Studies on structure and acid-base properties of high silica MFI-type zeolite modified with methylamine

Investigations with XRD, C-13 and Si-29 MAS NMR, FT-IR, NH3-TPD and CO2-TPD, nitrogen adsorption, composition analysis and TG/DTG/DTA real that adsorbed methylamine (MA) strongly interacts with the framework of high silica MFI-type zeolite. The interaction results in the structural symmetry of MFI zeolite changing from monoclinic to orthorhombic. At 298K the H atom of the amine group attacks the [Si-O] framework to form O---H---N bonds. On raising the temperature to 323K, the signal belonging to Si-N connection appears in the FT-IR spectrum and Si-29 MAS NMR pattern of the modified zeolite, respectively, showing a linkage of Si-N-Si in the framework. The MA modified MFI zeolite exhibits evident and strong basic properties. (c) 2004 Elsevier Inc. All rights reserved.