Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/78840
Type: Artigo de periódico
Title: Temperature-induced transformations in CoAPO-34 molecular sieve: A combined in situ X-ray diffraction and FTIR study
Author: Martucci, A
Alberti, A
Cruciani, G
Frache, A
Marchese, L
Pastore, HO
Abstract: Thermally induced processes of CoAPO-34, an aluminophosphate molecular sieve with chabasite-type structure, synthesized in the presence of morpholine as a structure-directing agent and HF as a mineralizing agent, have been studied by in situ X-ray synchrotron powder diffraction augmented with Fourier transform (FT) IR analysis. A time-resolved experiment was performed using a translating imaging plate system. At room temperature, the structure refinement by full-profile Rietveld analysis showed P-I symmetry and the presence of one Al site with sixfold coordination. At around 400 degrees C, both fluorine and morpholine are lost, and the four-connected chabazite (CHA)-type topology is restored. Notwithstanding the metrically rhombohedral values of the cell parameters, the symmetry remains triclinic P-1. Inhomogeneous dealumination of the framework begins at 725 degrees C, accompanied by a strong triclinization of the unit cell and followed by the collapse of the structure above 775 degrees C. The insertion of cobalt ions within the CHA framework was monitored by FTIR spectroscopy, which showed that bridged Co2+-O(H)-P hydroxyls are present after morpholine removal.
Country: EUA
Editor: Amer Chemical Soc
Rights: fechado
Identifier DOI: 10.1021/jp050777k
Date Issue: 2005
Appears in Collections:Artigos e Materiais de Revistas Científicas - Unicamp

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