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Síntese de titanatos alcalinos e avaliação na transesterificação catalítica
(Universidade Federal de São Carlos, 2012-06-11) Marciniuk, Letícia Ledo; Cardoso, Dilson; https://lattes.cnpq.br/2462847535959232; https://lattes.cnpq.br/9243858170287624
Three methods for the synthesis of sodium titanates were investigated: solid state treatment (800 oC), hydrothermal treatment (110 oC) and sol-gel method (55 oC). The titanium oxide was used as starting compound for xerothermal and hydrothermal treatments. The titanium (IV) n-butoxide was used in the sol-gel method. The samples were characterized by X-ray diffraction, energy-dispersive X-ray, atomic absorption spectroscopy, scanning electron microscopy, thermogravimetry coupled to mass spectroscopy, nitrogen physisorption, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS). The materials synthesized were used as heterogeneous-basic catalysts in the transesterification reaction between ethyl acetate and methanol, performed under mild conditions: 50 oC, 30 min of reaction time, 4 wt. % of catalyst and molar ratio of ester:alcohol 1:6. The solid prepared by sol-gel method was the most active leading to esters yields around 30 %. This non-calcined material showed high catalytic stability. The loss of activity on the fourth cycle was accompanied by the appearance of a new species of oxygen, identified using XPS analysis. The XPS spectrum showed that the basic character of this oxygen species was inferior to that of the original species, which could explain the loss of catalytic activity. The deactivation was accompanied by the intensification of a second Na 1s component at higher binding energy. The migration of these ions to the catalyst surface reduced their availability for the formation of active Ti-O-Na+ sites, which explain the loss of catalytic activity after the fourth test cycle or after calcination of the material, both of which resulted in the same effect.
Sobre a estabilidade de catalisadores de cobalto suportados durante a reforma do etanol
(Universidade Federal de São Carlos, 2012-06-11) Ávila Neto, Cícero Naves de; Bueno, José Maria Corrêa; https://lattes.cnpq.br/0157452280626031; https://lattes.cnpq.br/5876235459236551
Cobalt-based catalysts supported on γ-alumina and magnesium aluminate modified with lanthanum and cerium have been applied to various conditions of reforming of ethanol. The initial challenge was to control the rate of carbon accumulation, a major cause of deactivation of catalysts under steam reforming of ethanol. In situ X-ray absorption spectroscopy analyses showed that the rate of carbon accumulation is inversely proportional to the amount of Co2+ species and directly proportional to the amount of Co0 species. X-ray photoelectron spectroscopy analyses showed that, after reducing the catalysts in hydrogen, the oxidized fraction of the particles is mainly on their surface. Both the oxidized and reduced fractions of cobalt crystallites have face-centered cubic structure. The concentration of superficial oxygen under reforming conditions is determined by the curvature of the surface of the particles, the nature of the supports and the presence of promoters such as platinum and copper. The concentration of superficial oxygen is also highly sensitive to reaction conditions such as the composition and amount of oxidizing agents, such as oxygen and water, and reaction temperature. The rate of accumulation of carbon could be controlled with co-feeding oxygen to the reactor, process called oxy-reforming of ethanol, and using ceria as support. However, stability tests showed that catalyst deactivation may also occur by oxidation of metal sites. The ignition of the reforming process takes place in a microregion at the entrance of the catalyst bed where ethanol is fully oxidized, releasing energy and increasing the local temperature. Spatial-resolved X-ray absorption spectroscopy analyses showed that the ratio Co2+/Co0 is much greater than one inside this microregion. The high local temperature and the presence of oxidized species in the entrance of the bed produce the appropriate conditions which lead the Co2+ ions to diffuse into the defect spinel structure of γ-alumina, leading to loss of potentially active sites for reforming of ethanol. This phenomenon is unleashed as a wave that propagates from the entrance of the bed downstream to the regions where Co2+ species exist. However, one can prevent the diffusion of Co2+ species to the structure of γ- alumina using aluminates as supports.
As representações sociais das mudanças do clima e suas implicações no processo de territorialização: os Bijagós da ilha de Formosa, Guiné-Bissau
(Universidade Federal de São Carlos, 2012-06-11) Santy, Boaventura Rodrigues Vaz Horta; Valêncio, Norma Felicidade Lopes da Silva; https://lattes.cnpq.br/7161606146208875; https://lattes.cnpq.br/8398564807934695
The study describes and analyzes sociologically, from a qualitative approach, the social representations of the people of the island of Formosa Bijagó about possible threats related to climate change, its consequences in terms of the form of territorial occupation and way of life characteristic of that group. For this, we adopted the following methodological procedures: a) A review of the state of the art about the concepts of vulnerability related to climate change, the increasing vulnerability, risk and social representations, b) documentary research and fieldwork. For Bijagó the natural and the social are inextricably linked, to the extent that a crisis in the social system would have negative effects on natural sistem. Thus, the adverse changes that are occurring in nature around them, would be signs of displeasure from their ancestors about the differences and crises with the community, which are in power to control and manipulate the events of nature.
Processamento digital de imagens para inferência de risco de doença fúngica da bananicultura
(Universidade Federal de São Carlos, 2012-06-11) Bendini, Hugo do Nascimento; Cruvinel, Paulo Estevão; https://lattes.cnpq.br/7924553462118511; https://lattes.cnpq.br/0260327521376255
The digital image processing has been used to solve a significant number of problems in the agricultural sector, especially with the evolution of remote sensing systems. This work presents a computational model based on digital image processing and remote sensing to infer about the risk in the agricultural environment. To validate the method, a experimental study was conducted about the risk of fungal disease in banana plantations. Temporal series of meteorological and monitoring data of the disease, organized in classes for the definition of probability distribution models, based on polynomial functions were used to validate results as well as satellite images integrated by fusion techniques, geometric corrections and re-sampling with interpolators based on kriging techniques. Fusion methods by IHS (Intensity, Hue, and Saturation) and PCA (Principal Component Analysis) and the Gaussian models, exponential and cylindrical for the ordinary kriging were tested. The IHS fusion technique demonstrated to be more interesting in relation the PCA technique, with correlation coefficients between bands 2, 3 and 4 originals and hybrids, of 0.2318, 0.0304 and 0.1800, respectively. The method of ordinary kriging for re-sampling of the images showed better results when adjusted by the Gaussian model. The proposed method is feasible to the development of risk maps of disease occurrence, since confer spatial and temporal variability in relation to the model existing on the literature for the region.