ROGER VASCONCELOS CAVALLARI

ROGER VASCONCELOS CAVALLARI

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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.
Preparação de suporte de catalisador a partir de biocarbono
2018 - CAVALLARI, ROGER V.; DE LIMA, NATASHA B.; SILVA, JULIO C.M.; BERGAMASHI, VANDERLEI S.; FERREIRA, JOAO C.
O uso exagerado de recursos não renováveis, nas ultimas décadas, deflagrou consequências negativas para a sociedade, havendo necessidade de buscar soluções diante dos efeitos deletérios causados pelo avanço da devastação do meio ambiente. Visando contribuir com a ampliação das estratégias de controle de poluentes através do desenvolvimento de tecnologia de baixo custo, o presente trabalho tem como objetivo principal o desenvolvimento de materiais ativos com elevada resistência térmica e boa área especifica para adsorção e impregnação de metais. Neste sentido foram estudados três rotas de tratamento do biocarvão. Na caracterização do biocarbono usaram-se métodos analíticos como: Espectroscopia de Infravermelho (IV), Espectroscopia RAMAM, Medida da Área Superficial (BET), Análise Térmica (TG), Difração de Raios X (DRX) e Microscopia Eletrônica de Varredura (MEV). As diferentes condições de tratamento resultaram em mudanças na estrutura carbonácea do biocarbono com características adequadas para serem utilizados como suporte em catalisadores, apresentando sítios ativos com cargas negativamente carregadas para promover a fixação de metais em sua superfície. Verificou-se também um aumento na área superficial específica, variando entre 341,4 a 749,7 m2 g-1 e alterações nas bandas D e G do carvão e uma alta resistência à temperatura, o que promove reações catalíticas com baixa perda de catalisador.
Palladium nanoparticles supported on mesoporous biocarbon from coconut shell for ethanol electro‑oxidation in alkaline media
2018 - FERREIRA, JOAO C.; CAVALLARI, ROGER V.; BERGAMASCHI, VANDERLEI S.; ANTONIASSI, RODOLFO M.; TEIXEIRA-NETO, ANGELA A.; LINARDI, MARCELO; SILVA, JULIO C.M.
Palladium nanoparticles supported on carbon Vulcan XC72 (Pd/C) and biocarbon (Pd/BC) synthesized by sodium borohydride process were used as catalysts for ethanol electro-oxidation in alkaline media. The biocarbon (BC) from coconut shell with mesoporous and high surface area (792 m2 g−1) was obtained by carbonization at 900 °C and the hydrothermal treatment in a microwave oven. The D-band and G-band intensity ratio (ID/IG) from Raman analysis showed high disorder of the biocarbon, while X-ray photoelectron spectroscopy (XPS) suggests higher percentage of oxygen groups on the surface of biocarbon than of Vulcan XC72. From X-ray diffraction (XRD), it was observed peaks in 2θ degree related to the face centered cubic (fcc) structure of palladium and the mean crystallite sizes calculated based on the diffraction peak of Pd (220) were 5.6 nm for Pd/C and 5.3 nm for Pd/BC. Using Transmission Electron Microscope (TEM), it was observed particles well dispersed on both carbons support materials. The electrocatalytic activity of the materials was investigated by cyclic voltammetry (CV) and chronoamperometry (CA) experiments. The peak current density (on CV experiments) from ethanol electro-oxidation on Pd/BC was 50% higher than on Pd/C, while the current density measured at 15 min of CA experiments was 80% higher on Pd/BC than on Pd/C. The higher catalytic activity of Pd/BC might be related to the large surface area of the biocarbon (792 m2 g−1) vs (239 m2 g−1) of Vulcan carbon, the defects of the biocarbon structure and higher amount of oxygen on the surface than Carbon Vulcan XC 72.
Uso do Reformador a Vapor do Etanol e Vinhaça de Cana para Geração de Hidrogênio
2017 - CAVALLARI, ROGER V.; FERREIRA, JOAO C.