Low silica MCM-41 composites and mesoporous solids

Aluminosilicate MCM-41 mesophase solids have been prepared under alkaline c onditions with high degrees of mesoscopic order and silicon-to-aluminum mol ar ratios approaching unity. One- and two-dimensional solid-state NMR techn iques, in conjunction with elemental analyses, infrared spectroscopy, and p owder X-ray diffraction (XRD), establish that high concentrations of alumin um have been incorporated into the aluminosilicate MCM-41 frameworks, with retention of mesoscopic order. Hexagonal low silica MCM-41 has been prepare d with a bulk molar Si/Al ratio as low as 1.3, while retaining a minimum of three indexable p6mm reflections in the XRD pattern prior to calcination. Following calcination to remove the structure-directing surfactant molecule s, the hexagonal MCM-41 structures are preserved. The decreased thermal sta bilities and dealumination of the materials with higher aluminum contents h ave been studied using 2D Al-27{H-1} heteronuclear correlation NMR and Al-2 7 MAS intensity calibration techniques to examine surface structures and qu antify Al species present before and after calcination.