Bochmites were precipitated hydrothermally from different inorganic aluminum salt solutions under similar conditions using urea as the precipitating agent. It was observed that the hydrolysis of Al-2(SO4)(3) starts at a lower temperature due to formation of hydroxy sulfates in comparison to AlCl3 and Al(NO3)(3) solutions. The boehmite obtained from Al-2(SO4)(3) has a lower water content, and a higher surface area than the boehmites obtained either from AlCl3 or Al(NO3)(3). The boehmite obtained from Al-2(SO4)(3) was lighter giving lower tap density value. Depending on the nature of anion present during synthesis, the TG-DTA showed the endothermic peak between 460 and 480 T, characteristic of transformation of boehmite to gamma-Al2O3. No other phase transformation occurred up to 1000 T, indicating enhanced thermal stability of gamma-Al-2-O-3 prepared through the present hydrothermal route. (C) 2002 Elsevier Science B.V. All rights reserved.
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