result may possibly be due to increased acidity of the material and its morphological characteristics, such as type and diameter of pores etc. and/or the crystallite size of zeolites used. / O objetivo deste estudo foi verificar a influência da razão Si/Al (11,5, 15,0, 25,0, 40,0 e 140,0) na zeólita ZSM-5 através da conversão, atividade, seletividade e estabilidade de catalisadores bifuncionais (Pt/H-ZSM-5) aplicados a reação de isomerização do n-hexano. Para preparar os catalisadores bifuncionais, inicialmente as zeólitas foram submetidas, sucessivamente, a troca iônica das zeólitas com cátions amônio, troca iônica com cátions platina, processos de calcinação e ativação. A partir dos resultados da isomerização do nhexano observou que com o aumento da razão Si/Al, isto é, diminuição da quantidade de alumínio, obteve-se uma redução na atividade e conversão. Tal fato se deve a diminuição do número de sítios ácidos presentes, sendo que os mesmos são responsáveis por isomerizar os carbocátions gerados nos sítios. Em contrapartida, o aumento da razão Si/Al acarreta em uma melhor seletividade a formação dos isômeros. Dentre os catalisadores Pt/H-ZSM-5, o catalisador Pt/H-ZSM-5 (15,0) foi o que apresentou melhor resultado de atividade e conversão. A fim de comparar os catalisadores Pt/H-ZSM-5, a reação de isomerização do nhexano foi realizada utilizando o catalisador Pt/H-Beta (9,0). O mesmo obteve melhor resultado que todos os outros, podendo tal resultado ser, possivelmente, devido a maior acidez do material e suas características morfológicas, como tipo e diâmetro de poros etc. e/ou pelo tamanho do cristalito das zeólitas utilizadas.

Submitted by ANA KARLA PEREIRA RODRIGUES (anakarla_@hotmail.com) on 2017-07-31T11:39:39Z No. of bitstreams: 1 arquivototal.pdf: 9429450 bytes, checksum: 4a660a5b5c0d6e333014749a35080084 (MD5) / Made available in DSpace on 2017-07-31T11:39:39Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 9429450 bytes, checksum: 4a660a5b5c0d6e333014749a35080084 (MD5) Previous issue date: 2016-07-28 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The present study develops bifunctional optical magnetic materials with high lantanide content. For this purpose, magnetite was pepared by co-precipitation method and chelating groups were introduced on the Fe3O4 surface with organosilanes containing ethylenediaminetetraacetic acid (EDTA) derivative, which were previously prepared via reaction between EDTA-dianhydride and aminoalkyl alkoxysilanes agents: 3- (Trimethoxysilyl)propylamine (1N), N-[3(trimethoxysilyl)propyl] ethylenediamine (2N) and N1-(3-trimethoxysilylpropyl)diethylenetriamine) (3N). After coordination of lanthanide ions (Gd3+, Eu3+, Tb3+ or Sm3+), the first coordination sphere of the lanthanide ions in the Ln-EDTA complexes, present on the modified surfaces of Fe3O4 particles, were completed by addition of -diketonate ligands (tta: thenoyltrifluoroacetonate, dbm: dibenzoylmetane, bzac: benzoylacetone and acac: acetylacetone) in order to improve their luminescence properties. The materials were characterized by powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), wavelength dispersive X-ray fluorescence (WDXRF) and Fourrier-transform infrared spectroscopy (FT-IR) as well as by zeta potential measurements and luminescence spectroscopy. The hybrid materials exhibited intense red emission assigned to the 4f-4f transitions of the Eu3+ ion, likewise characteristic green and orange emissions of Tb3+ and Sm3+, respectively, indicating an efficient intramolecular ligand-to-metal energy transfer. The experimental intensity parameters ( 2 and 4), lifetimes (t), as well as radiative (Arad) and non-radiative (Anrad) decay rates of the Eu3+ ion were determined and discussed. / O presente trabalho desenvolve materiais bifuncionais óptico magnéticos contendo altos teores de íons lantanídeos. Para este propósito, a fase magnética foi preparada pelo método de coprecipitação e grupos quelantes foram introduzidos em sua superfície a partir da utilização de organosilanos derivados do ácido etilenodiamino tetra-acético (EDTA), os quais foram sintetizados previamente através da reação entre o dianidrido de EDTA (EDTA-DA) e os seguintes aminoalquil alcoxissilanos: 3-(Trimetoxissilil)propilamina (1N), N-[3(trimetoxissilil)propil]etilenodiamina (2N) e N1-(3-trimetoxissililpropil) dietilenotriamina. Após a coordenação do metal (Gd3+, Eu3+, Tb3+ ou Sm3+), a primeira esfera de coordenação dos íons lantanídeos nos complexos Ln-EDTA, presentes na superfície modificada das partículas de Fe3O4, foi complementada pela adição de ligantes -dicetonas (tta: tenoiltrifluoroacetona, dbm: dibenzoilmetano, bzac: benzoilacetona e acac: acetilacetona) com o objetivo de otimizar as propriedades luminescentes dos materiais. Os materiais foram caracterizados por difração de raios X de pós (XRD), magnetometria de amostra vibrante (VSM), microscopia eletrônica de varredura (SEM), microsopia eletrônica de transmissão (TEM), análise termogravimétrica (TGA), fluorescência de raios X por dispersão em comprimento de onda (WDXRF) e espectroscopia de absorção no infravermelho com transformada de Fourier (FTIR), bem como medidas de potencial zeta e espectroscopia de luminescência. Os materiais híbridos exibiram intensa emissão na cor vermelha, atribuída às transições 4f–4f do íon Eu3+ ion, da mesma forma que emissões na cor verde e laranja, características dos íons Tb3+ e Sm3+, respectivamente, indicando uma eficiente transferência de energia intramolecular do ligante para o metal. Os parâmetros de intensidade ( 2 e 4), o tempo médio de vida do estado emissor (t) e as taxas de decaimento radiativo (Arad) e não radiativo (Anrad) do íon Eu3+ foram determinadas e discutidas.