A comparison of post-synthesis alumination and sol-gel synthesis of MCM-41with high framework aluminum content

Aluminum-containing mesoporous MCM-41 materials were prepared by post-synth esis modification of a purely siliceous MCM-41 using different Al sources: AlCl3, aluminum isopropoxide and NaAlO2. The structure, thermal stability a nd acidity of these materials have been investigated and compared with Al-M CM-41 prepared by direct hydrothermal synthesis. Irrespective of the prepar ation method, the surface area, pore diameter, crystallinity and thermal st ability of Al-MCM-41 decrease with increasing Al content. Post-synthesis mo dified materials possess better thermal stability, and this method allows f or the incorporation of more aluminum without disintegration of the mesopor ous structure as compared to Al-MCM-41 prepared by direct hydrothermal synt hesis. The post-synthesized Al-MCM-41 has a moderate acidity, comparable to that of the direct hydrothermally-synthesized material. (C) 1999 Elsevier Science B.V. All rights reserved.