THENNER SILVA RODRIGUES
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Artigo IPEN-doc 25672 Ethanol steam reforming2019 - 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.Artigo IPEN-doc 25155 Sub-15 nm CeO2 nanowires as an efficient nonnoble metal catalyst in the room-temperature oxidation of aniline2018 - SILVA, ANDERSON G.M. da; BATALHA, DANIEL C.; RODRIGUES, THENNER S.; CANDIDO, EDUARDO G.; LUZ, SULUSMON C.; FREITAS, ISABEL C. de; FONSECA, FABIO C.; OLIVEIRA, DANIELA C. de; TAYLOR, JASON G.; TORRESI, SUSANA I.C. de; CAMARGO, PEDRO H.C.; FAJARDO, HUMBERTO V.We described herein the facile synthesis of sub-15 nm CeO2 nanowires based on a hydrothermal method without the use of any capping/stabilizing agent, in which an oriented attachment mechanism took place during the CeO2 nanowire formation. The synthesis of sub-15 nm CeO2 nanowires could be achieved on relatively large scales (∼2.6 grams of nanowires per batch), in high yields (>94%), and at low cost. To date, there are only a limited number of successful attempts towards the synthesis of CeO2 nanowires with such small diameters, and the reported protocols are typically limited to low amounts. The nanowires displayed uniform shapes and sizes, high surface areas, an increased number of oxygen defects sites, and a high proportion of Ce3+/Ce4+ surface species. These features make them promising candidates for oxidation reactions. To this end, we employed the selective oxidation of aniline as a model transformation. The sub-15 nm CeO2 nanowires catalyzed the selective synthesis of nitrosobenzene (up to 98% selectivity) from aniline at room temperature using H2O2 as the oxidant. The effect of solvent and temperature during the catalytic reaction was investigated. We found that such parameters played an important role in the control of the selectivity. The improved catalytic activities observed for the sub-15 nm nanowires could be explained by: i) the uniform morphology with a typical dimension of 11 ± 2 nm in width, which provides higher specific surface areas relative to those of conventional catalysts; ii) the significant concentration of oxygen vacancies and high proportion of Ce3+/Ce4+ species at the surface that represent highly active sites towards oxidation reactions; iii) the crystal growth along the (110) highly catalytically active crystallographic directions, and iv) the mesoporous surface which is easily accessible by liquid substrates. The results reported herein demonstrated high activities under ambient conditions, provided novel insights into selectivities, and may inspire novel metal oxide-based catalysts with desired performances.Artigo IPEN-doc 25099 Synthesis of highly dispersed gold nanoparticles on Al2O3, SiO2, and TiO2 for the solvent-free oxidation of benzyl alcohol under low metal loadings2019 - 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. deWe 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.