Silica-doped alumina cryogels with high thermal stability

Alumina cryogels with a dopant of silica in the content range of 0-10 wt% were synthesized from aqueous boehmite sol through the sol-gel technique and subsequent freeze drying. The higher thermal stability was achieved by the addition of 10 wt% silica; a gamma-Al2O3 phase still remained after heating at 1200 degrees C for 5 h, and the surface area and pore volume were 47 m(2) g(-1) and 105 mm(3) g(-1), respectively. The marked stability was ascribed to the synergetic effect of the very low bulk density (0.05 g cm(-3)) and the dopant. The thermal stability was lower for the cryogels than for the corresponding aerogels; however, it was also suggested that cryogel was highly durable in water in contrast to aerogel. (C) 2007 Elsevier B.V. All rights reserved.