Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/25140
Type: Artigo de periódico
Title: Antimony (V) Oxide Adsorbed on a Silica-Zirconia Mixed Oxide Obtained by the Sol-Gel Processing Method: Preparation and Acid Properties
Author: Zaitseva, Galina
Gushikem, Yoshitaka
Abstract: The preparation, degree of dispersion, thermal stability and Lewis and Brønsted acidity of antimony (V) oxide adsorbed on SiO2/ZrO2 mixed oxide, previously prepared by the sol-gel processing method, are described herein. The samples SiO2/ZrO2/Sb2O5, with compositions (in wt %): (a) Zr= 8.1 and Sb= 6.3; (b) Zr= 14.9 and Sb= 11.4, were prepared. Scanning electron microscopy images connected to a X-ray energy dispersive spectrometer showed that both metals, Zr and Sb, were highly dispersed in the matrices. The X-ray diffraction patterns of SiO2/ZrO2/Sb2O5 heated at different temperatures showed that, up to 1023 K, the matrix was amorphous. At 1273 K a crystalline phase of ZrO2 (baddeleyite) was observed and raising the temperature to 1573 K, crystalline phases of SiO2 (cristobalite) and presumably of ZrO2/Sb2O5 were observed. Using pyridine as a molecular probe, Brønsted acid sites on the SiO2/ZrO2/Sb2O5 matrix, heat treated up to 523 K, were shown to be very stable.
A preparação, o grau de dispersão, estabilidade térmica e a acidez de Lewis e de Brønsted do óxido de antimônio (V) adsorvido sobre SiO2/ZrO2, preparado previamente pelo processo sol-gel, são descritas neste trabalho. Amostras de SiO2/ZrO2/Sb2O5 de composições (% em massa): (a) Zr= 8,1 e Sb= 6,3; (b) Zr= 11,4 e Sb= 11,4, foram preparadas. As imagens de microscopia eletrônica de varredura conectada a um espectrômetro de energia dispersiva de raios X mostraram que os metais, Zr e Sb, estão homogeneamente dispersos em ambas as matrizes. Os padrões de difração de raios X de SiO2/ZrO2/Sb2O5 aquecido a diversas temperaturas mostraram que até 1023 K a amostra apresentou-se amorfa. Em 1273 K a formação da fase cristalina ZrO2 (baddeleita) foi observada e elevando-se a temperatura a 1573 K, as fases cristalinas de SiO2 (cristobalita) e possivelmente de ZrO2/Sb2O5 foram observadas. Utilizando a piridina como sonda molecular, sítios ácidos de Brønsted do sólido SiO2/ZrO2/Sb2O5, aquecido até 523 K, mostraram ser bastante estáveis.
Subject: sol-gel method
silica-zirconia-antimony mixed oxide
Brønsted
Lewis acid sites
Editor: Sociedade Brasileira de Química
Rights: aberto
Identifier DOI: 10.1590/S0103-50532002000500011
Address: http://dx.doi.org/10.1590/S0103-50532002000500011
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532002000500011
Date Issue: 1-Sep-2002
Appears in Collections:Artigos e Materiais de Revistas Científicas - Unicamp

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