Raman studies of nanocomposites catalysts: temperature and pressure effects of CeAl, CeMn and NiAl oxides

Raman studies of nanocomposites catalysts: temperature and pressure effects of CeAl, CeMn and NiAl oxides

Author Silva, Antonio N. da Google Scholar
Neto, Antonio B. S. Google Scholar
Oliveira, Alcemira C. Google Scholar
Junior, Manoel C. Google Scholar
Junior, Jose A. L. Google Scholar
Freire, Paulo T. C. Google Scholar
Filho, Josue M. Google Scholar
Oliveira, Alcineia C. Google Scholar
Lang, Rossano Autor UNIFESP Google Scholar
Abstract High temperature and pressure effects on the physicochemical properties of binary oxides catalysts were investigated. The nanocomposites catalysts comprising of CeAI, CeMn and NiAl were characterized through various physicochemical techniques. A study of the temperature and pressure induced phenomena monitored by Raman spectroscopy was proposed and discussed. Spectral modifications of the Raman modes belonging to the CeMn suggest structural changes in the solid due to the MnO2 phase oxidation with increasing temperature. The thermal expansion and lattice anharmonicity effects were observed on CeMn due to lack of stability of the lattice vacancies. The CeAI and NiAl composites presented crystallographic stability at low temperatures however, undertake a phase transformation of NiO/Al2O3 into NiAl2O4, mostly without any deformation in its structure with increasing the temperature. It was also inferred that the binary oxides are more stables in comparison with monoxides. Detailed pressure-dependent Raman measurements of the T-2g phonon mode of CeMn and NiAl revealed that the pressure contributes to modify bonds length and reduces the particles sizes of the solids. On the contrary, high pressure on CeAI sample improved the stability with addition of Al2O3 in the CeO2 lattice. The results then suggest a good stability of CeAl and NiAl composite catalysts at high pressure and low temperature and show how to prospect of tuning the catalysis for surface reactions entirely through in situ spectroscopic investigations means. (C) 2018 Elsevier B.V. All rights reserved.
Keywords Nanocomposites binary oxides
Raman spectroscopy
High pressure and temperature
Language English
Sponsor CAPES/FUNCAP
CAPES
CNPq
Grant number CAPES/FUNCAP: 23038.008860/2013-92
CAPES/FUNCAP: 23038.007964/2012-07
CNPq: 470793/2013-9
Date 2018
Published in Spectrochimica Acta Part A-Molecular And Biomolecular Spectroscopy. Oxford, v. 198, p. 160-167, 2018.
ISSN 1386-1425 (Sherpa/Romeo, impact factor)
Publisher Pergamon-Elsevier Science Ltd
Extent 160-167
Origin http://dx.doi.org/10.1016/j.saa.2018.02.064
https://doi.org/10.1016/j.saa.2018.03.054
Access rights Closed access
Type Article
Web of Science ID WOS:000432234800019
URI http://repositorio.unifesp.br/handle/11600/45979

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