Surface acidity of MCM-41 by in situ IR studies of pyridine adsorption

The nature and concentration of the acid sites of MCM-41 material as a function of Si/Al ratio have been monitored by in situ IR using pyridine as a probe molecule. The thermal stability of aluminium in the framework of these materials is studied using 27Al MAS NMR spectroscopy. The tetrahedral to octahedral aluminium ratio is found to increase with higher aluminium incorporation. The sample with the lowest Si/Al ratio is found to exhibit higher acidity compared to the other samples. However, the acidity of these mesoporous aluminosilicates is less compared to the conventional H-Y zeolite. © 1999 Elsevier Science B.V. All rights reserved.