Abstract
First direct spectroscopic evidence for the existence of Brønsted acid sites in AlPO4-5 (AFI) single crystal molecular sieves substituted with divalent metal cations is reported. Ammonia and pyridine were used as probe molecules. Compared with unsubstituted AlPO4-5 single crystals, the metal substituted samples exhibit well-developed bands of isolated hydroxyl groups and a broad absorption band indicating the existence of hydrogen bonded OH groups. Upon adsorption of pyridine on the metal substituted samples the formation of a new, relatively free vibrating hydroxyl group (¿oh = 3690¿3694 cm¿1 was observed, giving evidence for a strong Lewis type interaction leading to the cleavage of a metal-oxygen bond close or at the position of the substituting metal cation.
Original language | Undefined |
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Pages (from-to) | 173-178 |
Number of pages | 6 |
Journal | Journal of molecular structure |
Volume | 410-41 |
Issue number | 410-4 |
DOIs | |
Publication status | Published - 1997 |
Keywords
- IR-10198
- METIS-105542