Orientador: Ronaldo Aloise Pilli / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-04T07:43:02Z (GMT). No. of bitstreams: 1 Lapis_AlexandreAugustoMoreira_D.pdf: 8284160 bytes, checksum: ba07d6bcefdd0d627c338d01a09fa12e (MD5) Previous issue date: 2005 / Doutorado / Quimica Organica / Doutor em Quimica

[pt] O processo industrial para a síntese de amônia utiliza um catalisador de ferro triplamente promovido, operando em condições drásticas a temperaturas entre 400 e 700°C e a uma pressão bastante elevada (aproximadamente 300 atm). Novos catalisadores vêm sendo estudados, em substituição ao ferro, para aumentar ainda mais a produção de NH3. A principal vantagem dos catalisadores a base de rutênio é que eles são menos sensíveis à contaminação pela amônia que os catalisadores a base de ferro. O objetivo deste trabalho foi avaliar catalisadores de rutênio suportados em zeólitas e hidrotalcita promovidos por cátions básicos para a síntese de amônia. Foi verificada a influência do tipo de suporte nos catalisadores de rutênio, do tipo e forma de introdução dos precursores de rutênio, o papel da adição de cátions promotores (Ba e Cs) sobre a interação metal-suporte e na atividade dos catalisadores de rutênio na reação de síntese de amônia. Os catalisadores de rutênio suportados na hidrotalcita apresentaram as maiores conversões na reação de síntese de amônia. Eles apresentaram os mais altos níveis de dispersão e redução das partículas metálicas. O bário, apesar de ter diminuído menos a interação do rutênio com o suporte, se mostrou um promotor mais efetivo na reação de síntese de amônia que o césio. A ordem de introdução do bário apresentou efeitos diferentes, dependendo do suporte, sobre o desempenho dos catalisadores de rutênio. O método de impregnação com carbonila de rutênio se mostrou o mais efetivo, conduzindo a catalisadores de rutênio mais básicos e mais ativos na reação de síntese de amônia. / [en] The industrial ammonia synthesis process uses a triple promoted iron catalyst, operating at drastic temperature conditions between 673K and 973K, and high pressure (300atm). New catalysts have been studied, replacing iron, to increase NH3 production. The main advantage of Ru-based catalysts is that they are less sensitive to poisoning by ammonia than Fe-based catalysts. The aim of this work was to evaluate ruthenium catalysts supported on zeolites and hydrotalcite promoted by basic cations for ammonia synthesis reaction. The influence of the support type on the ruthenium catalysts and of introduction way of the ruthenium precursors was verified. Also the hole of the cationic promoters (Ba and Cs) on the metal-support interaction and on the ruthenium catalysts activity in the ammonia synthesis reaction was examined. The ruthenium catalysts supported on hydrotalcite had the highest conversion in the ammonia synthesis reaction. They presented the highest degrees of dispersion and reduction of metallic particles. The barium, despite having decreased the interaction between the ruthenium and the support, showed to be a more effective promoter on the synthesis of ammonia than the cesium. The barium introduction order resulted in different effects over the ruthenium catalysts performance depending on the support. The impregnation method with ruthenium carbonil was the most effective, leading to more basic ruthenium catalysts and more actives in the ammonia synthesis reaction.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-09-26T13:21:16Z No. of bitstreams: 1 Versão final_Juliane Lima.pdf: 3005841 bytes, checksum: ce8a2d085212284f1f3504f349cae58c (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-26T14:18:35Z (GMT) No. of bitstreams: 1 Versão final_Juliane Lima.pdf: 3005841 bytes, checksum: ce8a2d085212284f1f3504f349cae58c (MD5) / Made available in DSpace on 2016-09-26T14:18:35Z (GMT). No. of bitstreams: 1 Versão final_Juliane Lima.pdf: 3005841 bytes, checksum: ce8a2d085212284f1f3504f349cae58c (MD5) / CNPq / O biodiesel é um combustível limpo derivado de fontes renováveis, óleos vegetais ou gordura animal. Na sua produção, cerca de 10% em massa do óleo vegetal utilizado como insumo é convertido em glicerina, existindo, dessa forma, grande incentivo para a utilização deste subproduto. Por outro lado, a reforma a vapor da glicerina é um processo com grande potencial para a produção de hidrogênio destinado às células a combustível e aos motores de combustão interna. De modo a obter catalisadores alternativos para a reforma a vapor de glicerina, neste trabalho, foram preparados sólidos baseados em níquel e/ou rutênio suportado(s) em óxido de lantânio a partir de dois métodos: (i) impregnação de nitrato de níquel e/ou de rutênio em óxido de lantânio para obter amostras do tipo (NiO)1-x(RuO)x/La2O3 e (ii) decomposição de sólidos com estruturas perovskita do tipo LaNi1-xRuxO3 (x= 0, 0,1 e 1). Os catalisadores foram obtidos por redução desses precursores a 650, 800 ou 1000 oC, dependendo do método de preparação ou amostra, sob fluxo de hidrogênio. As amostras foram caracterizadas por espectroscopia no infravermelho com transformada de Fourier, difração de raios X, medida de área superficial específica e redução à temperatura programada. A avaliação dos catalisadores na reação de reforma a vapor do glicerol (como molécula modelo) foi conduzida sob pressão atmosférica a 600 ºC, por 5 h. Após a reação, determinou-se o teor de coque depositado sobre os catalisadores. Os sólidos obtidos por impregnação, constituídos por óxido de lantânio, óxido de rutênio, óxido de níquel (NiO) e/ou de compostos de níquel e lantânio (LaNiO3 e La2NiO4), apresentaram áreas superficiais específicas baixas (1,5-11 m².g-1). No caso das amostras obtidas por aquecimento de perovskitas, houve a formação de sólidos com estruturas cristalinas com simetria romboédrica ou ortorrômbica, com áreas superficiais específicas ainda mais baixas (0,5-4,7 m².g-1). Esses sólidos foram mais redutíveis que aqueles obtidos por impregnação e, em todos os casos, o rutênio aumentou a redutibilidade dos sólidos. A atividade e seletividade dos catalisadores obtidos variaram com o método de preparação e a composição dos catalisadores. Quando introduzido no catalisador por impregnação, o rutênio diminuiu a atividade do catalisador de níquel, que foi aumentada no sólido oriundo de perovskitas. As conversões variaram de 68 a 97 % e, em todos os casos, o níquel foi mais ativo que o rutênio. O rendimento a hidrogênio também variou com a presença do rutênio e com o método de preparação dos sólidos. Quando preparados por impregnação, os catalisadores monometálicos conduziram a valores mais elevados que os bimetálicos. Quando obtidos por decomposição de perovskitas, o catalisador isento de níquel levou aos mais baixos valores de rendimento, enquanto aquele contendo os dois metais levou ao valor mais elevado. A presença de rutênio diminui a quantidade de coque formado sobre os catalisadores, durante a reforma a vapor da glicerina, apenas quando os sólidos foram obtidos por impregnação. A amostra contendo níquel e rutênio, e obtida por decomposição de perovskitas, foi o catalisador mais promissor, conduzindo a uma conversão de 97%, rendimento a hidrogênio de 76%. / Biodiesel is a clean renewable fuel derived from vegetable oils or animal fat. About 10% by weight of vegetable oil used as a feedstock is converted into glycerin in its production and thus its use is largely encouraged. On the other hand, the steam reforming of glycerin is a great potential process for the production of hydrogen to feed fuel cells and internal combustion engines. In order to obtain alternative catalysts for steam reforming of glycerin nickel and/or ruthenium supported on lanthanum oxide were prepared in this work by two methods: (i) by impregnation of nickel nitrate and/or ruthenium on lanthanum oxide to obtain (NiO)1-x(RuO)x/La2O3 samples and (ii) by decomposition of solids with perovskite-type structures such as LaNi1-xRuxO3 (x = 0, 0.1 and 1). The catalysts were obtained by reduction of these precursors at 650, 800 or 1000 oC, depending on the method of preparation or sample under hydrogen flow. The samples were characterized by Fourier transform infrared spectroscopy, X- ray diffraction, specific surface area measurements and temperature programmed reduction. The catalysts were evaluated in steam reforming of glycerol (as a molecule model) under atmospheric pressure at 600 oC, for 5 h. After reaction, the coke deposited on the catalyst was determined. The solids obtained by impregnation consisted of lanthanum oxide, ruthenium oxide, nickel (NiO) and/or nickel and lanthanum compounds (LaNiO3 and La2NiO4) oxide, showed low specific surface areas (1.5-11 m². g-1). In the case of the samples prepared by heating perovskites, solid crystalline structures with rhombohedral or orthorhombic symmetry were obtained with specific surface areas even lower (0.5-4.7 m².g-1). These solids were more reducible than those obtained by impregnation and ruthenium increased the reducibility of the solids for all cases,. The activity and selectivity of the catalysts changed with the preparation method and with the catalysts composition. When introduced into the catalyst by impregnation, ruthenium decreased the activity of the nickel-based catalyst, whose activity increased in the solid originating from perovskites. The conversions ranged from 68 to 97% and nickel was more active than ruthenium for all cases. The hydrogen yield also varied depending on ruthenium and on the preparation method of the solid. When prepared by impregnation, the monometallic catalysts led to higher values than the bimetallic ones When obtained by decomposition of perovskite, the free-nickel catalyst led to lower yields while those containing the two metals led to the highest value. The presence of ruthenium reduces the amount of coke formed on the catalyst during the steam reforming of glycerin, only when the solids were prepared by impregnation. The sample containing nickel and ruthenium and obtained by decomposition of perovskites was the most promising catalyst, leading to a conversion of 97%, hydrogen yield 76%.

Ruthenium-based homogenous catalysis is a broad and extremely useful branch of transition metal catalysis. Surely, the most famous example is olefin metathesis, for which Yves Chauvin, Robert Grubbs and Richard Schrock were awarded the 2005 Chemistry Nobel Prize. Although some of the most well-known catalysts are widely used and considered benchmark catalysts, the research around this topic has not stopped. The modification of known systems to achieve better performance and better understanding of the catalytic mechanism is very important and an example of such modification is reported in this thesis. The newly synthesised catalysts were compared to the parent commercially available catalyst showing better reactivity. Ruthenium catalysis, though, is not limited to olefin metathesis and C-H activation, for example, it has become a useful approach to the functionalisation of organic molecules. In this field, the deuteration of C-H bonds is an interesting transformation, which has many applications. The synthesis of new hydridosilylruthenium complexes and their application in the deuteration of a variety of substrates is reported in this manuscript. The unprecedented synthesis of tetradeuterated Ketoprofene is also reported. Recently, ruthenium-based catalysts have found application in the dehydrogenation of suitable compounds, such as formic acid, ammonia-borane and other hydrogen-rich substances. The driving force behind these discoveries is the use of H2 as an energy vector in place of fossil fuels. A hydrido-ruthenium catalyst was shown to catalyse the decomposition of formic acid in CO2 and H2 and to catalyse the reduction of olefinic substrates. The released CO2 from the reaction did not interfere with the fuel cell due to its inertness. This property makes its employment as C1 source very challenging, although its use would also be extremely attractive because of the abundance of this gas. In these regards, both frustrated Lewis pairs (FLPs) and gold catalysts have shown interesting reactivity in the activation of CO2. A new FLP and a silica supported gold catalyst were synthesised to test them in CO2 activation and the results are reported in this manuscript.

Des catalyseurs Ru supporté sur TiO2 actifs et sélectifs pour l’hydrogénation de l’acide lévulinique en γ-valérolactone en présence d’acide formique comme source interne d’hydrogène ont été développés. L’élaboration d’un nouveau support, TiO2 modifié par Ca2+, permet d’améliorer la production de γ-valérolactone, grâce à la fois à une décomposition de l’acide formique plus sélective en hydrogène et à une hydrogénation de l’acide lévulinique plus efficace. Ces performances améliorées sont associées à l’existence d’interactions Ru/support plus fortes avec une adsorption du CO plus faible, et à une basicité accrue du support. Elles ont été exaltées par la mise en œuvre d’une synthèse photo-assistée sous lumière solaire comme alternative soutenable à l’imprégnation par voie humide, permettant d’obtenir des particules sub-nanométriques de distribution de taille étroite. Il a été montré qu’un profile de type volcano centré sur 1.5 nm relie l’activité catalytique à la taille des particules. / Active and selective Ru catalysts based on TiO2 supports have been developed for the combined hydrogenation of levulinic acid to γ-valerolactone with internal hydrogen supply via in-situ formic acid decomposition. A controlled modification of the TiO2 support by Ca2+ improved the catalytic performance in the one-pot hydrogenation, as a result of enhanced performances in both the formic acid dehydrogenation and the levulinic acid hydrogenation. The improved performances were associated to stronger Ru/support interactions with weaker CO adsorption, as well as to an increased support basicity. The performances were further exalted thanks to a one-step solar light photon-assisted synthesis method used as sustainable alternative to classical wet impregnation. It enabled the uniform dispersion of sub-nanometric metallic Ru particles with narrow distribution and fine size monitoring, and a volcano-type profile centered at 1.5 nm was demonstrated between the nanoparticle size and the activity.

In this thesis, firstly, carbon-supported platinum nanoparticle catalysts have been prepared by using PtCl4 and H2PtCl6 as starting materials and 1-hexanethiol, and tert-octanethiol, as surfactants for the first time. Secondly, these prepared catalysts were heated to 200 &deg / C, 300 &deg / C, and 400 &deg / C for 4 h under argon gas. Lastly, PtRu/C catalysts, which have different atomic percent ratios of Pt and Ru (Pt/Ru: 0.8, 2.1 and 3.5), were prepared using PtCl4 and RuCl3 as starting materials and tert-octanethiol as a surfactant. Each was characterized by X-ray diffraction, transmission electron microscopy, energy dispersive analysis, X-ray photoelectron spectroscopy, cyclic voltammetry, and elemental analysis, and their activities were determined toward the methanol oxidation reaction. It has been found that all prepared catalysts are more active toward methanol oxidation reaction compared to the commercial catalysts. It was also found that increasing the temperature during the heat treatment process results in an enlargement of platinum particle size and a decrease in catalytic activity in the methanol oxidation reaction. Transmission electron microscopy shows that platinum nanoparticles are homogeneously dispersed on the carbon support and exhibited a narrow size distribution with an average particle size of about 2-3 nm in diameter. X-ray photoelectron spectra of all catalysts indicated that most of the platinum nanoparticles (&gt / 70 %) have an oxidation state of zero and rest (&lt / 30 %) have a +4 oxidation state with (Pt 4f7/2) binding energies of 71.2-72.2 and 74.3-75.5 eV, respectively.

Στην παρούσα διατριβή μελετάται η δυνατότητα αναμόρφωσης βιοκαυσίμων με ατμό, και συγκεκριμένα του βιοελαίου και της βιοαιθανόλης, με σκοπό την παραγωγή ρεύματος πλούσιου σε υδρογόνο για την τροφοδοσία κυψελίδων καυσίμου. Η χρήση υδρογόνου σε κυψελίδες καυσίμου αποτελεί μια από τις πλέον υποσχόμενες διεργασίες για την παραγωγή ενέργειας τόσο σε σταθερές όσο και σε κινητές εφαρμογές. Το υδρογόνο ως καύσιμο έχει το πλεονέκτημα ότι δεν παράγει ρυπαντικές ουσίες για την ατμόσφαιρα κατά την παραγωγή ενέργειας, ενώ οι κυψελίδες καυσίμου αποδίδουν πολύ μεγαλύτερη απόδοση σε σχέση με τις συμβατικές μηχανές εσωτερικής καύσης. Όταν δε το υδρογόνο προέρχεται από τη βιομάζα, οι εκπομπές στην ατμόσφαιρα σε CO2 είναι μηδενικές, αφού το ισοζύγιο του άνθρακα παραμένει κλειστό, μη επιβαρύνοντας έτσι το φαινόμενο του θερμοκηπίου. Το βιοέλαιο και η βιοαιθανόλη ανήκουν στην κατηγορία των βιοκαυσίμων, αφού προέρχονται από τη βιομάζα, και συγκεκριμένα παράγονται μέσω της πυρόλυσης και της ζύμωσής της, αντίστοιχα. Η αντίδραση αναμόρφωσής τους με ατμό είναι εφικτή από θερμοδυναμικής απόψεως, ενώ η απόδοση της συγκεκριμένης διεργασίας σε υδρογόνο είναι αρκετά υψηλή. Θερμοδυναμικά, η αντίδραση αναμόρφωσης ευνοείται σε υψηλές θερμοκρασίες και μικρές πιέσεις. Λόγω της πολυπλοκότητας του βιοελαίου, που αποτελεί μίγμα εκατοντάδων οξυγονούχων οργανικών ενώσεων, αρχικά επιλέγονται πρότυπες ενώσεις αντιπροσωπευτικές αυτού. Ως τέτοια επιλέχθηκε το οξικό οξύ που βρίσκεται σε σημαντικά ποσοστά (~10%) στο βιοέλαιο. Δοκιμάστηκαν διάφοροι υποστηριγμένοι καταλύτες μετάλλων για την ενεργότητά τους στην αντίδραση αναμόρφωσης του οξικού οξέος με ατμό. Διάφοροι παράμετροι που επιδρούν στην καταλυτική ενεργότητα και εκλεκτικότητα διερευνήθηκαν υπό συνθήκες αντίδρασης, όπως η σύσταση του καταλύτη (επίδραση της φύσης του μετάλλου και του φορέα), η θερμοκρασία αντίδρασης και ο χρόνος αντίδρασης. Η μεταλλική φάση των καταλυτών αυτών αποτελούνταν από διάφορα μέταλλα, όπως Pt, Pd, Rh, Ru και Ni, τα οποία ήταν διασπαρμένα σε διάφορους φορείς μεταλλικών οξειδίων, όπως Al2O3, La2O3/Al2O3, MgO/Al2O3 και CeO2/Al2O3. Βρέθηκε ότι οι καταλύτες Ru και Ni παρουσιάζουν την υψηλότερη ενεργότητα και εκλεκτικότητα προς παραγωγή υδρογόνου. Ιδιαίτερα, οι καταλύτες Ru που είναι εναποτεθιμένοι σε φορείς La2O3/Al2O3 και MgO/Al2O3 επιδεικνύουν και πολύ καλή σταθερότητα συναρτήσει του χρόνου αντίδρασης. Επιπλέον, υπολογίστηκε ο ρυθμός εναπόθεσης άνθρακα στην καταλυτική επιφάνεια κατά τη διάρκεια της αντίδρασης και βρέθηκε ότι επηρεάζεται ισχυρά από τη φύση του καταλυτικού υλικού. Η διερεύνηση του δικτύου αντιδράσεων που λαμβάνουν χώρα υπό συνθήκες αναμόρφωσης του οξικού οξέος με ατμό, παρουσία καταλυτών νικελίου αλλά και των φορέων Al2O3 και La2O3, έγινε με τη χρήση δυναμικών τεχνικών με φασματογράφο μάζας, αλλά και τεχνικών μόνιμης κατάστασης. Το οξικό οξύ αλληλεπιδρά έντονα με το φορέα Al2O3 και λιγότερο έντονα με το La2O3. Σε ενδιάμεσες θερμοκρασίες, οι κύριες αντιδράσεις που πραγματοποιούνται είναι αυτές της διάσπασης και της κετονοποίησης του οξικού οξέος, ενώ σε υψηλότερες αυτές της αναμόρφωσης του οξικού οξέος και της μετατόπισης του CO. Παρουσία του Ni, η ενεργότητα μετατοπίζεται σημαντικά προς χαμηλότερες θερμοκρασίες. Το νικέλιο προωθεί τις αντιδράσεις αναμόρφωσης και επιβραδύνει το ρυθμό εναπόθεσης άνθρακα στην καταλυτική επιφάνεια. Επίσης, βρέθηκε ότι η εναπόθεση άνθρακα ευνοείται σε χαμηλές θερμοκρασίες, όξινους φορείς και μεγάλους λόγους τροφοδοσίας άνθρακα-ατμού. Αντίστοιχα δυναμικά πειράματα, για τη διερεύνηση του δικτύου αντιδράσεων υπό συνθήκες αντίδρασης, πραγματοποιήθηκαν και σε καταλύτες Ru διασπαρμένους σε φορείς Al2O3 και MgO/Al2O3. Και σε αυτή την περίπτωση, σε ενδιάμεσες θερμοκρασίες ευνοείται η αντίδραση κετονοποίησης και σε μικρότερο βαθμό αυτή της διάσπασης του οξικού οξέος. Παρουσία του ρουθηνίου η ενεργότητα μετατοπίζεται προς χαμηλότερες θερμοκρασίες και παρατηρείται παραγωγή υδρογόνου με υψηλούς ρυθμούς. Το ρουθήνιο προωθεί τις αντιδράσεις αναμόρφωσης και επιβραδύνει το ρυθμό εναπόθεσης άνθρακα στην καταλυτική επιφάνεια. Επίσης, διερευνήθηκε ο ρόλος του MgO στον καταλύτη Ru/MgO/Al2O3 και εάν και πώς η παρουσία του επιδρά θετικά στην ενεργότητα του συγκεκριμένου καταλύτη. Βρέθηκε ότι η αντίδραση των οξειδίων του αλουμινίου και μαγνησίου είναι πλήρης, οδηγώντας στο σχηματισμό ενός σπινελίου μαγνησίου-αλουμινίου. Η αυξημένη ενεργότητα του καταλύτη Ru/MgO/Al2O3, σε σύγκριση με τον Ru/Al2O3, σχετίζεται με το γεγονός ότι το σπινέλιο Mg-Al προσφέρει αυξημένη κινητικότητα των ιόντων Ο- και ΟΗ- (spillover) από το φορέα στο μέταλλο, μειωμένη οξύτητα σε σύγκριση με το φορέα Al2O3, καθώς και αυξημένη ικανότητα στον καταλύτη για προσρόφηση ατμού. Ο καταλύτης 5% Ru/MgO/Al2O3 δοκιμάστηκε και υπό συνθήκες αναμόρφωσης του υδατικού κλάσματος του βιοελαίου, και μάλιστα χρησιμοποιήθηκαν δομημένα υποστρώματα, όπως πελλέτες, κεραμικοί μονόλιθοι ή σπόγγοι, έτσι ώστε να αποτελέσματα των συγκεκριμένων πειραμάτων να έχουν άμεση εφαρμογή. Βρέθηκε ότι όλες οι διαφορετικές δομές παρουσιάζουν πολύ καλή ενεργότητα, μετατρέποντας εξ’ ολοκλήρου το βιοέλαιο, καλή εκλεκτικότητα προς παραγωγή υδρογόνου και σταθερή λειτουργία σε σχέση με το χρόνο αντίδρασης. Ωστόσο, ο καταλύτης ρουθηνίου σε πελλέτες βρέθηκε να παρουσιάζει την καλύτερη συμπεριφορά από όλους τους υπόλοιπους. Οι αντιδράσεις αναμόρφωσης και, επομένως, η παραγωγή υδρογόνου ευνοούνται σε υψηλές θερμοκρασίες και μικρές ταχύτητες χώρου. Η εναπόθεση του άνθρακα αποτελεί ένα από τα σημαντικότερα προβλήματα σε αυτού του είδους τις διεργασίες. Μόνο ένα μικρό μέρος του παρεχόμενου άνθρακα εναποτίθεται στην καταλυτική επιφάνεια, κυρίως στη μορφή CHx. Ωστόσο, ο σχηματισμός ανθρακικών εναποθέσεων είναι αρκετά πιο έντονος στα τοιχώματα του αντιδραστήρα πάνω από την καταλυτική κλίνη, λόγω του ομογενούς πολυμερισμού των ασταθών συστατικών του βιοελαίου. Τέλος, διάφοροι καταλύτες ευγενών μετάλλων (Pt, Pd, Ru, Rh) υποστηριζόμενοι σε φορέα Al2O3¬ δοκιμάσθηκαν ως προς την καταλυτική τους ενεργότητα και εκλεκτικότητα υπό συνθήκες αναμόρφωσης αιθανόλης με ατμό, στο θερμοκρασιακό εύρος των 280-450 0C. Βρέθηκε ότι ο Pt και το Pd είναι τα πιο ενεργά από τα μέταλλα που εξετάστηκαν. Η διερεύνηση της επίδρασης του φορέα στην καταλυτική ενεργότητα και εκλεκτικότητα έγινε σε καταλύτες Pt διεσπαρμένους σε διάφορους φορείς μεταλλικών οξειδίων (Al2O3, CeO2, ZrO2, YSZ). Οι συγκεκριμένοι καταλύτες δοκιμάστηκαν και για την σταθερότητά τους συναρτήσει του χρόνου αντίδρασης. Ο καταλύτης Pt/Al2O3 βρέθηκε να παρουσιάζει την μεγαλύτερη ενεργότητα και την υψηλότερη εκλεκτικότητα, υπό συνθήκες αντίδρασης, αλλά και πολύ σταθερή λειτουργία με το χρόνο αντίδρασης. Τέλος, παρουσία του συγκεκριμένου καταλύτη διερευνήθηκε το δίκτυο αντιδράσεων που λαμβάνει χώρα σε συνθήκες αναμόρφωσης της αιθανόλης. / In the present study is investigated the process of steam reforming reaction of bio-fuels, such as bio-oil and bio-ethanol, for the production of a gas stream rich to hydrogen, in order to feed fuel cells. Hydrogen, in combination with fuel cells, is being considered as an environmentally friendly source of energy for automotive as well as stationary applications. Hydrogen has the significant advantage of producing no air or other pollutants in its transformation to energy, while fuel cells, which operate primarily on hydrogen, offer enhanced efficiency in power generation. However, real environmental benefits are linked to the ability to produce hydrogen from renewable sources with no net production of greenhouse gasses. A viable renewable source, gaining attention in recent years, is bio-fuels. Bio-oil and bio-ethanol are bio-fuels because they are originated from biomass treatment, and, in particular, via the fast pyrolysis and the fermentation of biomass, respectively. Their steam reforming reaction is entirely feasible from the thermodynamic point of view, while the efficiency of such process in hydrogen production is significantly high. Thermodynamically the reaction of steam reforming is favored at high temperatures and low pressures. Due to the complexity of bio-oil, which is consisted of hundreds of organics oxygenates, model compounds representatives of bio-oil, are initially used. Acetic acid was chosen as a model compound, because it is present in significant amounts in bio-oil (~10%). A variety of supported metal catalysts were tested under conditions of steam reforming of acetic acid. The influence of several parameters on catalytic activity and selectivity were examined, including catalyst composition, i.e. nature of the metal and the carrier, reaction temperature and time on stream. The metallic phase of such catalysts was comprised of various metals, such as Pt, Pd, Rh, Ru and Ni, which were supported on metal oxides carriers, such as Al2O3, La2O3/Al2O3, MgO/Al2O3 and CeO2/Al2O3. It was found that Ni-based and Ru-based catalysts present high activity and selectivity toward hydrogen production. Ru catalysts supported on La2O3/Al2O3 and MgO/Al2O3 carriers, showed good long term stability as a function of time on stream. However, Ni catalysts were not as stable as Ru catalysts. The amount of carbon deposited on each catalyst was estimated, and it was found that it depends strongly on the nature of the catalyst. The reaction network under conditions of steam reforming of acetic acid was investigated over Al2O3 and La2O3, and Ni catalyst supported on La2O3/Al2O¬3 carrier, employing transient and steady-state techniques. It was found that acetic acid interacts strongly with the Al¬2O3 carrier and less strongly with La2O3. Decomposition reactions as well as the ketonization reaction take place, especially at intermediate temperatures. Reforming reactions and the WGS reaction occur at higher temperatures. In the presence of Ni, catalytic activity is shifted toward lower temperatures. Nickel promotes steam reforming reactions and retards the rate of carbon deposition onto the catalyst surface. It was also found that carbon formation is affected by reaction temperature, the HAc/H2O ratio, and catalyst composition. Carbon deposition is favoured at low reaction temperatures, at more acidic carriers and at high HAc/H2O ratio. Transient experiments were also conducted for the Ru catalysts supported on Al2O3 and MgO/Al2O3 carriers. It was found that, in this case as well, the ketonization reaction firstly, and decomposition reaction of acetic acid secondly, favoured at intermediate temperatures. In the presence of Ru, catalytic activity is shifted towards lower temperatures and hydrogen production occurs at high rates. Ru catalysts promote the steam reforming reaction and retard the rate of carbon deposition onto the catalytic surface. Also, the role of MgO in catalyst formulation was elucidated. It has been found that the solid-state reaction of alumina with magnesium oxide is complete, forming magnesium aluminate spinel. The enhanced activity of the Ru/MgO/Al2O3 catalyst, as compared to the Ru/Al2O3 one, seems to be associated with the fact that the magnesium aluminate spinel offers enhanced O and/or –OH anion spillover from the carrier onto the metal particles, reduced acidity as compared to the alumina carrier, as well as enhanced ability for H2O adsorption. A series of Ru/MgO/Al2O3 catalysts supported on cordierite monoliths, ceramic foams and γ-Al2O3 pellets were prepared and tested for the production of hydrogen by catalytic steam reforming of the aqueous fraction of bio-oil. All different structural forms of the catalyst exhibited satisfactory activity, converting completely the bio-oil, good selectivity toward hydrogen and satisfactory stability with time on stream. However, the catalyst supported on pellets exhibited the best catalytic performance, among all catalysts investigated. Reforming reactions, and thus hydrogen production, are favoured at high temperatures and low space velocities. Coking is one of the most significant problems encountered in these processes. It was found that only a small part of the incoming carbon is deposited on the catalyst surface, which is mainly present as CHx. However, coke deposition is more intense on the reactor wall above the catalytic bed, due to homogeneous polymerization of unstable ingredients of bio-oil. Finally, a variety a noble metal catalysts (Pt, Pd, Ru, Rh), supported on the Al2O3 carrier were tested with respect to their catalytic activity and selectivity under conditions of steam reforming of ethanol, in the temperature range of 280-450 0C. It was found that Pt and Pd are the most active metal among all catalysts tested. The effect of the carrier nature was investigated for Pt catalysts supported on a variety of metal oxide carriers, such as Al2O3, CeO2, ZrO2 and YSZ. These catalysts were also tested for their stability as a function of time on stream. The Pt/Al2O3 catalyst presents the highest activity and selectivity among all catalysts tested, as well as very stable performance with time on stream. Finally, the reaction network under conditions of ethanol reforming, in the presence of the specific catalyst, was investigated.

117 f. / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-05-20T13:36:45Z No. of bitstreams: 1 TESE DOUTORADO - GUILLERMO P BERROCAL.pdf: 2123714 bytes, checksum: dbd07cf34792ac2cac402476f9c17a8a (MD5) / Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-06-06T15:58:28Z (GMT) No. of bitstreams: 1 TESE DOUTORADO - GUILLERMO P BERROCAL.pdf: 2123714 bytes, checksum: dbd07cf34792ac2cac402476f9c17a8a (MD5) / Made available in DSpace on 2013-06-06T15:58:28Z (GMT). No. of bitstreams: 1 TESE DOUTORADO - GUILLERMO P BERROCAL.pdf: 2123714 bytes, checksum: dbd07cf34792ac2cac402476f9c17a8a (MD5) Previous issue date: 2009 / FAPESB / Níquel suportado em alumina tem sido reconhecido como um catalisador efetivo das reações de reforma de metano. No entanto, ele apresenta desativação por coque e problemas de estabilidade térmica, em altas temperaturas, principalmente devido à transição de fase do suporte e sinterização do metal. Uma opção atrativa, para obter suportes mais adequados para esses catalisadores, é a combinação da alumina com a zircônia que possui elevada estabilidade térmica, dureza e propriedades anfotéricas. Por outro lado, a adição de metais nobres ao catalisador de níquel usado na reforma de metano poderia evitar a desativação por formação de coque, assim como conduzir a atividades mais elevadas. Desta forma, neste trabalho, foram estudados catalisadores de níquel associados, ou não, ao rutênio suportados em óxidos de alumínio e zircônio, destinados à reforma a vapor e reforma autotérmica de metano. . Foram sintetizados catalisadores monometálicos de níquel (15 %) e bimetálicos de níquel (15 %) e rutênio (razão molar Ru/Ni = 0,1), por impregnação em óxidos de alumínio e/ou zircônio. Estes sólidos foram preparados por métodos de precipitação à temperatura ambiente, a partir de soluções de oxicloreto de zircônio e nitrato de alumínio, obtendo-se materiais com razões molares Al/Zr = 1, 2, 5 e 10 além do óxido de zircônio e de alumínio puros. As amostras foram caracterizadas por espectroscopia no infravermelho com transformadas de Fourier, termogravimetria, análise térmica diferencial, difração de raios X, redução a temperatura programada e medidas de área superficial específica e porosidade. Os catalisadores foram testados na reação de reforma a vapor e autotérmica de metano na faixa de 450 a 750 ºC. . Observou-se a formação da fase γ-Al2O3 na alumina pura e a fases tetragonal e monoclínica na zircônia pura. Com a adição de alumínio à zircônia houve a estabilização da fase tetragonal em todos os casos, em detrimento da monoclínica. A adição de pequenas quantidades de zircônio ao óxido de alumínio produziu um aumento na área superficial especifica da alumina, associado à ação textural do zircônio como espaçador entre as partículas de óxido de alumínio ou à geração de tensões no sólido, causando o deslocamento do equilíbrio para a formação de partículas menores. A adição dos metais (níquel e rutênio) ao suporte causou diminuição da área superficial específica, o que pode estar associado ao bloqueio de alguns poros por esse metal e/ou à sinterização da amostra após a impregnação e calcinação ou a uma combinação desses efeitos. A redução do níquel foi facilitada pela presença do zircônio e/ou do rutênio. Todos os catalisadores foram ativos na reação de reforma a vapor e na reforma autotérmica de metano, observando-se aumento na conversão de metano com a temperatura. Na reação de reforma a vapor e na reforma autotérmica, observouse, que em temperaturas típicas dessas reações, o catalisador de níquel impregnado no suporte com razão molar Al/Zr =10 levou às conversões mais elevadas. O rutênio produz um efeito similar, em catalisadores de níquel isentos de zircônio. Dessa forma, as amostras mais promissórias são aquelas contendo níquel suportado em alumina contendo zircônio ou rutênio. / Salvador

The continuous decreasing of fuel fossil sources has been accelerating the seek for alternative energetic sources. The difficulty in consuming all glycerol produced, which is three times bigger than the demand, is the main concern around the biofuels process production. Given that this glycerol has different characteristics from the well consumed glycerol in the pharm business, such as color and impurities. Besides, there is a lack of defined standards in Brazil in the sense of how to dispose such product. However, alternative uses for glycerol (by-product from the biofuels production) will confirm the feasibility of the biodiesel process, particularly if we take into account its decentralized production. The glycerol steam reforming can yield up to 4 moles of H2 and 3 moles of CO per consumed mole of glycerol. In this work, the catalytic tests were performed with monometallic and bimetallic ruthenium and platinum catalyst in a tubular reactor with 30% wt of glycerol in the feed, using 6 and 20 pressures conditions. It was also carried out tests with 100 hours of reaction in order to verify its activity and stability. Along with the catalyst studies, the effects of temperature, feed flow and ruthenium particle size under monometallic and bimetallic catalyst were analyzed. Besides, it was also evaluated the reaction thermodynamics of glycerol steam reforming due to temperature, pressure and mass composition of glycerol over the production profiles of the most valuable products in the chemical equilibrium. Therefore, the objective of this work is to present the study of glycerol steam reforming employing different catalysts and under different operational conditions and evaluating its performances in the production of chemical products with high commercial value. / A redução das reservas de combustíveis fósseis tem acelerado o desenvolvimento de fontes alternativas de energia. A dificuldade de acomodação de uma oferta de glicerina quase três vezes maior que a demanda se agrava porque a glicerina resultante da produção de biodiesel tem características diferentes da que ´e utilizada na indústria de higiene, pois há impurezas e colorações diferentes, o que dificulta seu uso em fábricas de glicerina tradicional. Além disso, não há no Brasil legislação especifica sobre a forma de descarte dessa glicerina, apenas para efluentes industriais em geral. Portanto, alternativas de uso deste insumo são essenciais para conferir viabilidade ao processo, particularmente se considerarmos a sua produção tipicamente descentralizada. A reação catalítica de reforma a vapor do glicerol pode gerar estequiometricamente até 4 moles de H2 e 3 moles de CO por mol de glicerol consumido. Os testes catalíticos foram realizados com catalisadores monomet álicos e bimetálicos de ruténio e platina em um reator tubular, com alimentação de glicerol com 30% em massa, com pressões variando entre 6 e 20 bar. Neste projeto foram realizados testes de duração de até 100 horas de reação com cada catalisador no intuito de verificar a atividade e a estabilidade. Dentro do estudo dos catalisadores, avaliou-se os efeitos de temperatura, vazão de alimentação da solução reacional (WHSV) e tamanho de partícula de ruténio sobre catalisadores monometálicos e bimetálicos. Avaliou-se também a termodinâmica da reação de reforma a vapor do glicerol e a influência das condições de temperatura, pressão e composição mássica do glicerol sobre os perfis de produção de produtos de alto valor no equilíbrio químico. Assim, o objetivo deste trabalho é apresentar um estudo da reação de reforma sob diferentes catalisadores e avaliando o desempenho destes na produção de compostos químicos de alto valor, testando diversas condições reacionais. / Mestre em Engenharia Química

The study of normal N-heterocyclic carbenes (NHCs), which probably represent one of the most important families of ligands in organometallic chemistry and homogeneous catalysis, has indubitably led to the usage of other related ligands beyond di-amino carbenes. So far, such species are only marginally used as ligands due to their relative novelty and stability. The following chapters describe the exciting journey into the development of new synthetic accesses of various abnormal, remote N-heterocyclic, mesoionic and carbocyclic carbene transition metal complexes. The uses of a number of these ruthenium- and copper-based complexes as catalysts in several applications are also disclosed. Halfway between the study of the electronic effect of mixed NHC/phosphite ruthenium in olefin metathesis reactions (Chapter 1) and NHC copper-catalysed transformations (Chapters 5 and 6), resides the core of this dissertation that links the book end chapters. Indeed, the NHC-Cuᴵ transfer or “transmetalation” reaction is disclosed as a powerful and reliable tool to access new transition metal catalysts in a relatively general manner. The syntheses of a series of various non-conventional NHC-Cu complexes as precursors for the transmetalation reaction are also described in Chapter 2. The dissertation finally closes with some preliminary results on what represents the first experimental and theoretical evidence for the mechanism of the NHC transfer by transmetalation. The exploration of the reaction by exchange from copper to platinum has begun to reveal what was so far unknown through the isolation of reactive intermediate species formed during the process.