Acidic property of YNU-5 zeolite influenced by its unique micropore system
Résumé
The Brønsted acid strength of YNU-5 zeolite (YFI-type framework) was analyzed by means of the ammonia IRMS-TPD (infrared/mass spectroscopy temperature-programmed desorption) method. In addition, the accessibility of Brønsted acid sites was evaluated by IR spectroscopy using pyridine as a probe molecule. Most of the YNU-5 Brønsted acidic OH groups reacted with pyridine vapor at 343 K to form pyridinium cations, indicating that the Brønsted acid sites are highly accessible through the large 12-member ring (12-ring) channel. The number of Brønsted acid sites was close to the aluminum content in the H-form of YNU-5 zeolite. Enthalpy of ammonia desorption from the Brønsted acid site was in the following order as an indicator of acid strength: FAU < MOR (12-ring) < *BEA < MFI < MWW ≈ YFI < MOR (8-ring). These data will serve to develop new catalytic materials based on YNI-5 zeolite.
Domaines
Matériaux
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