The main objective of this Thesis is the synthesis, characterization and application in the PROX reaction of several series of catalysts synthesized using different methods, in order to find efficient materials with high catalytic activity. This work has been divided in six chapters. Chapter I presents an introduction about current energy problems and hydrogen (energy carrier) as a solution, with its limitations and advances on its use: storage, transport and security. Finally, its use as a fuel in PEMFC (Proton Exchange Membrane Fuel Cells) and the advantages comparing other existent fuel cells has been discussed. A brief summary was done about the catalytic systems studied in literature for PROX reaction and their characteristics. Following, Chapter 2 describes all the characterization techniques which were used to study the properties of the synthesized supports and catalysts, together with the experimental system employed for the catalytic tests. Most of these equipments belong to SSTTI of University of Alicante or are hand-made systems in the LMA group. DRIFTs and DTP were done at TUDelft, Catalysis Engineering Section. Next chapters contain the most important results obtained during the complete research work; they have been divided in two parts. On one hand, Chapter 3 describes the synthesis of pure TiO2 using five different methods, and its use as platinum support for PROX catalysts. On the other hand, taking into account the obtained results, three synthesis methods were chosen, and the study was centered in the addition of CeO2 to TiO2. Chapter 4 discusses the TixCe(1-x)O2 series synthesized using the sol-gel method. In Chapter 5 a solvothermal procedure was employed for the synthesis of supports with similar composition and, finally, impregnation of cerium over commercial P25 titania was compared in Chapter 6. Each chapter contains a complete study of characterization of both supports and catalysts. Synthesis parameters, pretreatment and reaction conditions were also modified for the best catalyst of the three series. Analyzing the catalysts’ behavior, a reaction mechanism was proposed. Finally, general conclusions summarize the most relevant results obtained in each chapter.

The toxicology of aerosols in occupational settings is often performed through particle collection on a filter followed by reconstitution into cell culture media which can alter the biological effects. Current in vitro exposure systems require additional instruments to control temperature and humidity, making the system bulky and difficult to take to the field. The Portable In Vitro Exposure Cassette (PIVEC) was designed for personal monitoring, characterized using copper nanoparticles, tested with alveolar cells, and set-up for real-time monitoring. Three differently sized copper nanoparticles, 40-800 nm, were dispersed as a dry aerosol and measured gravimetrically and on a number concentration basis to determine the deposition efficiency of the PIVEC. A549 cells, a human alveolar adenocarcinoma epithelial line, were exposed to the aerosols and oxidative stress and cell viability were monitored post-exposure. The deposition efficiency ranged from 0.5% to 18% depending on method of analysis and size of particle. Oxidative stress increased within the first two hours post exposure, however there was no significant difference in cell viability at the four hour time point at deposited doses up to 1.63 mg/cm2. Validation of the PIVEC was done in the laboratory using diesel exhaust. Metal oxide fuel additives are used to reduce emissions; however, additives have been shown to increase emitted nanoparticles. The PIVEC was used to determine the potential cytotoxicity and oxidative activity changes in A549 cells after exposure to either model particles or exhaust generated with or without a commercial, nano-cerium oxide based additive. Acellular experiments suggest a correlation between the deposition and the type of fuel used for the newly designed PIVEC. Cellular results suggest a decrease in cytotoxicity and no statistically significant effect on reactive oxygen species generation with the use of the nano-cerium oxide additive. Rapid monitoring of oxidative stress was performed using an enzyme-based biosensor. The functionalized biosensor uses cytochrome c to measure reactive oxygen species through electrochemical detection during aerosol exposures. When compared to a traditional biological assay, the biosensor response was similar. The PIVEC is a unique device, designed to monitor aerosols using air-liquid interface in vitro techniques including a real-time monitor for oxidative stress.

Facile, one-step synthesis of self-assembling, cationic block copolymers of poly(2-N-(dimethylaminoethyl) methacrylate) (pDMAEMA) and PEO-PPO-PEO (Pluronic®) is developed. The copolymers are obtained via free-radical polymerization of DMAEMA initiated by Pluronic-radicals generated by cerium (IV). The copolymers possess surface activity, are polycationic at pH<7.1, and self-assemble into micelle-like aggregates when neutralized. Potential applications of the novel copolymers for DNA transfection in gene therapy are discussed. / Singapore-MIT Alliance (SMA)

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A new reactor and a novel in-situ sampling technique were developed for the study of the synthesis of Ce02 powders produced from dissolved cerium nitrate salts. The reactor minimized particle recirculation and provided a highly symmetric and undisturbed plasma flow suitable for the analysis of the phenomena affecting the formation of Ce02 powders. The sampling probe provided in-situ sampling of in-flight CeCb particles and allowed continuous sampling without cross contamination. The sampled particles were collected using a wet collection system composed of a mist atomizer acting as a scrubber and a custom-made spray chamber. The entire collection system is portable and it was tested in the particle range of 20 nm to 100 jam. This information provided a picture of how Ce02 particles were formed. A numerical simulation of different plasma operating parameters using Fluent was presented. A comprehensive droplet-to-particle formation mechanism was deduced based on calorimetry. thermodynamics of Ce02 formation, numerical simulations and collected particles. The effect of adding water soluble fuels (alanine and glycine) to the original cerium nitrate solutions was investigated. Fuel addition decreased the temperature of CeC>2 formation by acting as a local heat source as a result of fuel auto-ignition. The addition of fuel caused “particle size discrimination’*, and a single mode particle size distribution centered between 50-140 nm was achieved along the centerline of the reactor. [...] / Un nouveau reacteur et une technique innovatrice d’echantillonnage in situ furent developpes pour etudier la synthese de poudres de Ce02 produites a partir de sels de nitrate de cerium dissous. Le reacteur minimise la recirculation des particules et fournit un plasma non perturbe et grandement symetrique approprie pour l’analyse des phenomenes affectant la formation de poudres de Ce02. De plus, une sonde permet un echantillonnage in situ et en vol des particules de Ce02 et ce, en continu et sans contamination croisee. Les particules ainsi captees sont recueillies grace a un systeme de collecte par voie humide qui est compose d’un atomiseur de brume (mist atomizer) qui joue le role d’un recureur (scrubber) et d’une chambre d’atomisation (spray chamber) maison. Le systeme d’echantillonnage est mobile et fut teste sur des particules ayant des tailles de 20 nm a 100 jam. C’est grace a l’analyse des particules ainsi recueillies que nous sommes en mesure de comprendre comment les particules de Ce02 sont formees. Nous presentons aussi une simulation numerique, effectuee avec le logiciel Fluent, qui utilise les differents parametres d’experimentation. Le mecanisme detaille de la formation des particules a partir de gouttelettes fut deduit grace a des etudes calorimetriques, a une etude thermodynamique de la formation du Ce02, a des simulations numeriques et a l’analyse des particules recueillies. Nous avons aussi etudie l’effet d’un ajout de combustibles hydrosolubles (l’alanine et la glycine) a la solution originale de nitrate de cerium. Cette addition de combustibles diminue la temperature de formation du Ce02 en agissant comme une source locale de chaleur resultant de 1’auto-ignition du combustible. Aussi, le combustible cause une « segregation des particules » selon leur taille.