Antimony (V) Oxide Adsorbed on a Silica-Zirconia Mixed Oxide Obtained by the Sol-Gel Processing Method: Preparation and Acid Properties
نویسندگان
چکیده
A preparação, o grau de dispersão, estabilidade térmica e a acidez de Lewis e de Brφnsted do óxido de antimônio (V) adsorvido sobre SiO 2 /ZrO 2 , preparado previamente pelo processo sol-gel, são descritas neste trabalho. Amostras de SiO 2 /ZrO 2 /Sb 2 O 5 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 SiO 2 /ZrO 2 /Sb 2 O 5 aquecido a diversas temperaturas mostraram que até 1023 K a amostra apresentou-se amorfa. Em 1273 K a formação da fase cristalina ZrO 2 (baddeleita) foi observada e elevando-se a temperatura a 1573 K, as fases cristalinas de SiO 2 (cristobalita) e possivelmente de ZrO 2 /Sb 2 O 5 foram observadas. Utilizando a piridina como sonda molecular, sítios ácidos de Brφnsted do sólido SiO 2 /ZrO 2 /Sb 2 O 5 , aquecido até 523 K, mostraram ser bastante estáveis.
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تاریخ انتشار 2002