THENNER SILVA RODRIGUES

THENNER SILVA RODRIGUES

Página do item completo

Resultados de Busca

Agora exibindo 1 - 10 de 11

Controlling the sintering of ceria by shape-controlled synthesis of nanoparticles
2019 - FONSECA, FABIO C.; MACHADO, MARINA F.S.; MORAES, LETICIA P.R.; RODRIGUES, THENNER S.; KABIR, AHSANUL; MARANI, DEBORA; VAN NONG, NGO; ESPOSITO, VINCENZO
The influence of surface energy of Gd-doped CeO2 nanometric crystals with different morphologies on mass diffusion mechanisms is studied. Depending on the starting morphology (nanocubes, nanorods, and random nanoparticles) extremely different microstructures, ranging from rapidly densified to thermodynamically stable porous structures. We investigate Gd-doped ceria (10% molar, GDC) both for its relevance in several chemical, environmental and energy technologies, and because the extensive knowledge on diffusion effects ruling this compound. We synthesized GDC as nanocubes (NC) and nanorods (NR) by a hydrothermal method whereas randomly oriented nanoparticles (RD) were obtained by co-precipitation. All samples were measured as single phase GDC powders with narrow nanoparticle size distributions. The high surface area NR exhibit lower green density as compared to NC. Dilatometric analyses revealed that NR have a pronounced linear retraction starting at low temperatures (~200°C) with maximum sintering activity at ~1100°C. High surface energy in NRs leads to a rapid rod to sphere transformation as well as to a rapid densification despite relatively low green density. On the other hand, the solid state diffusion in NCs is significantly inhibited, as confirmed by the highly porous microstructure of sintered samples. The results indicated the possibility of controlling microstructure of GDC by defining the shape of nanoparticles for different application in which dense or stable pores are required.
Lowering the sintering temperature of a SOFC by morphology control of the electrolyte powder
2019 - MACHADO, M.; MORAES, L.P.R.; RODRIGUES, L.N.; RODRIGUES, T.S.; FONSECA, F.C.
Solid oxide fuel cells are fabricated by two-step sintering at low temperature by controlling the morphology of the gadolinium-doped cerium oxide (GDC) electrolyte powders. The GDC electrolyte was synthesized by a hydrothermal route to obtain highly reactive nanorods that can fully densify at temperatures around 1150 °C. The developed system consists of the GDC electrolyte support, lanthanum strontium cobalt ferrite (LSCF) cathode and Ni/GDC anode. The electrolyte support was prepared by uniaxial die pressing and sintered at 1150 °C, and fuel cells were obtained by co-sintering electrode layers at the same temperature. The performance of the cell was evaluated in hydrogen at intermediate temperatures (IT). The experimental results indicate that high-performance IT-SOFC can be obtained at low sintering temperatures by controlling the morphology of electrolyte powder.
Ethanol steam reforming
2019 - RODRIGUES, THENNER S.; SILVA, FELIPE A. e; CANDIDO, EDUARDO G.; SILVA, ANDERSON G.M. da; GEONMONOND, RAFAEL dos S.; CAMARGO, PEDRO H.C.; LINARDI, MARCELO; FONSECA, FABIO C.
We reported herein a systematic investigation on how the nature of the support affected the catalytic performances of Rh nanoparticles. The prepared catalysts were denoted as Rh/MxOy, where M corresponded to Ce, Ti, Si, Zn, and Al, and Rh was Rh3+ reduction to Rh nanoparticles on the surface of oxides. This strategy was performed in a single step using urea as a mediator and in the absence of any other stabilizer or capping agent. The Rh nanoparticles displayed relatively similar sizes, shapes, and uniform distribution over the supports, differing only in terms of the nature of the support. This strongly affected the metal–support interaction between Rh nanoparticles and the respective oxides, leading to significant differences in their catalytic performances toward the ethanol steam reforming. Here, not only the catalytic activity (in terms of ethanol conversion) was affected, but both the selectivity and stability were also influenced by the nature of the oxide support. Interestingly, the reaction paths as well as the deactivation profile were completely changed as function of the employed support. Such differences were associated with differences in the oxygen storage, oxygen mobility, and acidity/basicity of the supports. We believe that our results can contribute to the development and understanding of Rh-supported catalysts for the applications toward gas-phase transformations such as the ethanol steam reforming reaction.
Synthesis and characterization of catalysts based on nickel, cerium, and lanthanum supported on biocarbon for ethanol steam reforming
2018 - FERREIRA, J.C.; CAVALLARI, R.V.; LIMA, N.B.; RODRIGUES, T.S.; BERGAMASCHI, V.S.; SILVA, F.A. e
Ethanol steam reforming (ESR) is considered asa promising alternative for hydrogen production due to some differentadvantages that include the large availability, relatively low cost, andsuperior reactivity of ethanol as compared to other compounds. Thus, thistechnology is also considered more sustainable and greener as compared to othermethods usually employed for hydrogen production. However, the currentindustrial catalysts suffer from strong deactivation because the extensivecarbon deposition, which limits their performances and utilization. In order toovercome this limitation, we report herein the synthesis of a catalyst based onnickel, cerium and lanthanum supported on activated biocarbon by a microwaveassisted hydrothermal method. In this method, we first performed a hydrothermalactivation of the biocarbon support at 120 °C using nitric acid (0.3 M) in areactor coupled to a microwave source aiming the formation of acid groups atthe surface of our carbonaceous matrix. In a next step, the adsorption of La3+,Ce3+, and Ni3+ onto the activated biocarbon was performed by the addition ofLa(NO3)3.6H2O, Ce(NO3)3.6H2O, and Ni(NO3)3.6H2O in the suspension containingthe activated biocarbon and potassium thiosulfate for stabilization (pH 8.0) at75 °C. The obtained catalyst was then characterized by scanning electronmicroscopy, X-ray dispersive spectroscopy, X-ray diffraction, temperatureprogramed reduction, and surface area by the BET method. After this step, the catalystwas then evaluated towards the ESR, in which 100 % of ethanol conversion wasobserved with the formation of only H2 (~ 60%) and CO2 (ESR products) and COand CH4 as byproducts (both in low concentrations), indicating a goodselectivity for ESR. Good stability was also achieved with no significant lossof activity even after 24 hours of reaction at 550 °C. The reactants and thereaction products were analyzed by gas chromatograph (Agilent 7890A), equippedwith a thermal conductivity detector (TCD) and a flame ionization detector(FID) connected in series.
Preparação de catalisadores de níquel e cério suportados em carvão de coco
2018 - FERREIRA, JOAO C.; CAVALLARI, ROGER V.; SILVA, FELIPE A. e; RODRIGUES, THENNER S.; SILVA, JULIO C.M.; BERGAMASCHI, VANDERLEI S.
O carvão de coco foi ativado pelo processo hidrotermal assistido por microondas (HMO) usando ácido nítrico (2,42 M) nas condições de temperatura de 120 ºC, patamar de 45 minutos, rampa de aquecimento de 10 ºC min-1 e pressão de 3,0 kgf / cm2. Na caracterização usaram-se métodos analíticos como: espectroscopia Raman, medidas de área superficial (BET), análise térmica (TG), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e redução à temperatura programada (TPR). Os catalisadores foram avaliados na reforma a vapor do etanol objetivando a formação de hidrogênio. Foram observadas boas atividades catalíticas com conversão completa do etanol e formação predominante de produtos de reforma (H2 e CO2) e CO e CH4 como subprodutos e em baixas concentrações, indicando uma boa seletividade e estabilidade para a reação de reforma a vapor do etanol com a manutenção total de atividade mesmo após 24 horas de reação a 550 °C.
Synthesis and characterization of catalysts based on nickel, cerium, and lanthanum supported on biocarbon for ethanol steam reforming
2018 - FERREIRA, J.C.; CAVALLARI, R.V.; SILVA, F.A. e; RODRIGUES, T.S.; BERGAMASCHI, V.S.
Ethanol steam reforming (ESR) is considered asa promising alternative for hydrogen production due to some differentadvantages that include the large availability, relatively low cost, andsuperior reactivity of ethanol as compared to other compounds. Thus, thistechnology is also considered more sustainable and greener as compared to othermethods usually employed for hydrogen production. However, the currentindustrial catalysts suffer from strong deactivation because the extensivecarbon deposition, which limits their performances and utilization. In order toovercome this limitation, we report herein the synthesis of a catalyst based onnickel, cerium and lanthanum supported on activated biocarbon by a microwaveassisted hydrothermal method. In this method, we first performed a hydrothermalactivation of the biocarbon support at 120 °C using nitric acid (0.3 M) in areactor coupled to a microwave source aiming the formation of acid groups atthe surface of our carbonaceous matrix. In a next step, the adsorption of La3+,Ce3+, and Ni3+ onto the activated biocarbon was performed by the addition ofLa(NO3)3.6H2O, Ce(NO3)3.6H2O, and Ni(NO3)3.6H2O in the suspension containingthe activated biocarbon and potassium thiosulfate for stabilization (pH 8.0) at75 °C. The obtained catalyst was then characterized by scanning electronmicroscopy, X-ray dispersive spectroscopy, X-ray diffraction, temperatureprogramed reduction, and surface area by the BET method. After this step, the catalystwas then evaluated towards the ESR, in which 100 % of ethanol conversion wasobserved with the formation of only H2 (~ 60%) and CO2 (ESR products) and COand CH4 as byproducts (both in low concentrations), indicating a goodselectivity for ESR. Good stability was also achieved with no significant lossof activity even after 24 hours of reaction at 550 °C. The reactants and thereaction products were analyzed by gas chromatograph (Agilent 7890A), equippedwith a thermal conductivity detector (TCD) and a flame ionization detector(FID) connected in series.
Nanopartículas metálicas suportadas em óxidos sólidos comerciais
2018 - SILVA, FELIPE A. e; RODRIGUES, THENNER S.
Nanoestrelas de óxido de zinco decorados com ouro e níquel para aplicações em catálise e reforma de etanol
2018 - CANDIDO, EDUARDO G.; RODRIGUES, THENNER S.
Synthesis of highly dispersed gold nanoparticles on Al2O3, SiO2, and TiO2 for the solvent-free oxidation of benzyl alcohol under low metal loadings
2019 - GUALTEROS, JESUS A.D.; GARCIA, MARCO A.S.; SILVA, ANDERSON G.M. da; RODRIGUES, THENNER S.; CANDIDO, EDUARDO G.; SILVA, FELIPE A. e; FONSECA, FABIO C.; QUIROZ, JHON; OLIVEIRA, DANIELA C. de; TORRESI, SUSANA I.C. de; MOURA, CARLA V.R. de; CAMARGO, PEDRO H.C.; MOURA, EDMILSON M. de
We reported the organic template-free synthesis of gold (Au) nanoparticles (NPs) supported on TiO2, SiO2, and Al2O3 displaying uniform Au sizes and high dispersions over the supports. The Au-based catalysts were prepared by a deposition– precipitation method using urea as the precipitating agent. In the next step, the solvent-free oxidation of benzyl alcohol was investigated as model reaction using only 0.08–0.05 mol% of Au loadings and oxygen (O2) as the oxidant. Very high catalytic performances (TOF up to 443,624 h-1) could be achieved. Specifically, we investigated their catalytic activities, selectivity, and stabilities as well as the role of metal–support interactions over the performances. The conversion of the substrate was found to be associated with the nature of the employed support as the Au NPs presented similar sizes in all materials. A sub-stoichiometric amount of base was sufficient for the catalyst activation and the observation of the catalysts profile over the time enable insights on their recyclability performances. We believe this reported method represents a facile approach for the synthesis of uniform Au-supported catalysts displaying high performances.
Ni supported Ce0.9Sm0.1O2-δ nanowires
2019 - RODRIGUES, THENNER S.; MOURA, ARTHUR B.L. de; SILVA, FELIPE A. e; CANDIDO, EDUARDO G.; SILVA, ANDERSON G.M. da; OLIVEIRA, DANIELA C. de; QUIROZ, JHON; CAMARGO, PEDRO H.C.; BERGAMASCHI, VANDERLEI S.; FERREIRA, JOAO C.; LINARDI, MARCELO; FONSECA, FABIO C.
We reported herein the synthesis in high yields (> 97%) of Ce0.9Sm0.1O2-δ nanowires displaying well-defined shape, size, and composition by a simple, fast, and low-cost two-step hydrothermal method. The Ce0.9Sm0.1O2-δ nanowires synthesis was followed by the wet impregnation of Ni without the utilization of any stabilizing agent. The Ni/Ce0.9Sm0.1O2-δ nanowires showed higher surface area, high concentration of oxygen vacancies at surface, and finely dispersed Ni particles with significantly higher metallic surface area as compared with catalysts prepared from commercial materials with similar compositions. Such unique and improved properties are reflected on the catalytic performance of the Ni/Ce0.9Sm0.1O2-δ nanowires towards ethanol steam reforming. The nanowires exhibited high yields for hydrogen production (∼60% of selectivity) and an exceptional stability with no loss of activity after 192 h of reaction at 550 °C. The reported results provide insights and can inspire highyield production of nanostructured catalysts displaying controlled and superior properties that enable practical applications in heterogeneous catalysis.