TAP Reactor Development and Application in the Kinetic Characterization of Catalysts for Heterogeneously Catalyzed Gas Phase Reactions

This manuscript describes the application and further development of the TAP technique in kinetic characterization of heterogeneous catalysis. The major application of TAP systems is to study mechanisms, kinetics and transport phenomena in heterogeneous catalysis, all of which is made possible by the sub-millisecond time resolution. Furthermore, the kinetic information obtained can be used to gain an insight into the mechanism occurring over the catalyst system. This is advantageous as heterogeneous catalysts with an improved efficiency can be developed as a result. TAP kinetic studies are carried out at low pressure (~1x10-7 mbar) and TAP pulses are sufficiently small (1013-1015 molecules) so as to maintain this low pressure. The use of a small number of molecules in comparison to the total number of active sites means the state of the catalyst remains relatively unchanged. The use of the low intensity pulses also makes the pressure gradient negligible and so allows the TAP reactor system to operate in the Knudsen Diffusion regime, where gas-gas reactions are eliminated. Hence only gas-catalyst reactions are investigated and, by the use of moment analysis of observed exit flow, rate constants of elementary steps of the reaction can be obtained.

In this manuscript, two attempts to further the TAP technique are reported. Firstly, the work undertaken at QUB to attempt to control the number of molecules of condensable reagents that can be pulsed during a TAP pulse experiment is disclosed. Secondly, a collaborative project with SAI Ltd Manchester is discussed in a separate chapter, where technical details and validation of a customised time of flight mass spectrometer (ToF MS) for the QUB TAP-1 system are reported. A collaborative project with Cardiff Catalysis Institute focusing on the study of CO oxidation over hopcalite catalysts is also reported. The analysis of the experimental results has provided an insight into the possible mechanism of the oxidation of CO over these catalysts. A correction function has also been derived which accounts for the adsorption of reactant molecules over inert materials that are used for the reactor packing in TAP experiments. This function was then applied to the selective reduction of O2 in a H2 rich ethene feed, so that more accurate TAP moment based analysis could be conducted.

Evolution and Enabling Capabilities of Spatially Resolved Techniques for the Characterization of Heterogeneously Catalyzed Reactions

The development and optimization of catalysts and catalytic processes requires knowledge of reaction kinetics and mechanisms. In traditional catalyst kinetic characterization, the gas composition is known at the inlet, and the exit flow is measured to determine changes in concentration. As such, the progression of the chemistry within the catalyst is not known. Technological advances in electromagnetic and physical probes have made visualizing the evolution of the chemistry within catalyst samples a reality, as part of a methodology commonly known as spatial resolution. Herein, we discuss and evaluate the development of spatially resolved techniques, including the evolutions and achievements of this growing area of catalytic research. The impact of such techniques is discussed in terms of the invasiveness of physical probes on catalytic systems, as well as how experimentally obtained spatial profiles can be used in conjunction with kinetic modelling. Furthermore, some aims and aspirations for further evolution of spatially resolved techniques are considered.

Modified electrodes with Keggin-type polyoxotungstates

O objectivo deste trabalho é a produção de novos eléctrodos modificados com polioxotungstatos (POMs) do tipo Keggin, incluindo POMs lacunares e substituídos por metais de transição. A preparação e caracterização dos polioxotungstatos encontram-se descritas no Capítulo 2. No Capítulo 3 descreve-se a produção de eléctrodos de carbono vítreo funcionalizados com sais híbridos de tetra-n-butilamónio de vários silicotungstatos pelo método de evaporação da gota. As propriedades electroquímicas dos polioxotungstatos imobilizados foram comparadas com as das espécies solúveis correspondentes. A morfologia dos depósitos foi avaliada por microscopia óptica e por microscopia electrónica de varrimento. No capítulo 4 descreve-se a preparação de novos eléctrodos compósitos de carbono e poli(hexilmetacrilato) com fosfotungstatos. Os estudos electroquímicos revelaram que as principais características dos POMs são mantidas e que os processos de redução são controlados por difusão, dependendo da difusão dos protões da solução. O Capítulo 5 descreve a construção de filmes em multicamadas ultrafinos contendo POMs e polietilenimina, preparados pelo método de auto-montagem camada-sobre-camada em eléctrodos de carbono vítreo. Os filmes em multicamada foram caracterizados por voltametria cíclica e por microscopia electrónica de varrimento e foi usada a espectroscopia de absorção de UV-Vis em placas de quartzo para monitorar o crescimento de filme. Os resultados voltamétricos revelaram que os processos de redução dos POM são confinados à superfície. Alguns destes eléctrodos modificados revelaram propriedades electrocatalíticas relativamente à redução dos aniões nitrito, bromato e/ou iodato. A espectroscopia de impedância electroquímica também foi usada na caracterização destes filmes e os resultados revelaram que a resistência à transferência de carga aumenta com o aumento do número de bicamadas para ambas as espécies redox, indicando que a espessura do filme tem um efeito importante sobre a cinética de reacções de transferência de carga. No capítulo 6 descreve-se a síntese de filmes híbridos orgânicos/inorgânicos compostos por poli(3,4-etilenodioxitiofeno) (PEDOT) e por silicotungstatos do tipo Keggin através da polimerização electroquímica, em condições aquosas, na superfície de electrodos de carbono vítreo. A voltametria cíclica revelou que as características principais dos POMs são mantidas nos filmes. Verificou-se que estes filmes são muito estáveis, possivelmente devido a fortes interacções electrostáticas entre os POMs aniónicos e o polímero positivamente carregado. A espectroscopia de impedância electroquímica foi também utilizada e os resultados mostraram que a resistência de transferência de carga aumenta com o aumento do pH e para valores de potenciais mais elevados. O capítulo 7 apresenta as conclusões finais e possíveis trabalhos futuros.

Synthesis and biological activities of polyphenolic hybrids - evaluation of anti-cancer, anti-inflammatory and antioxidant activities

Os compostos polifenólicos constituem uma classe de metabolitos secundários de plantas, mas existe também uma enorme quantidade de derivados sintéticos ou semi-sintéticos contendo múltiplas unidades fenólicas. Estes compostos apresentam importantes características biológicas, que dependem das suas estruturas básicas. Certos derivados desta família de compostos, tais como flavonoides, cromonas e cumarinas contribuem para os benefícios da dieta humana, e partilham o núcleo de benzopiran-(2 e 4)-ona ou benzofuran-3-ona. A presente dissertação inclui uma introdução geral e três capítulos que descrevem as novas rotas sintéticas estabelecidas para a preparação de novos híbridos de diversos compostos polifenólicos, assim como a sua elucidação estrutural e termina com a presentação dos resultados da avaliação biológica desses mesmos compostos. No segundo capítulo discute-se a preparação de híbridos de pirimidina- e imidazolidina-polifenóis, especialmente a síntese diastereoseletiva de novos híbridos benzofuran-3-ona-hidantoína e derivados de uracilo. A rota sintética envolve a ação de carbodiimidas sobre os ácidos cromona-(2- e 3)-carboxílicos num só passo ou em dois passos sequenciais, catalisada por uma base orgânica ou inorgânica. O terceiro capítulo descreve reações do tipo adições conjugadas 1,4 - hetero-ciclisações em cascata de compostos 1,3-dicarbonílicos em ácido cromona-3-carboxílico catalisadas por uma base orgânica, que originaram novas cromonas, cromanonas e flavonas polissubstituídas. As bispiranonas [bispiran-2 e 4)-onas] foram elaboradas numa reacção de acoplamento da 4-hidroxicumarina ou da lactona do ácido triacético com o ácido cromona-3-carboxílico ou precursores formil-funcionalizados (ω-formil-2’-hydroxy acetofenonas e cromona-3-carbaldeídos) utilizando organocatálise básica. Finalmente, alargou-se o estudo das adições conjugadas 1,4 para uma variedade de 4-hidroxipiran-2-onas e cetonas α,β-insaturadas para originar novos análogos de warfarina. Obteve-se uma variedade de estruturas complexas por hibridação das unidades de 4-hidroxicumarina ou da lactona do ácido triacético com os novos derivados de cromonas polissubstituídas. Todos as reações foram executadas em condições suaves e ambientalmente favoráveis, utilizando a 4-pirrolidinopiridina como organocatalisador básico. As estruturas dos novos híbridos polifenólicos foram caracterizados por técnicas espectroscópicas de alta resolução, incluindo espectroscopia de ressonância magnética nuclear (1D e 2D) e por difractometria de raios-X, que nos permitiram resolver o complexidade estrutural dos compostos sintetizados. O quarto capítulo apresenta os resultados da avaliação biológica obtidos com os híbridos polifenólicos sintetizados neste trabalho, mostrando a possibilidade de seu envolvimento na terapia do cancro. A maioria dos compostos foram avaliados quanto ao seu efeito sobre a citotoxicidade e proliferação de células leucémicas e ao seu envolvimento na regulação de via pró-inflamatória NF-kB, na qual, os híbridos de biscumarinas exibiram actividades elevadas (IC50 = 6-19 μM para inibição de NF-kB depois de 8 horas de incubação e IC50 = 15-39 μM para efeitos citotóxicos em células cancerosas, após 24 horas de incubação). Uma inibição moderada das enzimas HDAC e Cdc25 foi induzida pelos derivados de benzofuran-3-ona-hidantoína. Catorze dos novos derivados polifenólicos polissubstituídos, tendo como estrutura básica a benzopiran-4-ona, foram avaliados pela sua actividade quimiopreventiva do cancro mediada pela indução de sinalização citoprotectora Nrf2 (fator 2 relacionado com o fator nuclear da proteína E2) e capacidade para inibir a proliferação das células de cancro da mama. Os derivados da classe das cromanonas foram identificados como os indutores mais potentes da actividade Nrf2. As concentrações necessárias para aumentar a actividade de luciferase em 10 vezes (C10) foram de 2,8-21,3 μM. Todos os novos híbridos polifenólicos que apresentam atividade citotóxica e anti-proliferativa não afectam o crescimento de células saudáveis periféricas do sangue (PBMC) (IC50 > 50 μM), indicando a sua seletividade para as células cancerosas e sugerindo que alguns deles são estruturalmente interessantes para posteriores análises. A avaliação da atividade antioxidante utilizando os testes do radical livre DPPH e o poder redutor do ião férrico FRAP foram realizados em algumas estruturas híbridas polifenólicas.

Materials and concepts for CO2 lean ironmaking by pyroelectrolysis

The main purpose of this PhD thesis was to provide convincing demonstration for a breakthrough concept of pyroelectrolysis at laboratory scale. One attempted to identify fundamental objections and/or the most critical constraints, to propose workable concepts for the overall process and for feasible electrodes, and to establish the main requirements on a clearer basis. The main effort was dedicated to studying suitable anode materials to be developed for large scale industrial units with molten silicate electrolyte. This concept relies on consumable anodes based on iron oxides, and a liquid Fe cathode, separated from the refractory materials by a freeze lining (solid) layer. In addition, one assessed an alternative concept of pyroelectrolysis with electron blocking membranes, and developed a prototype at small laboratory scale. The main composition of the molten electrolyte was based on a magnesium aluminosilicate composition, with minimum liquidus temperature, and with different additions of iron oxide. One studied the dynamics of devitrification of these melts, crystallization of iron oxides or other phases, and Fe2+/Fe3+ redox changes under laser zone melting, at different pulling rates. These studies were intended to provide guidelines for dissolution of raw materials (iron oxides) in the molten electrolyte, to assess compatibility with magnetite based consumable anodes, and to account for thermal gradients or insufficient thermal management in large scale cells. Several laboratory scale prototype cells were used to demonstrate the concept of pyroelectrolysis with electron blocking, and to identify the most critical issues and challenges. Operation with and without electron blocking provided useful information on transport properties of the molten electrolyte (i.e., ionic and electronic conductivities), their expected dependence on anodic and cathodic overpotentials, limitations in faradaic efficiency, and onset of side electrochemical reactions. The concept of consumable anodes was based on magnetite and derived spinel compositions, for their expected redox stability at high temperatures, even under oxidising conditions. Spinel compositions were designed for prospective gains in refractoriness and redox stability in wider ranges of conditions (T, pO2 and anodic overpotentials), without excessive penalty for electrical conductivity, thermomechanical stability or other requirements. Composition changes were also mainly based on components of the molten aluminosilicate melt, to avoid undue contamination and to minimize the dissolution rate of consumable anodes. Additional changes in composition were intended for prospective pyroelectrolysis of Fe alloys, with additions of different elements (Cr, Mn, Ni, Ti).

Boronic acids as partners in multicomponent reactions

Tese de doutoramento, Farmácia (Química Farmacêutica e Terapêutica), Universidade de Lisboa, Faculdade de Farmácia, 2014

Cellular polarity in aging: role of redox regulation and nutrition

Cellular polarity concerns the spatial asymmetric organization of cellular components and structures. Such organization is important not only for biological behavior at the individual cell level, but also for the 3D organization of tissues and organs in living organisms. Processes like cell migration and motility, asymmetric inheritance, and spatial organization of daughter cells in tissues are all dependent of cell polarity. Many of these processes are compromised during aging and cellular senescence. For example, permeability epithelium barriers are leakier during aging; elderly people have impaired vascular function and increased frequency of cancer, and asymmetrical inheritance is compromised in senescent cells, including stem cells. Here, we review the cellular regulation of polarity, as well as the signaling mechanisms and respective redox regulation of the pathways involved in defining cellular polarity. Emphasis will be put on the role of cytoskeleton and the AMP-activated protein kinase pathway. We also discuss how nutrients can affect polarity-dependent processes, both by direct exposure of the gastrointestinal epithelium to nutrients and by indirect effects elicited by the metabolism of nutrients, such as activation of antioxidant response and phase-II detoxification enzymes through the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In summary, cellular polarity emerges as a key process whose redox deregulation is hypothesized to have a central role in aging and cellular senescence.

Reactivity of bulky tris(Phenylpyrazolyl) methanesulfonate copper(I) complexes towards small unsaturated molecules

Reaction of the tris(3-phenylpyrazolyl)methane sulfonate species (Tpms(Ph))Li with the copper(I) complex [Cu(MeCN)(4)][PF6] affords [Cu(Tpms(Ph))(MeCN)] 1. The latter, upon reaction with equimolar amounts of cyclohexyl-(CyNC) or 2,6-dimethylphenyl (XylNC) isocyanides, or excess CO, furnishes the corresponding Cu(I)complexes [Cu(Tpms(Ph))(CNR)] (R = Cy 2, Xyl 3) or [Cu(Tpms(Ph))(CO)] 4. The ligated isocyanide in 2 or 3 (or the acetonitrile ligand in 1)is displaced by 3-iminoisoindolin-1-one to afford 5, the first copper(I) complex containing an 3-iminoisoindolin-1-one ligand. The ligated acetonitrile in 1 undergoes nucleophilic attack by methylamine to give the amidine complex [Cu(Tpms(Ph)){MeC(NH)NHMe}] 6, whereas only the starting materials were recovered from the attempted corresponding reactions of 2 and 3 with methylamine. Complexes 1 or 6 form the trinuclear hydroxo-copper(II)species [(mu-Cu){Cu(mu-OH) (2)(Tpms(Ph))}(2)] 7 upon air oxidation in moist methanol. In all the complexes the scorpionate ligand facially caps the metal in the N,N,O-coordination mode.

Metal ions and protein folding: conformational and functional interplay

Dissertation presented to obtain a PhD degree in Biochemistry at Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa

Modulação do estado redox em bactérias por quinoxalinas

As quinoxalinas são compostos heterocíclicos que têm, entre outras, capacidades antimicrobianas, inclusivamente contra bactérias resistentes aos antimicrobianos convencionais. Os mecanismos pelos quais estes compostos exercem a sua atividade ainda não está completamente esclarecido. O objetivo do presente estudo é avaliar o efeito redox em sinergismo/antagonismo com as quinoxalinas em modelos de bactérias com e sem resistências a antimicrobianos. No que se refere aos compostos foram utilizados a quinoxalina 1,4-dióxido (QNX), 2-metil-3-benzilquinoxalina-1,4-dióxido (2M3BQNX), 2-metilquinoxalina-1,4-dióxido (2MQNX) e a 2-amino-3-cianoquinoxalina-1,4-dióxido (2A3CQNX). Quanto aos modelos procariotas, foram utilizados a Salmonella enterica, Klebsiella pneumoniae, Enterococcus faecalis, Staphylococcus saprophyticus, Enterobacter aerogenes, Enterobacter cloacae, Staphylococcus aureus ATCC 25923, Methicillin-resistant Staphylococcus aureus ATCC 43300, Escherichia coli TEM 201 e Escherichia coli TEM 180. Nos compostos químicos em que se verificou a Concentração Mínima Inibitória (CMI), realizou-se o estudo do comportamento do crescimento bacteriano. Relativamente ao estado redox, foi avaliado para cada estirpe sensível, através do rácio GSH/GSSG, nas doses inibitórias e não inibitórias de cada composto. Os resultados apresentam que todos os compostos testados, à exceção do 2M3BQNX, têm atividade antimicrobiana na maioria das estirpes, excetuando a E. faecalis e a S. saprophyticus. Os rácios GSH/GSSG apontam para o efeito oxidante em K. pneumoniae e S. enterica e antioxidante na E. aerogenes. A conclusão do estudo sugere que os compostos apresentam elevada capacidade antibacteriana e influência no equilíbrio redox das bactérias, podendo contribuir para o esclarecimento do mecanismo de ação dos derivados das quinoxalinas 1-4 dióxido, nas bactérias.

Functional characterization and directed engineering of redox proteins for a rational improvement of Bioelectrochemical systems

In recent years, new methods of clean and environmentally friendly energy production have been the focus of intense research efforts. Microbial fuel cells (MFCs) are devices that utilize naturally occurring microorganisms that feed on organic matter, like waste water, while producing electrical energy. The natural habitats of bacteria thriving in microbial fuel cells are usually marine and freshwater sediments. These microorganisms are called dissimilatory metal reducing bacteria (DMRB), but in addition to metals like iron and manganese, they can use organic compounds like DMSO or TMAO, radionuclides and electrodes as terminal electron acceptors in their metabolic pathways.(...)

The role of humor in television advertisement: A study regarding Portuguese consumers’ emotions and reactions

The purpose of this study is to explore the humorous side of television advertisement and its impact on Portuguese consumers’ hearts, minds and wallets. Both qualitative (through in-depth interviews) and quantitative (through an on-line survey and subsequent statistical data analysis) methods were used, guaranteeing a more consistent, strong and valid research. Twenty-five interviews with randomly chosen consumers were conducted face-to-face and three interviews via e-mail with marketers and television advertisers were performed in order to explore profoundly the subject. Moreover, 360 people have answered the on-line survey. Through the analysis of the data collected humor perception was found to be positively correlated with persuasion and intention to purchase the product; intention to share the advert; message comprehension; product liking and development of positive feelings towards the brand and brand credibility variables. The main implication of these findings relies on the fact that humor in advertising is able to boost its effectiveness.

Intramolecular carbenoid insertions : the reactions of [alpha]-diazoketones derived from furanyl, thienyl, benzofuranyl and benzothienyl acetic acids with rhodium (II) acetate /

A number of synthetically useful ring systems can be prepared via the intramolecular insertion of a metal-stabilized carbenoid into a heteroaromatic systems. The chemical outcome of these reactions are dependent not only on the nature of the heteroatom but also on the length of the aliphatic tether linking the carbenoid moiety with the aromatic fragment. Our work with furanyl and thienyl systems containing a single methylene tether have allowed for some rather atypical chemistry. For example, treatment of l-diazo-3-(2-thienyl)-2-propanone (6) with catalytic rhodium (II) acetate yields 5,6- dihydro-4^-cyclopenta[Z>]thiophen-5-one (3) while, the isomeric l-diazo-3-(3-thienyl)-2- propanone(15) gives a spiro-disulphide (20). Novel chemistry was also exhibited in the analogous furanyl systems. While treatment of l-diazo-3-(3-furanyl)-2-propanone (52) with Rh2(OAc)4 resulted in the expected 2-(4-Oxo-2-cyclopentenyliden)acetaldehyde (54), isomeric l-diazo-3-(2- furanyl)-2-propanone (8) undergoes vinylogous Wolff rearrangement to give a mixture of 6a-methyl-2,3,3a,6a-tetrahydrofuro[2,i-^>]furan-2-one (44) and 2-(2-methyl-3-furyl)acetic acid (43). Rhodium acetate catalyzed decomposition of l-diazo-3-(3-benzofuranyl)-2- propanone (84) and l-diazo-3-(2-benzofuranyl)-2-propanone (69)also allows for vinylogous Wolff rearrangement, a chemistry unseen in benzofuranyl systems with longer tethers. A number of interesting products were isolated from the trapping of intermediate ketenes. Decomposition of l-diazo-3-(3-benzothienyl)-2-propanone (100) resulted in the formation of 2,3-dihydro-l//-benzo[^]cyclopenta[^thiophen-2-one (102). However, in addition to (102), a dimer was also generated from the decomposition of l-diazo-3-(2- benzothienyl)-2-propanone (109). The insight into the mechanistic underpinnings of the above reactions are provided by molecular modeling at a PM3 level.