Alumina supports for high-temperature catalysts were synthesized by different sol-gel methods, including one xerogel dried by simple evaporation and two aerogels dried by supercritical drying in CO2 or in alcohol. The influence of the gel synthesis technique and the additives used for gelation on the porous structure of alumina and its evolution during heat treatment at 400, 900, and 1200 degrees C was analyzed by X-ray diffraction and by the BET nitrogen adsorption method. Complexation with acetic acid at the gel step followed by supercritical drying at low temperature (35 degrees C) caused a retardation of alpha-alumina formation with a significant residual specific surface area after heating for 5 h at 1200 degrees C in air, namely 70 m(2)/g.