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Novos avanços no processo de fabrico de espumas de céria para produção de hidrogénio pela via termoquímica solar
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Abstract(s)
RESUMO: Este trabalho reporta um processo alternativo ao utilizado anteriormente para a produção de espumas de céria, pelo método de replicação de esponjas polimérica patenteado, em 1963, por Schwartzwalder e Somers. As referidas espumas destinam-se a servir de catalisadores à reação de separação da água pela via termoquímica solar. Esta via envolve um ciclo redox, em que a redução endotérmica da céria ocorre a T~1400ºC, em atmosfera de árgon, e a oxidação tem lugar a T~1000ºC, em presença de vapor de água. O aquecimento foi efetuado por radiação solar concentrada em fornos solares de 1,5 kW, concebidos para o efeito, disponíveis no Laboratório PROMES-CNRS (Odeillo, França). A adição de 5% PVA à suspensão permitiu evitar o colapso da estrutura celular durante a etapa de queima do substrato de PU, permitindo obter uma microestrutura mais porosa, que promoveu a formação de H2 pela via termoquímica solar. Ficou assim demonstrado que a microestrutura deste novo material teve um efeito benéfico na produção de H2, ou seja, estima-se que o H2 produzido por este material (CF5) seja cerca do dobro do anterior (CF), com base nos teores de CO e O2 registados.
ABSTRACT: This work highlights an alternative approach to the manufacturing of ceria foams by the polymeric sponge replica method patented, in 1963, by Schwartzwalder and Somers. These foams are intended to serve as catalysts for the solar hydrogen production via a two-step water-splitting thermochemical cycle route. This involves a redox cycle, in which the endothermic reduction of the ceria occurs at T~1400ºC, in argon atmosphere, and oxidation takes place at T~1000ºC, in the presence of water vapour. Concentrated solar radiation was used as heating source in suitably designed solar furnaces of 1.5 kW available at the PROMES-CNRS Laboratory (Odeillo, France). Additions of 5 wt.% PVA to the slurries played a crucial role in preventing the collapse of the cell structure during the burning out of the PU template, resulting in a more porous microstructure, which promoted the formation of H2 by redox reactions involved in the solar thermochemical cycle. It was thus demonstrated that the microstructure of this new material had a beneficial effect on the production of H2, i.e., one estimates that the H2 yield of the developed material (CF5) is about twice the reported for the previous one (CF), based on the CO and O2 yields recorded.
ABSTRACT: This work highlights an alternative approach to the manufacturing of ceria foams by the polymeric sponge replica method patented, in 1963, by Schwartzwalder and Somers. These foams are intended to serve as catalysts for the solar hydrogen production via a two-step water-splitting thermochemical cycle route. This involves a redox cycle, in which the endothermic reduction of the ceria occurs at T~1400ºC, in argon atmosphere, and oxidation takes place at T~1000ºC, in the presence of water vapour. Concentrated solar radiation was used as heating source in suitably designed solar furnaces of 1.5 kW available at the PROMES-CNRS Laboratory (Odeillo, France). Additions of 5 wt.% PVA to the slurries played a crucial role in preventing the collapse of the cell structure during the burning out of the PU template, resulting in a more porous microstructure, which promoted the formation of H2 by redox reactions involved in the solar thermochemical cycle. It was thus demonstrated that the microstructure of this new material had a beneficial effect on the production of H2, i.e., one estimates that the H2 yield of the developed material (CF5) is about twice the reported for the previous one (CF), based on the CO and O2 yields recorded.
Description
CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia Solar
Keywords
Hydrogen Water splitting Solar fuels Thermochemical cycle Materials Cerium
Citation
Oliveira, F.A.C... [et.al.] - Novos avanços no processo de fabrico de espumas de céria para produção de hidrogénio pela via termoquímica solar. In: CIES2020: As Energias Renováveis na Transição Energética: Livro de Comunicações do XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia Solar. Helder Gonçalves, Manuel Romero (Ed.). Lisboa, Portugal: LNEG, 3-5 Novembro, 2020, p. 769-772
Publisher
LNEG - Laboratório Nacional de Energia e Geologia