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Nanopartículas de Co suportadas em SiO2: síntese, caracterização e propriedades catalíticas para a reforma a vapor do etanol
(Universidade Federal de São Carlos, 2007-03-16) Ribeiro, Renata Uema; Bueno, José Maria Corrêa; https://lattes.cnpq.br/0157452280626031; https://lattes.cnpq.br/9202692096525582
Colloidal Co Nanoparticles (Co-NPs) were used to prepare supported Co catalysts. The Co- NPs were obtained by thermal decomposition of the precursor Co2(CO)8 in the presence of oleic acid and trioctylphosphine oxide (TOPO), in an inert atmosphere (Ar). The Co- NPs/SiO2 were obtained by impregnation of a colloidal suspension of nanoparticles on the support no-porous SiO2. The effect of the solvent (ethanol and methanol) used in the step of precipitation of the particles, and by tuning the oleic acid/precursor ratio in the catalytic properties for the steam reforming of ethanol were investigated. The catalysts were characterized by Specific Superficial Area (SBET) and Fourier Transform Infrared Spectroscopy of the CO adsorbed (FTIR-CO). By tuning the oleic acid/precursor ratio it was possible to obtain particles sizes in the 2 and 17nm range. The results of FTIR-CO showed that the samples present the band of CO lineally adsorbed in the same position independent of the synthesis conditions, suggesting similar electronic density of the sites of Co. The results of adsorption of H2 and CO suggest that the fraction of acessible sites of Co so much to H2, as to CO, depends on the particles sizes and the residual oleic acid . Then with the increase of the particles sizes, there is a maximum of accessible sites of Co. For the same particle size, it is obtained an increase of the number of accessible sites of Co, using methanol as solvent for precipitation, suggesting smaller recovering. The catalysts prepared with Co-NPs present profiles of similar catalytic activity for the steam reforming of ethanol. Starting from reaction data a mechanism was proposed: in low temperatures, the molecule of ethanol adsorbs in the catalyst surface and it suffers dehydrogenation producing acetaldehyde. The increase of the temperature favors the formation of species CH4 and CO, suggesting the crack of the C-C bond of acetaldehyde for the formation of these products. The activity for the reforming reactions on the Co-NPs/SiO2 begins in approximately 350ºC, suggesting that the activation of the water occurs in this temperature. Therefore it is suggested the oxidation of adsorbed species CHx and CO for the formation of the products CO e CO2, respectively, occurred in temperatures above 350ºC. The catalytic activity depends on the fraction of accessible sites of Co. The reactions results demonstrate that the catalysts prepared with methanol presented higher catalytic activity for the reforming reaction, possibly due to the presence of a larger number of accessible sites of Co.
Nanopartículas de Pt suportadas em Al2O3 e CeO2-Al2O3: síntese, caracterização e propriedades catalíticas para reforma do metano
(Universidade Federal de São Carlos, 2007-03-16) Prieto, Paulo Juliano dos Santos; Bueno, José Maria Corrêa; https://lattes.cnpq.br/0157452280626031; https://lattes.cnpq.br/7186588387858943
A new method to prepare Pt nanoparticles (NPs) dispersed on Al2O3 and CeO2-Al2O3 is described in this work. The Pt-NPs were used to prepare CeO2-Al2O3-supported Pt nanocatalysts (Pt-NPs/Al2O3 and Pt-NPs/CeO2-Al2O3). The catalysts were characterized by BET surface area (SBET), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) reaction of dehydrogenation of cyclohexane to measure Pt dispersion and transmission electronic microscopy (MET). The Pt-NPs were obtained from solution of [PtCl6]2-, poly(Nvinyl- 2-pyrolidone) (PVP) and methanol. The Al2O3 and CeO2-Al2O3 supports were obtained by sol-gel methods. The Pt-NPs/Al2O3 and Pt-NPs/CeO2-Al2O3 catalysts were obtained by addition of Pt-NPs sol during sol-gel synthesis Al2O3 and CeO2-Al2O3. TEM analysis show that the synthesis of the Pt-NPs resulted in particles with average size of 3.2 nm and the results of TEM of the catalysts indicate that Pt particles, finely dispersed on the support occupying probably the interior of the pores of the support. The comparison between FTIR-CO results of Pt-NPs/Al2O3 and Pt-NPs/CeO2-Al2O3 catalysts indicated that the particles in the different catalysts show the same electronic density superficial and that there is a geometric modification on the surface of the particles of the Pt- NPs/CeO2-Al2O3 catalyst provoked by presence of CeOx on the surface of particles. The nanocatalysts Pt-NPs/Al2O3 and Pt-NPs/CeO2-Al2O3 exhibited a high catalytic activity and stability for the steam reforming of methane and for the partial oxidation of methane. The CH4 turnover rate of Pt-NPs/CeO2-Al2O3 catalysts for the steam reforming of methane is around two orders of magnitude higher compared to that of Pt-NPs/Al2O3 catalyst. The high activity for Ce-contaning catalysts is assigned to higher accessibility of the Pt sites to CH4. The high stability of Pt-NPs/Al2O3 and Pt-NPs/CeO2-Al2O3 nanocatalysts in partial oxidation of methane is assigned to the high contact metal-support, which can be caused by preparation method that improves the accessibility of methane to Pt sites.
Cinética do consumo de oxigênio no domínio severo: comparação entre homens e mulheres saudáveis e sedentários
(Universidade Federal de São Carlos, 2007-03-16) Azevedo, Paulo Henrique Silva Marques de; Perez, Sergio Eduardo de Andrade; https://lattes.cnpq.br/9408953831211309; https://lattes.cnpq.br/6559911217770194
The objective of the present study was to analyse and compare the kinetics of oxygen consumption between groups during running in severe domain. Eighteen healthy and sedentary participants were separated by sex, nine men and women (25,20 ± 2,60 years; 22,10 ± 1,80 years and, 77,30 ± 12,30 kg; 58,60 ± 9,60 kg, respectively). An incremental test was realized at treadmill to determine the associated speed to VO2max (vVO2max) and running to exhaustion (Tlim) at vVO2max to determine the VO2 kinetics, with data expressed by average and standard desviation. The VO2max (3,29 ± 0,62 vs 1,90 ± 0,39 L/min) (p≤0,0001); vVO2max (14 ± 2 vs 10 (3) km.h-1) (p<0,0108); amplitude (3 ± 0,70 vs 1,80 ± 0,40 L/min) (p<0,0003) was significantly increased to men. There was not detected a statistic difference between men and women to the constant time [35,80 (22,30) s vs 36,50 (6,60) s] (p<0,2973); Tlim [271 (118) s vs 261 (73) s] (p<0,6849); Target time to achieve VO2max [142,30 (84,50) s vs 175,80 (24,60) s] (p<0,2973); %Tlim to TAVO2max [43,70 (24,40) vs 72,50 (17,70)] (p<0,1903); time maintained at VO2max (TMVO2max) [145,10 (72,50) s vs 64,20 (65,30) s] (p<0,1359), expressed values by median and interquartil amplitude. We conclude that the VO2 kinetics is similar between young and sedentary men and women, despite the biggest VO2 value demonstrated by men. The prescription value to the aerobic intervalled training do not have make off the proposed by literature for medium and high performance athletes.
Content-based Instruction para professores pré-serviço: uma análise da problemática do processo de avaliação
(Universidade Federal de São Carlos, 2007-03-16) Donadio, Luis Felipe Pereira dos Santos; Augusto-Navarro, Eliane Hercules; https://lattes.cnpq.br/5716027350340906; https://lattes.cnpq.br/1226583051013296
There are many foreign language teacher Education courses in Brazil which try to teach the pre-service teachers some language apart from theory studies and the practice needed to the professional development of these future teachers. We have seen that the theory and the classroom practice are almost always placed at the end of the courses in just some semesters. The language and literature course analyzed in this research tries to break with this tradition by using a different methodology which integrates aspects concerning theory studies and classroom practice through language studies (more specifically English). When adopting an innovative methodology to the Brazilian teacher education context, the course we propose to analyze brings many possibilities for research attempting to clarify the results in the usage of this methodology. Among other possibilities, this work focuses the students assessment. Through our personal experience in dealing with this course - since the researcher is a former English teacher of the course in study - we could notice a lot of questioning relating to the students assessment process. During the development of many competences in the course, we found some dilemmas in order to find assessment instruments and procedures which could serve to the integration proposed by the course. As a result, we invited three former teachers from the course to take part in this work in order to investigate how these teachers understood the methodology used in the course and how they performed the assessment process with their students. We have come to the conclusion that the assessment process is done intuitively and there is the need of developing a more appropriate assessment process for this context. We also try to define and characterize the methodology used in the course based on what has been developed in terms of learning-teaching theory.