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Journal of Chemistry
Volume 2016, Article ID 5353490, 6 pages
http://dx.doi.org/10.1155/2016/5353490
Research Article

Effects of Different Raw Materials in the Synthesis of Boehmite and γ- and α-Alumina

1National Centre for Metallurgical Research (CSIC), Avda. Gregorio del Amo 8, 28040 Madrid, Spain
2Department Crystallography and Mineralogy, Faculty of Geology, UCM, C/Jose A. Novais, 28040 Madrid, Spain

Received 4 September 2016; Revised 10 October 2016; Accepted 19 October 2016

Academic Editor: Jean-Marie Nedelec

Copyright © 2016 Isabel Padilla et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Two alumina polymorphs, the metaestable γ-Al2O3 and the stable α-Al2O3, were obtained from thermal treatment of the precursor γ-AlOOH (boehmite). This precursor was prepared by a precipitation method employing different raw materials in order to study their effect on the synthesis process and several characteristics of the materials, such as the crystallite size, the thermal behavior, and the surface area. Aluminum chloride (AlCl3·6H2O) and an aluminum waste were used as the source of aluminum. A 1 M NaOH solution and a 1 M n-butylamine solution were used as alkalizing agents, due to their strong and weak alkaline characteristics, respectively. The XRD profiles of the boehmites obtained from waste show lower crystallinity than samples obtained from aluminum chloride. The content of water, from TG studies, was higher in the samples obtained from waste, which fit well with the smaller crystallite size. The use of n-butylamine as alkalizing agent favors the formation of γ-alumina with higher surface area (177.2 cm2 g−1, for aluminum waste, and 159.4 cm2 g−1, for aluminum pure reagent). The temperature of transformation from gamma to alpha, from DTA results, is higher for samples obtained from the waste, and accordingly the presence of impurities in the waste stabilizes the metastable alumina phase.