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X-Ray Diffraction, FTIR, and NMR Characterization of Sol–Gel Alumina Doped with Lanthanum and Cerium

✍ Scribed by A. Vázquez; T. López; R. Gómez; Bokhimi; A. Morales; O. Novaro

Publisher
Elsevier Science
Year
1997
Tongue
English
Weight
309 KB
Volume
128
Category
Article
ISSN
0022-4596

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✦ Synopsis

Alumina doped with La and Ce was prepared by using the sol-gel technique. The doping concentrations were alternatively 2 and 5 wt% for each element. Samples were characterized as a function of temperature by using X-ray powder diffraction and FTIR spectroscopy. MAS-NMR studies showed that lanthanum and cerium interacted with alumina and produced a compound with aluminum ions in tetrahedral symmetry. These interactions stabilized alumina structure and shifted its transformations to higher temperatures. When cerium-doped samples were heated at temperatures higher than 1000 °C, CeO 2 was segregated. For La doping such segregation was not observed. Brø ønsted acid sites were generated for the low doping concentrations of both elements. At the high doping concentration, however, only Lewis acid sites existed in a higher concentration than in undoped alumina.

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