Navegando por Assunto "Catalisadores"

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Acesso aberto (Open Access)
Estudo de eletrocatalisadores de PtRu, PtRuRh e PtRuPd obtidos por modificação no Método Borohidreto de Sódio para eletro-oxidação de metanol e etanol
(Universidade Federal do Pará, 2016-01-25) ANDRADE, Flávio Vargas; SOUZA, José Pio Iúdice de; http://lattes.cnpq.br/1448978342555218
PtRu, PtRuRh and PtRuPd electrocatalysts supported on carbon has been widely studied for electro-oxidation of methanol and ethanol. Among different possibilities of preparing these electrocatalysts is the method of reducing with sodium borohydride. For the catalytic activity is optimized, it is necessary that the electrocatalyst is distributed evenly. One possibility is the use of complex precursor salts, including those with amine linker. In this work, we tried to assess the effect of adding an ammonium hydroxide solution (NH4OH) the solution of precursors. The electrocatalysts were characterized physically by Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX) and X-ray diffraction (XRD). For the electrochemical characterization, the techniques of chronoamperometry and cyclic voltammetry were used. The results of EDX showed that the compositions of the electrocatalysts were very close to the nominal composition. The crystallite size and the lattice parameter obtained by XRD showed changes with the change of the method. The TEM results show a homogeneous distribution more particle on electrocatalysts preparations with the addition of NH4OH solution 4 mol L-1 although this is not be determinant in electrocatalytic activity. Nos electrochemical testicles, as chains were for standard electro-oxidation of CO and load monolayer for the mass activity and compared this way. The cyclic voltammetry and chronoamperometry results showed different activities paragraph an electro-oxidation of methanol and ethanol. The results of DEMS electrocatalysts trimetallic of PtRuRh and PtRuPd showed different amounts of products and volatile. This way possible and establish an activity order these electrocatalysts.
Acesso aberto (Open Access)
Estudo do crescimento de nanofitas de céria dopada com gadolínio por sistema de aquecimento por micro-ondas
(2013-09) GONÇALVES, Rosana de Fátima; CASTRO, D. A.; SANTOS, Maria Rita de Cássia; FIGUEIREDO, Alberthmeiry Teixeira de; BARRADO, Cristiano Morita; LEITE, Edson Roberto; GODINHO JÚNIOR, Mario
Cerium oxide (ceria) has attracted attention because of its important applications such as solid oxide fuel cells, catalysts for automobile exhaust gas, catalysts to obtain hydrogen, UV blockers, biomaterials, etc.. Control methods for synthesis of ceria are of great importance to explain or predict these properties. Thus, the objective of this work was to study the growth of cerium oxide nanobelts in a microwave-assisted hydrothermal system, where in 8 min 330 nm nanobelts were obtained at 130 ºC and 3 atm. The results collaborate to the research on reformers for ethanol and/or solid oxide fuel cells anode.
Acesso aberto (Open Access)
Influência do método de preparação de eletrocatalisadores PtRu/C sobre a atividade catalítica frente à reação de oxidação de etanol em meio ácido
(2013) GOMES, Walber dos Santos; SILVA, Uriel Lean Valente; SOUZA, José Pio Iúdice de
In this work the influence of variations in the borohydrate reduction method on the properties of PtRu/C electrocatalysts was investigated. The electrocatalysts were prepared using 1:1 ; 2:1; 5:1; 50:1 and 250:1 molar ratios of NaBH4 to metals. The reduction was also performed by dripping or by fast addition of the solution. The results showed that PtRu nanoparticles obtained by fast addition had the smallest crystallite sizes. It was also noted that the catalytic activity increased as the borohydrate:metal molar ratio increased. The PtRu/C electrocatalyst (50:1) obtained by fast addition presented the best catalytic activity for ethanol electro-oxidation.
Acesso aberto (Open Access)
A statistical evaluation of the effects of process variables during catalytic hydrogenation of passion fruit (passiflora edulis) seed oil
(1998-03) ANDRADE, Géssie Maria Silva de; ROCHA FILHO, Geraldo Narciso da; TAQUEDA, Maria Elena Santos
Hydrogenation of passion fruit (passiflora edulis) seed oil was carried out with a commercial nickel/silica catalyst under different experimental conditions. The influence of reaction parameters (reaction temperature, hydrogen pressure, amount of catalyst, agitation rate and reaction time) on the response variable (iodine value) was studied using a central composite rotatable design and six center points for replication. Under the experimental conditions used, the model response equations for the iodine value showed good agreement with the experimental results.