Highly dispersed gold nanoparticles on metal oxide surfaces have recently been reported to exhibit high catalytic activity for low-temperature carbon monoxide oxidation. Amongst the metal oxides, titanium dioxide, more often the commercial form Degussa P25, has been the most studied support for gold as a catalyst for CO oxidation because it yields some of the most active and stable catalysts. Physical and chemical modification of catalysts supports has been shown to affect their catalytic properties. In this research, modified gold supported catalysts have been prepared, characterized and tested for CO oxidation. Their properties have been compared with those of the unmodified catalysts. Catalysts containing1wt% Au supported on MxOy and TiO2/MxOy mixed oxide (M = Zn, Mg, Ni, Fe, Cr, Cu, Mn and Co; TiO2:MxOy mole ratio of 5:1; TiO2 = Degussa P25) were prepared by the single step borohydride reduction method and it was found that TiO2 gave the most superior activity as support for gold for CO oxidation, followed by TiO2/MxOy and the corresponding MxOy. The specific activities for CO oxidation of Au/TiO2 catalysts per unit of prepared in the range 0.05 to 1 wt% of Au indicates that for catalysts prepared by deposition precipitation, there is a significant decrease in specific activities with an increase with gold loading. For the single step borohydride reduction procedure, specific activities decrease less significantly with increasing gold content, implying that for economic and practical reasons, it would be advantageous to prepare gold catalysts with low gold loadings. Cyanide leaching of 1 wt% Au/TiO2 catalysts at different Au:CN- ratios, to selectively remove some of the gold in the catalysts, shows the activity per unit mass of gold to increases as more gold is removed from the catalyst. This is consistent with the idea that gold exists in more than one oxidation state in the systems and a significant fraction of the gold present in the catalysts do not contribute to catalytic activity. A number of anions and cations have been incorporated into TiO2 as support for gold catalysts and also into as-prepared Au/TiO2 catalysts at levels ranging from 0.05 mol% to 2.5 mol% with respect to the support. The activities of the catalysts for CO oxidation reveal that at the highest concentration levels of the ions, in all cases, a decrease in activity compared with unmodified Au/TiO2 is observed. However, addition of 0.05 to 0.4 mol% of the ions with respect to the support, prior to gold addition, in most cases, resulted in activity enhancement which increased with a decrease in the ion content. Similar addition of 0.05 to 0.4 mol% of the ions with respect to TiO2 to Au/TiO2 resulted in a decrease in activity. Attempts to understand the origins of these effects show that there is a degree of chemical interaction between the added ions and gold.

Bifunctional iminophosphoranes, containing a triaryl-substituted iminophosphorane and bis(3,5- trifluoromethyl)phenyl thiourea on a single enantiomer scaffold are novel asymmetric superbase organocatalysts reported by the Dixon group in 2014. This thesis describes our efforts to expand their scope and utility in a variety of challenging chemical transformations. Chapter 2 describes the development and application of immobilised bifunctional iminophosphorane organocatalysts. We have successfully immobilised bifunctional iminophosphoranes on a crosslinked polystyrene support and applied this sold-supported catalyst to three challenging asymmetric reactions; namely the nitro-Mannich reaction of phosphinoyl ketimines and the conjugate addition of alkylmalonates and N,N-dimethyl β-keto amides to nitrostyrene. Very good yields, enantio- and diasteroselectivities were obtained in all cases. We have also demonstrated their use in a range of conjugate additions of cyclic 1,3-dicarbonyl compounds to nitroalkenes, which suffered from very slow reaction rates under tertiary amine-based bifunctional catalysis. In all cases, the immobilised bifunctional iminophosphoranes performed very well in comparison to their homogeneous counterparts. We have also demonstrated catalyst recycling over 10 cycles and application in a continuous flow system with a productivity of 7.20 mmol _producth^-1g_catalyst^-1. to the ring-opening polymerisation (ROP) of cyclic esters. We have demonstrated the performance of bifunctional iminophosphorane organocatalysts in the ROP of L-lactide (LA), δ-valerolactone (VL) and ε-caprolactone (CL). The polymerisation of LA and VL proceeded rapidly and was well controlled, while only short lengths (> 100 DP) of poly(CL) could be prepared in a controlled fashion due to hypothesised competing initiation from the catalyst. We have shown that the polymerisation of LA using our catalyst may be considered a living polymerisation. Di-block co-polymers could also be successfully prepared via sequential monomer addition or through the use of macroinitiators. We then investigated the roles of the iminophosphorane and the thiourea component of the catalyst.

Αντικείμενο της παρούσας μελέτης ήταν η χρήση της φασματοσκοπικής μεθόδου Raman για τη διερεύνηση των δομικών και δονητικών ιδιοτήτων καταλυτικών συστημάτων βασιζόμενα σε οξείδια μετάλλων μετάπτωσης (V2O5, MoO3). Η δυνατότητα της μεθόδου Raman να εφαρμοστεί κάτω από in situ ελεγχόμενες συνθήκες, όπως για παράδειγμα κάτω από συνθήκες καταλυτικής λειτουργίας, επέτρεψε το χαρακτηρισμό των καταλυτών που μελετήθηκαν κάτω από ρεαλιστικές συνθήκες αντίδρασης, για διάφορες εφαρμογές καταλυτικών διεργασιών. Πιο συγκεκριμένα, διερευνήθηκε η μοριακή δομή των συμπλόκων βαναδίου που είναι παρόντα στην καταλυτικά ενεργή, υγρή φάση βιομηχανικών καταλυτών παραγωγής θειϊκού οξέος (Haldor Topsøe AS, Denmark), διενεργώντας φασματοσκοπικές in situ μετρήσεις Raman σε διαφορετικές αέριες συνθήκες και θερμοκρασίες λειτουργίας. Παρουσία Ο2, η επιφάνεια των καταλυτών καλύπτεται από ένα τηγμένο άλας στο οποίο κυριαρχεί το μονοπυρηνικό σύμπλοκο VVO2(SO4)23-, ενώ ανιχνεύτηκαν επίσης και κρυσταλλικά θειϊκά άλατα. Κατόπιν ενεργοποίησης των δειγμάτων σε ατμόσφαιρα SO2/O2/N2 στους 480oC, η υγρή φάση των καταλυτών φαίνεται ότι αποτελείται από ομάδες (VVO)2O(SO4)44- (σε διμερείς ή δι-πυρηνικούς σχηματισμούς) και ομάδες VVO2(SO4)23-. Κάτω από μια συγκεκριμένη θερμοκρασία, τα φάσματα Raman είναι ενδεικτικά της αναγωγής VV®VIV και του σχηματισμού του τηγμένου συμπλόκου VIVO(SO4)22-, το οποίο καθώς συσσωρεύεται προκαλεί καταβύθιση κρυσταλλικών συμπλόκων VIV, ¨ξεπλένοντας¨ έτσι την ενεργή φάση από είδη βαναδίου. Eίναι η πρώτη φορά που εξετάζεται η μοριακή δομή των συστατικών που αποτελούν την καταλυτικά ενεργή φάση των βιομηχανικών καταλυτών για την οξείδωση του SO2, με χρήση in situ φασματοσκοπίας Raman. Μια σειρά από στηριζόμενους καταλύτες V2O5 σε TiO2 και ZrO2 εξετάστηκε επίσης με in situ φασματοσκοπία Raman, κάτω από οξειδωτικές και αναγωγικές συνθήκες, καθώς επίσης και κάτω από συνθήκες αντίδρασης οξειδωτικής αφυδρογόνωσης του προπανίου. Η μοριακή δομή των επιφανειακών ειδών βαναδίου σχετίζεται με το σχηματισμό απομονωμένων μονομερών ειδών και μεγαλύτερων πολυμερικών ομάδων βαναδίου, με αύξηση της φόρτισης, ενώ για καλύψεις μεγαλύτερες της μονοστρωματικής σχηματίζονται κρυσταλλικό V2O5 και ZrV2O7 στην TiO2 και ZrO2, αντίστοιχα. Η εξέταση των φασμάτων Raman κάτω από συνθήκες μόνιμης κατάστασης αντίδρασης του προπανίου, είναι ενδεικτική της μερικής αναγωγής των επιφανειακών ειδών βαναδίου ενώ κάτω από αναγωγικές συνθήκες C3H8, η αναγωγή είναι περισσότερο εκτεταμένη. Ο ρυθμός οξειδωτικής αφυδρογόνωσης (ανά άτομο V) βρέθηκε να αυξάνει με τη θερμοκρασία αντίδρασης ενώ για σταθερή θερμοκρασία μειώνεται με αύξηση της επιφανειακής πυκνότητας V. Η επίδραση της παρουσίας υδρατμών στο αέριο μίγμα τροφοδοσίας στα φάσματα Raman των καταλυτών, διερευνήθηκε επίσης για ένα ευρύ φάσμα θερμοκρασιών. Η ανάγκη να κατανοηθεί πλήρως η συμπεριφορά των καταλυτών κάτω από ρεαλιστικές συνθήκες καταλυτικής λειτουργίας και να καταστρωθούν αξιόπιστοι συσχετισμοί μεταξύ μοριακής δομής και καταλυτικής ενεργότητας και εκλεκτικότητας, οδήγησε στην ανακατασκευή της πειραματικής κυψελίδας αντίδρασης – Raman και στην παράλληλη χρήση αέριας χρωματογραφίας για την ταυτοποίηση της σύστασης εξόδου του αερίου ρεύματος από την κυψελίδα, επιτρέποντας την ταυτόχρονη συλλογή φασματοσκοπικών και καταλυτικών δεδομένων από το ίδιο δείγμα καταλύτη και κάτω από τις ίδιες πειραματικές συνθήκες λειτουργίας (operando φασματοσκοπία Raman). Η βελτιωμένη αυτή τεχνική, operando Raman-GC, χρησιμοποιήθηκε για τη διερεύνηση της επίδρασης του φορέα (ZrO2, Al2O3) στις δομικές και καταλυτικές ιδιότητες στηριζόμενων καταλυτών MoO3, στην αντίδραση οξειδωτικής αφυδρογόνωσης του αιθανίου. Η εξέταση των φασμάτων Raman κάτω από συνθήκες Ο2 έδειξε ότι το ΜοΟ3 παραμένει υψηλά διεσπαρμένο στο φορέα ZrO2 έως το όριο της μονοστρωματικής κάλυψης, σχηματίζοντας μονομερή και πολυμερή επιφανειακά είδη ενώ ίχνη της μεικτής κρυσταλλικής φάσης Zr(MoO4)2 ανιχνεύονται για φορτίσεις πάνω από τη μονοστρωματική. Η διασπορά των ειδών Μο φαίνεται ότι είναι λιγότερο αποτελεσματική στο φορέα Al2O3, καθώς ανιχνεύεται κρυσταλλικό Al2(MoO4)3 πριν από τη συμπλήρωση μονομοριακού στρώματος ΜοΟx. H επιλογή συγκεκριμένου υποστρώματος για τη διασπορά των ειδών Μο φάνηκε επίσης να είναι καθοριστική για την καταλυτική ενεργότητα των δειγμάτων, καθώς οι διαφορές στις τιμές TOF ήταν ως και μία τάξη μεγέθους μεγαλύτερες για τους στηριζόμενους καταλύτες MoO3/ZrO2. Οι διαφορές ως προς τη δομή και την καταλυτική συμπεριφορά ανάμεσα στα δείγματα από τις δύο σειρές καταλυτών εξετάζονται στη βάση αυτής της νέας φασματοσκοπικής μεθοδολογίας. / The present study is concerned with the application of in situ Raman spectroscopy on studying the molecular structure and the properties of catalytic systems based on transition metal oxides (V2O5, MoO3), under various gas atmospheres and operating temperatures. In situ Raman spectroscopy has been used to study the molecular structure of the vanadium complexes present in the active liquid phase of industrial supported molten salt sulfuric acid catalysts. Under oxidizing conditions (O2, 480oC) the surface of the catalysts is covered by a molten salt in which the mononuclear VVO2(SO4)23- complex (in monomeric or oligomeric form) is predominant. Crystalline sulfate salts are also detected. After being subjected to activation (i.e. in SO2/O2/N2 atmosphere at 480oC), the molten phase of the catalysts is shown to consist of (VVO)2O(SO4)44- (dimeric or binuclear fragments of oligomers) and VVO2(SO4)23-. Below a certain temperature, the Raman data are indicative of VV®VIV reduction and formation of the molten VIVO(SO4)22- complex, the accumulation of which results in precipitation of VIV crystalline compounds and depletion of the active phase in terms of vanadium. The molecular structure of the components constituting the active liquid phase of industrial SO2 oxidation catalysts is for the first time studied by in situ Raman spectroscopy. A series of supported vanadium oxide catalysts on TiO2 and ZrO2 supports has also been examined by means of in-situ Raman spectroscopy, under oxidizing, reducing and ODH of propane conditions, in order to establish molecular structure-reactivity/selectivity relations for the catalysts. The molecular structures of the surface V2O5 species evolve from monovanadates to larger two-dimensional polyvanadate domains, as the surface coverage increases, while for surface densities exceeding the theoretical monolayer, bulk V2O5 and ZrV2O7 are formed on the TiO2 and ZrO2 respectively. The evaluation of the Raman spectra taken under steady state reaction conditions suggests a partial reduction of the surface species, whereas under a C3H8 environment, the reduction is much more extensive. Oxidative dehydrogenation rates (per V-atom) were found to increase linearly with the operating temperature, while for a given temperature were found to decrease with increasing surface density. The effect of water vapors on the surface vanadium oxide species over a wide temperature range was also investigated. The need to fully understand the behavior of the catalytic materials during realistic reaction conditions and to establish accurate structure – activity/selectivity relationships, has led to the reconstruction of the experimental Raman - reaction cell with the simultaneous use of on line gas chromatography, allowing the simultaneous collection of spectroscopic and catalytic performance data, from the same catalyst sample under the same operating conditions (operando Raman spectroscopy). The effect of the supporting material (ZrO2, Al2O3) on the structural and catalytic properties of MoO3 supported catalysts for ethane ODH was then explored, by means of the combined spectroscopic technique operando Raman-GC. The evolution of the Raman spectra under oxidising conditions showed that molybdena is highly dispersed on ZrO2 support up to approximately a monolayer forming both monomeric and polymeric MoOx surface species and only traces of Zr(MoO4)2 above monolayer. The dispersion of Mo species was shown to be less extended in the case of Al2O3 support, as bulk Al2(MoO4)3 clusters form before the formation of a polymolybdate monolayer. Switching between the two selected supporting materials was also shown to be determinative for the catalytic efficiency of the samples during ethane ODH reaction conditions, as the differences between the TOF values of the samples were over than an order of magnitude higher in the case of MoO3/ZrO2 supported catalysts. The differences in structure and catalytic activity between the two sets of catalysts are discussed on the basis of this new spectroscopic technique.

O petróleo é a principal matéria-prima empregada para produzir combustíveis, lubrificantes e produtos petroquímicos. Atualmente, devido ao fato desta fonte não ser renovável e estimar-se a sua extinção, busca-se por fontes renováveis de energia que possam vir a substituí-la. Nesse contexto, o etanol vem sendo investigado por ser uma alternativa sustentável para a obtenção de hidrocarbonetos de maior valor agregado, tais como, eteno, propeno, benzeno, tolueno, entre outros, através de sua conversão catalítica em condições controladas. Este trabalho teve por finalidade avaliar o efeito de diferentes catalisadores metálicos suportados em zeólita HZSM-5 na reação de conversão do etanol em produtos de maior valor agregado. Para isso, prepararam-se catalisadores com 2,5 % em massa dos metais La, Ca, Li, Mg e Ni impregnados na zeólita HZSM-5 comercial. A seguir foram preparados catalisadores a partir da modificação da zeólita HZSM-5 com diferentes teores de Ni e, na sequência, amostras com diferente combinação de Ni e La. Posteriormente, a zeólita HZSM-5 foi sintetizada em laboratório e impregnada através da combinação entre os metais Ni e Zn. Os catalisadores antes do seu emprego nos ensaios catalíticos foram caracterizados por medidas de área específica SBET, DRX e TPD-NH3. As amostras após a reação foram caracterizadas por TPO. Os ensaios de atividade foram conduzidos em reator tubular de leito fixo, com carga de catalisador de 100 mg, na faixa de temperaturas entre 300 e 400 °C, utilizando-se uma vazão de alimentação de etanol na faixa de 0,2 a 1,2 mL.h-1. Foram realizados três tipos de ensaios: com diferentes temperaturas de reação, teste de influência do tempo de residência e teste de estabilidade dos catalisadores. Os testes de atividade catalítica da zeólita comercial modificada, conduzidos em diferentes temperaturas de reação, sugerem que o metal e sua quantidade, assim como a temperatura de reação, influenciam na seletividade para formação dos hidrocarbonetos superiores. Quanto aos catalisadores preparados a partir da modificação da zeólita sintetizada através da combinação de Ni e Zn, observou-se a influência do teor de cada metal e a necessidade de serem empregadas temperaturas de reação mais elevadas (400 °C) para obtenção dos hidrocarbonetos pesados. O teste de avaliação do tempo de residência mostrou que vazões menores (0,3-0,4 mL.h-1) favorecem a formação dos produtos pesados. Através do teste de estabilidade constatou-se que ao final de 10 horas de reação a conversão do etanol ainda foi de 100%, mas que a seletividade dos catalisadores para os hidrocarbonetos superiores foi diminuindo ao longo da reação devido à deposição de carbono sobre o catalisador. / The crude oil is the main raw material used to produce fuels, lubricants and petrochemicals. Currently, due to its increasing price some alternatives for petroleum replacement are being investigated. Among them, the renewable ones, such as ethanol, are receiving great attention. The catalytic conversion of ethanol is a potential source for obtaining liquid hydrocarbons, such as benzene, toluene, etc., that are of great interest in chemical industry. This work aim to evaluate the effect of different metals on HZSM-5 supported catalysts for the ethanol conversion into variable products. A series of catalysts containing 2.5 wt% of the metals La, Ca, Li, Mg and Ni were impregnated on commercial HZSM-5. Other series were prepared with different amounts of Ni, and with different combination of Ni and La on commercial HZSM-5. Subsequently, the HZSM-5 zeolite was synthesized in the laboratory and impregnated with Ni and/or Zn. Samples were characterized by specific area SBET, XRD and NH3-TPD. The spent catalysts were characterized by TPO. The catalyst activity was evaluated by catalytic conversion of ethanol experiments, carried out in a tubular fixed bed reactor with catalyst weight of 100 mg in the temperature range between 300 and 400 °C, using a feed rate of ethanol in the range of 0.2 to 1.2 mL.h-1. Three types of experiments were performed: with different reaction temperatures, different residence time and test of catalyst stability. The results with different reaction temperatures suggest that the type and the amount of metal used for the modification of commercial HZSM-5 zeolite influence the selectivity for the formation of higher hydrocarbons as well as the reaction temperature. For the catalysts prepared by modification of the synthesized HZSM-5 using Ni and/or Zn, the influence of the content of each metal and the reaction temperature can be observed. The residence time test showed that the lower flow rates favor the formation of heavy products. Total ethanol conversion was obtained during the 10 h reaction experiments for catalysts stability evaluation. However the catalysts selectivity for higher hydrocarbons decreased toward the end of the reaction due to the formation and deposition of coke on the catalyst surface.

O petróleo é a principal matéria-prima empregada para produzir combustíveis, lubrificantes e produtos petroquímicos. Atualmente, devido ao fato desta fonte não ser renovável e estimar-se a sua extinção, busca-se por fontes renováveis de energia que possam vir a substituí-la. Nesse contexto, o etanol vem sendo investigado por ser uma alternativa sustentável para a obtenção de hidrocarbonetos de maior valor agregado, tais como, eteno, propeno, benzeno, tolueno, entre outros, através de sua conversão catalítica em condições controladas. Este trabalho teve por finalidade avaliar o efeito de diferentes catalisadores metálicos suportados em zeólita HZSM-5 na reação de conversão do etanol em produtos de maior valor agregado. Para isso, prepararam-se catalisadores com 2,5 % em massa dos metais La, Ca, Li, Mg e Ni impregnados na zeólita HZSM-5 comercial. A seguir foram preparados catalisadores a partir da modificação da zeólita HZSM-5 com diferentes teores de Ni e, na sequência, amostras com diferente combinação de Ni e La. Posteriormente, a zeólita HZSM-5 foi sintetizada em laboratório e impregnada através da combinação entre os metais Ni e Zn. Os catalisadores antes do seu emprego nos ensaios catalíticos foram caracterizados por medidas de área específica SBET, DRX e TPD-NH3. As amostras após a reação foram caracterizadas por TPO. Os ensaios de atividade foram conduzidos em reator tubular de leito fixo, com carga de catalisador de 100 mg, na faixa de temperaturas entre 300 e 400 °C, utilizando-se uma vazão de alimentação de etanol na faixa de 0,2 a 1,2 mL.h-1. Foram realizados três tipos de ensaios: com diferentes temperaturas de reação, teste de influência do tempo de residência e teste de estabilidade dos catalisadores. Os testes de atividade catalítica da zeólita comercial modificada, conduzidos em diferentes temperaturas de reação, sugerem que o metal e sua quantidade, assim como a temperatura de reação, influenciam na seletividade para formação dos hidrocarbonetos superiores. Quanto aos catalisadores preparados a partir da modificação da zeólita sintetizada através da combinação de Ni e Zn, observou-se a influência do teor de cada metal e a necessidade de serem empregadas temperaturas de reação mais elevadas (400 °C) para obtenção dos hidrocarbonetos pesados. O teste de avaliação do tempo de residência mostrou que vazões menores (0,3-0,4 mL.h-1) favorecem a formação dos produtos pesados. Através do teste de estabilidade constatou-se que ao final de 10 horas de reação a conversão do etanol ainda foi de 100%, mas que a seletividade dos catalisadores para os hidrocarbonetos superiores foi diminuindo ao longo da reação devido à deposição de carbono sobre o catalisador. / The crude oil is the main raw material used to produce fuels, lubricants and petrochemicals. Currently, due to its increasing price some alternatives for petroleum replacement are being investigated. Among them, the renewable ones, such as ethanol, are receiving great attention. The catalytic conversion of ethanol is a potential source for obtaining liquid hydrocarbons, such as benzene, toluene, etc., that are of great interest in chemical industry. This work aim to evaluate the effect of different metals on HZSM-5 supported catalysts for the ethanol conversion into variable products. A series of catalysts containing 2.5 wt% of the metals La, Ca, Li, Mg and Ni were impregnated on commercial HZSM-5. Other series were prepared with different amounts of Ni, and with different combination of Ni and La on commercial HZSM-5. Subsequently, the HZSM-5 zeolite was synthesized in the laboratory and impregnated with Ni and/or Zn. Samples were characterized by specific area SBET, XRD and NH3-TPD. The spent catalysts were characterized by TPO. The catalyst activity was evaluated by catalytic conversion of ethanol experiments, carried out in a tubular fixed bed reactor with catalyst weight of 100 mg in the temperature range between 300 and 400 °C, using a feed rate of ethanol in the range of 0.2 to 1.2 mL.h-1. Three types of experiments were performed: with different reaction temperatures, different residence time and test of catalyst stability. The results with different reaction temperatures suggest that the type and the amount of metal used for the modification of commercial HZSM-5 zeolite influence the selectivity for the formation of higher hydrocarbons as well as the reaction temperature. For the catalysts prepared by modification of the synthesized HZSM-5 using Ni and/or Zn, the influence of the content of each metal and the reaction temperature can be observed. The residence time test showed that the lower flow rates favor the formation of heavy products. Total ethanol conversion was obtained during the 10 h reaction experiments for catalysts stability evaluation. However the catalysts selectivity for higher hydrocarbons decreased toward the end of the reaction due to the formation and deposition of coke on the catalyst surface.

O petróleo é a principal matéria-prima empregada para produzir combustíveis, lubrificantes e produtos petroquímicos. Atualmente, devido ao fato desta fonte não ser renovável e estimar-se a sua extinção, busca-se por fontes renováveis de energia que possam vir a substituí-la. Nesse contexto, o etanol vem sendo investigado por ser uma alternativa sustentável para a obtenção de hidrocarbonetos de maior valor agregado, tais como, eteno, propeno, benzeno, tolueno, entre outros, através de sua conversão catalítica em condições controladas. Este trabalho teve por finalidade avaliar o efeito de diferentes catalisadores metálicos suportados em zeólita HZSM-5 na reação de conversão do etanol em produtos de maior valor agregado. Para isso, prepararam-se catalisadores com 2,5 % em massa dos metais La, Ca, Li, Mg e Ni impregnados na zeólita HZSM-5 comercial. A seguir foram preparados catalisadores a partir da modificação da zeólita HZSM-5 com diferentes teores de Ni e, na sequência, amostras com diferente combinação de Ni e La. Posteriormente, a zeólita HZSM-5 foi sintetizada em laboratório e impregnada através da combinação entre os metais Ni e Zn. Os catalisadores antes do seu emprego nos ensaios catalíticos foram caracterizados por medidas de área específica SBET, DRX e TPD-NH3. As amostras após a reação foram caracterizadas por TPO. Os ensaios de atividade foram conduzidos em reator tubular de leito fixo, com carga de catalisador de 100 mg, na faixa de temperaturas entre 300 e 400 °C, utilizando-se uma vazão de alimentação de etanol na faixa de 0,2 a 1,2 mL.h-1. Foram realizados três tipos de ensaios: com diferentes temperaturas de reação, teste de influência do tempo de residência e teste de estabilidade dos catalisadores. Os testes de atividade catalítica da zeólita comercial modificada, conduzidos em diferentes temperaturas de reação, sugerem que o metal e sua quantidade, assim como a temperatura de reação, influenciam na seletividade para formação dos hidrocarbonetos superiores. Quanto aos catalisadores preparados a partir da modificação da zeólita sintetizada através da combinação de Ni e Zn, observou-se a influência do teor de cada metal e a necessidade de serem empregadas temperaturas de reação mais elevadas (400 °C) para obtenção dos hidrocarbonetos pesados. O teste de avaliação do tempo de residência mostrou que vazões menores (0,3-0,4 mL.h-1) favorecem a formação dos produtos pesados. Através do teste de estabilidade constatou-se que ao final de 10 horas de reação a conversão do etanol ainda foi de 100%, mas que a seletividade dos catalisadores para os hidrocarbonetos superiores foi diminuindo ao longo da reação devido à deposição de carbono sobre o catalisador. / The crude oil is the main raw material used to produce fuels, lubricants and petrochemicals. Currently, due to its increasing price some alternatives for petroleum replacement are being investigated. Among them, the renewable ones, such as ethanol, are receiving great attention. The catalytic conversion of ethanol is a potential source for obtaining liquid hydrocarbons, such as benzene, toluene, etc., that are of great interest in chemical industry. This work aim to evaluate the effect of different metals on HZSM-5 supported catalysts for the ethanol conversion into variable products. A series of catalysts containing 2.5 wt% of the metals La, Ca, Li, Mg and Ni were impregnated on commercial HZSM-5. Other series were prepared with different amounts of Ni, and with different combination of Ni and La on commercial HZSM-5. Subsequently, the HZSM-5 zeolite was synthesized in the laboratory and impregnated with Ni and/or Zn. Samples were characterized by specific area SBET, XRD and NH3-TPD. The spent catalysts were characterized by TPO. The catalyst activity was evaluated by catalytic conversion of ethanol experiments, carried out in a tubular fixed bed reactor with catalyst weight of 100 mg in the temperature range between 300 and 400 °C, using a feed rate of ethanol in the range of 0.2 to 1.2 mL.h-1. Three types of experiments were performed: with different reaction temperatures, different residence time and test of catalyst stability. The results with different reaction temperatures suggest that the type and the amount of metal used for the modification of commercial HZSM-5 zeolite influence the selectivity for the formation of higher hydrocarbons as well as the reaction temperature. For the catalysts prepared by modification of the synthesized HZSM-5 using Ni and/or Zn, the influence of the content of each metal and the reaction temperature can be observed. The residence time test showed that the lower flow rates favor the formation of heavy products. Total ethanol conversion was obtained during the 10 h reaction experiments for catalysts stability evaluation. However the catalysts selectivity for higher hydrocarbons decreased toward the end of the reaction due to the formation and deposition of coke on the catalyst surface.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20579号 / 工博第4359号 / 新制||工||1678(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 河瀬 元明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

No description available.

Aliphatic polyesters such as polycaprolactone and polylactide have received more attention in recent years for their use in biomedical applications because of their biodegradable nature. These polymers are often synthesized using homogeneous metal complexes. Unfortunately, using homogeneous metals as catalysts leads to metal contamination in the product polymer, a result which is highly undesirable in a polymer intended for biomedical use. More recent work has shown that these polymers can be synthesized using homogeneous metal-free complexes. These catatlysts are generally less active than metal catalysts, and although they do not contaminate the polymer with metal residue, they are still difficult to recover and hence recycle for further use. In this work, we attempted to create a metal-free, silica-supported catalyst for use in the synthesis of polycaprolactone or polylactide. Ultimately, n-propylsulfonic acid-functionalized porous and nonporous silica materials are evaluated in the ring-opening polymerization of epsilon-caprolactone. All catalysts allow for the controlled polymerization of the monomer, producing polymers with controlled molecular weights and narrow polydispersities. Polymerization rates are low, with site-time-yields generally one to three orders of magnitude lower than metal-based systems. The catalysts are easily recovered from the polymerization solution after use and are shown to contain significant residual adsorbed polymer. Solvent extraction techniques are useful for removing most of the polymer, although the extracted solids are not effective catalysts in recycle experiments. These new materials represent a green alternative to traditional metal-based catalysts, as they are recoverable and leave no metal residues in the polymer.

Ο κύριος στόχος της παρούσας εργασίας είναι η αποσαφήνιση του τρόπου εναπόθεσης και της τοπικής δομής των ειδών κοβαλτίου που σχηματίζονται στην διεπιφάνεια «τιτάνια / ηλεκτρολυτικό διάλυμα» κατά το στάδιο του εμποτισμού. Προκειμένου να επιτευχθεί ο στόχος αυτός προβήκαμε σε κατάλληλη θεωρητική και υπολογιστική επεξεργασία δεδομένων, που προέρχονται από την εφαρμογή ηλεκτροχημικών τεχνικών, την εκτέλεση πειραμάτων προσρόφησης και την εφαρμογή φασματοσκοπικών τεχνικών, καθώς επίσης και σε ab-initio υπολογισμούς για την εξακρίβωση του είδους των επιφανειακών οξυγόνων, των φορτίων τους και των συγκεντρώσεών τους. Συγκεκριμένα, εκτελέστηκαν πειράματα στα οποία μελετήθηκε η μεταβολή του pH κατά την εναπόθεση των ειδών του κοβαλτίου στην επιφάνεια της τιτάνιας, πειράματα τιτλοδοτήσεων Co-H+ σε σταθερό pH, καθώς και πειράματα “adsorption edges” προκειμένου να ληφθεί μια γενική εικόνα της έκτασης της προσρόφησης των ιόντων κοβαλτίου σε μια ευρεία περιοχή pH. Επιπλέον, μελετήθηκε η μεταβολή του σημείου μηδενικού φορτίου και του ισοηλεκτρικού σημείου της τιτάνιας, εκτελώντας πειράματα ποτενσιομετρικών τιτλοδοτήσεων μάζας και μικροηλεκτροφόρησης, αντιστοίχως, παρουσία των ιόντων αυτών. Όλα τα παραπάνω, σε συνδυασμό με την φασματοσκοπική τεχνική της διάχυτης ανάκλασης υπέδειξαν το σχηματισμό μονοπυρηνικών / ολιγοπυρηνικών συμπλόκων εσωτερικής σφαίρας κατά την εναπόθεση των ιόντων [Co(H2O)6]2+ στη διεπιφάνεια “τιτάνιας / ηλεκτρολυτικού διαλύματος”. Η αποσαφήνιση όμως της ακριβούς δομής των συμπλόκων αυτών καθώς και η εξακρίβωση της σχετικής τους συγκέντρωσης, σε διάφορες επιφανειακές συγκεντρώσεις Co(II) κατέστη δυνατή με την συνδυασμένη χρήση ημιεμπειρικών κβαντομηχανικών υπολογισμών, στερεοχημικών θεωρήσεων καθώς και προσομοίωσης των δεδομένων εναπόθεσης. Στο συμπαγές τμήμα της διεπιφάνειας “τιτάνιας / ηλεκτρολυτικού διαλύματος” και για χαμηλές καθώς και μεσαίες επιφανειακές συγκεντρώσεις Co(II) σχηματίζονται μονοπυρηνικά σύμπλοκα. Είναι πολύ πιθανός ο σχηματισμός μιας μονο-υδρολυμένης Ti2O-TiO διαμόρφωσης καθώς και μιας δι-υποκατεστημένης TiO-TiO, η οποία έχει υποστεί δυο υδρολύσεις. Στην πρώτη διαμόρφωση ένα υδατικός υποκαταστάτης αντικαθίσταται από ένα γεφυρωμένο επιφανειακό οξυγόνο ενώ ένας άλλος από ένα ακραίο επιφανειακό οξυγόνο. Στην δεύτερη διαμόρφωση δυο υδατικοί υποκαταστάτες αντικαθίσταται από δυο ακραία επιφανειακά οξυγόνα. Επίσης σε υψηλές επιφανειακές συγκεντρώσεις Co(II) παρατηρείται και ο σχηματισμός διπυρηνικών και τριπυρηνικών συμπλόκων εσωτερικής σφαίρας. / The interfacial chemistry of the impregnation step involved in the synthesis of cobalt catalysts supported on titania was investigated with regard to the mode of interfacial deposition of the aqua complex [Co(H2O)6]2+ on the “titania/electrolyte solution” interface, the structure of the inner-sphere complexes formed, and their relative interfacial concentrations. Several methodologies based on the application of deposition experiments and electrochemical techniques were used in conjunction with diffuse-reflectance spectroscopy. These suggested the formation of mononuclear/ oligonuclear inner-sphere complexes on deposition of the [Co(H2O)6]2+ ions at the “titania/electrolyte solution” interface. The joint application of semiempirical quantum-mechanical calculations, stereochemical considerations and modeling of the deposition data revealed the exact structure of these complexes and allowed their relative concentrations at various Co(II) surface concentrations to be determined. It was found that the interface speciation depends on the Co(II) surface concentration. Mononuclear complexes are formed at the compact layer of the “titania/electrolyte solution” interface for low and medium Co(II) surface concentrations. Formation of mono-hydrolyzed Ti2O–TiO and the dihydrolyzed TiO–TiO disubstituted configurations is very probable. In the first configuration one water ligand of the [Co (H2O)6]2+ ion is substituted by a bridging surface oxygen atom and another by a terminal surface oxygen atom. In the second configuration two water ligands of the [Co(H2O)6]2+ ion are substituted by two terminal surface oxygen atoms. Binuclear and trinuclear inner-sphere complexes are formed, in addition to the mononuclear ones, at relatively high Co(II) surface concentrations