resumo
This work focuses on designing highly-porous cellular NiAl2O4-based spinet ceramics through combined suspension emulsification/reactive sintering and further decoration of the pore surfaces by Ni nanoparticles for potential applications in heterogeneous catalysis. Due to kinetic limitations and specific porous structure, the reduction occurs without affecting the integrity of the cellular monoliths. The reaction mechanism, assessed by XRD and TEM/ EDS, includes both partial decomposition and reduction, resulting in the formation of metastable Al-enriched phases, mainly NiAl32O49, and metallic Ni phase, respectively. The results suggest that the cellular bulk framework can be decorated with Ni catalyst in a controlled way, by proper selection of the initial cation stoichiometry of the NiAl2O4 spinel and appropriate reduction conditions. In selected conditions the reduction results in Ni nanoparticles of various dimension scales, finely dispersed at the pore surfaces, with a significant fraction below 50 nm, as confirmed by TEM/EDS. The results of thermodynamic analysis emphasize that the redox tolerance of the spinel phase is dependent on the Ni:Al activity ratio, suggesting the prospects for tuning the catalytic activity and stability by designing the initial composition and resulting content of metallic Ni and Ni- and Al-containing metastable phases. (C) 2017 Elsevier Ltd. All rights reserved.
palavras-chave
NICKEL ALUMINATE CATALYSTS; EMULSIFIED SUSPENSIONS; ELECTRICAL-CONDUCTIVITY; THIN-FILMS; METHANE; SPINELS; STABILITY; SUPPORTS
categoria
Materials Science
autores
Vitorino, NMD; Kovalevsky, AV; Ferro, MC; Abrantes, JCC; Frade, JR
nossos autores
Andrei Kavaleuski
Investigador principal
João Carlos de Castro Abrantes
Professor Adjunto
Jorge Ribeiro Frade
Professor(a) Jubilado(a)
Marta Ascenção Carmona Ferro
Técnico de Laboratório
Nuno Miguel Dias Vitorino
Bolseiro de pós-DoutoramentoProjectos
CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013)
Cellular oxide catalysts for emission lean combustion in porous media (LEANCOMB)
agradecimentos
This work was developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), PTDC/CTM-ENE/2942/2014 and PEst-C/CTM/LA0011/2013, and grants SFRH/BPD/99367/2013 and IF/00302/2012, financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. SEM and XRD facilities were funded by FEDER Funds through QREN - Aviso SAIECT-IEC/2/2010, Operacao NORTE-07-0162-FEDER-000050.