No description available.

This report gives a general overview on biodiesel production, its motivations, characteristics and recent developments, mainly focused in the Brazilian case. The Brazilian National Program for Production and Use of Biodiesel (PNPB) launched 2003 created a demand of biodiesel and stimulated the biodiesel production. Biodiesel is being produced from soybean oil, followed by animal fats and cottonseed oil, with palm and castor bean oil contributing in small portions. The biodiesel expansion has impacts on environmental and social issues such as deforestation from soya expansion and a decrease of employment levels due to the high degree of mechanization of the soya harvest. Experimental work was developed, using corn oil, ethanol and NaOH as a catalyst. Experiments were made varying significant parameters to find the optimum reaction temperature, reaction time, catalyst amount and molar ratio between ethanol and corn oil. Besides that, another experiment aimed to describe the yield behavior as a function of the reaction time. The produced biodiesel has been characterized by measurements of density, refraction index and viscosity. The amount of 0.4 wt % NaOH, based on the weight of raw oil, was enough to catalyze the reaction of transesterification effectively. A higher amount of alcohol in excess provides a higher yield at mild temperature conditions. But the higher amount of alcohol used, the higher the amount of alcohol in excess presented in the biodiesel phase which has to be eliminated. An increase of the temperature from 40˚C to 50˚C  does not increase the yield in a considerable way. Thus due to the energy saving it is not recommended to increase the temperature to 50˚C. Regarding the evaluation of the conversion as function of time, a high conversion is obtained after 90 min. An extension of the reaction time from 90 to 150min had no significant effect.

Para llevar a cabo en forma sistemática el proceso de descubrimiento de conocimiento en bases de datos, conocido como minería de datos, es necesaria la implementación de una metodología. Actualmente las metodologías para minería de datos se encuentran en etapas tempranas de madurez, aunque algunas como CRISP-DM ya están siendo utilizadas exitosamente por los equipos de trabajo para la gestión de sus proyectos. En este trabajo se establece un análisis comparativo entre las metodologías de minería de datos más difundidas en la actualidad. Para lograr dicha tarea, y como aporte de esta tesis, se ha propuesto un marco comparativo que explicita las características que se deberían tener en cuenta al momento de efectuar esta confrontación.

L’amélioration de la qualité de l’air est un enjeu majeur pour la santé et l’environnement. Le challenge pour les fabricants de convertisseurs catalytiques pour la dépollution automobile est d’optimiser leur formulation pour répondre aux normes réglementant les émissions polluantes se durcissant, tout en rentabilisant l’utilisation de métaux précieux dont les ressources s’épuisent. Dans cette thèse, un nouveau support catalytique MgAl2O4 méso-poreux a été synthétisé par atomisation d’un sol aqueux contenant un copolymère tri-blocs. Les nano-cristallites de MgAl2O4 en contact quasi-ponctuel permettent d’atteindre des taux de dispersion de la phase active Pt-Pd supérieurs à ceux d’un catalyseur d’oxydation Diesel commercialisé, pris comme référence par la société Renault. La phase active d’un catalyseur 2,5%m.PtPd(3:2)[450°C]/MgAl2O4[900°C] présente une stabilité hydrothermale similaire à celle ce dernier grâce aux ancrages chimiques (croissance épitaxiale, solutions solides) et mécaniques (marches atomiques, pores). Bien que la totalité des métaux précieux ne soit pas accessible (insertion, encapsulation) pour l’oxydation du CO, des HC et de NO, les performances catalytiques atteintes par ce catalyseur au cours de vieillissements hydrothermaux sont comparables à celle d’un DOC de référence. La conversion des HC est similaire à celle du DOC de référence et dépendante de la concentration locale des sites actifs. La conversion du CO est légèrement pénalisée car les particules sont de trop petite taille et à l’état oxydé. Enfin, ce catalyseur ne réduit pas les NOx, en revanche il assure une oxydation plus importante de NO en NO2 après vieillissement hydrothermal que le DOC de référence, ainsi que le stockage de NO2. Cela représente un avantage majeur pour le bon fonctionnement du filtre à particules situé en aval du DOC. / The improvement of air quality is a major issue for the health and the environment. The challenge for the manufacturers of catalytic converters for automotive depollution is to optimize their formulation to meet the standards regulating the polluting emissions hardening, while making a profitable use of the precious metals whose resources are becoming exhausted. In this thesis, a new, mesoporous, MgAl2O4, catalytic support was synthesized by atomization of an aqueous sol containing a tri-block copolymer. The MgAl2O4 nanocristallites in point contact enable to reach higher dispersion rates of the Pt-Pd active phase than those of a commercialized DOC taken as reference by Renault. The active phase of the 2,5%m.PtPd(3:2)[450°C]/MgAl2O4[900°C] catalyst presents similar hydrothermal stability to that of the reference DOC thanks to chemical anchoring (epitaxial growth, solid solutions) and mechanical anchoring (atomic steps, pores). Although the totality of the precious metal content is not accessible (insertion, encapsulation) for CO, HC and NO oxidation, the catalytic performances reached by this catalyst during hydrothermal aging are comparable with that of the reference DOC. The conversion of the HC is similar to that of the reference DOC and depends on the local concentration of the active sites. The CO conversion rate is slightly penalized since the particles are too smalls and in an oxidized state. Lastly, this catalyst does not reduce NOx but ensures a more important oxidation of NO in NO2 after a hydrothermal aging than the reference DOC and also the storage of NO2 which have a positive impact on the proper functioning of the downstream diesel particulate filter.

Biodiesel is an attractive alternative fuel for diesel engines.The feedstock for biodiesel production is usually vegetable oil, pure oil or waste cooking oil, or animal fats The most common way today to produce biodiesel is by transesterification of the oils with an alcohol in the presence of an alkaline catalyst. It is a low temperature and low-pressure reaction. It yields high conversion (96%-98%) with minimal side reactions and short reaction time. It is a direct conversion to biodiesel with no intermediate compounds. This work provides an overview concerning biodiesel production. Likewise, this work focuses on the commercial production of biodiesel. The Valdescorriel Biodiesel plant, located in Zamora (Spain), is taken like model of reference to study the profitability and economics of a biodiesel plant. The Valdescorriel Biodiesel plant has a nominal production capacity of 20000 biodiesel tons per year. The initial investment for the biodiesel plant construction is the 4.5 millions €. The benefits are 2 million €/year. The investment is possible to recuperate in less than 3 years. The biodiesel yield can up to 98% with catalyst in excess. The energy used for the biodiesel production is 30% less than the obtained energy from the produced biodiesel. Replacing petro diesel by the biodiesel produced in the plant, the CO2 reduction can reach the 48%. It means that 55 000 tons CO2 per year can be reduced The production of biodiesel from sunflower oil and ethanol using sodium hydroxide as catalyst was performed in the laboratory and the results are discussed. The results are analyzed using the statistic method of Total Quality. The effect of the ethanol/oil ratio and the amount of used catalyst on the yield as well on the properties of the produced biodiesel is studied. The measured properties of the biodiesel are density, viscosity and refraction. The ethanol/oil ratio influences on the biodiesel production. The yield of biodiesel increases with the ethanol/oil ratio.  Regarding the influence of the amount of catalyst on biodiesel production in the studied condition is not possible to achieve a definitive conclusion. But a tendency showing an increasing of the biodiesel yield with the amount of catalyst can be appreciated. The study of the evolution of the transesterification during time shows that a reaction time of one hour is sufficient enough in order to reach the highest yield of biodiesel.

SiC is a hard man-made material and has emerged as an excellent material for a wide range of applications which are exposed to extreme conditions such as high temperatures and harsh chemical environments. These applications range from SiC being used as an abrasive, to a refractory material, to a semiconductor material for high power and high frequency electronic devices. The properties of the material for each application is different, with the semiconductor grade material for electronic devices being the most refined. SiC, with its excellent thermal properties and high resistance to harsh chemical environments, lends itself to being an ideal support for catalyst systems. Various characterisation & analysis techniques such as Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography (GC) are used in this thesis to investigate the suitability of single crystal SiC for high temperature catalytic systems. Low temperature oxidation of methane was used to investigate the catalytic activity of: Porous and standard 4H-SiC with and without Pd Porous and Standard 6H-SiC with and without Pd. Nanocrystalline Beta-SiC powder with and without Pd. Part of the samples were impregnated with Pd using Palladium Nitrate (Pd (NO3)2) which is a common precursor for Pd. Activation treatments which were investigated were oxidation and reduction. Oxidation was generally better in activating the catalyst, as was expected, since the PdO phase is known to be more active in oxidising methane. A mixed set of Pd and PdO were observed by SEM and EDS which were the main characterisation techniques used to analyze the structure of the catalysts before and after the reaction. The Beta-SiC showed by far the best activity which could be attributed to the micro-crystalline powder format in which it was used, where as all other catalysts studied here were derived from crushed wafer pieces. Type II porous 4H-SiC was another of the samples which registered impressive results, vis-à-vis catalytic activity.