ANA RITA NOBORIKAWA PAIVA

ANA RITA NOBORIKAWA PAIVA

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AuCu/TiO2 catalysts prepared using electron beam irradiation for the preferential oxidation of carbon monoxide in hydrogen-rich mixtures
2021 - ALENCAR, C.S.L.; PAIVA, A.R.N.; SILVA, L.G.A.; SOMESSARI, E.S.R.; VAZ, J.M.; SPINACE, E.V.
The major part of the world production of hydrogen (H2) is originated from a combination of methane steam reforming and water gas shift reaction resulting in an H2 rich mixture known as reformate gas, which contains about 1% vol (10,000 ppm) of carbon monoxide (CO). The preferential oxidation reaction of CO in H2 rich mixtures (CO PROX) has been considered a very promising process for H2 purification, reducing CO for values below 50 ppm allowing its use in PEMFC Fuel Cells. Au nanoparticles supported on TiO2 (Au/TiO2) catalysts have been shown good activity and selectivity for CO PROX reaction in the temperature range between 20 80 ºC; however, the catalytic activity strongly depends on the preparation method. Also, the addition of Cu to the Au/TiO2 catalyst could increase the activity and selectivity for CO PROX reaction. In this work, AuCu/TiO2 catalysts with composition 0.5%Au0.5%Cu/TiO2 were prepared in a single step using electron beam irradiation, where the Au3+ and Cu2+ ions were dissolved in water/2 propanol solution, the TiO2 support was dispersed and the obtained mixture was irradiated under stirring at room temperature using different dose rates (8 64 kGy s 1) and total doses (144 576 kGy). The catalysts were characterized by energy dispersive X ray analysis, X ray diffraction transmission electron microscopy, temperature programmed reduction and tested for CO PROX reaction. The best result was obtained with a catalyst prepared with a dose rate of 64 kGy s 1 and a total dose of 576 kGy showed a CO conversion of 45% and a CO2 selectivity of 30% at 150 ºC.
One-Step synthesis of PtFe/CeO2 catalyst for the Co-Preferential oxidation reaction at low temperatures
2021 - ANTONIASSI, RODOLFO M.; MACHADO, ARTHUR P.; PAIVA, ANA R.N.; QUEIROZ, CARLA M.S.; VAZ, JORGE M.; SPINACE, ESTEVAM V.; SILVA, JULIO C.M.; CARMINE, EDUARDO; CAMARGO, PEDRO H.C.; TORRESI, ROBERTO M.
Active Pt-based catalysts at low temperature towards the preferential oxidation of carbon monoxide in hydrogen-rich stream reaction (CO-PROX) are of great importance for H2-fueled fuel cells, but still remain a challenge. Herein, we propose a simple approach to synthesize a highly active Pt20Fe/CeO2 catalyst employing the borohydride reduction process. Transmission electronic microscopy revealed monodispersed 2.8 nm-Pt nanoparticles on CeO2, and the role of Fe species on the activity is discussed. The excellent CO conversion of 99.6% and CO2 selectivity of 92.3% carried out at ambient temperature meet the CO-PROX requirements for an adequate supply of hydrogen in fuel cell device.
One-step synthesis of AuCu/TiO2 catalysts for CO preferential oxidation
2020 - ALENCAR, CATARINE S.L.; PAIVA, ANA R.N.; SILVA, JULIO C.M. da; VAZ, JORGE M.; SPINACE, ESTEVAM V.
Au/TiO2 (1wt% Au), Cu/TiO2 (1wt% Cu) and AuCu/TiO2 (1wt% AuCu) catalysts with different Au:Cu mass ratios were prepared in one-step synthesis using sodium borohydride as reducing agent. The resulting catalysts were characterized by X-ray diffraction (XRD), X-ray Dispersive Energy (EDX), Transmission Electron Microscopy (TEM) and Temperature Programmed Reduction (TPR) and tested for the preferential oxidation of carbon monoxide (CO-PROX reaction) in H2-rich gases. EDS analysis showed that the Au contents are close to the nominal values whereas for Cu these values are always lower. X-ray diffractograms showed only the peaks of TiO2 phase; no peaks of metallic Au and Cu species or oxides phases were observed. TPR and high-resolution TEM analysis showed that AuCu/TiO2 catalysts exhibited most of Au in the metallic form with particles sizes in the range of 3-5 nm and that Cu was found in the form of oxide in close contact with the Au nanoparticles and well spread over the TiO2 surface. The AuCu/TiO2 catalysts exhibited good performance in the range of 75-100 °C and presented a better catalytic activity when compared to the monometallic ones. A maximum CO conversion of 98.4% with a CO2 selectivity of 47% was obtained for Au0.50Cu0.50/TiO2 catalyst at 100°C.
Preparação de nanopartículas de cobre e ouro suportadas em TiO2 para uso como catalisador na oxidação preferencial de CO em misturas ricas em hidrogênio (CO-PROX)
2019 - ALENCAR, CATARINE S.L.; PAIVA, ANA R.N.; VAZ, JORGE M.; SPINACE, ESTEVAM V.
Os catalisadores Au/TiO2 têm apresentado boa atividade e seletividade para a reação de oxidação preferencial de monóxido de carbono em misturas ricas em hidrogênio (CO-PROX). É proposto um catalisador contendo os metais Au e Cu (CuAu/TiO2) que será preparado por meio de redução química de forma simultânea de ambos os metais, utilizando borohidreto de sódio como agente redutor. Realizou-se também a síntese de catalisadores monometálicos de Cu/TiO2 e Au/TiO2 sob as mesmas condições e os resultados foram comparados. Os catalisadores foram caracterizados por Difração de Raios X (DRX), Energia Dispersiva de Raios X (EDX), Microscopia Eletrônica de Transmissão (MET) e Redução por temperatura programada (TPR). O catalisador CuAu/TiO2 apresentou melhor atividade catalítica para a reação CO-PROX se comparado aos seus respectivos catalisadores monometálicos.
Preparação de catalisadores Pt/CeO2 promovidos por Fe e Sn via método de redução por álcool para a oxidação preferencial de CO em misturas ricas em hidrogênio (PROX-CO)
2019 - QUEIROZ, CARLA M.S.; MACHADO, ARTHUR P.; PAIVA, ANA R.N.; VAZ, JORGE M.; SPINACE, ESTEVAM V.
A reação de oxidação preferencial do CO (PROX-CO) é considerada uma alternativa eficiente e econômica para remoção de CO presente em correntes de H2 que são empregadas para a produção de energia limpa e sustentável via tecnologia de células a combustível. Isto porque, a reação de PROX-CO catalisada é capaz de reduzir a concentração deste contaminante para níveis menores que 50 ppm, evitando assim o envenenamento e consequente desativação dos eletrodos da célula. Os catalisadores de Pt têm se mostrado bastante promissores para emprego na reação de PROX-CO, apresentado altas conversões e seletividades, numa ampla faixa de temperatura. Assim, este trabalho tem o objetivo de estudar o desempenho de catalisadores de Pt/CeO2 promovidos com óxidos de Fe ou Sn destinados à reação de PROX-CO. Os sólidos foram sintetizados pelo método de redução por álcool e caracterizados pelas técnicas de EDX, DRX e MET. Os desempenhos catalíticos foram conduzidos sob pressão atmosférica e em temperaturas variando entre 50 °C e 200 °C. Os resultados revelam que os catalisadores de Pt suportados em céria apresentaram máxima conversão de CO e seletividade em CO2 a 50 °C.
AuCu/TiO2 catalysts prepared using electron beam irradiation for the preferential oxidation of carbono monoxide in hydrogen-rich mixtures
2019 - ALENCAR, CATARINE S.L.; PAIVA, ANA R.N.; SILVA, LEONARDO G. de A. e; SOMESSARI, ELIZABETH S.R.; VAZ, JORGE M.; SPINACE, ESTEVAM V.
The major part of the world production of hydrogen is originated from a combination of methane steam reforming and water gas shift reaction resulting in a n H 2 rich mixture known as reformate gas, which contains about 1% vol (10, 000 p pm) of carbon monoxide (CO). The preferential oxidation reaction of CO in H 2 rich mixtures (CO PROX) has been considered a very promising process for H 2 purification, reducing CO for values below 50 ppm allowing its use in Proton Exchange Membrane Fuel Cells (PEMFC). Au nanopart icles supported on TiO 2 (Au/TiO 2 ) catalysts have been shown good activity and selectivity for CO PROX reaction in the temperature range between 20 ºC and 80 ºC; however, the catalytic activity strongly depend s on the preparation method. Also, the addition of Cu to the Au/TiO 2 catalyst could increase the activity and selectivity for CO PROX reaction. In this work, AuCu/TiO 2 catalysts with composition 0.5%Au0. 5%Cu/TiO 2 were prepared in a single step using electron beam irradiation, where the Au 3+ and Cu 2+ ion s were dissolved in water/2 propanol solution , the TiO 2 support was dispersed and the obtained mixture was irradiated under stirring at room temperature using different dose rates ( 8 64 kGy s 1 ) and doses 144 576 kGy The catalysts were characterized by energy dispersive X ray analysis (EDX), X ray diffraction (XRD), transmissi on electron microscopy (TEM), temperature programmed reduction (TPR) and tested for CO PROX reaction In the studied conditions, it was observed that the increase of t he dose rate and the total dose contributed to a decrease in the mean nanoparticle sizes. The best result was obtained with a catalyst prepared with a dose rate of 64 kGy s 1 and a dose of 576 kGy showed a CO conversion of 45% and a CO 2 selectivity of 30% at 150 o C.
Active Pt/CeO2 catalysts prepared by an alcohol‑reduction process for low‑temperature CO‑PROX reaction
2019 - QUEIROZ, CARLA M.S.; MACHADO, ARTHUR P.; PAIVA, ANA R.N.; ANTONIASSI, RODOLFO M.; VAZ, JORGE M.; SPINACE, ESTEVAM V.
Pt/CeO2 catalysts were prepared with 0.5 and 1 wt% of Pt loadings by an alcohol-reduction process using a solution of ethylene glycol and water as a reducing agent and solvent. The obtained catalysts were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy. Transmission electron micrographs showed Pt nanoparticles with average sizes of 2.2 and 2.4 nm for Pt content of 0.5 and 1 wt%, respectively. The preferential oxidation of carbon monoxide in hydrogen-rich stream (CO-PROX reaction) was studied in the temperature range of 25–150 °C. Pt/CeO2 catalysts showed maximum CO conversions in the range of 80–98% and CO2 selectivity in the range of 50–70% at 50 °C.