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

Abstract

Aluminum-containing mesoporous MCM-41 materials were prepared by post-synthesis modification of a purely siliceous MCM-41 using different Al sources: AlCl3, aluminum isopropoxide and NaAlO2. The structure, thermal stability and acidity of these materials have been investigated and compared with Al-MCM-41 prepared by direct hydrothermal synthesis. Irrespective of the preparation method, the surface area, pore diameter, crystallinity and thermal stability of Al-MCM-41 decrease with increasing Al content. Post-synthesis modified materials possess better thermal stability, and this method allows for the incorporation of more aluminum without disintegration of the mesoporous structure as compared to Al-MCM-41 prepared by direct hydrothermal synthesis. The post-synthesized Al-MCM-41 has a moderate acidity, comparable to that of the direct hydrothermally-synthesized material.