Characterization of Silica-Containing Aluminum Hydroxide and Oxide Aerogels

✍ Scribed by Marcella Trombetta; Guido Busca; Ronald J. Willey

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 253 KB
• Volume: 190
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1997.4893

✦ Synopsis

of a-Al 2 O 3 is likely associated with the octahedral coordina-Pure and silica-containing Al hydroxide aerogels were prepared tion of Al cations. a-Al 2 O 3 finds application as a support in by the supercritical drying method. The samples were later calheterogeneous catalysis just in relation to its surface incined, giving rise to alumina and Si-Al mixed oxides. The materiertness, as well as to its mechanical strength and resistance als were characterized from the points of view of their bulk and to abrasion (2, 3).

surface structures. The Si-free material before calcination is well-To stabilize transitional aluminas against sintering and crystallized boehmite that converts to g-alumina by calcination.

phase transformations, silica can be added to them (5-7).

The silica-containing hydroxides are composed of boehmite layers with silicates in the interlayer region. The resulting mixed oxides Silica can be deposed at the surface of alumina in relatively present silica essentially in the bulk. The surface structure of alusmall amounts, giving rise to the so-called silicated alumina mina seems poorly sensitive to silica addition. Surface silanol catalysts, which have been patented as good catalysts for groups appear only for SiO 2 more than 4%. No Brønsted acidity olefin isomerization (8) and have recently been characterappears. Silica addition allows mixed oxides with higher surface ized (9-11). Silica-containing aluminas are commercially areas to be obtained.