Aluminum in mesoporous silica–alumina

Abstract

Quantitative 27Al MAS NMR spectral decomposition, employing a Gaussian distribution of anisotropic parameters, along with triple-quantum spectroscopy were used to examine the aluminum nuclei in mesoporous silica–alumina (MSA). Only half of the Al nuclei in H-MSA were detected by MAS NMR analysis at 7Tesla field strength. Complete hydration provided full detection and revealed large amounts of AlO6 sites (ca. 40% mole). All these sites were converted to AlO4 sites, with NH3 protonation, using a pressurized ammonia–water treatment. 27Al and 29Si MAS NMR spectral changes indicated this occurred by partial reformation of the aluminosilicate.