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 γ-Al2O3 phase still remained after heating at 1200 °C for 5 h, and the surface area and pore volume were 47 m2 g−1 and 105 mm3 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.