Rh(III) and Ir(III) dimeric complexes with tunable cyclopentadienyl (Cp) rings have proven versatile for both catalysis and as synthetic precursors. An efficient microwave method to synthesize Rh(III) and Ir(III) dimeric complexes [(η5-ring)MCl]2(μ2-Cl)2, (where (η5-ring)MCl = (η5-Me4C5R)Rh(III)Cl or (η5-Me4C5R)Ir(III)Cl) was developed. A modular design for the substituted cyclopentadienes HC5Me4R was based on Grignard reactions of 2,3,4,5-tetramethylcyclopent-2-en-1-one (R = alkyl, 12 examples; R = aryl, 3 examples) or by SNAr reactions of potassium tetramethylcyclopentadienide with perfluoroarenes (R = perfluoroaryl, 3 examples). Reaction of the Me4CpHR ligands with [M(COD)](μ2-Cl)2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) produced the dimeric complexes [Cp*RMCl]2(μ2-Cl)2 in moderate to excellent yield. The resulting dimers were characterized by nuclear magnetic resonance (NMR) spectroscopy, single-crystal X-ray diffraction (XRD), high-resolution mass spectrometry (HRMS), elemental analysis, and examined as catalysts for oxidative lactonization of 1,4- and 1,5-diols. Oxidative lactonization of 1,4-butanediol to afford γ-butyrolactone proceeded selectively and efficiently using [(η5-Me4C5R)IrCl]2(μ2-Cl)2 as the catalyst. Several R substituents were tested to assess electronic substituent effects. The most active complex contained an electron donating group, R = CHMe2 and successfully catalyzed the formation of diols to lactones across a range of 1,4- and 1,5-diols, generally in high yield. Computational analysis of the rate-determining b-hydrogen elimination reactions provided an atomistic account of observed trends in reaction yield and selectivity as a function of substrate structure, while accounting neatly for the observed selective formation of lactones (vs. succinaldehyde) in the transfer dehydrogenation of 1,4-butyrolactone. / Doctor of Philosophy / Rhodium(III) and iridium(III) complexes are useful synthetic precursors, catalysts, and biologically active compounds. This dissertation explores a rapid synthesis of these metal complexes and their subsequent catalytic applications with 1,4- and 1,5-diols. The oxidative lactonization of diols with rhodium and iridium complexes is an attractive one-pot synthesis, opening a variety of lactones to be produced. Structural studies involving novel fluorinated rhodium and iridium chloro-bridged dimers are discussed in detail.

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>

Relata-se um estudo sobre o processo de eletrossorção do n-propanol sobre eletrodos de platina eletrodispersa em soluções de H2SO4 1 N, a diferentes temperaturas (12 a 51 ºC) e potencíais (0,30 a 0,60 V). São abordados os aspectos relacionados com a cinética de adsorção dos possíveis intermediários formados na desidrogenação do n-propanol, bem como a determinação das constantes de velocidade em cada etapa. São apresentadas as energias de ativação do processo de adsorção para graus de cobertura, &#952; = 0 e &#952; &#8800; 0. A adsorção do álcool estudado a potencial controlado na região da dupla camada elétrica, ocorre através da desidrogenação da molécula, seguida pela ionização do hidrogênio adsorvido. A isoterma cinética de adsorção foi obtida a partir dos cronoamperogramas de desidrogenação do álcool e mostra uma variação linear de &#952; com o logaritmo do tempo de adsorção (t), para 0,25 < &#952; < 0,80. Por outro lado, a relação entre E = f (log li), onde li é a máxima corrente não estacionária obtida a t = 0, é linear com coeficiente angular igual a 2,3 (2 RT/F). Esse valor indica que no início da adsorção do n-propanol, apenas um elétron está envolvido no processo. Da mesma maneira que no metanol, supõe-se que a desidrogenação do n-propanol não ocorre através da eliminação simultânea dos dois átomos de hidrogênio ligados no carbono-&#945;, mas por duas etapas consecutivas de desidrogenação: R - CH2 - OH j1&#8594; R - .CH - OH + H+ + e- ( 1 ) R - .CH - OH j2&#8594; R - ..C - OH + H+ + e- ( 2 ) Desse modo, a corrente anódica não estacionária (j), proveniente da ionização do hidrogênio formado na desidrogenação do n-propanol é resultante da soma das correntes j>SUB>1 e j2 produzidas nas reações descritas nas equações (1) e (2). Quando o tempo de adsorção é muito curto, isto é , j2 = 0, a corrente não estacionária é determinada apenas pela adsorção da espécie R-.CH-OH. Considerando esta hipótese e as isotermas de Temkin e Elovich foi obtida uma equação que descreve o grau de cobertura pela espécie R-.CH-OH, (&#952;1) em função do tempo. &#952;1 = - Qmáx B/k2t (1-A-B ln t) + k1/k2 onde Qmáx é a carga máxima de cobertura, k1 e k2 são as constantes de velocidade de adsorção das espécies R-.CH-OH e R-..C-OH, respectivamente, A e B são as constantes da equação de Elovich. A equação precedente permitiu determinar as constantes de velocidade de adsorção k1 e k2. A partir desses valores em diferentes temperaturas foram obtidas as energias de ativação para as reações (1) e (2). Verificou-se que os tempos de máxima cobertura por R.CHOH e de inflexão, obtidos respectivamente de &#952;1= f (log t) e j-1 = f(t), são comparáveis para dada temperatura e potencial. / The kinetics and mechanism of n-propanol adsorption on a platinized platinum electrode was studied in 1 N H2SO4 at several temperatures, by means of the potential pulse method. Between 0.30 V and 0.60 V (RHE), the adsorption occurs via a dehydrogenation of the &#945;-carbon, followed by a rapid ionization of the adsorbed hydrogen atoms. The kinetic isotherms obtained by integration of the chronoamperograms show a linear variation of the surface coverage, &#952;, with logarithm of the adsorption time, tads, in the range 0.25 &#8804; &#952; &#8804; 0.80. This indicates that the adsorption rate can be expressed in tems of an Elovich equation. It is shown that the relation Eads vs log Ii, where Eads is the adsorption potential and Ii is the maximum non-stationary current at t = 0, is a straight line with a slope equal to 2.3[2RT/F], independently of the temperature. These data show that the initial adsorption step envolves a monoelectronic charge transfer, and can be represented by the following equation: R-CH2-OH j1&#8594; R-.CH-OH + H+ + e- ( 1 ) Therefore, it is assumed that the adsorption occurs via a two step consecutive reaction, given by equations (1) and (2): R-.CH-OH j2&#8594; R-..C-OH + H+ + e- ( 2 ) with the two adsorbed species R-.CH-OH and R-..C-OH characterized by their degree of coverage &#952;1 and &#952;2, respect ively. The non-stationary anodic current, j, is then the sum of currents j1 and j2 resulting from reactions described by equations (1) and (2). When the adsorption time is very short, it can be assumed that j = j1 + j2 &#8776; j1, and that &#952; = &#952; 1 + &#952;2 &#8776; &#952;1. From those assumptions, the following equation relating &#952;1 with t was obtained: &#952;1 = -Qmáx . B/[k2.t (1-A-B). ln t ] + k1/k2 (3) where Qmáx is the charge related with the maximum surface coverage, k1 and k2 the apparent rate constants of reactions (1) and (2), respectively, and A and B are constants from the Elovich equation. Equation (3) permitted the evaluation of the rate constants k1 and k2 for distinct Eads values. From the data at different temperatures, the apparent activation energies of both reactions were calculated.

Submitted by Jaqueline Silva (jtas29@gmail.com) on 2014-09-15T18:32:41Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-09-15T18:36:32Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) / Made available in DSpace on 2014-09-15T18:36:32Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) Previous issue date: 2014-03-11 / In this work, activated carbon beads were prepared through carbonization of styrene-divinylbenzene (Sty-DVB) copolymers synthesized in the presence of soybean oil as diluent and cobalt ferrite nanoparticles dispersed in the organic phase. Firstly, a cobalt ferrite gel was prepared through co-precipitation technique with posterior surfactant action by oleic acid. The copolymer and the composites containing cobalt ferrite were obtained through suspension polymerization. Four matrixes were obtained, which have the following differences: the cobalt ferrite content (2 or 5 %), the amount of hydroxyethylcellulose used in the synthesis and the realization or not of a purification step before thermal treatments. Soybean oil was chosen as diluents in order to evaluate its effects on the synthesized materials considering the polymerization possibility due fat acid unsaturations and its low volatility. All synthesized materials were characterized by the following analysis: DRX, FTIR, TGA, nitrogen adsorption measurements (specific surface area, pore volume and pore size distribution), MEV and catalytic activity in the ethyl-benzene dehydrogenation reaction. Further, the composites had metal content evaluate by AAS. The soybean oil and the ferrite gel had a strong influence on the textural properties of copolymers and their respective activated carbons. All obtained activated carbons were active in relation to ethylbenzene dehydrogenation reaction. However, the activated carbon obtained from pure copolymer, i.e., without cobalt ferrite, presented the highest specific surface area, catalytic activity and selectivity. This catalyst also had the best stabilization of catalytic properties during evaluated reaction time. / Neste trabalho, esferas de carvão ativado foram preparadas através da carbonização de copolímeros estireno-divinilbenzeno (Sty-DVB) sintetizados na presença de óleo de soja como diluente e de nanopartículas de ferrita de cobalto dispersas na fase orgânica. Inicialmente, preparou-se um gel de ferrita de cobalto através da co-precipitação da ferrita de cobalto e posterior surfactação da mesma por ácido oleico. O copolímero e os compósitos poliméricos contendo gel de ferrita de cobalto foram obtidos através da técnica de polimerização em suspensão. Quatro matrizes foram sintetizadas, diferenciando-se apenas quanto ao conteúdo de gel de ferrita de cobalto (2 ou 5%), quantidade de hidroxietilcelulose usada na síntese e realização ou não de uma etapa de purificação antes dos tratamentos térmicos. O óleo de soja foi escolhido como diluente, a fim de avaliar a interferência de suas propriedades nos materiais sintetizados considerando a possibilidade de polimerizar-se devido à insaturações dos ácidos graxos e a sua baixa volatilidade. Todos os materiais sintetizados foram submetidos à caracterização através de análises de DRX, FTIR, TGA, adsorção física de nitrogênio (medidas de área superficial específica, volume de poros e distribuição de tamanhos de poros), MEV e atividade catalítica na reação de desidrogenação do etilbenzeno. Além disso, os compósitos (copolímeros contendo gel de ferrita de cobalto) tiveram os teores de metais quantificados por AAS. Foi verificado que o óleo de soja e a presença do gel de ferrita durante a polimerização influenciam nas propriedades texturais dos copolímeros e dos carvões sintetizados. Todos os carvões ativados obtidos mostraram-se ativos na reação de desidrogenação do etilbenzeno. Entretanto, o carvão obtido do copolímero puro (sem ferrita de cobalto) foi o que apresentou maiores valores de área superficial específica, taxas de conversão e de seletividade, além de uma maior estabilização durante os testes catalíticos realizados.

Relata-se um estudo sobre o processo de eletrossorção do n-propanol sobre eletrodos de platina eletrodispersa em soluções de H2SO4 1 N, a diferentes temperaturas (12 a 51 ºC) e potencíais (0,30 a 0,60 V). São abordados os aspectos relacionados com a cinética de adsorção dos possíveis intermediários formados na desidrogenação do n-propanol, bem como a determinação das constantes de velocidade em cada etapa. São apresentadas as energias de ativação do processo de adsorção para graus de cobertura, &#952; = 0 e &#952; &#8800; 0. A adsorção do álcool estudado a potencial controlado na região da dupla camada elétrica, ocorre através da desidrogenação da molécula, seguida pela ionização do hidrogênio adsorvido. A isoterma cinética de adsorção foi obtida a partir dos cronoamperogramas de desidrogenação do álcool e mostra uma variação linear de &#952; com o logaritmo do tempo de adsorção (t), para 0,25 < &#952; < 0,80. Por outro lado, a relação entre E = f (log li), onde li é a máxima corrente não estacionária obtida a t = 0, é linear com coeficiente angular igual a 2,3 (2 RT/F). Esse valor indica que no início da adsorção do n-propanol, apenas um elétron está envolvido no processo. Da mesma maneira que no metanol, supõe-se que a desidrogenação do n-propanol não ocorre através da eliminação simultânea dos dois átomos de hidrogênio ligados no carbono-&#945;, mas por duas etapas consecutivas de desidrogenação: R - CH2 - OH j1&#8594; R - .CH - OH + H+ + e- ( 1 ) R - .CH - OH j2&#8594; R - ..C - OH + H+ + e- ( 2 ) Desse modo, a corrente anódica não estacionária (j), proveniente da ionização do hidrogênio formado na desidrogenação do n-propanol é resultante da soma das correntes j>SUB>1 e j2 produzidas nas reações descritas nas equações (1) e (2). Quando o tempo de adsorção é muito curto, isto é , j2 = 0, a corrente não estacionária é determinada apenas pela adsorção da espécie R-.CH-OH. Considerando esta hipótese e as isotermas de Temkin e Elovich foi obtida uma equação que descreve o grau de cobertura pela espécie R-.CH-OH, (&#952;1) em função do tempo. &#952;1 = - Qmáx B/k2t (1-A-B ln t) + k1/k2 onde Qmáx é a carga máxima de cobertura, k1 e k2 são as constantes de velocidade de adsorção das espécies R-.CH-OH e R-..C-OH, respectivamente, A e B são as constantes da equação de Elovich. A equação precedente permitiu determinar as constantes de velocidade de adsorção k1 e k2. A partir desses valores em diferentes temperaturas foram obtidas as energias de ativação para as reações (1) e (2). Verificou-se que os tempos de máxima cobertura por R.CHOH e de inflexão, obtidos respectivamente de &#952;1= f (log t) e j-1 = f(t), são comparáveis para dada temperatura e potencial. / The kinetics and mechanism of n-propanol adsorption on a platinized platinum electrode was studied in 1 N H2SO4 at several temperatures, by means of the potential pulse method. Between 0.30 V and 0.60 V (RHE), the adsorption occurs via a dehydrogenation of the &#945;-carbon, followed by a rapid ionization of the adsorbed hydrogen atoms. The kinetic isotherms obtained by integration of the chronoamperograms show a linear variation of the surface coverage, &#952;, with logarithm of the adsorption time, tads, in the range 0.25 &#8804; &#952; &#8804; 0.80. This indicates that the adsorption rate can be expressed in tems of an Elovich equation. It is shown that the relation Eads vs log Ii, where Eads is the adsorption potential and Ii is the maximum non-stationary current at t = 0, is a straight line with a slope equal to 2.3[2RT/F], independently of the temperature. These data show that the initial adsorption step envolves a monoelectronic charge transfer, and can be represented by the following equation: R-CH2-OH j1&#8594; R-.CH-OH + H+ + e- ( 1 ) Therefore, it is assumed that the adsorption occurs via a two step consecutive reaction, given by equations (1) and (2): R-.CH-OH j2&#8594; R-..C-OH + H+ + e- ( 2 ) with the two adsorbed species R-.CH-OH and R-..C-OH characterized by their degree of coverage &#952;1 and &#952;2, respect ively. The non-stationary anodic current, j, is then the sum of currents j1 and j2 resulting from reactions described by equations (1) and (2). When the adsorption time is very short, it can be assumed that j = j1 + j2 &#8776; j1, and that &#952; = &#952; 1 + &#952;2 &#8776; &#952;1. From those assumptions, the following equation relating &#952;1 with t was obtained: &#952;1 = -Qmáx . B/[k2.t (1-A-B). ln t ] + k1/k2 (3) where Qmáx is the charge related with the maximum surface coverage, k1 and k2 the apparent rate constants of reactions (1) and (2), respectively, and A and B are constants from the Elovich equation. Equation (3) permitted the evaluation of the rate constants k1 and k2 for distinct Eads values. From the data at different temperatures, the apparent activation energies of both reactions were calculated.

Steroids are important biological regulators existing in hormones which are used to control metabolism of the body. There are widespread applications in the pharmaceutical industry. Drugs of steroid nature - anti-inflammatory and antiallergic corticosteroids, diuretics, anabolics, androgens, gestagens, contraceptives, antitumor medications, etc. - are now widely used in human and veterinary medicine. Nowadays, biotechnological modifications of steroids are preferred over chemical modifications as a green chemistry since they are more likely to be natural. In this work four different Fusarium species were screened for bioconversion of steroids into pharmaceutically important derivatives of steroids by reduction, dehydrogenation, side-chain degradation etc. on A and D-rings containing many active sites. Fusarium spp. used in this work, namely Fusarium roseum OUT 4019, Fusarium anguioides OUT 4017, Fusarium bulbigenum OUT 4115 and Fusarium solani OUT 4021 are filamentous fungi, which belong to the class of Deuteromyces. They can grow using simple carbohydrates and nitrogen sources. 4-androstene-3,17-dione conversion is used as a model system. Under same environmental conditions it is found that whole cells of Fusarium roseum OUT 4019 can dehydrogenate at C-1 and C-2 producing androsta-1,4-diene-3,17-dione and also reduce at C-17 in addition to dehydrogenate at C-1 and C-2 producing 17-hydroxyandrosta- 1,4-dien-3-one, Fusarium anguioides OUT 4017 can reduce at C-17 producing 17-hydroxy-androst-4-en-3-one, Fusarium solani OUT 4021 can reduce at C-3 and C-17 producing androst-4-ene-3,17-diol at 25 C&deg / and 160 rpm with uncontrolled pH. In these conversions, androsta-1,4-diene-3,17-dione, 17-hydroxy-androsta-1,4-dien- 3-one, 17-hydroxy-androst-4-en-3-one, androst-4-ene-3,17-diol were isolated with 54 %, 22 %, 26 %, 90 % yields, respectively. In another study, bioconversion reactions of aromatic methyl ethers by Fusarium roseum OUT 4019 were investigated and for some compounds, cleavage of methyl ether was observed.

Biomass valorization is an interesting alternative to fossil resources, which is frequently performed via heterogeneous catalysis. Designing new catalysts is a challenging task that can be significantly accelerated in silico. However, biomass molecules are often complex and highly oxygenated, hence rendering calculations more difficult and time consuming. Among these compounds, polyols are particularly important. We developed linear relations of the Brønsted-Evans-Polanyi (BEP) type from the DFT study of C-H or O-H bond dissociation elementary steps for a family of monoalcohol molecules on metallic catalysts (Co, Ni, Ru, Rh, Pd, Ir, Pt). Such relations aim at predicting activation energies from reaction energies. The accuracy of the obtained linear energy models is better than 0.10 eV on the sampling set. Then, the relations were applied for the prediction of the dehydrogenation elementary steps of glycerol, chosen as a prototype of polyalcohols, with an accuracy better than 0.10 eV and with a systematic error around ±0.10 eV for Rh. Keeping in mind that the main difference between glycerol and monoalcohols comes from intramolecular H-bonds present in the former, we designed linear relations for water-assisted dehydrogenation of monoalcohols. These new relations allowed us to improve the prediction on glycerol and to eliminate the systematic deviation in the case of OH bond breaking. Even if in this study we focused on glycerol dehydrogenation, similar methods may be applied to other polyols with other chemical reactions, and considerably speed up the computational design of solid catalysts. This work paves the way for the development of novel numerical techniques to address the issue of biomass conversion.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-08-30T16:14:19Z No. of bitstreams: 1 Tese de Doutorado - Sérgio Botelho de Oliveira.pdf: 18232715 bytes, checksum: b87397cefa6c939563af6c9f1aeaa634 (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-02T15:22:42Z (GMT) No. of bitstreams: 1 Tese de Doutorado - Sérgio Botelho de Oliveira.pdf: 18232715 bytes, checksum: b87397cefa6c939563af6c9f1aeaa634 (MD5) / Made available in DSpace on 2016-09-02T15:22:42Z (GMT). No. of bitstreams: 1 Tese de Doutorado - Sérgio Botelho de Oliveira.pdf: 18232715 bytes, checksum: b87397cefa6c939563af6c9f1aeaa634 (MD5) / Resinas de estireno e divinilbenzeno são materiais atrativos para muitos propósitos por causa das suas propriedades, variedade de grupos funcionais na superfície e porosidade, que podem ser controlados na síntese. Essas características também favorecem a produção de suportes e catalisadores baseados em carvão, com elevada áreas superficiais específicas e com grupos funcionais na superfície, que podem agir como sítios ativos. Eles podem ser usados em muitas reações, entre elas, a desidrogenação do etilbenzeno para produzir estireno. Esse monômero é comercialmente produzido pela desidrogenação do etilbenzeno em presença de vapor de água, mas este processo possui um custo elevado e, portanto, há a necessidade de novas alternativas de produção. A substituição do vapor pelo dióxido de carbono é uma das opções mais atrativas para diminuir o custo energético e, dessa forma, muitos estudos têm sido conduzidos para obter novos catalisadores para essa reação. Com este objetivo, neste trabalho foi descrita a preparação de catalisadores de cobre suportado em carvão ativado polimérico, assim como sua avaliação na desidrogenação do etilbenzeno em presença de dióxido de carbono. O carvão ativado polimérico foi preparado a partir do copolímero estireno e divinilbenzeno sulfonado, seguido da calcinação (250 oC), carbonização (900 oC) e ativação (800 oC). Os íons cobre foram adsorvidos nesse sólido por diversos métodos. O efeito dos metais alcalinos (magnésio e sódio) nas propriedades texturais e catalíticas dos sólidos foi também estudado. As amostras foram caracterizadas por espectrofotometria de absorção atômica, espectroscopia de infravermelho com transformada de Fourier, medidas de área superficial específica e de porosidade, difração de raios X, microscopia eletrônica de varredura e espectroscopia de energia dispersiva. Os catalisadores foram avaliados na desidrogenação do etilbenzeno em presença de dióxido de carbono, a 1 atm e em diversas temperaturas (400, 500 e 600oC). Foram obtidos sólidos com diferentes propriedades texturais e catalíticas, dependendo do método de preparação, assim como da presença de metais. O uso de uma razão de estireno/divinilbenzeno de 15/85 levou à produção de um carvão ativado com a elevada área superficial específica, capaz de adsorver grandes quantidades de cobre, devido aos grupos funcionais gerados na superfície. As propriedades texturais e catalíticas do carvão ativado com cobre foram fortemente dependentes do método de incorporação do cobre. O catalisador mais ativo foi produzido quando o cobre foi adsorvido no carvão ativado previamente oxidado por quatro vezes sucessivas, utilizando-se uma mistura de oxigênio em nitrogênio. Em ambos os sólidos CA e CON, o cobre e os grupos funcionais superficiais no carvão ativado foram ativos na reação. A adição do magnésio aumentou a seletividade a estireno, devido à neutralização de sítios ácidos residuais. O catalisador produzido foi mais ativo do que uma amostra de um catalisador comercial avaliado na presença de vapor, mostrando que o catalisador é promissor para fins industriais / Styrene and divinylbenzene resin is an attractive material for several purposes because of its properties, such as the variety of surface functional groups and porosity, which can be controlled during the synthesis. These characteristics also favor the production of carbon-based supports and catalysts with high specific surface areas and with functional groups on the surface, which can act as active sites. They can be used for several reactions, among them, the ethylbenzene dehydrogenation to produce styrene. This monomer is commercially produced by the ethylbenzene dehydrogenation in the presence of steam but it is a high cost process and thus new alternatives are much needed. The replacement of steam by carbon dioxide is one of the most attractive options to decrease the energy cost and thus several studies have been carried out to find new catalysts for this reaction. With this goal in mind, the preparation of catalysts based on polymeric activated carbon-supported copper, as well as their evaluation in ethylbenzene dehydrogenation in the presence of carbon dioxide, was described in this work. The polymeric activated carbon was prepared from sulfonated styrene- divinylbenzene copolymer, followed by calcination (250 oC), carbonization (900 oC) and activation (800 oC). Copper ions were adsorbed in these solids by several methods. The effect of alkaline metals (magnesium and sodium) on the textural and catalytic properties of the solids was also studied. Samples were characterized by atomic absorption spectrometry, Fourier transform infrared spectroscopy, specific surface area and porosity measurements, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The catalysts were evaluated in ethylbenzene dehydrogenation in the presence of carbon dioxide at 1 atm and several temperatures (400, 500 and 600 oC). Solids with different textural and catalytic properties were obtained depending on the preparation method as well as on the presence of metals. The use of a styrene to divinylbenzene ratio of 15/85 leads to the production of an active carbon with the highest specific surface area, which is also able to adsorb a large amount of copper, due to the surface functional groups generated. The textural and catalytic properties of the activated carbon- supported copper largely depended on the method of the copper incorporation. The most active catalyst was produced when copper was adsorbed on activated carbon previously oxidized four times successive with a gas mixture of oxygen in nitrogen. In these solids CA and CON, both copper and the surface functional groups on the activated carbon were active for the reaction. The addition of magnesium increased the selective to styrene, due to the neutralization of the acidic sites on the surface, active for the production of toluene and benzene. The further rising of the catalyst with a sodium hydroxide solution increased the selectivity even more, due to the neutralization of the residual acidic sites. The catalyst produced was more active than a commercial sample evaluated in t

Orientador: Teresa Massako Kakuta Ravagnani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-08T19:44:43Z (GMT). No. of bitstreams: 1 Araujo_PauloJardelPereira_M.pdf: 1672087 bytes, checksum: 39df6a7017efe009f53dbd9aecb301b1 (MD5) Previous issue date: 2007 / Resumo: Estireno é um importante monômero na fabricação de termoplásticos e borrachas sintéticas. Grande parte de sua produção é baseada na desidrogenação catalítica do etilbenzeno. O aumento da produtividade do estireno pode ser alcançado utilizando-se membranas permseletivas para remoção do hidrogênio, suprimindo as reações reversíveis e secundárias. Este trabalho apresenta a simulação do processo de desidrogenação em um reator tubular de leito fixo catalítico envolto em membrana composta permseletiva. A modelagem matemática desenvolvida considera os diferentes mecanismos de transporte de massa que prevalecem nas várias camadas da membrana e no leito fixo catalítico. A remoção do Hidrogênio do leito catalítico foi realizada estabelecendo-se um gradiente de potencial químico de hidrogênio através da membrana. Duas formas de remoção de hidrogênio foram estudadas: pela aplicação de uma diferença de pressão através da membrana e pelo arraste com gás inerte. Um programa computacional foi implementado para descrever os perfis de temperatura, pressão e concentração ao longo de todo o reator, bem como a conversão do etilbenzeno, seletividade e produtividade de estireno. Comparando os resultados obtidos no leito fixo convencional operando na condição industrial padrão com os obtidos na aplicação de diferença de pressão através da membrana, observou-se um acréscimo na conversão de etilbenzeno de 19,89 % na mesma seletividade do estireno, representando um aumento de 19,12 % na produtividade de estireno. Este mesmo aumento foi também alcançado com o uso de gás de arraste inerte. Por este motivo, este procedimento é a opção mais recomendada, por agregar custo menor ao processo. Através da simulação do sistema em diferentes condições do processo e configurações do reator e da membrana, obteve-se um acréscimo de 40,98 % na produtividade de estireno comparada a do processo com leito fixo convencional / Abstract: Styrene is an important monomer in the manufacture of thermoplastic and synthetic rubbers. Most of the production is based on the catalytic dehydrogenation of ethylbenzene. The increase of the styrene productivity can be reached using permselectives membranes for hydrogen removal, suppressing the reversible and secondary reactions. This work presents the simulation of dehydrogenation process in tubular fixed bed reactor wrapped with permselective composite membrane. The mathematical modeling was developed considering the different mechanisms of mass transport that prevail in several membrane layers and in catalytic fixed bed. The removal of the permeated hydrogen was carried out establishing a gradient of chemical hydrogen potential through the membrane. Two forms of hydrogen removal were studied: the application of transmembrane pressure drop and the employment of inert sweep gas. A computational program was implemented to describe the profiles of temperature, pressure and concentration throughout all reactor, as . well as the ethylbenzene conversion, styrene selectivity and productivity. Comparing the simulation results obtained for conventional fixed bed reactor carried on standard industrial operation condition with application transmembrane pressure drop form, it shows an increase of 19.89 % in ethylbenzene conversion in the same styrene selectivity for, meaning an increase of 19.12% in styrene productivity. The same addition was obtained when the inert sweep gas was employed. Therefore, this last proceeding has been recommended as the better option, due to its lower operation cost. Through the system simulation at various operation conditions, using different reactor and membrane configurations, an increase of 40.98 % in the styrene productivity was reached comparing to conventional fixed bed process / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

L'un des objectifs de l'industrie aéronautique est, aujourd'hui, de fournir une flotte aérienne plus efficace et plus respectueuse de l'environnement. C'est dans ce contexte qu'une nouvelle génération d'avions dit plus « électrifiés » (MEA, More Electrified Aircraft) est développée. Dans cette optique, l'utilisation multifonctionnelle d'une pile à combustible multifonctionnelle dans l'aéronef permettrait de réduire et de simplifier le nombre de systèmes embarqués. Toutefois l'intégration d'une pile à combustible à l'intérieur d'un avion pose un problème majeur :l'approvisionnement en hydrogène. Pour surmonter cet obstacle, la génération d'hydrogène à bord de l'avion semble être une solution appropriée étant donné la possibilité de produire le combustible à partir du kérosène JET-A1. Les technologies de reformage classique d'hydrocarbures comme le steam reforming, l'oxydation partielle et le reformage autothermique ne sont pas réalisables à bord d'un avion. C'est pourquoi un nouveau concept de génération d'hydrogène, à bord de l'aéronef, a été développé dans ce travail : La déshydrogénation partielle (PdH, PartialDeshydrogenation) du kérozène. Le kérosène modifié par la déshydrogénation est alors réinjecté dans le pool de carburant. L'objectif d'Airbus concernant ses futurs avions est d'embarquer un système de production d'hydrogène avec une capacité volumétrique de 80 gL-1 et une production d'hydrogène de 7.5 kg h-1 pour alimenter une pile à combustible d'une puissance de 125 KW. Dans ce projet, la cible à atteindre pour l'unité de production est : 1000 NLH2kgcat-1h-1 d'hydrogène avec une pureté supérieure à 98 % et une durée de vie de 100 heures.Ce travail s'intéresse à la faisabilité du concept PDh à partir d'études théoriques et expérimentales. Les études théoriques ont pour but de répondre aux questions fondamentales telles que la possibilité de déshydrogéner un hydrocarbure à basse température, la nature des espèces hydrocarbonées dans le carburant et sa pression de vapeur, la température idéale assurant le meilleur compromis entre la production d'hydrogène et la formation de coke qui désactive le catalyseur. Les études expérimentales ont été conduites à la fois à partir de catalyseurs d'hydrogénation-déshydrogénation commerciaux et à partir de catalyseurs optimisés pour la réaction PDh, préparés en laboratoire. A la lumière de ce travail, le matériau présentant les meilleures performances est un catalyseur bimétallique à base de platine et d'étain supporté sur l'alumine-g. Les résultats des différentes études expérimentales sont positifs et montrent qu'à basse température (350 °C) et P = 10 bar, la production d'hydrogène est de 435.3 NLH2kgcat-1h-1 avec une pureté supérieure à 98 % et avec une durée de vie extrapolée à 21.7 h. A haute température (450 °C) et P = 10 bar la pureté du gaz chute à 36.3% mais la production d'hydrogène de 1157.05 NLH2kgcat-1h-1, pour une durée de vie de21.7 h, est plus élevée que la cible fixée. Les courtes durées de vie observées dans les deux conditions d'expérience sont attribuées au dépôt de coke sur le catalyseur et à la présence de soufre au sein du kérosène.Toutefois ces travaux ont permis de montrer la pertinence et la faisabilité du concept PDh même si des recherches complémentaires demeurent nécessaires pour une application embarquée. / The aviation industry is in support to bring greener and more efficient aircraft into the skies, as new generation of more electrified aircraft (MEA) are being developed. One technology on this roadmap is to implement a fuel cell on-board an aircraft, which has a “multi-functional” approach and can reduce many on-board systems & simplify operations for an aircraft. However, the implementation of a PEMFC on-board has one drawback – the supply of hydrogen. On-board hydrogen generation poses certain advantageous as there is already a hydrogen-rich material on all aircrafts, aviation fuel Kerosene Jet A-1. However, conventional fuel reforming technologies such as steam reforming, partial oxidation (thermal or catalytic) and autothermal reforming are not feasible for aircraft application. Therefore, a novel hydrogen generation concept was developed in this work that is geared towards on-board operation called Partial Dehydrogenation (PDh). For future aircraft, Airbus is aiming to have a hydrogen delivery system with a volumetric capacity of ca. 80 g L--1, delivering 7.5 kg hr-1 of hydrogen to power a 125 kWe PEMFC on-board. However to nurture this new hydrogen generation concept, milestones were set to focus the development which is limited to 1000 NLH2 kgcat-1 hr-1 with >98 % pure hydrogen with a lifetime of 100 hours. This work investigates the feasibility of the concept of PDh, from theoretical studies to experimental investigations, paving the way to appraise the discoveries so far for aircraft applicability. Theoretical studies were aimed at answering fundamental questions such as the potential of low temperature dehydrogenation, hydrogen availability from Kerosene Jet A-1, hydrocarbon species within the fuel, the vapour pressure of such a complex fuel, and the ideal temperature range to operate for hydrogen liberation with limit coke formation. Experimental investigations were performed with commercial hydrogenation-dehydrogenation catalysts, as well as experimental catalysts designed for the PDh process. In which the best catalyst found thus far is a bimetallic Tin-Platinum catalyst on ã-alumina. The overall findings of the experimental investigation were positive and can be summed up in two different stages of development. At low temperature of 350 °C at 10 bar, hydrogen produced was at 435.3 NLH2 kgcat-1 hr-1, hydrogen purity exceeding 98 % were obtained but with an extrapolated lifetime of 21.7 hours. At higher temperature of 450 °C at 10 bar, hydrogen purity dropped to 36.3 % but exceeded the activity goal with 1157.05 NLH2 kgcat-1 hr-1, however, the lifetime was still extrapolated to be in the region of 21.7 hours. Coke deposition and the influence of sulphur can be explained by the short lifetime found within the experiments. Nevertheless, the novel hydrogen production concept PDh has been showed to be possible, but further research and development is required to achieve on-board applicability.